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Reservoir Compaction and Surface Subsidence

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During the depletion of reservoirs comprising high porosity formations, the stresses acting in the reservoir gradually increase as the depletion increases. If the maximum 'deviatoric' stress magnitudes remains below the rock strength, the rock behaves elastically with relatively small strains and deformations. Once these stresses exceed the rock strength the deformations become much larger, are plastic in nature, and irreversible.

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These plastic deformations are the cause of significant reservoir compaction and subsidence. This has been experienced in numerous fields since the early 1920s, and continues today.

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Addis & Yassir have experience of working on a number of reservoir compaction and subsidence evaluations, starting with the landmark reservoir compaction and subsidence estimate for the Ekofisk Field in 1984/5, and were part of the first team to determine the expected reservoir subsidence of at least 6m. We have experience of defining rock testing programmes, compressibility assessments, rock constitutive modelling, analytical screening assessment of the reservoir compaction as well as more advanced 3D compaction and subsidence modelling.

 

Currently, the depletion and blowdown of mature fields, as well as depletion of HP/HT fields, can be monitored using the deformation and stress changes accompanying reservoir compaction and the overburden deformations using 4D time lapse seismic technologies, fibre optic technologies as well as more standard well monitoring of casing collar monitoring, and nuclear bullet monitoring.  Surface monitoring and asset risk assessment for both compacting field or fields experiencing 'surface heave' (the opposite of subsidence accompanying injection strategies) use a combination of GPS surface monitoring and InSar related satellite.

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These technologies are used to help calibrate compaction and subsidence estimates from well and field-wide analyses.

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Publications

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  1. Bauer, A., Lehr, C., Korndorffer, F., van der Linden, A., Dudley, J., Addis, T., Love, K., and Myers, M. 2008. Stress and pore-pressure dependence of sound velocities in shales: Poroelastic effects in time-lapse seismic. SEG Extended Abstract, SEG annual meeting 2008, Las Vegas, Nevada.

  2. Yassir, N., Lehr, B. C., van der Linden, A. J., Korndorffer, F. and Dudley, J.W. 2006. The effect of stress path on the sonic response of the Pierre shale. ARMA/USRMS 06-1067. Golden Rocks 2006, The 41st U.S. Symposium on Rock Mechanics (USRMS), 17-21 June, Golden, Colorado. Paper presented in Golden Rocks and in the FORCE Workshop in Stavanger (September), 

  3. Lehr., B. C., Yassir, N., Korndorffer, F., van der Linden, A. J., Dudley, J. W. and Kenter, K. 2006. The dynamic response of shale for reservoir surveillance. EP Journal of Technology Special Issue 7021 (Reservoir Surveillance).

  4. Jones, M. E., Leddra, M. J., Goldsmith, A. S. and Yassir, N. A. (1991) Mechanisms of compaction and flow in porous sedimentary rocks. In: Neotectonics and Resources, Cosgrove, J. and Jones, M. (eds.): 16-42.

  5. Addis, M.A.1989.  The behaviour and modelling of weak rocks.  Proc. Int. Rock Mechanics Symp.: Rock at Great Depth, Pau, September 1989, V. Maury and D. Fourmaintraux (eds.), Vol. 2, pp.899-905.

  6. Addis, M.A.and Jones, M.E. 1989.  Mechanical behaviour and strain rate dependence of high porosity chalk.  Proc. Int. Chalk Symp., Brighton, September 1989; pp.239-244.

  7. Jones, M.E., Leddra, M.J. and Addis, M.A. 1987.  Reservoir compaction and surface subsidence due to hydrocarbon extraction. Offshore Technology Report, OTH 87 276.  Department of Energy, HMSO, 1987.

  8. Addis, M.A.1987.  Material metastability in weakly cemented sedimentary rocks.  Memoirs of the Geological Society of China, Vol. 9, pp.495-512.

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