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This paper presents a case study of a geomechanical evaluation used in sand management decisions in a mature oil field offshore Malaysia. Elements of a field-wide geomechanical model were constrained from various data types from a vast number of wells drilled in 1980s and new re-development wells drilled in 2013–15. Extensive production from multilayer stacked reservoirs has resulted in large pressure depletion; hence drilling of infill wells and water injection is used to enhance oil production in the field. A poroelastic analytical sand production prediction approach was used to investigate the risk of sanding in both existing and new wells under high depletion conditions. Historical production data were used to calibrate and verify the sand production predictions. The analysis also included rock mechanics laboratory experiments on core samples saturated with mineral oil and brine to characterize the amount of rock weakening in the presence of water, which showed target sandstones may weaken by 13–16% when they are exposed to brine compared to the mineral oil saturated condition. The results showed a very low risk of sanding for the target oil reservoirs over the field life, using expected final reservoir pressures of 100 psi for cased and perforated completions drilled in any direction. The risk of sanding for open holes, however, was found to be slightly higher with further depletion from the current reservoir pressures, particularly with the likely rock weakening effect under water production and injection conditions. Moreover, hole instability and solids production resulting from the failure of the shale interbeds under low downhole pressures and water production could be a well integrity risk, jeopardizing production in open hole completions. The sand production prediction model is used to identify the optimum completion strategy in new wells considering the strength of target reservoir rock, well trajectory, and reservoir pressure and production conditions on a well by well basis. For most planned wells, cased hole completions with oriented and selective perforations appeared adequate to mitigate the sanding risks in both production wells and water injectors. Sand-free production to date from recently-drilled cased and perforated infill wells confirms the accuracy of the pre-drill sanding evaluation and sand management decisions.

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