Advantage of miscible fluid injection and tight oil production through a single-well alternating production-injection procedure over other single-well EOR methods

Abstract Tight oil reservoirs on primary production show less than 10% recovery in the US, creating a strong incentive to develop and apply suitable techniques for enhanced recovery. Enhanced oil recovery (EOR) techniques applied to tight oil include huff-and-puff (a cyclic injection-soaking-production approach) and flooding (continuous injection of an oil displacing fluid). Both approaches have seen limited success because of fundamental reasons. Huff-and-puff (HnP) requires substantial fluid transfer into and out of a tight oil formation during each injection-soaking-production cycle, a task that is inherently challenging because of low formation permeability. Similarly, flooding using fractured horizontal wells for injection and production faces the challenge of short-circuits created by fractures communicating from injector to producer. An alternative EOR approach for tight oil is to rely on a single well with a dual-conduit completion that allows for continuous injection and production through spatially alternating injection and production fracture sections, separated from each other by packers. This approach risks effective short-circuiting through cement leaks or high-conductivity secondary fractures. An alternative that mitigates these risks is to use a single-tubing completion featuring multiple remotely activated valves that can asynchronously inject into and produce from the spatially alternating fracture sections in a single-well alternating production (SWAP). While the well concepts considered in this work have been previously presented, operating aspects and quantitative effects of various reservoir, well completion, and operational variables have not been studied. This paper investigates the effects of reservoir permeability, secondary fractures, diffusion coefficient, cement leaks, resolution of completion control (fractures per section), and the injection and production cycling duration on SWAP performance and compares the performance of SWAP to HnP and the single-well alternating simultaneous injection and production (SWASIP) concept. Computer simulation is used to identify the merits of SWAP and compare it to SWASIP and HnP. Overall, SWAP appears to offer a cost-effective approach to increasing recovery from tight oil formations and deserves further development.