Design optimisation of swellable elastomeric seals using ... · Elastomer is vulcanized to the base...
1
Design optimisation of swellable elastomeric seals using advanced material modelling and FEM simulations Yevgen Gorash , Alan Bickley and Francisco Gozalo 1 2 3 * 1 – Dep. of Mechanical & Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ, UK 2 – Weir Advanced Research Centre, Technology and Innovation Centre, Glasgow G1 1RD, UK 3 – Weir Oil & Gas, Weir Rubber Engineering, Salt Lake City, UT 84119, USA [email protected], [email protected], [email protected] Emails: Advanced Research Centre the place of useful learning Robust Simulation of Swellable Packers • Standard Water Swell (SSW) Series • High Salinity Water Swell (SHSW) Series • Hybrid Oil and Water Swell (SHYB) Series • Stampede™ Sleeve (SSLV) Series • Standard Oil Swell (SSO) Series Available Options: Design Features and Benefits: High-quality elastomers that are critical to the life of the packer Multiple set screws and end ring design prevents extrusion ? ? ? Proprietary elastomer compound provides predictable swell when in contact with well fluids and with changes in temperature. Robust end ring design, with multiple set screws, protects the rubber during run- in, and provides a barrier against extrusion. Elastomer is vulcanized to the base pipe, allowing the packer to have one effective annular seal. Stampede™ Swellable Packers 1 [1] Lou, Y. & Chester, S. (2014) "Kinetics of swellable packers under downhole conditions." : 1450073. Int. J. Appl. Mechanics 06 [2] Flory, P.J. & Rehner Jr., J. (1943) "Statistical mechanics of cross-linked polymer networks: II. Swelling." : 521–526. [3] Dassault Systèmes (2015) Providence, USA [4] Treloar, L. R. G. (1944) “Stress-strain data for vulcanised rubber under various types of deformation.” : 59–70. [5] Wagner, N. & Helfrich, R. (2016) "Topology and Shape Optimization of Structures under Contact Conditions." , 12-13 October 2016, Manchester, UK J. Chem. Phys. SIMULIA Abaqus 2016 Documentation, Trans. Faraday Soc. European Conference: Simulation-Based Optimisation 11 40 References Planned Research Outcomes ? ? ? ? ? ? ? ? ? Design and manufacturing of tools for mechanical testing of swellable elastomeric specimens and mechanical behaviour of packers in conditions resembling downhole operation. Mechanical characterisation of swellable elastomers used by Weir Oil & Gas USA for packers through experimental studies in Advanced Materials Research Laboratory (AMRL) in the University of Strathclyde ( ) Implementation of an advanced material model of hyperelasticity with moisture swelling in FE-code and identification of corresponding material constants for it. Linking of moisture swelling with the fluid pressure penetration feature in order to simulate realistic non-uniform material expansion, which is more intensive on the areas that are in contact with fluids. Development of an optimisation procedures for available FEA packages (ABAQUS, ANSYS, MSC.Marc etc.) based on packers downhole behaviour simulation using an advanced material model. Implementation of parametric optimisation - to find an optimal length of a packer, and non-parametric (shape and topology) optimisation - to find an optimal packer profile. For this purpose Isight (parametric) and Tosca Structure (non-parametric) optimisation engines will be used. Optimised packers geometry is obtained by running the optimisation studies on the regional supercomputer centre at the University of Strathclyde – ARCHIE-WeSt ( ). Provision of packers design recommendations and optimal designs based on a number of optimisation studies for variety of downhole conditions in form of tables and/or mathematical relations. Delivery of the ABAQUS plugin to Weir industrial partners as a conventional tool for simulation-based design analysis and improvement. https://www.strath.ac.uk/amrl/ https://www.archie-west.ac.uk Discussion 1. for fluid pressure penetration: To account for the asperities on the contacting surfaces, a critical contact pressure, below which fluid penetration starts to occur, is introduced. The higher this value, the easier the fluid penetrates. The default value of the critical contact pressure is zero, in which case fluid penetration occurs only if contact is lost. How much is it dependent on following? pressure and type of fluid, surface quality and material type of borehole, type of packer elastomeric material. 2. in hourglass control: Critical mechanical contact pressure Amount of stiffness ? ? ? Hourglassing is essentially a spurious deformation mode of a FE- mesh, resulting from the excitation of zero-energy degrees of freedom. It typically manifests as a patchwork of zig-zag or hourglass like element shapes, where individual elements are severely deformed, while the overall mesh section is undeformed. This happens on hexahedral 3D solid reduced integration elements and on the respective tetrahedral 3D shell elements and 2D solid elements. Assigning stiffness to the finite elements is used to suppress hourglassing. Therefore, the following questions arise: Can we relate this artificial stiffness to the "surface layer effect"? How much stiffness is right to be assigned to the elements? How do we measure the stiffness of the surface layer in elasmoters? Which mechanical tests are needed? Indentation tests? ? ? ? ? element stiffness critical contact pressure fluid pressure how related? Introduction & Objectives Swellable elastomeric seal is a type of specifically engineered packer that swell upon contact with wellbore fluids. Such packers have been widely employed in various oil-&-gas and minerals applications including slimming of well design, zonal isolation, water shut-off, and multi-stage fracturing. Downhole conditions are difficult to be reproduced using physical testing environment, but feasible to be simulated in virtual environment using CAE software. A better understanding of packers’ mechanical behaviour in downhole conditions would provide a higher confidence and improvement of existing engineering design practices for manufacturing of packers. The numerical simulation can be incorporated into optimisation procedure searching for an optimal shape of packers with the goals to minimise the time to seal the borehole and maximise the contact pressure between the seal and borehole. Such an optimisation would facilitate the development of a packer with various designs optimised for different downhole conditions. The objective of this research project is to develop a design tool integrated into a CAE to implement parametric numerical studies using FEM simulation. However, development of such a CAE plugin is associated with a number of technical challenges specific to this class of multiphysics problems. Hyperelasticity with swelling The key component is an advanced material model comprising both hyperelasticity and moisture swelling. It has to consider two-way interaction between mechanical properties and swelling capacity. Implementation of such material model requires programming of a Fortran subroutine for the user defined material using the Flory-Rehner theoretical background [2]. In polymer science Flory–Rehner equation is an equation that describes the mixing of polymer and liquid molecules as predicted by the equilibrium swelling theory of Flory and Rehner. It describes the equilibrium swelling of a lightly crosslinked polymer in terms of crosslink density and the quality of the solvent. The theory considers forces arising from three sources [2]: The entropy change caused by mixing of polymer and solvent. The entropy change caused by reduction in numbers of possible chain conformations via swelling. The heat of mixing of polymer and solvent, which may be positive, negative, or zero. The equation is written as where is the volume fraction of polymer in the swollen mass, the molar volume of the solvent, is the number of network chain segments bounded on both ends by crosslinks, and is the Flory solvent-polymer interaction term. ? ? ? ν n χ 2 1 1 V ( ) 1 2 2 3 2 2 1 2 1 2 ln 1 2 Vn æ ö é ù - - + + = - ç ÷ ë û è ø n n n cn n Adaptive remeshing without adaptive remeshing with adaptive remeshing Non-uniform swelling can be associated with a localised increase of material volume. So it may cause a significant distortion of FE mesh and result into analysis convergence problems. To overcome this, an adaptive mesh-to-mesh solution mapping (rezoning) may be required. Fluid pressure penetration The moisture swelling process is not uniform and develops from the surfaces which are subject to fluid. Adsorption, which governs the progress of swelling can occur only at open surfaces. Therefore, the fluid pressure penetration technique needs to be involved into simulation. This is an automated application of fluid pressure dependent on changes of contact conditions. 3 2 Parametric study assumes going through a big number of different geometric configurations, looking at material properties variation and different downhole conditions. This means a search for an optimal geometry through a sensitivity study, which would result into specific design recommendations for the geometry of a packer. It is reasonable to automate the analysis procedure through a Plugin with a convenient GUI, which provides access to the parameters of geometry, material, service conditions, etc. ABAQUS plugin with GUI 4 Shape optimisation with Tosca Structure 2.0 original optimised contact area R=3.25 *dimensions are in inches pipe side borehole side 0.75 0 1 2 3 4 5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Contact pressure (MPa) Normalised length of contact area original optimised Benchmark problem for leakage and extrusion FE-simulation of Pressure penetration & leakage in packer 16.00 0.25 0.5 0.75 R = 3.0 R = 4 R = 4.5 packer pipe rock end ring Max. Principal Strain 0.068 0.197 0.325 0.454 0.582 0.710 0.839 0.967 1.096 1.224 1.352 1.481 1.609 critical contact pressure 4 MPa fluid pressure to cause failure by extrusion ~ 14.2 MPa *dimensions are in inches Strain Max. Principal 0.060 0.106 0.152 0.198 0.244 0.289 0.335 0.381 0.427 0.473 0.519 0.565 0.611 Strain Max. Principal 0.064 0.128 0.191 0.255 0.319 0.382 0.446 0.509 0.573 0.636 0.700 0.763 0.827 Strain Max. Principal 0.061 0.152 0.242 0.333 0.424 0.514 0.605 0.696 0.786 0.877 0.968 1.058 1.149 Strain Max. Principal 0.055 0.169 0.284 0.399 0.514 0.628 0.743 0.858 0.972 1.087 1.202 1.316 1.431 Strain Max. Principal 0.065 0.194 0.322 0.451 0.579 0.708 0.837 0.965 1.094 1.222 1.351 1.480 1.608 Strain Max. Principal 0.066 0.200 0.333 0.467 0.600 0.733 0.867 1.000 1.133 1.267 1.400 1.533 1.667 0 3 6 8 10 10.7 fluid pressure fluid pressure fluid pressure fluid pressure fluid pressure fluid pressure critical contact pressure 0.6 MPa Max. Principal Strain 0.05 0.10 0.14 0.19 0.23 0.28 0.32 0.37 0.42 0.46 0.51 0.55 0.60 Max. Principal Strain 0.04 0.11 0.17 0.24 0.31 0.37 0.44 0.51 0.57 0.64 0.70 0.77 0.84 Max. Principal Strain 0.04 0.15 0.26 0.36 0.47 0.58 0.69 0.79 0.90 1.01 1.12 1.23 1.33 Max. Principal Strain 0.04 0.16 0.28 0.39 0.52 0.64 0.76 0.88 0.99 1.11 1.23 1.35 1.47 0 5 14 15 16.2 fluid pressure fluid pressure fluid pressure fluid pressure Max. Principal Strain 0.04 0.18 0.33 0.47 0.61 0.76 0.90 1.04 1.19 1.33 1.48 1.62 1.76 fluid pressure critical contact pressure 1.0 MPa
Transcript of Design optimisation of swellable elastomeric seals using ... · Elastomer is vulcanized to the base...
Design optimisation of swellable elastomeric sealsusing advanced material modelling and FEM simulations
Yevgen Gorash , Alan Bickley and Francisco Gozalo1 2 3*
1 – Dep. of Mechanical & Aerospace Engineering, University of Strathclyde, Glasgow G1 1XJ, UK2 – Weir Advanced Research Centre, Technology and Innovation Centre, Glasgow G1 1RD, UK
3 – Weir Oil & Gas, Weir Rubber Engineering, Salt Lake City, UT 84119, [email protected], [email protected], [email protected]:
Advanced Research Centre
the placeof usefullearning
RobustSimulation
of SwellablePackers
• Standard Water Swell (SSW) Series• High Salinity Water Swell (SHSW) Series• Hybrid Oil and Water Swell (SHYB) Series• Stampede™ Sleeve (SSLV) Series• Standard Oil Swell (SSO) Series
Available Options:
Design Features and Benefits:
High-quality elastomersthat are critical to thelife of the packer
Multiple set screwsand end ring designprevents extrusion
�
�
�
Proprietary elastomer compound provides predictable swell when in contactwith well fluids and with changes in temperature.Robust end ring design, with multiple set screws, protects the rubber during run-in, and provides a barrier against extrusion.Elastomer is vulcanized to the base pipe, allowing the packer to have oneeffective annular seal.
Stampede™ Swellable Packers
1
[1] Lou, Y. & Chester, S. (2014) "Kinetics of swellable packers under downhole conditions." : 1450073.Int. J. Appl. Mechanics 06
[2] Flory, P.J. & Rehner Jr., J. (1943) "Statistical mechanics of cross-linked polymer networks: II. Swelling." : 521–526.
[3] Dassault Systèmes (2015) Providence, USA
[4] Treloar, L. R. G. (1944) “Stress-strain data for vulcanised rubber under various types of deformation.” : 59–70.
[5] Wagner, N. & Helfrich, R. (2016) "Topology and Shape Optimization of Structures under Contact Conditions.", 12-13 October 2016, Manchester, UK
J. Chem. Phys.
SIMULIA Abaqus 2016 Documentation,
Trans. Faraday Soc.
European Conference:Simulation-Based Optimisation
11
40
References
Planned Research Outcomes
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Design and manufacturing of tools for mechanical testing ofswellable elastomeric specimens and mechanical behaviour ofpackers in conditions resembling downhole operation.
Mechanical characterisation of swellable elastomers used byWeir Oil & Gas USA for packers through experimental studies inAdvanced Materials Research Laboratory (AMRL) in theUniversity of Strathclyde ( )
Implementation of an advanced material model ofhyperelasticity with moisture swelling in FE-code andidentification of corresponding material constants for it.
Linking of moisture swelling with the fluid pressure penetrationfeature in order to simulate realistic non-uniform materialexpansion, which is more intensive on the areas that are incontact with fluids.
Development of an optimisation procedures for available FEApackages (ABAQUS, ANSYS, MSC.Marc etc.) based onpackers downhole behaviour simulation using an advancedmaterial model.
Implementation of parametric optimisation - to find an optimallength of a packer, and non-parametric (shape and topology)optimisation - to find an optimal packer profile. For this purposeIsight (parametric) and Tosca Structure (non-parametric)optimisation engines will be used.
Optimised packers geometry is obtained by running theoptimisation studies on the regional supercomputer centre atthe Un ivers i t y o f S t ra thc lyde – ARCHIE-WeSt( ).
Provision of packers design recommendations and optimaldesigns based on a number of optimisation studies for variety ofdownhole conditions in form of tables and/or mathematicalrelations.
Delivery of the ABAQUS plugin to Weir industrial partners as aconventional tool for simulation-based design analysis andimprovement.
https://www.strath.ac.uk/amrl/
https://www.archie-west.ac.uk
Discussion
1. for fluid pressure penetration:To account for the asperities on the contacting surfaces, a critical contact pressure, below whichfluid penetration starts to occur, is introduced. The higher this value, the easier the fluid penetrates.The default value of the critical contact pressure is zero, in which case fluid penetration occurs onlyif contact is lost.
How much is it dependent on following?
pressure and type of fluid,
surface quality and material type of borehole,
type of packer elastomeric material.
2. in hourglass control:
Critical mechanical contact pressure
Amount of stiffness
�
�
�
Hourglassing is essentially a spurious deformation mode of a FE-mesh, resulting from the excitation of zero-energy degrees offreedom. It typically manifests as a patchwork of zig-zag orhourglass like element shapes, where individual elements areseverely deformed, while the overall mesh section is undeformed.This happens on hexahedral 3D solid reduced integration elementsand on the respective tetrahedral 3D shell elements and 2D solidelements.
Assigning stiffness to the finite elements is used to suppress hourglassing. Therefore, the followingquestions arise:
Can we relate this artificial stiffness to the "surface layer effect"?
How much stiffness is right to be assigned to the elements?
How do we measure the stiffness of the surface layer in elasmoters?
Which mechanical tests are needed? Indentation tests?
�
�
�
�
element stiffness critical contact pressure
fluid pressure
how related?
Introduction & Objectives
Swellable elastomeric seal is a type of specifically engineered packer that swell upon contact with wellbore fluids.Such packers have been widely employed in various oil-&-gas and minerals applications including slimming of welldesign, zonal isolation, water shut-off, and multi-stage fracturing. Downhole conditions are difficult to be reproducedusing physical testing environment, but feasible to be simulated in virtual environment using CAE software. A betterunderstanding of packers’ mechanical behaviour in downhole conditions would provide a higher confidence andimprovement of existing engineering design practices for manufacturing of packers. The numerical simulation can beincorporated into optimisation procedure searching for an optimal shape of packers with the goals to minimise the timeto seal the borehole and maximise the contact pressure between the seal and borehole. Such an optimisation wouldfacilitate the development of a packer with various designs optimised for different downhole conditions. The objectiveof this research project is to develop a design tool integrated into a CAE to implement parametric numerical studiesusing FEM simulation. However, development of such a CAE plugin is associated with a number of technicalchallenges specific to this class of multiphysics problems.
Hyperelasticity with swelling
The key component is an advanced material model comprising both hyperelasticity and moisture swelling. It has to consider two-wayinteraction between mechanical properties and swelling capacity. Implementation of such material model requires programming of aFortran subroutine for the user defined material using the Flory-Rehner theoretical background [2].
In polymer science Flory–Rehner equation is an equation that describes the mixing of polymer and liquid molecules as predicted by theequilibrium swelling theory of Flory and Rehner. It describes the equilibrium swelling of a lightly crosslinked polymer in terms ofcrosslink density and the quality of the solvent. The theory considers forces arising from three sources [2]:
The entropy change caused by mixing of polymer and solvent.
The entropy change caused by reduction in numbers of possible chain conformations via swelling.
The heat of mixing of polymer and solvent, which may be positive, negative, or zero.
The equation is written as
where is the volume fraction of polymer in the swollen mass, the molar volume of the solvent, is the number of network chain
segments bounded on both ends by crosslinks, and is the Flory solvent-polymer interaction term.
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ν n
χ2 1
1
V
� �1
2 23
2 2 1 2 1 2ln 1
2V n
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Adaptive remeshing
withoutadaptive
remeshing
withadaptive
remeshing
Non-uniform swelling can be associated with a localised increase ofmaterial volume. So it may cause a significant distortion of FE meshand result into analysis convergence problems. To overcome this, anadaptive mesh-to-mesh solution mapping (rezoning) may be required.
Fluid pressure penetration
The moisture swelling process isnot uniform and develops fromthe surfaces which are subject tofluid. Adsorption, which governsthe progress of swelling canoccur only at open surfaces.Therefore, the fluid pressurepenetration technique needs tobe involved into simulation. Thisis an automated application offluid pressure dependent onchanges of contact conditions.
3
2
Parametric study assumes going through a bignumber of different geometric configurations, lookingat material properties variation and different downholeconditions. This means a search for an optimalgeometry through a sensitivity study, which wouldresult into specific design recommendations for thegeometry of a packer. It is reasonable to automate theanalysis procedure through a Plugin with a convenientGUI, which provides access to the parameters ofgeometry, material, service conditions, etc.
ABAQUS plugin with GUI
4
Shape optimisation with Tosca Structure
2.0
original
optimised
contact area
R=
3.2
5
*dimensionsare in inches
pipe side
borehole side
0.7
5
0
1
2
3
4
5
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Conta
ct pre
ssure
(M
Pa)
Normalised length of contact area
original
optimised
Benchmark problem for leakage and extrusion
FE-simulation of Pressure penetration & leakage in packer
16.0
0
0.25
0.5
0.75
R =
3.0
R = 4
R = 4.5
packer
pipe
rock
endring
Max. Principal Strain
0.0680.1970.3250.4540.5820.7100.8390.9671.0961.2241.3521.4811.609
criticalcontactpressure4 MPa
fluid pressureto cause failure byextrusion ~ 14.2 MPa
*dimensionsare in inches
Strain
Max. Principal
0.0600.1060.1520.1980.2440.2890.3350.3810.4270.4730.5190.5650.611
Strain
Max. Principal
0.0640.1280.1910.2550.3190.3820.4460.5090.5730.6360.7000.7630.827
Strain
Max. Principal
0.0610.1520.2420.3330.4240.5140.6050.6960.7860.8770.9681.0581.149
Strain
Max. Principal
0.0550.1690.2840.3990.5140.6280.7430.8580.9721.0871.2021.3161.431
Strain
Max. Principal
0.0650.1940.3220.4510.5790.7080.8370.9651.0941.2221.3511.4801.608
Strain
Max. Principal
0.0660.2000.3330.4670.6000.7330.8671.0001.1331.2671.4001.5331.667
0 3 6 8 10 10.7
fluid pressure fluid pressure fluid pressure fluid pressure fluid pressure fluid pressure
criticalcontactpressure0.6 MPa
Max.PrincipalStrain
0.050.100.140.190.230.280.320.370.420.460.510.550.60
Max.PrincipalStrain
0.040.110.170.240.310.370.440.510.570.640.700.770.84
Max.PrincipalStrain
0.040.150.260.360.470.580.690.790.901.011.121.231.33
Max.PrincipalStrain
0.040.160.280.390.520.640.760.880.991.111.231.351.47
0 5 14 15 16.2
fluid pressure fluid pressure fluid pressure fluid pressure
Max.PrincipalStrain
0.040.180.330.470.610.760.901.041.191.331.481.621.76
fluid pressure
criticalcontactpressure1.0 MPa
