WellFlo Quick Start Guide 20090130

WellFlo™Petroleum Engineering Software

Quick Start GuideSoftware Version 4.0

We l l F l o

Q U I C K S T A R T G U I D ESoftware Version: 4.0

COPYRIGHT AND WARRANTY

WellFlo 4.0

© 2008 Weatherford International

This document contains information proprietary to Weatherford International, with all rights reserved worldwide. Any reproduction or disclosure of this publication, or any part hereof, to persons other than Weatherford International personnel is strictly prohibited, except by written permission of Weatherford International.

DISCLAIMER

Information in this guide is subject to change without notice and does not constitute a commitment on the part of Weatherford International. It is supplied on an “as is” basis without any warranty of any kind, either explicit or implied. Information may be changed or updated in this guide at any time.

THIRD-PARTY SOFTWARE

The following products and organizations have been mentioned in this documentation. Various trademarks are owned by the respective owners.

Microsoft®, Windows 95®, Windows 98®, Windows 2000®, Windows NT® and Windows XP® are either registered trademarks or trademarks of Microsoft Corporation in the United States and/or other countries, http://www.microsoft.com.

USING THIS MANUAL

This manual is designed to address the needs of both the new and advanced user. It assumes you have knowledge of basic oil field terminology and have minimal familiarity with Microsoft Windows®.

2

CONTENTS

CHAPTER 1: Overview ............................................................................................ 5

Introduction ........................................................................................................................ 6Deliverability Applications ........................................................................................... 6Diagnostic Applications ................................................................................................ 7

WellFlo Interface ................................................................................................................ 8

CHAPTER 2: Tutorial I: Building a Well Model ....................................................... 11

Building a Model ............................................................................................................. 12Creating a New Model ................................................................................................ 13Setting Flow Correlations ............................................................................................ 17Setting Reference Depths ............................................................................................ 18Setting Fluid Parameters ............................................................................................. 19

Reservoir Layers ............................................................................................................... 24Setting General Parameters ......................................................................................... 24Plotting IPR ................................................................................................................... 25Relative Permeability ................................................................................................... 25

Wellbore Data ................................................................................................................... 29Wellbore Equipment .................................................................................................... 30

Surface Data ...................................................................................................................... 34Surface Equipment ....................................................................................................... 35

Temperature Model ......................................................................................................... 38Gas Lift Data ..................................................................................................................... 40

CHAPTER 3: Tutorial III: Systems Analysis ............................................................. 43

Systems Analysis ............................................................................................................. 44Setting Operating Conditions ..................................................................................... 44Running Sensitivities ................................................................................................... 48Plotting ........................................................................................................................... 50

CHAPTER 4: Tutorial IV: Gas Lift Design ................................................................ 53

Gas Lift Data ..................................................................................................................... 54Adding Valves .............................................................................................................. 54

WellFlo | Quick Start Guide 3

Gas Lift Design ................................................................................................................. 56Designing Gas‐lift Systems ......................................................................................... 57Sizing .............................................................................................................................. 75Sample Gas‐Lift Plots .................................................................................................. 76

CHAPTER 5: Tutorial V: ESP Design ....................................................................... 79

ESP Design and Analysis Overview ............................................................................. 80Designing an ESP Installation .................................................................................... 82Analyzing an ESP Installation .................................................................................... 86Plotting ........................................................................................................................... 88

4 Quick Start Guide | WellFlo

Chapter 1OVERVIEW

This chapter gives an overview of WellFlo and describes its basic features. This chapter also describes the WellFlo interface and how to use it to set up and run a WellFlo model, including well configuration, tuning, analysis and results.

Introduction ........................................................................................ 6Deliverability Applications ........................................................... 6Diagnostic Applications ................................................................ 7

WellFlo Interface ................................................................................ 8


1 OVERVIEWIntroduction

INTRODUCTION

WellFlo is a Nodal Analysis program designed to analyze the behavior of petroleum fluids in wells. This behavior is modeled in terms of the pressure and temperature of the fluids, as a function of flow rate and fluid properties.

The program takes descriptions of the reservoir, the well completion (i.e. the hardware within the well), and the surface hardware (i.e. pipelines etc.), combined with fluid properties data. The program then performs calculations to determine the pressure and temperature of the fluids.

Different modes of operation can be employed to either solve for flow rate given controlling pressures (typically deliverability calculations), or solving for pressure drops given measured flow rates (typically diagnostic calculations).

Deliverability Applications• Calculating the Flow Potential (or Deliverability) of a Well: A technique

for determining the Operating Point is used, whereby the pressures at a point (i.e. node) in the system are calculated for a range of flow rates, by calculating downwards from the top of the system and upwards from the bottom. Only one flow rate will provide the same pressure at the solution node calculated in both directions — this is obtained from an intersection of curves. This flow rate and the corresponding pressure determine the Operating Point of the system.

• Designing the Completion of a Well: This is an extension of the previous application, where deliverability can be calculated as a function of different sizes of tubing, different perforations, etc., allowing the optimum completion to be chosen, given that a more expensive completion must justify itself in terms of higher production. Design facilities also include gas lift parameters like valve positioning, valve sizing and setting, and ESP selection.

• Modeling the Sensitivity of a Well Design to Different Factors That May Affect it in the Longer Term: These factors may include increasing water production or decreasing reservoir pressure. Sensitivity modeling may encompass the reservoir, well, surface configuration, or the operating conditions.


1OVERVIEWDiagnostic Applications

Diagnostic ApplicationsThis alternative mode of calculation is simpler: this is where the flow rate is known and the pressure at one point is required, given the pressure at another point. This is useful for the following reasons:

• Comparing measured and calculated data, which could be for one of several purposes, such as evaluating the best flow correlation within WellFlo, evaluating Match Parameters, which are impossible to measure, such as pipe roughness, or determining if a well is behaving as it is expected to (i.e. to detect faulty components).

• Monitoring work, such as predicting reservoir pressure from measured surface pressure and flow rate. This will enable the engineer to see if the system is behaving as predicted, even though they may not be able to measure all parameters at one time. This contrasts with the above application, where diagnostics are done by comparing measured and calculated data.

• Design work where it is required to calculate the pressure drop in a system (e.g. to determine whether a given system will be able to flow to surface and still leave enough pressure to operate surface equipment). Optional facilities also are available to select ESPs and motors appropriate to the conditions specified, or to space out and size Gas‐Lift valves.


1 OVERVIEWWellFlo Interface

WELLFLO INTERFACE

The main WellFlo window (see Figure 1‐1) contains a navigation pane and a Workbench. The Navigator is the pane on the far left of the application window and is used to navigate the system and open the main program menus. The Workbench is the main content pane with which you interact with the system. When a file is opened initially, the current Dashboard configuration for that file is shown in the Workbench. Open each of the following menus through the Navigator:

• Configuration. Lets you enter all data necessary to create a well model, including the well and flow type, flow correlations, reference depths, fluid parameters, reservoir layers data, wellbore and surface equipment, and specific artificial lift type data.

• Analysis. Lets you perform various nodal analysis tasks, such as calculating flow curves and performing operating point and pressure drop calculations. You also can export data through the Analysis menu.

• Design. Lets you design ESP and Gas Lift applications.

• Output. Lets you load previous saved data without having to re‐run the calculations.


1OVERVIEWWellFlo Interface

Figure 1-1: WellFlo Main Window


1 OVERVIEWWellFlo Interface


Chapter 2TUTORIAL I: BUILDING A WELL MODEL

This Tutorial explains how to build a well model in WellFlo.

Building a Model ............................................................................. 12Creating a New Model ................................................................ 13Setting Flow Correlations ........................................................... 17Setting Reference Depths ............................................................ 18Setting Fluid Parameters ............................................................. 19

Reservoir Layers .............................................................................. 24Setting General Parameters ........................................................ 24Plotting IPR ................................................................................... 25Relative Permeability ................................................................... 25

Wellbore Data ................................................................................... 29Wellbore Equipment .................................................................... 30

Surface Data ...................................................................................... 34Surface Equipment ....................................................................... 35

Gas Lift Data ..................................................................................... 40Temperature Model ......................................................................... 38


2 TUTORIAL I: BUILDING A WELL MODELBuilding a Model

BUILDING A MODEL

This Tutorial covers the basic data entry required to set up a well and reservoir description. The lessons in this Tutorial walks you through the Configuration process using the screens under the Model Navigator in the Configuration menu (see Figure 2‐1).

Figure 2-1: Configuration Menu

In this Tutorial, you will re‐create the example well, TEST1 (Test1.wfl), supplied in the WellFlo installation (Tutorials folder).


2TUTORIAL I: BUILDING A WELL MODELCreating a New Model

Creating a New ModelTo start a project, you must create a new WellFlo model and enter, at a minimum, the initialization data into the General Data and Well and Flow Type configuration screens.

TO START A NEW MODEL:

1 Launch WellFlo from its stored location or go to C:\Program Files\Weatherford\WellFlo 4.0 and double‐click WellFlo4.exe to start the program from the default location.

The initial WellFlo Getting Started screen is displayed (see Figure 2‐2).

Figure 2-2: WellFlo Getting Started

2 Click Create a new model under the Project Tasks menu.

A new Untitled model with empty data values is opened (see Figure 2‐3).


2 TUTORIAL I: BUILDING A WELL MODELCreating a New Model

Figure 2-3: New WellFlo Model

3 Go to File > Save As... to save the WellFlo model as a *.wfl file.

4 For the Save in: location, navigate to C:\Program Files\Weatherford\WellFlo 4.0\Example.

5 Enter Sample Well in the File name: box, and click Save.

You are prompted to choose whether to save the model in 3.x format to keep only the compatible data, or 4.0 format to keep compatible and incompatible data.

You now can follow the Configuration menu to set up the well model. A red X indicates screens that have not been configured sufficiently. A green check mark indicates that the screen has been configured. An amber check mark indicates that the screen has not been fully configured, but has sufficient data for calculations to run

Incomplete configuration screen. Mouse over to view a description of the invalid or missing data.


2TUTORIAL I: BUILDING A WELL MODELCreating a New Model

To configure a new well model, follow the items sequentially from top‐down in the Configuration Model Navigator tree.

6 Select General Data from the Configuration Model Navigator.

The General Data configuration screen is opened (see Figure 2‐4).

Figure 2-4: General Data

7 Fill in the basic data entry fields.

Completed configuration screen

Incomplete configuration screen, with sufficient data for calculations.

i For more information, or for specific definitions of the fields in this configuration screen, click Help at the bottom right of the screen to view the WellFlo Help System.


2 TUTORIAL I: BUILDING A WELL MODELCreating a New Model

8 Click Apply to save your changes.

Note that a green check mark appears beside General Data in the Model Navigator.

9 Click Forward to advance to the next configuration screen: Well and Flow Type.

The Well and Flow Type configuration screen is opened (see Figure 2‐5).

Figure 2-5: Well and Flow Type

The Well and Flow Type configuration screen is used to select the fluid flow direction and type for the well. The well type can be set to Producer, Injector or Pipeline, and fluid flow can occur in the tubing, annulus or both. Artificial Lift Method and Fluid Type are selected here also.

10 Make the selections shown in Figure 2‐5.

i When you select Continuous gas lift as the Artificial Lift Method, an additional configuration screen, Gas Lift Data, is added to the Well Model Navigator.


2TUTORIAL I: BUILDING A WELL MODELSetting Flow Correlations


12 Select Dashboard in the Model Navigator.

The Sample Well Dashboard displays the current well and flow type as well as default values for the remaining configuration properties (see Figure 2‐6).

Figure 2-6: Sample Well.wflx Dashboard

Setting Flow CorrelationsThe Flow Correlations configuration screen is used to select the correlations for the pressure drop calculations.

TO SET FLOW CORRELATIONS:

1 With Sample Well.wflx open, select Flow Correlations in the Model Navigator.

The Flow Correlations configuration screen is opened (see Figure 2‐7).


2 TUTORIAL I: BUILDING A WELL MODELSetting Reference Depths

Figure 2-7: Flow Correlations

2 Make the selections shown in Figure 2‐7 for all Correlations.

3 Click Apply.

4 Click Forward to advance to the next configuration screen, or go to File > Save to save the model.

Setting Reference DepthsThe Reference Depths configuration screen contains the information necessary to link the downhole and surface components to a common reference location from where depths are measured (Zero Depth). Depending on the well type — Onshore, Subsea or (offshore) platform well — the reference point selection varies.

i For more information, or for specific definitions of the fields in this configuration screen, click Help at the bottom right of the screen to view the WellFlo Help System.


2TUTORIAL I: BUILDING A WELL MODELSetting Fluid Parameters

TO SET REFERENCE DEPTHS:

1 With Sample Well.wflx open, select Reference Depths in the Model Navigator.

The Reference Depths configuration screen is opened (see Figure 2‐8).

Figure 2-8: Reference Depths

2 Select Kelly Bushing/Rotary Table in the Zero Depth section. This is the reference point from which all vertical depths are taken. This selection enables the Distance from area above.

3 Enter 105.4 for the Distance from Kelly Bushing to Wellhead (see Figure 2‐8).

4 Click Apply.

Setting Fluid ParametersThe Fluid Parameters configuration screen is used to enter fluid data and select correlations to be used for estimating fluid properties.


2 TUTORIAL I: BUILDING A WELL MODELSetting Fluid Parameters

There are facilities for checking and calibrating computed Fluid Properties against measured data. Most of the PVT Fluid Parameters can be Tuned individually. The Tuning Coefficients are stored as part of the WellFlo data file and will be applied in any subsequent calculation made here or in any other part of the program.

TO ENTER FLUID PARAMETERS:

1 With Sample Well.wflx open, select Fluid Parameters from the Model Navigator.

The Fluid Parameters configuration screen is opened (see Figure 2‐9).

Figure 2-9: Fluid Parameters

2 Enter the parameters shown in Figure 2‐9.

i Oil Specific Gravity and Oil API Gravity and Water Salinity (NaCl Equivalent) and Water Specific Gravity are linked pairs of fields (i.e. changing one automatically updates the other of the pair, so that data remain consistent).



3 Make the Black Oil Correlation selections shown in Figure 2‐9 for Bubble‐Point Pressure (Pb), Solution GOR (Rs), Oil Formation Volume Factor (Bo), Oil Viscosity (µo) and Gas Viscosity (µg).

4 For the Surface Tension of water (Sw), select Advanced. This option uses a correlation incorporating pressure and salinity effects on water surface tension, as opposed to Basic, which uses a simplistic correlation with no dependence on pressure and salinity.

5 Click Tune Correlations to PVT data.

The P‐V‐T Parameters screen is displayed. Any existing fluid models are listed under the Fluid Parameters.

6 In Fluid Model 1, enter the measured produced Gas/Oil Ratio at which the tuning will take place (i.e. this should be the value of Produced GOR (Rsp) at which all the test data were acquired.)

Adding Experiment Data

TO ADD EXPERIMENT DATA

1 Right‐click Fluid Model 1, select Add [Fluid Type] Experimental Data. A new empty experiment is added (see Figure 2‐10).


2 TUTORIAL I: BUILDING A WELL MODELSetting Fluid Parameters

Figure 2-10: PVT (Tuning Matching) Workbench

1 Enter the values of Saturation Pressure and Temperature.

2 To enter observed values, select the table and click the Insert Row button.

3 Observed data are entered into the table. You can also add PVT data by copying the data from Excel spreadsheet and pasting it in.

4 Click on Match. A message box confirmation box is displayed if the correlations are tuned successfully.

5 Click OK to close the message box.

The results are viewed under Tuning Output (see Figure 2‐11).

Insert Row: Adds a new, blank row to the table.



Figure 2-11: P-V-T Parameters - Tuning Results

6 Click Accept. The PVT Tuning window closes.

The Check tab may be used to examine the results of the selected correlations.

7 Enter the check Pressure, Temperature, produced GOR (Gas/Oil Ratio (Rsp)) and produced CGR (Condensate/Gas Ratio (Condensate only)) shown in Figure 2‐9.

8 Click Calculate to get the values of properties out.

9 Click Apply.

iThe calculations made in this section are not carried through to any other part of the program and are purely for reference only. All Fluid Properties for Nodal Analysis are calculated at prevailing conditions wherever necessary, based on the data contained in the Fluid Parameters configuration screen.


2 TUTORIAL I: BUILDING A WELL MODELReservoir Layers

RESERVOIR LAYERS

In this Tutorial, you will enter Reservoir Layers data in Test Point mode. In this mode, the Productivity Index (PI) and/or Flow Coefficient/s will be computed from one or two measured Bottom Hole Flowing Pressures (BHFPs) and flow rates.

Setting General Parameters

TO SET GENERAL PARAMETERS:

1 With Sample Well.wflx open, select Reservoir from the Model Navigator.

A new layer is opened in the Reservoir Layers Data configuration screen (see Figure 2‐12).

Figure 2-12: Reservoir Layers Data - General

2 Select Test data at the top of the configuration panel.


2TUTORIAL I: BUILDING A WELL MODELPlotting IPR

3 Enter the values shown in Figure 2‐12. You can also enter the data by selecting Layer Parameters or Manual at the top of the configuration panel.

4 Click Apply.

Plotting IPR5 Open the IPR tab.

The Layer IPR Plot is produced from the data you configured (see Figure 2‐13).

Figure 2-13: Plotting the Layer IPR

Relative PermeabilityRelative Permeability data are used in the computation of the Productivity Index (J), in the IPR Layer Parameters entry mode.

6 Open the Rel. Perm. tab (see Figure 2‐14).


2 TUTORIAL I: BUILDING A WELL MODELRelative Permeability

Figure 2-14: Relative Permeability

7 Click Plot.

The relative permeability is plotted in the chart at the right (see Figure 2‐15).

i These parameters will create a plot of Krg and Krw (Y-axes) versus Water Saturation (Sw) in the WellFlo Graphing Window.


2TUTORIAL I: BUILDING A WELL MODELRelative Permeability

Figure 2-15: Gas/Water End-Point Parameters Plot

i You can click the pin icon at the top right of the chart to unpin the plot and view or move it in a floating window (see Figure 2-16). This floating window remains in the foreground of your screen even when switching applications.


2 TUTORIAL I: BUILDING A WELL MODELRelative Permeability

Figure 2-16: Gas/Water End-Point Parameters Plot (unpinned)

8 Go to File > Save to save the model.

i Click the pin icon again to re-pin the plot to its original position.


2TUTORIAL I: BUILDING A WELL MODELWellbore Data

WELLBORE DATA

The Wellbore Deviation configuration screen is used to view, enter and edit well deviation data. You may chose to enter data in one of three ways, by entering or importing information in two of the three columns. The main deviation data three‐column table allows you to enter data from a deviation survey or import it in from a spreadsheet or other external source.

TO ENTER WELLBORE DEVIATION DATA:

1 With Sample Well.wflx open, select Deviation under Wellbore in the Model Navigator.

The Wellbore Deviation configuration screen is opened (see Figure 2‐17).

i The Segment Deviation from Vertical angle is the component deviation angle, not the average angle from the Wellhead/Xmas Tree to this point.


2 TUTORIAL I: BUILDING A WELL MODELWellbore Equipment

Figure 2-17: Wellbore Deviation

2 Click the Add a new row button to insert one blank row into the table. Enter deviation data shown in Figure 2‐17.

WellFlo translates this tabular well deviation data into an equivalent string of nodes for the Nodal Analysis.

3 Click Apply.

4 Click Forward to advance to the Wellbore Equipment configuration screen.

Wellbore EquipmentThe Wellbore Equipment configuration screen is used to view, enter and edit information on tubing, casing and restrictions, like SSSV.

The Wellbore Equipment configuration screen is opened (see Figure 2‐18).


2TUTORIAL I: BUILDING A WELL MODELWellbore Equipment

Figure 2-18: Wellbore Equipment

This option is used to add a length of Tubing to the well. The Segment Length increment is the measured length of the component. The Measured Depth refers to the total depth down to the node (i.e. at the bottom of the component or at the deepest fluid entry point (bottom‐most component — nominally the middle of the perforations)).

5 Select Depth in the Enter Data For section. Segment Length values are calculated in this mode.

6 Click the Add a new row button to insert one blank row into the table. Enter the tubing data shown in Figure 2‐18

Tubing data can be entered manually or inserted from the WellFlo catalog.


2 TUTORIAL I: BUILDING A WELL MODELWellbore Equipment

7 Open the Casing tab (see Figure 2‐19).

Figure 2-19: Wellbore Equipment - Casing

This option is used to add a length of Casing to the well. The only difference between a casing and tubing is that the latter is considered to have an external casing. This detail is significant for Heat Transfer modeling and for the Annular Flow option; otherwise for nodal analysis calculations, both component types are just regarded as tubulars, where multi‐phase flow is concerned. The casing components may be replaced by tubing components where required.

8 Select Depth in the Enter Data For section. Segment Length values are calculated in this mode.

i The Flow Configuration column is used to specify whether the flow is in the Tubing or (tubing-casing) Annulus or both. This feature is useful for changing flow path even when tubular sizes are same.


2TUTORIAL I: BUILDING A WELL MODELWellbore Equipment

9 Click the Add a new row button to insert one blank row into the table. Enter the casing data shown in Figure 2‐20.

10 Click Apply, then go to File > Save to save the model.

11 Open the Restrictions tab to enter the data of any Restriction or SSS valve.

12 Click the Add a new row button to insert one blank row into the table. Enter the data.

13 Open the Trace Points tab to enter the data of any Restriction or SSS valve (see Figure 2‐20).

Figure 2-20: Wellbore Equipment - Trace Points

14 Click the Add a new row button to insert one blank row into the table. Enter the data as shown.


16 Click Forward to advance to the next configuration screen.


2 TUTORIAL I: BUILDING A WELL MODELSurface Data

SURFACE DATA

The Terrain Data configuration screen is used to view, enter and edit Surface Deviation data. The convention for Surface Component measurement is different from the well components. Instead of Depth, WellFlo uses the more useful concept of Elevation; these are measured above the permanent datum of Mean Sea Level (MSL).

A deviation of 0° means vertical upward flow; 0° to 90° means inclined upward flow; 90° means horizontal flow; 90° to 180° means inclined downward flow, and 180° means vertical downward flow.

TO ENTER SURFACE TERRAIN DATA:

1 With Sample Well.wflx open, select Terrain Data under Surface Data in the Model Navigator.

The Terrain Data configuration screen is opened (see Figure 2‐21).


2TUTORIAL I: BUILDING A WELL MODELSurface Equipment

Figure 2-21: Terrain Data

2 Click the Add a new row button to insert a blank row into the table. Enter the terrain data shown in Figure 2‐21.

WellFlo translates any tabular terrain data into an equivalent string of nodes in the Terrain data chart.

3 Click Apply.

4 Click Forward to advance to the next configuration screen.

The Surface Equipment configuration screen is opened (see Figure 2‐22).

Surface EquipmentThe Surface Equipment configuration screen is used to view, enter and edit Surface Equipment Data. This dialog can be used to specify the following items of Surface equipment: Bend, Choke, Downcomer, Flow Line, Gas Injector, Manifold, Riser, Surface ESP, Trace Point, or Wellhead Gauge.


2 TUTORIAL I: BUILDING A WELL MODELSurface Equipment

Figure 2-22: Surface Equipment

5 Click the Add a new row button to insert a blank row into the table. Select the Choke type and enter the choke details shown in Figure 2‐22.

6 Click the Add a new row button to insert a second blank row into the table. Select the Flowline type and enter the flowline details shown in Figure 2‐23.


2TUTORIAL I: BUILDING A WELL MODELSurface Equipment

Figure 2-23: Surface Equipment - Flowline

7 Click the Add a new row button to insert a third blank row into the table. Select the Flowline type and enter the flowline details shown in Figure 2‐24.


2 TUTORIAL I: BUILDING A WELL MODELTemperature Model

Figure 2-24: Surface Equipment - Flowline

8 Click Apply.


TEMPERATURE MODEL

There are four models used in WellFlo for Temperature calculation: Manual, Calculated, Coupled and Calibrated.

TO CONFIGURE A TEMPERATURE MODEL:

1 With Sample Well.wflx open, select Temperature Model from the Model Navigator.

The Temperature Model configuration screen is opened (see Figure 2‐25).


2TUTORIAL I: BUILDING A WELL MODELTemperature Model

The Calibrated Temperature model is selected to tune the calculated model to temperatures measured at a known flow rate at the wellhead (or gauge) and at the Outlet Node (e.g. Separator). The calibration applies one Tuning Factor from the Reservoir to the Wellhead (or Gauge), and another Tuning Factor from the Wellhead (or Gauge) to the Outlet Node, such that the calculated temperatures at the specified Flow Rate match the specified Wellhead (or T Gauge) temperature and Outlet Node temperature.

Figure 2-25: Temperature Model - Calibrated

2 Enter the values shown in Figure 2‐25 for the Flow Rate, Outlet Temp, and Wellhead Temp.

3 For the Surface temperature, enter 60.0.

i For more information about the Calibrated Temperature Model, click Help at the bottom right of the screen to view the WellFlo Help System.


2 TUTORIAL I: BUILDING A WELL MODELGas Lift Data

In the Wellbore table, Calculated indicates whether the Heat Transfer Coefficient is calculated or manually input for each segment. Calculated is checked to allow WellFlo to calculate it automatically.

4 Open the Flowline tab (see Figure 2‐26).

Figure 2-26: Temperature Model - Flowline

5 Enter values for the Air and Water Standard heat transfer coefficients.

6 Click the Add a new row button to insert two blank rows into the table. Enter the data shown in Figure 2‐26.

7 Click Apply, then go to File > Save to save the model.

GAS LIFT DATA

The tabular Gas Lift Parameters configuration screen is used to view, enter and edit Gas‐Lift data.


2TUTORIAL I: BUILDING A WELL MODELGas Lift Data

Gas‐Lift is modeled in WellFlo by inserting one or more Gas‐Lift Valves in the well system; these are positioned at the bottom of the Tubing components. Gas‐Lift Valves can be declared as Active or Inactive.

Gas‐Lift Valves may be selected by Manufacturer, Model and Port Size. Depending on the selection of Valve Type, either PPO (Production Pressure Operated) valves or IPO (Injection Pressure Operated) valves will be mutually excluded from the valve models that become available.

TO SET GAS LIFT PARAMETERS:

1 With Sample Well.wflx open, select the Gas Lift Data configuration screen from the Model Navigator.

The Gas Lift Parameters configuration screen is opened (see Figure 2‐27).

Figure 2-27: Gas Lift Parameters

2 Click the Add a new row button to insert one blank row into the table. Enter the gas lift data shown in Figure 2‐27.

3 Click Apply.


2 TUTORIAL I: BUILDING A WELL MODELGas Lift Data


5 Click Dashboard in the Model navigator to view the completed Dashboard for this model.


Chapter 3TUTORIAL III: SYSTEMS ANALYSIS

This Tutorial explains how to perform nodal analysis tasks in WellFlo, including setting operating conditions, running sensitivities and plotting.

Systems Analysis ............................................................................. 44Setting Operating Conditions .................................................... 44Running Sensitivities ................................................................... 48Plotting .......................................................................................... 50


3 TUTORIAL III: SYSTEMS ANALYSISSystems Analysis

SYSTEMS ANALYSIS

In “Tutorial I: Building a Well Model”, you configured a well model with the same parameters as the example well, Test1 (Test1.wfl), supplied with the WellFlo installation files. This well requires a minimum Gas Injection before production can kick‐off.

If you have not completed Tutorial I, go to File > Open and select Test1.wfl from the following location: C:\Program Files\Weatherford\WellFlo 4.0\example. Review the example well model before continuing the Analysis tutorial.

The Analysis section of WellFlo consists of these main options:

• Operating Conditions — There is a choice of Pressure Drop calculations (e.g. end to end pressure drop, knowing one end Pressure and a Flow Rate) or Operating Point determination (e.g. flow rate and pressure at a given node, knowing both end pressures).

• Sensitivities — You can run a single base case, or up to two Sensitivities (i.e. study the effect on the results of two independent sets of variables ‐ 10 values per set). The choice of variable is limited to those appropriate for the models that have been selected.

Setting Operating ConditionsThe operation mode and other operating conditions are set in the Operating Conditions configuration screen, under the WellFlo Analysis menu.

TO SET OPERATING CONDITIONS:

1 Launch WellFlo from its stored location or go to C:\Program Files\Weatherford\WellFlo 4.0 and double‐click WellFlo.exe to start the program from the default location.

The initial WellFlo Getting Started screen is displayed.

2 If you completed “Tutorial I: Building a Well Model”, open Sample Well.wflx from the WellFlo example folder. If you did not complete the previous tutorial, go to File > Open and select Test1.wfl to view the example well model (see Figure 3‐1).


3TUTORIAL III: SYSTEMS ANALYSISSetting Operating Conditions

Figure 3-1: WellFlo Dashboard

3 Open the Analysis menu in the Model Navigator.

4 If necessary, select Operating Conditions in the Analysis menu.

The Operating Conditions menu is displayed in the center of the screen. Operating is selected as the default Operation Mode (see Figure 3‐2).

This option is used to perform operating point nodal analysis for the current well. For Operating mode, this means running Pressure Drop calculations at a range of flow rates, starting from opposite end nodes and calculating Inflow and Outflow pressure curves at an intermediate point called the Solution Node. The intersection of the Inflow and the Outflow pressure curves provides the Operating Point (i.e. the Pressure and Flow Rate at the solution node) for the well under analysis. In Operating mode, there are two end nodes and a Solution Node. Logic is used to keep the node selection consistent (i.e. the Top Node must be above the Bottom Node, and the Solution Node must be between the two).


3 TUTORIAL III: SYSTEMS ANALYSISSetting Operating Conditions

Figure 3-2: Operating Conditions

5 Select and enter Calculation Nodes data:

• Top Node. Select Outlet Node and enter 96.00 for the Top Node Pressure.

• Bottom Node. Select Layer 1 @ 15413 and enter 2171.00 for the Bottom Node Pressure

• Solution Node. Select Casing @ 15413.

6 Enter the Flow Rates at which the nodal analysis calculations will be performed. The defaults are 11 flow rates in a range from 5% to 95% of the AOF. Click % of AOF above the Flow Rates table, and enter From 5 to 95 in 10 Steps, and click Fill. The Flow Rates table is filled (see Figure 3‐2).

In an Operating point calculation, these will be arbitrary flow rates that (hopefully) span the actual operating point/s. The flow rates used should ensure that the intersection (if any) of Inflow and Outflow curves will be seen. At least two flow rates are required for an Inflow/Outflow Analysis.

7 Click Calculate.


3TUTORIAL III: SYSTEMS ANALYSISSetting Operating Conditions

The Flow Curve is calculated (see Figure 3‐3).

Figure 3-3: Flow Curve

8 Open the Configuration menu in the Model Navigator, and select Temperature Model to review the Temperature Model configuration screen.

The flowing temperature will be calculated at each of the production rates. The model is calibrated against temperatures that were measured at the wellhead and separator while the well was producing at 1332 STB/day (i.e. total liquid). Gas in the annulus will be assumed since this is a Gas‐lifted well.

The inflow calculations will start from the Reservoir (i.e. using the layer pressure 2171 psia) and the outflow calculations from the Outlet node (i.e. base case pressure 96 psia). The Casing has been selected as the Solution Node so that the Operating point pressures computed will be the “Bottom Hole Flowing Pressures.”


3 TUTORIAL III: SYSTEMS ANALYSISRunning Sensitivities

Owing to the low reservoir pressure, the Sample Well will not produce without Gas‐lift. A Sensitivity Analysis will be performed to examine the productivity at different injection GLRs, for different outlet node pressures. The objectives here will be to:

• Ascertain the minimum Injection GLR for production at each pressure.

• Determine the performance curves for the well when producing.

Running SensitivitiesTo run Sensitivity Analyses, you must select one or two sensitivities from the Sensitivity 1 and Sensitivity 2 drop‐down lists. If no sensitivities are selected, only the base case values entered in the various input fields will be used in the Nodal Analysis.

The Sensitivities and Sensitivity Groups offered when the Reservoir is included in a nodal analysis run are dependent on the current Reservoir Configuration.

In this Tutorial, you will create two new sensitivities and run a Sensitivity Analysis using both.

TO RUN A SENSITIVITY ANALYSIS:


2 Select Sensitivities from the Analysis menu.

Existing sensitivities are listed in the Manage Sensitivities list and are available in the drop‐down lists under Sensitivity 1 and Sensitivity 2 (see Figure 3‐4).


3TUTORIAL III: SYSTEMS ANALYSISRunning Sensitivities

Figure 3-4: Manage Sensitivities

3 Click Create... under the Manage Sensitivities window. The Sensitivities section is activated below.

4 Select Lift gas/liquid ratio, under the Artificial Lift category. In the Range table, enter From: 500 To: 3500 Steps: 6. Click Fill, then click Apply to add the new sensitivity to the Manage Sensitivities window.

5 Select Top/start node pressure, under the Pressure and Temperature category. Enter 50, 100 and 150 in the first three rows of the Values table, then click Apply to add the new sensitivity to the Manage Sensitivities window.

6 In the Sensitivity 1 drop‐down list, select Lift gas/liquid ratio. The seven values entered (500 to 3500 SCF/STB with a view to identifying kick off) will override the base case value in the Gas Lift Parameters configuration screen.

7 In the Sensitivity 2 drop‐down list, select Top/start node pressure. The three values entered span a reasonable operating range and will override the base case value entered for the Start Node pressure under Operating Conditions.

8 Click Calculate to run the selected sensitivities.


3 TUTORIAL III: SYSTEMS ANALYSISPlotting

The calculations will be performed using both Sensitivities, making a total of 11*7*3 (= 231) runs, from which a maximum of 7*3 (= 21) operating points could be determined if stable intersections were found in all cases.

Plotting9 Open Include in Plot on the Analysis menu.

The results of the sensitivity analysis are displayed.

10 Drag the row selector to select the values you want to plot in the chart.

11 Click Plot Selected.

The values selected are plotted in the chart windows (see Figure 3‐5).

Figure 3-5: Inflow/Outflow Plot

The Inflow/Outflow curves are plotted in the Flow Curves plot. Separate plots can be produced of the Sensitivity 1 curves and Sensitivity 2 curves versus the first case of the other sensitivity.


3TUTORIAL III: SYSTEMS ANALYSISPlotting

12 For an overall view of the effects of all the values of GLRi and Outlet Pressure on the Production Rate, open the Lift gas/liquid ratio performance tab (see Figure 3‐5). The Operating Point Rate can now be plotted for each case against both sensitivities.

Figure 3-6: Well Performance Plot for Lift-gas GLR

From this plot, it is clear that the well kicks off at a certain minimum Lift‐gas GLR and that the kick‐off requirement increases the Outlet pressure. There is no production at 500 SCF/STB from the well at the highest Outlet pressure (150 psia).

13 Open the Top/start node pressure performance tab (see Figure 3‐7). This plot illustrates a different way of looking at the same scenario. The curve shows a decline in production with increasing Top/start node pressure.


3 TUTORIAL III: SYSTEMS ANALYSISPlotting

Figure 3-7: Well Performance Plot for Outlet Pressure

14 Select the 2500 scf/STB Lift‐gas/liquid ratio and the 100 psia Top/start node pressure from the table, and click Calculate.

15 Open the Report tab to view the Analysis report.

The Analysis Report contains a summary of the input data and system description, followed by the calculated results. For Operating Point calculations, the pressures calculated at the Solution Node in the inflow direction and outflow direction will be listed for each flow rate, along with the Operating Point, and Depth of Gas‐Injected (i.e. provided a Gas‐Injection Analysis is being performed), on a case by case basis. The Operating Point report lists the flow rates of each Layer at each Operating Point. For Cross‐Flowing Layers in a production well, the Cross‐Flow Rate is listed, with a negative sign.

16 Click the Save Report button to save this report to the WellFlo Output sections.


Chapter 4TUTORIAL IV: GAS LIFT DESIGN

This chapter how to configure and design a Gas Lift well model in WellFlo.

Gas Lift Data ..................................................................................... 54Adding Valves .............................................................................. 54

Gas Lift Design ................................................................................. 56Designing Gas‐lift Systems ......................................................... 57Sizing ............................................................................................. 75Sample Gas‐Lift Plots .................................................................. 76


4 TUTORIAL IV: GAS LIFT DESIGNGas Lift Data

GAS LIFT DATA

For this Tutorial, you will use a pre‐configured WellFlo model, Gldesign.wfl located in the WellFlo Tutorials folder.

The Gas Lift Parameters configuration screen is used to view, enter and edit Gas‐Lift data. Gas‐Lift Valves may be selected by Manufacturer, Model and Port Size from those listed in the gasvalve.csv file. Depending on the selection of Valve Type, either PPO (Production Pressure Operated) valves or IPO (Injection Pressure Operated) valves will be mutually excluded from the valve models that become available.

Adding Valves

TO SET GAS LIFT PARAMETERS:

1 Launch WellFlo from its stored location or go to C:\Program Files\Weatherford\WellFlo 4.0 and double‐click WellFlo4.exe to start the program from the default location.


2 Go to File > Open and select Gldesign.wfl from the following location: C:\Program Files\Weatherford\WellFlo 4.0\example.

3 Open the Configuration menu in the Navigator.

4 Select Gas Lift Data from the Model Navigator. This configuration screen is added to the Model Navigator when Gas‐lift is selected as the Artificial Lift Method in the Well and Flow Type screen.

The Gas Lift Parameters configuration screen is opened (see Figure 4‐1).


4TUTORIAL IV: GAS LIFT DESIGNAdding Valves

Figure 4-1: Gas Lift Parameters

New valves are added to the system at set depths. The Temp. column is used to set the temperature at the valve when the Manual Temperature Model is selected. The Tro column represents the Test Rack Opening Pressure for Gas‐Charged and Spring‐Loaded Valves only.

The Port column lets you select a port size for the selected Manufacturer and Model (see “Port Size Calculation” on page 75 for more information on sizing). R displays either the Port‐to‐Bellows Ratio of the selected Port size for an IPO Valve (where Apt is the Port Area), or its complement (R = 1 ‐ Apt/Ab), for a PPO Valve. For an Orifice Valve, this column is blank.

i For an Orifice Valve, this column is blank.


4 TUTORIAL IV: GAS LIFT DESIGNGas Lift Design

The valve differential pressure is the quantity by which Casing Pressure must exceed Tubing Pressure at the valve in order for a valve to open. WellFlo models a Differential Gas Valve assuming a fixed differential. In case several valves could be open by this criterion, only the deepest is assumed to be open.

Use GLRi is selected to enable the Injection GLR field. The value entered here will be the base case Injection GLR.

This Deepest Point of Injection data is used only if the Analysis mode is Deepest Point of Injection: Operating Point, Deepest Point of Injection: Pressure Drop or Gas‐Lift Design ‐ Valve Positioning, where WellFlo is computing Gas‐Lift Valve depths rather than using specified depths. These fields are used to indicate the Deepest Point in the Well that a Gas‐Lift Valve can be inserted.

Use Tubing Shoe is checked to limit Gas‐lift valves to be as deep as the downstream end of the first Tubing Node above the shallowest Active Layer. When unchecked, the Max MD of Injection is used.

In Deepest Injection Point and Gas‐Lift Design modes, WellFlo Analysis is only allowed to position valves above the specified depth. It follows that the default Use Tubing Shoe option allows complete freedom, while Maximum MD of injection applies a depth constraint.

GAS LIFT DESIGN

The Gas Lift Design screen is used to determine the positions of the Unloading Valve/s and Operating Valve to produce the Well at a prescribed Flow Rate for a specified set of Casing and Gas‐Lift conditions, initial static Wellbore Fluid, etc.

iIf users decide later to select GLRi as a Sensitivity Variable (Go to Analysis > Sensitivities > Create > Artificial Lift > Lift gas/liquid ratio. See “Running Sensitivities” under the “Systems Analysis”section), the Injection GLRs entered there will override this value.


4TUTORIAL IV: GAS LIFT DESIGNDesigning Gas-lift Systems

Any specified Gas‐Lift Valve Depths that may already have been entered via the Gas‐Lift Data configuration screen (see “Gas Lift Data” on page 54) will be ignored in a Design run.

Normally, users will have made a reasonable estimate of the Operating Conditions from an Inflow/Outflow Analysis, using the Deepest Point of Injection: Operating Point option, to identify the optimum Operating Valve Depth and Operating Rate. Users should also have an idea of the range of Valve Depths (i.e. bracketing envelope) that might be required to allow for changing Operating Conditions (i.e. declining Reservoir Pressure, increasing Water‐Cut, Well Stimulation, etc.). This can be achieved by a careful Sensitivity Analysis of all relevant variables.

Set‐up the input data as described below, and run the Design option. The Valve Depths will be computed, and the results of the Design Analysis are plotted in the graphing window.

Designing Gas-lift Systems

TO ENTER GAS LIFT DESIGN DATA:

1 With Gldesign.wfl open, open the Design menu in the Navigator.

The Gas Lift Design screen is opened (see Figure 4‐2).

iThe Gas-Lift Valve (GLV) and Electrical Submersible Pump (ESP) Design options are separately licensed within WellFlo; users with a basic WellFlo license will not have access to these. This Design option will be disabled if your Software License is not configured (and activated) for WellFlo/Gas-Lift.


4 TUTORIAL IV: GAS LIFT DESIGNDesigning Gas-lift Systems

Figure 4-2: Gas Lift Design — Design Options

Design Options

2 Select Design Options from the menu at the left.

2a Enter Valve Type data:

— Select the type of Gas‐lift valves to size, either Injection (Casing) Pressure Operated (IPO) or Production (Tubing) Pressure Operated (PPO).

2b Enter Unloading Valve data:

— Model. This field displays the manufacturer and valve model to be used for the unloading valves in the design.

i The choice of Valve Type does not affect the Valve Spacing methodology, but does affect the Valve Sizing calculations.



— Browse Catalog. The Browse Catalog button allows users to browse the gas lift valve catalog and select the valve manufacturer, model, port size and correlation to use for sizing unloading valves in the design.

— Port Size. This field displays the default port size used in unloading valves for the given design. When gas passage requirements dictate that a different port size be used to meet the conditions, WellFlo will select a valve with the most suitable port size from same manufacture and model.

— Load Default.This option allows users to load the default unloading valve specified under Settings > Options >Preferences > Default Gas Lift Valves.

— Correlation. This field displays the gas passage correlation used for sizing the unloading valves. Note: certain correlations are only available to users who have licensed the data from the Valve Performance Clearinghouse.

— Check Use Catalog Discharge Coefficient. This option enables users to use the discharge coefficient (Cd) specified in the catalog for sizing the unloading valves. Note: this only applies when Thornhill‐Craver is selected for the gas passage correlation.

— Discharge Coefficient. This displays the discharge coefficient that is used in calculating gas passage for the unloading valves using the Thornhill‐Craver gas passage relationship.

2c Enter Casing Pressure Drop data:

— Check Pressure Drop at Top Valve (delta P line). This option enables users to apply a fixed differential pressure between available casing pressure and maximum casing head pressure for the purposes of spacing out the top gas lift valve. This additional differential pressure is intended to ensure that sufficient gas passage is available for the well to unload past the first gas lift valve.

— Select Constant Casing Pressure Drop to enter the Casing Closing Pressure Margin (optional): This correction reduces the casing pressure required to open each valve successfully down the hole. This helps ensure that the valve above will be closed when the next valve below is opened. This design margin is usually applied to Injection Pressure (Casing) Operated (IPO) Valve designs, where an



appropriate range of values (e.g. 20 ‐ 50 psi) should be entered.

— Check Use Recommended Casing Closing Pressure Margins. This option allows users to set casing closing pressure drops based on values specified in the gas lift valve catalog.

— Select Pt max - Pt min to enter the Safety Factor. This option allows users to base their design on the Ptmax – Ptmin method. The corresponding safety factor is used in the calculation of Ptmax in conjunction with this method. For more information on the Ptmax – Ptmin gas lift design method, refer to API RP 11V6: Recommended Practice for Design of Continuous Gas Lift Systems Using Injection Pressure Operated Valves, Second Edition, July, 1999.

2d Enter Deepest Point of Injection data:

— Check Use Tubing Shoe to limit Gas‐Lift valves to be as deep as the downstream end of the first Tubing Node above the shallowest Active Layer. When unchecked, the Max MD of Injection is used.

— Maximum MD. This is the maximum Measured Depth (MD) that the Operating Valve is expected to be set during the life of the well. This value must be between the Wellhead/Xmas Tree and the Tubing Shoe (at the downstream end of the first Tubular Node above the shallowest Active Layer). The default value (i.e. nominally Tubing Shoe Depth) is transferred from the Deepest Point of Gas Injection section of the Gas‐Lift Data configuration screen.

— Valve Differential Pressure. This is the quantity by which casing pressure must exceed tubing pressure for a Gas‐lift valve to open (i.e. for the operating valve to pass the required volume of gas). This value is shared between this screen and the Gas Lift Parameters configuration screen (see “Gas Lift Data” on page 54).

2e Enter Minimum Valve Spacing data.

i It is usually left at zero for Production Pressure (Tubing) Operated (PPO) Valves.



The minimum True Vertical Depth (TVD) spacing between Gas‐Lift valve positions to be used in the Design process. If the valve spacing is too close, in practice this will lead to unstable Gas‐lift.

— Manual. This option allows users to manually specify the minimum allowable distance (in true vertical depth) between valves in the well.

— Calculate (Valve Differential Pressure / Static Fluid Gradient). This option allows WellFlo to automatically calculate minimum valve spacing based on the specified valve differential at the depth of injection.

2f Enter Valve Positioning data:

— Select Top/Bottom or Bottom/Top for the Numbering Method.

— Enter the Round off Valve Depth (MD). This option allows users to define a round‐off for spacing of gas lift valves. By specifying that valves be spaced to the nearest X feet, users are able to provide a more field‐friendly gas lift design. Often it is not practical or necessary to space valves to the nearest foot as defined in the design. (nearest 50 feet is generally OK)

Flow Parameters

3 Select Flow Parameters from the menu at the left (see Figure 4‐3).



Figure 4-3: Gas Lift Design - Flow Parameters

3a Enter Design Conditions:

— Start Node. Select the node that the Design calculations will be started from. Users have the choice of starting at the Xmas Tree node or the Outlet Node. The default node is the one used for the last Nodal Analysis (Pressure Drop) mode calculation (if any).

— Start Node Pressure. After selecting the Start Node, enter the Flowing Pressure for this node at which the top‐down computations are to start.

— Casing Pressure. This value will be computed once the Operating Valve position has been calculated; its initial value is unimportant. It defaults initially to the Steady‐State Casing Head Pressure value (if any) entered in the Gas‐lift Data configuration screen, otherwise enter any value greater than 10 psia. Users will be given the opportunity to update the value from the Gas‐lift Data configuration screen (if any), with the new Design value, so it can be used for Nodal Analysis.



— Max. CH Pressure. This value (usually larger than the Casing Head Pressure defined above), is the Casing Head Pressure that users expect to be available at the Wellhead for Gas‐lift operations, and is required for the Unloading Valve computations. WellFlo reports the optimum Casing Head Pressure that follows from this maximum Casing Head Pressure value.

— Kickoff Pressure. The value entered here is used for the computation of the upper‐most Unloading Valve position if it is greater than the Maximum Casing Head Pressure; otherwise, it is ignored.

3b Enter Design Rates:

— Liquid rate. The total Liquid Operating Production rate to be used in the Design study.

— To select rates from a performance curve, click the Select Rate button.

— Select Use Qgi to use the Lift‐Gas Injection Rate.

— Gas Injection rate. The desired Operating Injection rate. This field is enabled only if Use Qgi is selected. The default value is transferred from the Gas‐Lift Parameters configuration screen.

— Select Use GLRi to use the Lift‐Gas/Liquid Ratio.

— Lift-Gas/Liquid. the desired Operating Injection Gas/Liquid ratio. This field is enabled only if Use GLRi is selected. The default value is transferred from the Gas‐Lift Parameters configuration screen.

3c Enter Gradients:

— Static Fluid Gradient. The Pressure Gradient of the Static Fluid (i.e. Kill Fluid) that is to be unloaded.

— Static Fluid Specific Gravity. the Specific Gravity of the Static Fluid (i.e. Kill Fluid) that is to be unloaded.

— Depth of Static Fluid Level. If this value is disabled (i.e. the associated check box is unchecked), the Static Fluid Pressure Profile is taken to

i For the upper-most Unloading Valve, this Maximum Casing Head Pressure value will be superseded by the Kick-Off Pressure value (described below) if this is greater.



start at the Producing Wellhead Pressure. This will be the specified Start Node Pressure if the Wellhead is assigned as the Start Node (see “Flow Parameters” on page 61). If the Outlet Node is assigned as the Start Node, WellFlo will use a computed Wellhead Pressure.

If this value is enabled (i.e. the associated checkbox is checked), the Static Fluid Pressure Profile for the unloading sequence is taken to start at corrected Atmospheric Pressure at the specified TVD from Reference Depth. This enables a Swab‐Out or other Static Fluid Removal process to be modeled.

Figure 4-4: Depth of static fluid level (TVD): 105.40

The setting above will start the Static Fluid Gradient at corrected Atmospheric Pressure, 105.4 ft TVD below the Reference Depth.



Figure 4-5: Depth of static fluid level (TVD): 0

The setting above will start the Static Fluid Gradient at corrected Atmospheric Pressure at the Reference Depth (i.e. unloading to the atmosphere).

— Injection gas gravity. This value is shared between this screen and the Gas‐Lift Data configuration screen (see “Gas Lift Data” on page 54); it does not have to be the same value as the Produced Gas Gravity.

3d Enter Extended Spacing Gradient.

— Check Display Extended spacing Gradient. This option allows the users to overlay a gradient that reflects a specified set of conditions. This is useful in depicting what future well conditions might look like in the context of the extended spacing region of the gas lift design.

— Start Node Pressure. This is the pressure of the upper‐most node (usually tubing head pressure) associated with the extended spacing gradient.

— Liquid Rate. This is the production rate associated with the extended spacing gradient.

— Water Cut. This is the water cut associated with the extended spacing gradient.

— GOR. This is the total produced gas‐oil‐ratio associated with the extended spacing gradient.

— List-Gas/Liquid. This is the gas injection rate (or injection gas to liquid ratio) associated with the extended spacing gradient.

Transfer Pressure Margins

4 Select Transfer Pressure Margins from the menu at the left (see Figure 4‐6).

iThe above two examples presume that Wellhead Depth is the same as Reference Depth (e.g. if the Wellhead Depth was 80 ft from the Reference Depth, a Static Level of 180 ft would be 100 ft below the Wellhead). Unloading can be represented against a back-pressure (i.e. flow lines) by entering a negative Depth here (i.e. so the pressure at the Wellhead is greater than zero).



The Transfer Pressure Margins panel is used to specify a number of (optional) Design Safety Factors to be applied during a Gas‐Lift Design; these act to modify the valve transfer pressure that is used to position the gas lift valves and perform the valve sizing calculations. In order to accommodate the various design philosophies used in the industry, WellFlo provides the user with a variety of options for determining transfer pressure bias. The user has to choose only one of the options.

Figure 4-6: Gas Lift Design — Transfer Pressure Margins

4a Use Bracketing: The Bracketing option allows users to space gas lift valves based on the bracketing design methodology. This methodology generates a design line based on a user‐specified error tolerance. This design line is drawn from the wellhead pressure to the target depth of injection at a pressure equal to (1 + error tolerance)* tubing pressure.



Users have an option to (a) not use the design line above the bracket, (b) display and use the design line or (c) not display but use the design line. If the user opts to use the design line, unloading valves are then spaced within this design line until the minimum valve spacing is reached. Valves are then evenly spaced until the maximum depth of injection is reached. The first valve for which the corresponding transfer pressure (at the valve above) is at or to the left of the objective tubing gradient is considered to be the operating valve. Stations beyond this point or used for extended spacing purposes. These stations can be disabled or retained, depending on whether the engineer wishes to install mandrels at these depths to accommodate future conditions. In addition, the user can overlay a pressure gradient that is reflective of future conditions to better assess how many extended spacing mandrels to use.

— Bracketing Error Tolerance: This is the fraction of tubing pressure by which the error tolerance line is offset in the bracketing method.

— Design Line Options: This field dictates the way in which the design line is displayed and/or used when the bracketing method is selected.

4b Use Design Line (relative to (Pcsg - Ptbg)) This option allows users to specify transfer pressures based on a design line. In this method, a design line is generated extending from a pressure at the surface that is equal to the top node pressure*[1+ (fraction at Xmas Tree) (Pcsg ‐Ptbg)] to the objective depth of injection at a pressure that is equal to (pressure at depth)* [1+(fraction at Point of Injection) (Pcsg ‐ Ptbg)]. All active gas lift valves are spaced such that their transfer pressures spaced using the minimum valve spacing until the maximum depth of injection is reached.

— Fraction at Xmas Tree: (Refer to the underlying note.).

4c Transfer Pressures Relative to Ptbg: If users prefer, they can select transfer pressures by applying transfer point bias equal to a fixed percentage of tubing pressure at depth. This is done by selecting Transfer Pressures Relative to Ptbg and specifying a fraction or percentage of tubing pressure to apply.

4d Transfer Pressures Relative to (Pcsg - Ptbg) Another method for calculating transfer pressures is to select Transfer Pressures Relative to (Pcasing ‐ Ptubing). This method will select transfer pressures that are shifted by an amount equal to a specified fraction of the difference



between casing pressure and tubing pressure at depth. (This is comparable to selecting the Calculate by Depth option in previous versions of WellFlo.) When this option is selected, the following information must be entered:

— Use MD. This option bases transfer pressure calculations on measured depths.

— Use TVD. This option bases transfer pressure calculations on true vertical depths.

— Fraction at Xmas Tree: (Refer to the underlying note).

— Reference Depth (MD or TVD): Nominally, this will either be the Tubing Shoe Depth or Maximum Valve Depth.

— Fraction at Reference Depth: (Refer to the underlying note).

So, at a Valve Depth (z):

and the Fraction f(z) is defined as:

Figure 4-7: f(z)r

For the settings illustrated in the example dialog below, at a Valve situated half‐way between the Wellhead and the Reference Depth, the Shift applied would be 35% (i.e. half‐way between 20% and 50%) of the Casing‐Tubing Pressure Differential P(z) at that Depth, and so on for other Valves.

iThe Transfer Pressure at a valve is calculated by shifting the original Tubing Pressure by a fraction of the prevailing Casing-Tubing Pressure Differential at that depth. The Fraction to be applied at each Depth is interpolated between the Xmas Tree/Wellhead and the Reference Depth.

Transfer Pressure = Original Tubing Pressure + f(z) x ΔP z( )whereΔP z( ) Pcsg PtbgatDepth z( )

–=



Figure 4-8: Exampler

4e User Defined Amount Per Station. The user has a final option for calculating transfer pressure, in whichthey can shift the transfer points by a User Defined Amount per Station. (This is similar to the method in previous versions of WellFlo where the Calculate by Valve Number option was selected.).

— Margin at Top Valve. This is a constant pressure shift applied to the objective Tubing Pressure Curve at all Valves, starting at the first Unloading Valve.

(Corrected Tubing Pressure) = (Original Tubing Pressure) + (Transfer Pressure Margin)

— Increment per Station. The Corrected Tubing Pressure (defined above) is given an extra Shift by this increment, at each successive Valve, starting at Valve #2.

i A value between 0 and 50 psi is usual.

i This increment can be positive or negative.



The total corrected Transfer Pressure at the nth Valve is therefore:

(Transfer Pressure) = (Original Tubing Pressure) + (Transfer Pressure Margin) + (n‐1) x (Transfer Pressure Increment).

4f Use Exact Maximum MD of Injection. If checked, this option will honor the maximum Measured Depth by inserting an additional Gas‐Lift valve at the maximum depth if the calculations have placed the lower‐most Gas‐Lift valve above this point by relaxing the Design Margin criteria to accommodate the extra Gas‐Lift valve. This will result in a general reduction in the spacing of the unloading valves, but the Minimum Valve Spacing still will be honored.

If this option is left unchecked, the Gas‐Lift Design calculations will honor the Minimum Valve Spacing and the other Design Margins. This may result in the lower‐most Gas‐Lift valve being placed above the maximum Measured Depth of Injection, which may or may not be considered a problem.

4g Use Spacing Factor. This option allows users to reduce the spacing between gas lift valves by specifying that the intersection of the transfer pressure gradient and valve depth line be a certain number of PSI less than the operating pressure at depth. This form of design bias provides additional certainty that the well will unload properly without affecting the gas lift valve set pressures.

GLV Calculations

5 Select GLV Calculations from the menu at the left (see Figure 4‐9).

iThis controls the re-positioning of valves for Case 1, described in “Sample Gas-Lift Plots” on page 76. If this check box is checked and the Design Operating Valve is one of a group of valves at the Min Valve Spacing, an additional valve is placed below the Max MD of Injection at the Min Valve Spacing. This additional valve is then re-positioned at the maximum depth, and all the higher valves are re-positioned accordingly.



Figure 4-9: Gas Lift Design - GLV Calculations

5a Enter Set Pressures:

— Temperature Correction Calculation Method: This provides the user the option to calculate the temperature correction factors for sizing dome pressure actuated gas lift valves based on one of three methods. These include the following:

• API. This is the method specified in API RP11V6. It applies the ideal gas laws using a number of assumptions. Specifically, the authors of this calculation method assumed a pressure of 1000 psi and a base temperature of 60 degrees F, with nitrogen as the gas in question. This can lead to inaccurate dome pressure calculations, particularly when test rack opening pressures exceed 1000 psi.

• Winkler-Eads. This method is based on the work of Winkler and Eads, as published in SPE 18871 ʺAlgorithm for More Accurately Predicting Nitrogen‐Charged Gas Lift Valve Operation at High Pressures and Temperaturesʺ byH.W. Winkler and P.T. Eads. This paper presents a correlation that was developed by the authors to



provide a more accurate calculation for test rack opening pressure in cases where pressures exceed 1200 psi.

• Rigorous. This method is consistent with the temperature correction methodology used in prior releases of WellFlo. It rigorously calculates Z factor for nitrogen to determine the precise dome pressure at in situ conditions.

— Set Pressure Round off. It is often desirable to round off the calculated test rack opening pressure by a user‐defined amount. This is because it is not practical for gas lift technicians to set valves in the lab to the nearest psi. Realistically, the level of precision that is achievable in practice is the nearest 5 psi at best. For this reason, a value of 5 psi is usual.

5b Enter Temperature Bias:

— Use Temperature Bias: This option prevents the re‐opening of upper dome pressure actuated gas lift valves.

During the unloading process, the temperatures will be somewhere between the flowing gradient and the static gradient. For this reason, it is advisable that temperatures for the upper valves be based on a “compromise gradientʺ that is between the static and flowing temperature gradients.

— Static Wellhead Temperature. This is the static wellhead temperature used in constructing the static temperature gradient and “compromise gradient” used in the temperature bias option.

— Use Flowing Temperature Gradient when:

• Pt Static > Pt Flowing. This option specifies that the “compromise gradient” will be extended from the static wellhead temperature to the flowing temperature gradient at the depth of the first valve for which the static temperature gradient is greater than the flowing temperature gradient. This is useful because this valve is the first unloading valve which could realistically serve as an operating point. Any shallower valve can only serve as an unloading valve.

• TVD >. This option allows users to manually define the depth at which the “compromise gradient” intersects the flowing temperature gradient based on a specified true vertical depth.



Gas-lift Valve Data Table

The default values initially appearing in this table correspond to any Gas‐Lift valves that were previously specified in the Gas‐Lift Data configuration screen (see “Gas Lift Data” on page 54). If users have not yet specified any Gas‐Lift valves, this section will be blank. Gas‐Lift valve depths will be re‐computed when users perform a Gas‐Lift Design run (by clicking Design). Users can then manually edit the data and click Re-calculate to verify the effect of any fine tuning.

To edit a field in the table, double‐click in a table cell to highlight the current entry and either overtype existing data or enter new data. If users are entering new data, only the valve depths (MD or TVD), and valve status (Active or Inactive) need to be initialized. The TVD field is automatically updated from MD, and vice‐versa using the Deviation Data entered in the Wellbore Deviation configuration screen (see “Wellbore Data” on page 29). The other fields (e.g. Casing Pressure, Tubing Pressure), will be calculated.

6 Click Design to perform the Gas‐Lift Design calculations. WellFlo will delete all the current valves and then calculate the Unloading Sequence and the Steady‐State Casing Head Pressure required to operate the well under normal conditions.

Plotting

On completion of the Design computation, a Pressure versus TVD plot is displayed automatically, showing the main features of the Nodal Analysis (see Figure 4‐10). TVD is used to facilitate the plotting of fluid gradients.

i Only Gas-Lift valves up to and including the Operating Valve have values displayed in the Casing Pressure, Tubing Pressure and Temperature fields. These fields are not editable.



Figure 4-10: Gas Lift Design — TVD Plot

Example plots and their associated input screens are illustrated in “Sample Gas‐Lift Plots” on page 76.

7 Adjust any parameters and click Re-calculate to re‐calculate the unloading sequences and pressures for the current valves. This performs a top‐down continuous flow Unloading and Injection calculation using the entered flow rate and gas‐lift data. It does not re‐compute valve positions.

!This facility enables users to perform "what if..." studies using the valve positions obtained with the Design facility (or the default valve positions specified in the system editor if they have not yet been overwritten with the design results, or a set of user-defined depths) and varying other parameters such as Flow Rate or Maximum Casing Head Pressure.


4TUTORIAL IV: GAS LIFT DESIGNSizing

SizingUsers can adjust valve properties on the Gas‐Lift valve data table, after running the design calculations, to determine valve spacings. Either click into a table cell to activate a drop‐down selection menu, or double‐click in a cell to enter/edit values, as appropriate, to:

• Determine the recommended orifice sizes.

• Compute Opening and Closing pressures for each valve.

• Select either Gas‐Charged, Spring or Orifice valves.

• Compute the required Dome Pressure and Test Rack Opening Pressure for each Valve.

• Depending on the valve type selected, the choice of Valve Models is limited to either:

— PPO (Production Pressure Operated) and Orifice valves

— IPO (Injection Pressure Operated) and Orifice valves

Port Size Calculation

The Port Size can only be selected from the sizes listed in the gasvalve.csv file for the currently selected model. On each port size selection, its associated Discharge Coefficient and Port‐to‐Bellows Ratio are shown as read‐only items. When a change in one of the input columns causes the Port Size to be re‐calculated, the smallest suitable Port Size is selected. When the largest listed Port Size is insufficient for a changed Qgi value, the Qgi that it will actually pass is given.

Port sizes are calculated to the nearest 1/64th inch, for the gas flow rate at the valve, at the valve temperature, using the Tubing Transfer Pressure and the Casing Pressure. They are subsequently rounded‐up to the next size listed in the gasvalve.csv file for the selected Manufacturer and Valve Model. The default value of 0.865 is typical for small port sizes, but a smaller value may be more appropriate for larger port sizes.

iIf the orifice size is edited and one of the above inputs to its calculation is subsequently altered, it will be re-calculated. The orifice size is not used elsewhere in WellFlo, so users can overtype with the rounded-up sizes required when the calculations are completed, for the purpose of reporting.


4 TUTORIAL IV: GAS LIFT DESIGNSample Gas-Lift Plots

The port sizes are calculated using the Thornhill‐Craver equation.

• Port-to-Bellows Ratio (R). R varies with the Port Size and Valve Model as defined in the gasvalve.csv file. The default (no entry) is 3.142 x (Size/128)2 / Area.

• Discharge Coefficient. Thornhill‐Craver Discharge Coefficient. Default (no entry) = 0.96 if the valve Type is Orifice. Otherwise, the coefficient is 0.865.

• Criticality Indicator. Shows whether the valve will be in Critical Flow for the given conditions.

Sample Gas-Lift PlotsThe Plot illustrated in Figure 4‐11 is an example of a Gas‐Lift Design Plot, created with the WellFlo example file Gldesign.wfl, using the Design input parameters for an Injection Pressure (Casing) Operated IPO Valve.

Figure 4-11: Gas-Lift Design Plot: Pressure versus TVD

The zig‐zag lines show the continuous flow Unloading Sequence, working between the corrected Transfer Pressures (red‐colored circles on left) and the corrected Valve Closing Pressures (green‐colored circles on right).


4TUTORIAL IV: GAS LIFT DESIGNSample Gas-Lift Plots

The Operating Valve (with all Safety Factors) #6, is positioned at 8,798 ft TVD (10,858 ft MD) (horizontal pink‐colored dashed line). This is because of the situation described in Case 1 above; the next valve would, if computed in the same way, lie too close (i.e. within 450 ft) to the valve above it.

Below this, valves are located using the minimum spacing. The lowest valve at which the Corrected Casing Pressure is still greater than the Tubing Pressure by at least 100 psi (the specified Differential Pressure) is at 9,698 ft TVD (12,046 ft MD) (horizontal pink‐colored solid line). This is the Design Operating Valve #8.

Figure 4-12: Details of previous Gas-Lift Design Plot

The Operating Casing Pressure Gradient Curve (dashed green‐colored line) is calculated from the Design Operating Valve Depth to surface, allowing for the appropriate Valve Differential Pressure (i.e. 100 psi in this case), at the Injection Point.


4 TUTORIAL IV: GAS LIFT DESIGNSample Gas-Lift Plots

All valve depths down to the Maximum Measured Depth of Injection are listed in the Gas‐Lift Valve data table, along with Design Operating Valve Casing Pressures, objective Tubing Pressures, Temperatures and Status (active or inactive) at each valve.

i The Design Operating Valve is the deepest valve marked Active in the Gas-Lift valve data table.


Chapter 5TUTORIAL V: ESP DESIGN

This Tutorial explains how to configure, design and analyze an ESP well model in WellFlo.

ESP Design and Analysis Overview ............................................. 80Designing an ESP Installation .................................................... 82Analyzing an ESP Installation .................................................... 86Plotting .......................................................................................... 88


5 TUTORIAL V: ESP DESIGNESP Design and Analysis Overview

ESP DESIGN AND ANALYSIS OVERVIEW

There are two main types of ESP‐Specific applications in WellFlo‐ESP:

• Designing an ESP installation. This means sizing the pump and selecting a pump/motor combination based on power consumption. Selection of suitable components is made from a catalog of Manufacturersʹ data.

• Analyzing an existing ESP. In this mode, the pump and motor are already selected for the well, but you may wish to run sensitivity studies, either for pump variables (e.g. frequency), or other variables, such as water‐cut or wellhead pressure.

For this Tutorial, you will use the Espexamp.wfl file is supplied with the installation disks (in the Tutorials folder). This example model includes an ESP Design and also the addition of non‐catalog pump data and motor data.

The model is of a vertical, low‐productivity oil well that has an ESP installed at 8000 ft. The perforations are at a depth of 8500 ft, but the Layer Pressure is only 3000 psia with a Productivity Index (J) of just over 5 STB/day/psi.

TO VIEW THE ESP DESIGN CRITERIA:

1 Launch WellFlo from its stored location or go to C:\Program Files\Weatherford\WellFlo 4.0 and double‐click WellFlo.exe to start the program from the default location.


2 Go to File > Open and select Espexamp.wfl from the following location: C:\Program Files\Weatherford\WellFlo 4.0\example.

3 Open the Configuration menu in the Model Navigator.

4 Select ESP Data from the Model Navigator.

The ESP Data configuration screen is opened (see Figure 5‐1).


5TUTORIAL V: ESP DESIGNESP Design and Analysis Overview

Figure 5-1: ESP Data

This well will not flow to surface without artificial lift of some kind (i.e. in this case, an ESP). This can be verified by switching from Analysis mode to Design mode. If an Operating Point calculation is performed, no Operating Point will be found as the Inflow Curves and Outflow Curves cannot intersect without a Pump in place.

5 Select Design pump only and click Apply.


7 If necessary, open the Operating Conditions screen and select Operating Point mode.

8 Click Calculate (see Figure 5‐2).


5 TUTORIAL V: ESP DESIGNDesigning an ESP Installation

Figure 5-2: Flow Curves - Design Mode

Designing an ESP InstallationIn this mode, an ESP is to be inserted in a well, without knowing which size of pump or motor will be required. You also can enter the flow rate you wish to achieve. The program calculates which pumps and motors will meet the set criteria, then you can select a combination from a drop‐down list based on correct sizes, capacities, power consumptions and efficiencies.

You can fine‐tune the Design (e.g. for a different Operating Frequency, Number of Stages, etc.), if required, and may also further extend the Design scope by studying the variation of key properties against the Setting Depth of the ESP.

TO DESIGN AN ESP INSTALLATION:

1 Open the Design menu in the Model Navigator.

The ESP Design screen is displayed (see Figure 5‐3).


5TUTORIAL V: ESP DESIGNDesigning an ESP Installation

Figure 5-3: ESP Design

This Design screen is used to enter the Design liquid rate at which the well is required to flow. Since the Design process has not yet been performed and a selection of suitable pumps and motors has not been identified at this stage, the Suitable Pumps area is empty.

2 Click Calculate to perform the Design calculations.

The Design calculation results are displayed under the Suitable Pumps tab (see Figure 5‐4).


5 TUTORIAL V: ESP DESIGNDesigning an ESP Installation

Figure 5-4: ESP Options

The Pump/Motor/Manufacturer combinations are listed in the table and the GN5200/540 SK Series/Reda #2 combination of Pump/Motor/Manufacturer is selected.

Before installing this ESP, it will be optimized.

3 Open the Optimize tab (see Figure 5‐5).


5TUTORIAL V: ESP DESIGNDesigning an ESP Installation

Figure 5-5: Optimize Pump Performance at 60 Hz

Suppose the power supply is restricted to a Frequency of 70 Hz. Although the Design was carried out assuming a Frequency of 60 Hz, the Design can be optimized here for an operating Frequency of 70 Hz, by altering the Frequency entry.

4 Enter 70 for the target Frequency, then click Optimize.

The results are calculated in the Optimization results table (Figure 5‐6).


5 TUTORIAL V: ESP DESIGNAnalyzing an ESP Installation

Figure 5-6: Optimize Pump Performance at 70 Hz

5 Click Install to install the pump.

6 Return to the ESP Data configuration screen by opening the Configuration menu in the Model Navigator. (Select ESP Data in the Navigator, if necessary.)

Analyzing an ESP InstallationThe Analyze pump option has been selected automatically (switched from Design pump only), since the Design stage for the pump has been completed. The details of the GN5200 Reda pump also have been entered (see Figure 5‐7).


5TUTORIAL V: ESP DESIGNAnalyzing an ESP Installation

Figure 5-7: ESP Data - Analyze Pump Mode

TO ANALYZE THE ESP:


2 Select Operating Point mode, and set the Solution Node at Tubing 1.

3 Click Calculate to perform an Operating Point calculation.

The Operating Point results are displayed in the plot (see Figure 5‐8).


5 TUTORIAL V: ESP DESIGNPlotting

Figure 5-8: Operating Point Results

4 Open the Report tab to view the results.

Plotting

TO VIEW DIAGNOSTIC PLOTS:

1 Open the Design menu in the Model Navigator.

2 Open the Vary Depth tab.

3 Enter up to ten ESP setting depths in the Depths table. You can enter these values manually or have WellFlo calculate and insert them automatically by entering From and to values, then entering the number of Steps and clicking Fill (see Figure 5‐9).

4 Click the Calculate button to perform Nodal Analysis at the selected Depth/s and make the results available for plotting.


5TUTORIAL V: ESP DESIGNPlotting

The calculated results are displayed in the plots. Select from one of the following.

• Pressure/Depth. Plots the Flowing Pressure Profiles for each ESP depth.

• Gassiness. Plots the Inlet Gassiness for each ESP depth.

• In-situ rates. Plots the variation with Setting Depth of the In‐Situ Flow Rates at the Pump Inlet and at the Pump Outlet.

• Total dynamic head. Plots the estimated Head required at each ESP depth.

Plotting and Reporting

5 Open the Plot tab at the top of the Design screen to view the Pressure/Depth plot or open the Report tab to view the ESP Design report.

i This plot makes no correction for the Viscosity of the Well Product.



Figure 5-9: Pressure/Depth Plot at Solution Rate

This Pressure/Depth plot demonstrates the pressure increase and temperature rise at the pump.

Running a Sensitivity to Water‐Cut (e.g. 60%, 75% and 90%) can demonstrate how the pump will cope with these changing conditions. The Plot displayed in Figure 5‐10 shows the Inflow/Outflow Curves for the 60%, 75% and 90% cases. For the 90% Water‐Cut case, the intersection of the two curves falls outside the range set by the minimum and maximum Pump Rates.



Figure 5-10: Sensitivity to Water Cut

Suppose that the highest anticipated Water‐Cut for this well is 99% and the installed pump is required to operate at this level of Water‐Cut. Running Sensitivities to Pump Frequency at 70 Hz, 80 Hz and 90 Hz and Water‐Cut shows that with a higher Frequency, such as 80 Hz, the Pump will flow at a Water‐Cut of 90% (see Figure 5‐11). However, this may not be a practical method of extending the use of the pump; it may be better to install the pump with more stages.



Figure 5-11: Sensitivity to Pump Frequency

Running additional sensitivities to Number of Stages and Water‐Cut shows that by increasing the Number of Stages to 80, the pump can still operate at a Water‐Cut of 99% (see Figure 5‐12). If the Pump is installed with 80 Stages when the Water‐Cut is still 60%, instead of producing at 3036 STB/day, the Well can make 3404 STB/day, and this is still within the recommended range of the Pump.



Figure 5-12: Sensitivity to Number of Stages




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WellFlo Quick Start Guide 20090130