Prosper Well Modeling

Step by Step Guide to Build & Match a Prosper Model of a Gas Lifted Oil Well

Starting a New Well File• Open Prosper• If a well model is loaded - From the Main Menu Bar - press File/NewOption• Click Options/Options• At the Artificial Lift – Method Pull Down Menu select Gas Lift• In the Type Pull Down Menu check that No Friction Loss in Annulus is selected• If the well is onshore – select Calculation Type – Predict Pressure and Temperature (Onshore)• If the well has an open hole completion – select Well Completion - Type Open Hole• Accept all other default Settings• Press Done

PVT• From the Main Menu Bar – Press PVT/Input Data• Enter Solution GOR• Enter Oil Gravity• Enter Gas Gravity• Enter Water Salinity• Press Match Data• Enter Temperature of PVT Match Data• Enter Bubble Point at this Temperature• Enter Pressure, Gas Oil Ratio, Oil Formation Volume Factor, and Oil Viscosity for each PVT Data Point available• Press Done• Press Regression• Press Match All• When the Calculation stops – Press OK• Press Parameters• Chose the Black Oil Model for Bubble Point, Solution GOR, and Oil Formation Volume Factor that has:o Parameter 1 closest to 1o Parameter 2 within + or – 1000o Lowest Standard Deviation

• Chose the Black Oil Model for Oil Viscosity that has:o Parameter 1 closest to 1o Parameter 2 within + or – 1000o Lowest Standard Deviation• Press Done• Select the choice of Black Oil Models in the Correlations pull down menu at the right of the screen• Press Plot• Press Variables at the top of the screen• Select Pressure as the X axis Variable• Select GOR as the Y axis Variable• Press Done• If the crosses – the data entered in the Match Data screen – do not lie on the line calculated by Prosper – Chose another Black Oil Correlation• Press Variables at the top of the screen• Select Oil FVF as the Y axis Variable• Press Done• If the crosses – the data entered in the Match Data screen – do not lie on the line calculated by Prosper – Chose another Black Oil Correlation• Press Variables at the top of the screen

• Select Oil Viscosity as the Y axis Variable• Press Done• If the crosses – the data entered in the Match Data screen – do not lie on the line calculated by Prosper – Chose another Black Oil Correlation• Press Finish• Press Done• Select the choice of Black Oil Models in the Correlations pull down menu at the right of the screen• Press Done

Data Required for Vertical Lift Calculations

• Press System/Equipment (Tubing etc)• Press All• Press Edit• Enter Deviation Survey Data• Press Done• Enter Temperature of Surroundings at Wellhead at the bottom right of the screen• Enter 8 BTU/h/ft2/Deg F for Overall Heat Transfer Coefficient

• Press Done• Enter Completion Details from the Completion Diagram in Downhole Equipmento Press in the Type Column to enter a tubing or SSSVo The depth entered should be at the bottom of each tubing section with a different internal diametero The depth should be referenced to a datum that is never changed – usually Rotary Tableo Use Restriction for equipment such as Nippleso If the tubing or casing is made of Stainless Steel enter 0.0006” for Roughnesso (Do not change Rate Multiplier – it must be 1)o Enter Casing down to the depth of the middle of the perforations• Press Done• Enter the depth of the wellhead referenced to datum and environmental temperature at the wellhead in Geothermal Gradient• Enter the bottom depth of the completion entered in Downhole Equipment and the reservoir temperatureo If there is data available on the temperature at the bottom of the sea and the sea water depth enter this between the wellhead and the bottom of the completion

• Enter a Overall Heat Transfer Coefficient of 8 BTU/h/ft2/Deg F – unless you know the value for the well• Press Done• Do not change the default values for Average Heat Capacitieso If you think these have been changed – Press Default• Press Done• Press Done

Data Required for Inflow Performance Relationship (IPR)

• Press System/Inflow Performance• If PI Entry is not selected – Press PI Entry• Enter Reservoir Pressure• Enter Reservoir Temperature• Enter Water Cut from the last well test• Enter the Total Gas Oil Ratio (GOR) being produced from the Reservoir• Press Input Data at the top right of the screen• Enter an estimate for the PI of the wello This does not have to be accurate – however, if you know an approximate value use it

• Press Calculate – Prosper will calculate the IPR curve• Press Finish – at the top left of the screen• Press Done

Data Required for Gas Lift Analysis

• Press System/Gas Lift Data• Enter Gas Lift Gravity• Select Fixed Depth of Injection• Enter the Depth of the Gas Lift Orifice in Gaslift Valve Depth (Measured)o If there is a gas lift survey – Enter the Depth that the Lift Gas is Injecting at• Make sure that the GLR Injected is 0• Press Done

Matching Prosper to a Well Test

The next sections explain how to match a Gas Lifted Well model:

Entering Well Test Data

• Press Matching/Matching/ VLP/IPR (Quality Check)• Enter the following Well Test Data:o Date of the Well Testo Wellhead Flowing Pressure (Tubing Head Pressure)o Wellhead Flowing Temperature (Tubing Head Temperature)o Water Cuto Liquid Rate (Making sure that the oil rate has been multiplied by the shrinkage so that it is in Stock Tank Barrels per day before being added to the water rate)o Downhole Gauge Depth – from either a permanent downhole gauge or at the deepest depth of a downhole pressure survey If there is no gauge data enter 0 deptho Downhole Gauge Pressure – from either a permanent downhole gauge or at the deepest depth of a downhole pressure survey If there is no gauge data enter 0 pressureo Produced GOR from the reservoiro Enter 0 for GOR freeo Enter Gaslift Gas Rate

o Enter Gaslift Injection Depth (Measured Depth) (This Depth should be the same as in the Data Required for Gas Lift Analysis Section)

Calculating the Overall Heat Transfer Coefficient• Press the 1 button at the left of the Well Test entered – under Match Data• Press Estimate U Value• Write down the Overall Heat Transfer Coefficient calculatedo The value should be between 1 to 20 BTU/h/ft2/Deg F• Press OK• Press Done• Press System/Equipment (Tubing etc)• Press the large button next to Geothermal Gradient• Enter the calculated Overall Heat Transfer Coefficient in the box on the right• Press Done• Press DoneSelecting the Vertical Lift Correlation for the WellDo not carry out this step if there is no downhole gauge data.

• Press Matching/Matching/ VLP/IPR (Quality Check)• Press the 1 button at the left of the Well Test entered – under Match Data• Press Correlation Comparison• When the Overall Heat Transfer Coefficient entered is displayed – Press OK• Select the following Vertical Lift Correlations:o Fancher Brown – which will Under Predict the pressure drop in the tubingo Duns & Ross Modified – which should Over Predict the pressure drop in the tubingo Petroleum Experts 2 – which should be close to predicting the pressure drop in the tubingo Petroleum Experts – which should be close to predicting the pressure drop in the tubing• Press Calculate• Press Calculate• Press OK• Press Plot• If the downhole gauge pressure point is not between Fancher Brown and Duns & Ross Modified there is probably a problem with the well test data

• Chose the closest correlation to the downhole gauge pressure point – between Petroleum Experts 2 and Petroleum Expertso Do Not Chose Duns & Ross Modified or Fancher Brown• Press Main

Matching the Vertical Lift Correlation for the Well

Do not carry out this step if there is no downhole gauge data.

Do not carry out this step if the multiphase correlation selected predicts the pressure drop in the well.

• Press Match• Select the Vertical Lift Correlation that was closest to predicting the downhole gauge pressure point• Press Match• Press OK• If the Parameter 1 value is greater than 1.05 or less than 0.95 do not use the well test data

• If the Parameter 2 value is greater than 1.6 or less than 0.8 do not use the well test data• Press Done

Matching the Productivity Index of the Well

• Press IPR• Select the Vertical Lift Correlation that has been matched – or the closest vertical lift correlation to the downhole gauge datao Make sure no other correlations are selected• Press Calculate• Press OK• Press IPR• Press Calculate

• If the %Difference between the Measured Liquid Rate and the Calculated Liquid Rate is Greater than 0.2 :o Press Finisho Drag the IPR screen a little to the right of the computer screen – so that the green buttons on the right of the screen are visible

o Press Input Datao Reduce the Productivity Index (PI)o Press Calculate

• If the %Difference between the Measured Liquid Rate and the Calculated Liquid Rate is Less than - 0.2 :o Press Finisho Drag the IPR screen a little to the right of the computer screen – so that the green buttons on the right of the screen are visibleo Press Input Datao Increase the Productivity Index (PI)• Press Calculate

• Keep changing the Productivity Index until the %Difference between the Measured Liquid Rate and the Calculated Liquid Rate is between –0.2 and 0.2• Press Main• Press Main

Check the Well Match in Quicklook

• Press Matching/Quicklook• Enter the following Well Test Data:o Wellhead (Tubing Head) Pressure o Wellhead (Tubing Head) Temperatureo Liquid Rateo Water Cuto Total Gas Rate – This is the Produced Gas Rate from the Reservoir + the Gas Lift Gas Injection Rateo Gas Injection Rateo Casing Head Pressureo Orifice Diameter – at the depth of injection used in the well test matchingo Injection Depth (Measured) – (Measured Depth)o Select the Vertical Flow Correlation that was used in Matching the Productivity Index of the Wello Select Dome Pressure Correction (above 1200 psig) to Yes• Press Calculate• Press Calculate• Press OK• Press Plot

• The Tubing Measured (arrows going down) and the Tubing Calculated (arrows going up) should overlay each other. If they do not, there is an inconsistency somewhere in the model. Press Main, check all input data and do the well matching again.• Check that the Casing Measured Line (arrows going up) approximately overlays the Casing Theoretical Line (arrows going down).o Theoretically, when injecting at the correct depth, the Casing Measured will be greater than or equal to the Casing Theoretical.. Uncertainties and errors in well test data can cause some deviation.o If the Casing Measured is within +- 50 psi of the Casing Theoretical pressure, the assumed injection depth is correct.o If the Casing Measured is more than 50-100 psi greater than the Casing Theoretical pressure, then: The assumed injection depth may be correct but there may be a problem such as a plugged orifice. The injection depth may be deeper than assumed. In this case, assume the injection occurs at the next valve down.o If the Casing Measured is more than 50-100 psi less than the Casing Theoretical the well can not lift at the depth entered. In this case, assume injection occurs at the next valve up.

o If the Casing Measured is greater than 100 psi less than Casing Theoretical at one injection depth and if Casing Measured is greater than 100 psi more than Casing Theoretical at the next valve up, then multipointing at the two depths is possible.• Press Main• If the assumed injection depth is changed, repeat the entire well matching process using the new injection depth. • If the assumed injection depth is correct, continue to the next step.Update the Gas Lift Data with the final injection depth• Press System/Gas Lift Data• Select Fixed Depth of Injection• Enter the injection depth determined from the well matching in Gaslift Valve Depth (Measured)• Press Done

Making Sure the Well Model can Predict the Well Test Result

• Press Calculate/System (Ipr + Vlp)• From the Well Test Enter:

o Wellhead Flowing Pressureo Water Cuto (No Surface Calculations will be carried out – so ignore Surface Equipment Correlation)o Select the Vertical Lift Correlation that was closest to the downhole gauge data or was matched to the downhole gauge data• Make sure the Solution Node is the Bottom Node• For Rate Method select Automatic - Linear• Press Continue• For Variable 1 select Total GOR• Press Enter Values to the right of Variable 1• Enter the Produced GOR from the Reservoir• Press Done• For Variable 2 select Gaslift Gas Injection Rate• Press Enter Values to the right of Variable 2• Enter the Gaslift Gas Injection Rate from the Well Test• Press Done• Press Continue• Press Calculate• Press OK

• Check that the Liquid Rate calculated is the same as the well testo If it does not go back to the section Entering Well Test Data• Press Plot• Press Main

Additional sensitivity calculations can now be carried out on the well model.