Geomechanical upscaling and modeling of interbedded shales within reservoirs
Date
2012
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Abstract
The concept of compaction of reservoirs, mainly sandstone layers, has often been studied and the methods for assessments of its impact on the subsidence have been developed in the oil and gas industry. However, the effect of the interbedded shales compaction on the subsidence has been rarely discussed in reservoir and geomechanical simulation studies for surface subsidence and reservoir compaction prediction. This study attempts to assess the effect of interbedded shales layers ( which are on a sub-grid scale) on the compaction behaviour of the reservoirs. The results can be considered as a "geomechanical upscaling" technique which can be used to make more accurate prediction of reservoir compaction and surface subsidence. The specific parameters considered are the geometry and permeability of the shale laminations, reservoir permeability, Young's modulus, Poisson ratio, reservoir average pressure, shale's pressure lag during reservoir depletion and desired flow rate. Parametric and numerical calculations, based on a semi-analytical solution and finite-difference solutions of a single element for uniaxial displacement conditions have been used to develop an upscaling formula which was implemented in the geomechanical simulator based on the Net-to-Gross (NTG) concept. The NTG is the ratio that represents the total thickness of the productive layers divided by the total (gross) thickness of the reservoir. In reservoir characterization and simulation, the NTG concept is applied to each computational cell. The results of the field application show that the inclusion of the NTG effect contributes a significant subsidence reduction for Neptune field due to the pressure lag of the shale layers.
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Bibliography: p. 102-109
Some pages are in colour.
Some pages are in colour.
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Citation
AlRuwaili, K. M. (2012). Geomechanical upscaling and modeling of interbedded shales within reservoirs (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca. doi:10.11575/PRISM/5053