Subsurface and Surface Deformation Analysis. Calibration with Field Observations

Transcription

1 Presentation to GNS Workshop on Environmental Impacts of Geothermal Development by Michael S. Bruno, PhD, PE GeoMechanics Technologies (formerly Terralog Technologies USA) Subsurface and Surface Deformation Analysis Simulation Methods Calibration with Field Observations Surface Displacement Measurements Subsurface Well Deformation Measurements Inversion of Measured Surface Deformations to Evaluate Subsurface Source Mechanisms Discussion

2 The weight of sediments overlying an oil or gas reservoir is supported partially by the rock matrix and partially by the pore fluid pressure. When fluid or gas is produced more of the overburden load is transferred to the rock matrix, resulting in reservoir compaction. Changing temperature will create additional compaction or expansion proportional p to the temperature change times the coefficient of thermal expansion. The subsurface dilation (or compaction), H, of a reservoir element of initial thickness, H, can therefore be estimated as: DH = * T*H H + Cm* P*H

3 Lost Hills, California Interferogram 3D or 2D Geomechanical Modeling to assess overburden stress and deformation details are best when calibrated against field data

4 Compaction and shear strains in a reservoir and resulting surface deformations can be estimated by techniques of varying complexity: 1. Relatively simple analytical models and spreadsheets 2. 3D influence function models (tied to reservoir simulation) 3. 2D cross-section geomechanical models (typically in parametric mode) 4. 3D geomechanical reservoir models and wellbore models Simple analytical estimates: S = 2 (1- )[H (R 2 +(D+H) 2 ) (R 2 +D 2 ) 0.5 ](Cm P+ T) ( subsidence ) c = 05(1 0.5(1+cos2 ) (Cm P+ T) ; (casing compression) c = 0.5(sin2 ) (Cm P+ T) ; ( casing shear )

5 Three-dimensional elastic models: Reservoir production layers can be discretized into a 3-D assembly of elements, which can often match reservoir simulation grids. Analytical solutions are then available to estimate displacements and strains induced on any well trajectory or on any horizon due to the combined influence all compacting reservoir cells. ij (x,y,z) = F ij (x-x x n,y-y y n,z-z z n, V n ) Layer Thickness (ft) Northing Easting

6 Apply geomechanical reservoir models or simple analytic equations to estimate t compression and shear along well trajectories Strain Plot Easting (ft) Depth Z Depth (ft) B45 B2 B3 B Strain

7 Y X Influence Function Technique Applied to Deepwater Gulf of Mexico Compaction Y Strain exx Strain eyy Strain ezz X De epth (fttvdss) Sigh(D)-122 perforation: ftTVDss compression tension -2.00% -1.50% -1.00% -0.50% 0.00% 0.50% 1.00% 1.50% MI623-C1 Strain ( )

8 2D FE Cross-Section Models to analyze Subsidence/Heave, Faulting, and Bedding Plane Slip 0.0 m 0.1 m 0.2 m Block Group Tertiary Cretaceous Jurassic Kungurian Reservoir Early_Paleozoic Vertical Displacement Within Model Total Vertical Displacement due to Pressure + Temperature Change (m)

9 Geomechanical Issues in Thermal Operations - Reservoir compaction and expansion - Bedding plane slip and associated well damage - Induced fracturing and faulting in caprock - Non uniform, anisotropic changes in permeability and mobility

10 Recommended Modeling Approach for Subsidence and Caprock Integrity Analysis 1. Start with detailed reservoir simulation model (if available) 2. Embed this grid into 3D influence function and/or FE type geomechanical model 3. Use log and core data and well test data to define geomechanical properties 4. Apply pressure and temperature results from reservoir simulation as input to geomechanical model (essentially one-way coupling) 5. Perform combined geomechanics/thermal simulation to assess induced stresses and deformation in overburden formations 6. Calibrate model against historical surface deformation data (if available) 7. Assess shear and tensile stresses induced in the reservoir and caprock by thermal injection and production operations. 8. History match for period over which field data is available, then perform forward simulations (with periodic updates).

11 Types of Field Measurements for Deformation 1. Precision level surveying of benchmarks with field crews 2. GPS monitoring (valuable for combined vertical and horizontal movements) 3. Satellite interferometry 4. Surface and shallow wellbore tiltmeters 5. Well deformation and damage surveys

12 Reservoir Compaction and Expansion: H/H = Cm P+ T Lost Hills, California Interferogram

13 +285 mm +200 Cold Lake Cyclic steam mm Vertical displacements (mm) over 86 days km -165 heave subsidence mod. Stancliffe & van der Kooij, AAPG 2001

14 WELL AGI1 DEPTH (m) 120 Mudstone & Sand 140 Oil Sand WELL AGI3 160 Limestone Phase A I Deflection (mm) Deflection (mm) ref Collins (1994); ref. Ito & Suzuki (1996)

15 Some Challenges and Approaches to Geomechanical/Thermal Simulation In general, there are no adequate models for fully coupled multiphase flow simulation and geomechanical simulation Therefore, a combination of models with one-way coupling provides better accuracy Detailed pressure/temperature simulation generally only available for reservoir formations ( primarily because that is where history matching can be done ) Therefore, only heat conduction simulation applied to overburden Detailed geomechanical data rarely available for overburden formations and full 3D modeling of formation and overburden problematic ( ~ 1,000,000 grid elements) Therefore, apply a limited full 3D model (1/4 of field), or a series of 2D sections in combination with influence function modeling.

16 3D Geomechanical Model Created to Simulation Steam Injection and Production for NE Quadrant of Pad 40 (where surface deformation data is available) Reservoir Sections

17 Surface and Subsurface Deformation Modeling TVD from Surface (m) TVD from Surface (m) Bulk Density (kg/m^3) Acoustic Velocity (micro-sec/m) Bulk density log and Sonic log from well 1AA031 and the resulting estimated Young s Modulus ace (m) TVD from Surfa E (GPa)

18 FLAC3D 2.10 Step 5701 Model Perspective 11:17:58 Tue Feb Center: Rotation: X: 3.602e+002 X: Y: 3.142e+002 Y: Z: 2.919e+002 Z: Dist: 2.374e+003 Mag.: 0.7 Ang.: Plane Origin: Plane Normal: X: 0.000e e+000 X: 0.000e e+000 Y: 0.000e+000 Y: 0.000e+000 Z: 5.100e+001 Z: 1.000e+000 Job Title: pad50_inj_jan30.dat: Peace River Pad_50 NE Section 3D Reservoir Modeling m Block Group Axes quaternary base_fish paddy_cadotte notikewin falher wilrich_sandstone wilrich_shale bluesky_sandstone detrital dblt debolt Linestyle Contour of Temperature (518943, ) Y Z X 0 sea level m (519543, ) Terralog Technologies USA, Inc. Arcadia, CA, 91006, USA (518943, ) Geomechanical model for Pad 50 NE Sector with dimension shown. Also showing sample contour plot of temperature distributions at reservoir level during injection period.

19 FLAC3D 2.10 Step 5501 Model Perspective 14:37:10 Thu Feb Job Title: inj_ _sh-sv_jan22: Peace River Pad_40 NE Section 3D Reservoir Modeling Center: Rotation: X: 6.859e+002 X: Y: 6.383e+002 Y: Z: 1.619e+002 Z: Dist: 4.583e+003 Mag.: 1.25 Ang.: Block Group quaternary base_fish paddy_cadotte notikewin Axes falher wilrich_sandstone wilrich_shale bluesky_sandstone detrital debolt Linestyle Y Z X Terralog Technologies USA, Inc. Arcadia, CA, 91006, USA Contour of reservoir dilation due to steam injection from to (deformed mesh magnified by a factor of 100).

20 Measured surface changes during 1 st production period from to Coordinate Y Coordinate X

21 mm Coordinate Y Y - Coordinate (m) Coordinate X X - Coordinate (m) Measured Simulated

22 QA-9 QA-13 QA-8 Water treatment and Steam Raising Plant QA-2 Aa Ab Ac Ad Ba Bb Flowline QA-17 QA-15 Dd Bc QA-10 fractu ture GOC 238 mss QA-20 QA-19 QA-18 QA-14 QA-16 QA-7 Steam injector Producer Observation well Monitoring well Dc Db Da Cd Cc Ca Cb Bd

23 Well QA-1H Sonic Log TVDss (m) TVDss (m m) Upper UER Middle UER Base UER Natih C Natih D Natih E Natih F Natih G Nahr Umr Shuaiba Kharaib Lekhwair Habshan Acoustic (ms/m) Lateral Distance (m)

24 FLAC3D 2.10 Step Model Perspective 11:28:35 Thu Jan Job Title: Yr25-Yr00_dT_Jan18: Qarn Alam Caprock Integrity Study, NE-SW X-Section Center: Rotation: X: 6.555e+003 X: Y: 1.000e+001 Y: Z: e+002 Z: Dist: 3.319e+004 Mag.: 3.05 Ang.: Block Group fars upper_uer middle_uer base_uer natih_c natih_d natih_e natih_f natih_g nahr_umr shuaiba kharaib lekhwair habshan reservoir m 0 m

25 D Geomechanical Model 3D Geomechanical Model Depth (m) ace Displacement (m) Surfa X - Easting (m) Lateral Distance (m) Ang.: Contour of Z-Displacement Magfac = 1.000e+003 Exaggerated Grid Distortion e-002 to e e+000 to e e-002 to e e-002 to e e-002 to e e to e e-001 to e e-001 to e e-001 to e-001 Interval = 2.5e-002

26 E E Field Data 8.00E+03 Displacement (mm) Model Results Sxz (kpa) 6.00E E E E E E E E+03 E-W Field Coordinates (m) -1.00E Lateral Distance (m)

27 Surface Deformation Analysis/Inversion Provides Good Estimates for the Location and Geometry of Subsurface Compaction Sources Bruno, M.S., (1998): Identifying Source Mechanisms Responsible for Subsidence Through Inversion of Measured Surface Displacements, Current Research and Case Studies of Land Subsidence, J. Borchers (ed), Land Subsidence, Case Studies and Current Research, Special Pub. No 8, Association of Engineering Geologist, 1998, pp Bruno, M.S. and Bilak, R.A., (1994): Cost-effective monitoring of injected steam migration using surface deformation analysis, SPE 2788, Proc. West. Reg. Mtg. of the Soc. Pet. Eng., March 23-25, 1994, pp Shape and extent of surface deformation indicates depth and extent of subsurface source mechanism

28 General Inversion Approach: 1. Discretize subsurface compaction (dilation) zone into source elements, which may be grid volumes (for distributed temp and pressure) or planes (for fractures or faults). 2. Develop 3D influence functions (or FE model) to predict surface deformation due to subsurface effects U i = f( P, T, x, y, z); U i,j = g( P, T, x, y, z); 3. Measure surface deformations (ideally vertical, horizontal, and tilt) 4. Iterate over a range of constrained subsurface parameters and pressure/temperature distributions to minimize error between measured and predicted values, identifying subsurface source mechanisms.

29 Contour of Z-Displacement Magfac = 0.000e e-002 to e e-002 to e e-002 to e e-002 to e e-002 to e e-002 to e e-002 to e e-002 to e e-002 to e e-003 to e e-003 to e e-003 to e-003 Interval = 2.5e-003 Terralog Technologies USA, Inc. Arcadia, CA Simulated vertical displacement contours with slipping fault Simulated vertical displacement contours with slipping fault extending through Cretaceous

30 Eleva ation Change (m) Benchmarks: May 01 - Sep 02 No-fault Model Truncated Fault Model Surface Fault Model Distance (m) Comparison of measured and simulated subsidence patterns for period from May, 2001 to September, 2002

31 Recommended Modeling Approach for Subsidence and Caprock Integrity Analysis 1. Start with detailed reservoir simulation model (if available) 2. Embed this grid into 3D influence function and/or FE type geomechanical model 3. Use log and core data and well test data to define geomechanical properties 4. Apply pressure and temperature results from reservoir simulation as input to geomechanical model (essentially one-way coupling) 5. Perform combined geomechanics/thermal simulation to assess induced stresses and deformation in overburden formations 6. Calibrate model against historical surface deformation data (if available) 7. Assess shear and tensile stresses induced in the reservoir and caprock by thermal injection and production operations. 8. History match for period over which field data is available, then perform forward simulations (with periodic updates).