FEA – Finite Element Analysis

November 2009

Ken Watson

FEA – Finite Element Analysis

Solving your sand control challenges.

Completions & Sand Control GBU

1© 2009 Weatherford. All rights reserved.

Presentation overview

• Abaqus – what is it ?

• Simulia Customer Conference

• Examples of work done

• Abaqus – day to day use of the software

• Results

• Trying out new methods

• Conclusions

• Q and A


Abaqus; www.simulia.com

The Completions and Sand Control GBU within Weatherford started using Abaqus FEA at the end of 2006 / start of 2007.

Since then, many reports, papers and presentations have been created.

One goal is to use the software along with the existing EWBS (simple analytical wellbore stability model) spreadsheet

that is currently in use for geomechanics.

Another goal is to use the software to help improve the reliability of existing tools and improve the collapse resistance of ESS.


Abaqus; what is it?

The heart of Abaqus is the analysis “solver” modules, Abaqus/Standard and

Abaqus/Explicit, which are complementary and integrated analysis tools.

Abaqus/Standard is a general-purpose finite element module. It provides a

large number of capabilities for analysing many different types of problems, including many non-structural applications.

Abaqus/Explicit is an explicit dynamics finite element module.

Abaqus/CAE incorporates the analysis modules into a

Complete Abaqus Environment (or Computer Aided Engineering) for

modelling, managing and monitoring Abaqus analyses and visualising results.

There are many other modules ….

Abaqus, founded in 1978 (acquired by Dassault Systèmes in 2005; www.3ds.com)

Headquarters in Providence, Rhode Island (USA)Offices and representatives throughout the industrialised world

Sole activities are the development and the support of simulation software for the

analysis of engineering problems


Simulia Customer Conference; London 2009

2009 Simulia Customer Conference; the opening speech for the conference, Scott Berkey, CEO of Simulia


Simulia Customer Conference

At the 2009 Customer Conference, in the opening speech for the conference, Scott Berkey, CEO of Simulia, spoke of Weatherford being a success story, having saved considerable time and money whilst using Abaqus;

Engineering / Test Report ESS/7000/111R FEA of Erosion Plate Designs for 7” ESS Transition Areas

But of course, conferences aren’t all about listening to papers and presentations – here’s Colin and myself letting our hair down

(such that it is) with Chris Smith, General Manager, Simulia U.K.

Reduce ten different Erosion Plate Designs down to just two physically tested designs


Examples of work done

Poster displayed at the SPE 3rd European Sand Management Forum, May 2008

Most papers and presentations are available on both Exchangeand Sharepoint



Paper and Presentation at Abaqus Users Conference, June 2008




Paper and Presentation at Simulia Customer Conference, June 2009




Paper and a possible Presentation at the SPE 4th European Sand Management Forum, 2010

Potential entry for the 2010 Simulia Customer Conference




Some of the variables that have been investigated for Conventional Well Screens (the perforated Basepipe);

Tensile and Compression, Burst and Collapse and Torque

Engineering / Test Reports are generally kept on a local server


Abaqus; first view of the software


Abaqus; options to be completed to get results

• Part – create within Abaqus or, for more complicated shapes, Pro-Engineer Wildfire 4

• Property – metallurgy (and/or rock) properties; Mass Density Elastic; Young's Modulus, Poisson's RatioPlastic; Yield Stress v Plastic Strain curve

• Assembly – assemble individual parts / components

• Step – create individual steps; with boundary conditions, constraints, interactions, loads and then specify which variables are monitored (outputs) and subsequently shown when the Job is run

• Interaction – specify how parts interact with each other; provide friction coefficients etc.

• Load – any force or pressure loading (etc.)

• Mesh – all the parts require meshing; we usually use a C3D8R (brick) mesh for more regular tubular shapes, but we can use C3D4 (pyramid) mesh also for irregular objects

• Job – submit the item for analysis and specify how many processors and RAM to allocate

Mohr Coulomb (Abaqus Standard) Mass Density Elastic; Young’s Modulus, Poisson’s RatioMohr Coulomb Plasticity; Friction Angle, Dilation Angle Hardening; Cohesion Yield Stress v Abs Plastic Strain curve


Part creation; Pro-Engineer Wildfire 4 (export as ACIS / SAT)

The Engineering department have already been using Pro-Engineer for a considerable time and most components have already been modelled in 3D – so it makes sense to use this capability for creating and importing parts into Abaqus.

There is a module for importing Pro-E parts directly into Abaqus; this maintains the parametric 3D model, i.e. if the part is changed in Pro-E, the part also changes in Abaqus (with a button click or two) – without having to redo any work already done within Abaqus. At this time, if a Pro-E model

changes, we have to reassign all the parameters; materials, boundary conditions, loads and re-assemble within Abaqus (quite painful).


Materials

First step was to establish material properties for our ESS components (316L basepipe and Perforated outer shroud)

Our metallurgist provided an engineering stress / strain curve for our use … however we were informed that in fact we required a true stress / strain curve for using within Abaqus.

A quick bit of Excel spreadsheet calculation work produced our new graph for use.

A footnote; it has often proved difficult to get other material stress / strain curves !


Meshing

• Earlier models that were analysed and compared to physical tests were adequate as a design tool but too slow for an analysis tool for screening multiple application scenarios.

• Therefore a simple representation of the ESS was developed. Thisequivalent ESS was a plain pipe with the ID/OD dimensions of expanded ESS. The Elastic and Plastic properties were adjusted to fit hydraulic collapse data and FEA models of the whole slotted system

Basepipe

Weave

Shroud

Basepipe33,000 elements (C3D8R)

Weave (not modelled)

Shroud 100,000 elements (C3D8R)

Detail of ESS construction showing complexity of the meshing on the shroud

Comparison of the measured deformation;

(1) the full scale simulation and (2) the equivalent (simple representation) simulation


Results; Expanding


Results; Forces

FEA model matches the observed behaviour.

• The models give predicted surplus expansion ~ 4%

• The required force to expand; Tested = 16,000 lbs, Model = 14,400 lbs.

– A reasonable comparison; the filter weave isn’t currently modelled, which would give a slight increase in the forces.

All sizes have been modelled and compared to previous tests; there is a good fit to the results.


Results; Collapsing


Results; Collapsing

• Initially the model matched the test data

• The major difference is that the model uses a constantly ramping pressure load,

whereas the test set-up is a constantly increasing volume of fluid.

– Surface based fluid cavities could be used in the future


Results; TWC expand and collapse


Results; TWC

• Reasonable fit to data

• Complicated behaviour

– Shear bands

– Compaction, dilatancy, creep, anisotropic


Vertical-Horizontal Well Application Screening Tool

A tool for screening potential applications for excessive deformation; simple enough to be run on a basic laptop!


Inclined Wellbore in a Sand Shale Sequence

Inclined wellbore in a 5m x 5m x 3m block

Detail of applied finer mesh close to the wellbore

Detail of the deformation in the Sandstone and Shale

Block was partitioned to allow for finer

meshing closer to the wellbore.

The central section is split into 5 sections

which allowed shale layers from 0.2m to 3m

to be modelled.

Very fine mesh at middle of block

Sand appears to support

the shale at the interfaces


Deformation in the central shale as a function of shale layer thickness

Three sets of simulations were run.

(1) A bare 8-1/2” wellbore with 0.2 – 1m layers of shale.

(2) A 8-1/2” wellbore with 5-1/2” ESS installed,

expanded out to 8-1/2” OD (with 0.2 – 1m shale)

(3) A 8-1/2” wellbore with 7” ESS installed,

expanded out to 8-1/2” OD (with 0.2 – 1m shale)

0.2 metre shale section 1 metre shale section


Deformation in the central shale as a function of shale layer thickness

Wellbore with 5-1/2” ESS Wellbore with 7” ESS

It is clear to see that the deformation starts earlier in the 5-1/2”

ESS system and is far less in the wellbore with 7” ESS present

1m shale section 29% deformation1m shale with 5-1/2" ESS 21% deformation

1m shale with 7" ESS 16% deformation ��


Underground Gas Storage; geology, model, materials

26

The use of Underground Gas Storage (UGS) is expected to increase considerably in the near future, due to a variety of

factors, including security of supply (whether due to technical or political issues). There are several geological structure types

for storing gas underground; salt caverns (either natural or manmade), Fig.1 porous rock in depleted gas or oil reservoirs, and

finally aquifers, where there would be an impermeable cap rock, with water filled rock strata below, with the injected gas

displacing the water.

Figure 1; depleted gas reservoir UGS

Figure 2; mesh detail for wellbore

and plain pipe (equivalent ESS)

A model was built to simulate an annual winter/summer cycling UGS application.

The rock mass Fig.2 was set up with the dimensions 1m x 1m x 2m deep,

complete with an 8.5" diameter wellbore running through the centre.

Figure 3; showing the percentage decrease

in Cohesion Yield Stress

From a technical note, we know that the material properties (UCS or uniaxial compressive strength) of the given rock will

decrease by a certain amount over a number of cycles during cyclic loading, but once a certain level is reached, the UCS

will remain relatively constant, having no further noticeable decrease in strength. It was decided that for a multi-step

(cycling) analysis, the first ten cycles would have properties reducing, then for the following cycles, the properties would

remain constant, Fig.3.


Underground Gas Storage; results

27

The graph, Fig.4, shows the wellbore displacement (complete with equivalent ESS installed) as the cycling load is applied. Although the material properties are only degraded over the first 10 cycles, it can be seen that it took considerably longer (around another 25 cycles) for the displacement to settle down to a reasonably constant value. It is important that the deformation stabilises, since excessive formation induced deformation of ESS could restrict access to the well and may ultimately cause a loss of sand control. Extensive testing in a joint industry project (PEA182) showed that ESS could withstand large deformations without collapsing or losing the ability to control the sand. A limit of 20% deformation was set based on the results of the joint industry project. The 20% value includes a large safety factor.For the weak sandstone used in this analysis, the extent of deformation prior to stabilisation is seen to be around 12%, which is well within the acceptable limit of 20%.

Figure 4; radial wellbore displacement as cycling load is applied showing both Horizontal and Vertical movement

Friction Angle = 25


Underground Gas Storage; results – varying friction angle

Figure 5; results when varying the Friction Angle

The graph, Fig.5, shows variations of the Friction Angle value.A deformation limit of 20% (this includes a safety factor) for ESS is acceptable, i.e. there should be no loss of sand controlThe Friction Angle of Weak Sandstone can typically vary between 20 and 40.As can be seen from the four trace lines, the weakest Sandstone will have too much movement in the wellbore and will minimally pass the 20% limit, however, anything from 22 and upwards, the ESS can reasonably be expected to cope with.


Trying out new methods; rotating rollers


Trying out new methods; element deletion


Conclusions

• Initial efforts at FEA modelling of ESS have been a success.

– Good fit to hydraulic collapse and line loading data

– Reasonable fit to TWC experiments

Engineering / Test Report ESS/4501/037R FEA on 4.5” ESS with various wall thicknesses and slot patterns and metallurgy

Reduce four different Designs down to just one physically tested designs


Conclusions; continued

Abaqus is now used extensively within Weatherford as a design tool, as an application screening tool and a research tool.

For research, simulations can be time consuming (but worthwhile for accuracy) due to complexity of the structure, which brings about the large number of mesh elements.

For screening of applications, a simplified representation of the ESS has been developed which allows for results to be produced very rapidly.

The equivalent ESS has been used to model more complex well architectures such as an inclined well crossing multiple layers. This has answered such questions as what happens at sand/shale interfaces and how deformation varies with shale layer thickness.

In a recent product enhancement project, using Abaqus helped reduce the timescale by 60% and reduced project costs by 75%


November 2009

Ken Watson

FEA – Finite Element Analysis

Solving your sand control challenges.

Completions & Sand Control GBU

Thank you for your attention

Please feel free to ask any questions

Documents

FEA – Finite Element Analysis