Single Well Completion and Management Strategies for Enhanced Recovery of Tight Oil Using Miscible Gas Injection

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Tight oil production relies on the multiple transverse fracture horizontal well completion design with 50 or more parallel propped hydraulic fractures distributed along a long horizontal well. Less than 10% primary oil recovery from these wells creates a strong incentive for enhancing recovery from tight oil reservoirs in the US. Attempts at well to well displacement using water and gas as injection fluid failed in tight oil largely due to short-circuits along fractures connecting adjacent injection and production wells. As an alternative, operators have tried alternating miscible gas injection with production in a single well mimicking the huff-and-puff (HAP) technique that originated with steam injection in heavy oil wells. HAP field tests in the Eagle Ford play have shown limited success. To improve the production performance of HAP, this research focused completion designs enabling displacements between alternating injection and production fractures in a single well. The single well configurations used in this study designate alternating fractures along the horizontal well as either injection or production. Two strategies are studied. The first strategy considers a continuous injection and production process in a single-well alternating simultaneous injection and production (SWASIP) configuration. The second strategy alternates injection and production as a single-well alternating production (SWAP) configuration. We use miscible carbon dioxide as the injection fluid. We use the GEM compositional simulator developed by Computer Modelling Group to model SWASIP and SWAP performance in a heterogeneous reservoir. We described the downhole completion components including monitoring and control devices required for managing many simultaneous displacements in the single well. SWASIP well management requires action in the event of a displacement short circuit, such as a cement leak. In contrast, the SWAP well configuration is more robust and will not suffer significant productivity or performance loss in the event of a displacement short circuit. Both SWASIP and SWAP significantly enhance oil recovery over HAP. SWAP recovery requires a longer time than SWASIP. However, SWASIP requires additional completion equipment for the well management that renders SWAP likely to be the more cost effective choice.

EOR, Tight oil, Gas injection