Increasing Recovery Potential in a Tight Oil Reservoir



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Low estimates for primary oil recovery from tight oil reservoirs ranging from 5 to 10 percent prompt growing interest in enhanced oil recovery. The key to the success of any displacement process is assuring no connection exists between hydraulic fractures in injection and production wells. Well patterns likely to succeed feature positioning injector hydraulic fractures between the hydraulic fractures of producer hydraulic fractures. This study compares economics and recovery factors for primary, huff-n-puff, and displacement strategies for a multi-well pattern capable of providing many simultaneous planar displacements. This study addresses enhanced oil recovery for tight oil reservoir with and without secondary fractures. We use carbon dioxide as the injection fluid. We use the GEM compositional simulator developed by Computer Modelling Group to model primary production, huff-n-puff, and displacement for two planar fractures using formation and fluid properties typical for Eagle Ford play. Simulations apply a dual porosity model to consider varying secondary fracture extents from 10% to 50% of the distance between injection and production fractures. Multiplying by the number of plane-to-plane displacements in the multi-well pattern scales up to the field application. The presence of secondary fractures greatly affects the enhanced oil recovery efficiency. Oil recovery by gas flooding is less in the case where the secondary fractures are distributed throughout the field as compared to those in which natural fractures are activated near the wellbore. In contrast, the presence of secondary fractures greatly enhances oil recovery by huff-n-puff. The economic analysis indicates that the presence of secondary fractures affects the performance of gas flooding but still it performs better than huff-n-puff when the secondary fracture distribution remains below 50%. As the percentage of secondary fracture in the field increases, the nature of the net present value curve reverses indicating that the performance of huff-n-puff is superior to that of the gas flooding.



Gas displacement, Huff-n-puff, Secondary fractures