Variability in formation pressure during drilling, well tests, injection operations, oil and gas recovery are accompanied by changes in rock permeability and consequent changes in well productivity, oil recovery factor, and land subsidence. A number of laboratory experiments have demonstrated that decreasing the rock permeability may be defined as relative permeability in connection with fluid replacement in rocks. Other experiments have demonstrated the same results by increasing grain-to-grain stress for the clastic rocks and fracture closing for the fractured carbonate reservoirs. Assessment of these factors can be based on the relationship between well production and well bore pressure drop, and this interaction can be demonstrated by the results of test operations and production history. In order to segregate these processes, it is necessary to study a reservoir and fluids as an inclusive system. The rate of compaction in the different parts of a reservoir depends on hydrocarbon extraction and maintenance of reservoir pressure that can be changed through injection of water or gas. Phase transition in the fluid system can also depend on formation pressure. Reservoir compaction provides the additional drive energy for production, whereas decrease in permeability deteriorates the condition of field development. These effects can be considered for both low and high permeability reservoirs.
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