Numerical Investigation of Total Stresses Change in Oil Reservoirs due to Extraction, Considering Non-linear Behavior for the Reservoir Rock

Document Type : Original Article

Authors

1 Master's student of geotechnical engineering, Sharif university of technology

2 Geotechnical engineering department, faculty of civil engineering, Sharif university of Technology

Abstract

As a result of extraction from underground oil reservoirs, the pore pressure in the reservoir decreases and the effective stress increases accordingly. Field measurements in the past two decades have shown that in addition to the change of effective stress, the total horizontal and vertical stress field can also change in and around the reservoir. As a result of the settlement that occurs at the upper part of the reservoir due to the consolidation phenomenon, the stability of this area is reduced and it causes “Stress Redistribution” inside and around the reservoir. The mechanism of stress redistribution is attributed to the “Stress Arching” phenomenon. By the stability reduction at the roof of the reservoir due to the compaction, this area will no longer bear the whole over-burden weight. A part of the over-burden is transferred to more stable areas such as the sides of the reservoir. The current research aims to investigate how the total stresses change around oil and gas reservoirs due to the extraction by a fully-coupled hydro-mechanical (HM) simulation. In order to simulate the process of fluid extraction from the reservoir and to consider the effect of production operations on the geo-mechanical properties of the depleting zone, a Non-linear elastic constitutive model has been used. In this research, a comparison is made between the amounts of the total stresses in the surrounding rock of three different reservoirs in terms of width. In addition, the effects of the difference between the initial stiffness of the reservoir rock and the surrounding medium on the intensity of the stress arching phenomenon are investigated by considering three different stiffness ratios. The conducted studies show that the changes in the total stresses are significant and it is necessary to consider their effect on aspects of the production and the development of field.

Keywords

References

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Journal of Petroleum Geomechanics
Volume 6, Issue 1
May 2023
Pages 13-31

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