Oil and gas production via horizontal wells with multistage fracture stimulation treatment completions in the Cretaceous shales of the Powder Rivers Basin of eastern Wyoming began in 2009. Since then, over 1500 horizontal shale oil wells have been completed and placed into production. There are multiple shale formations producing, including the Niobrara, Parkman, Turner, Sussex and Mowry. The Turner shale has proven to be a prolific producing formation and an important shale oil resource in the Powder River Basin, with an estimated 50-100 Billion barrels of oil in place.
Pressure depletion primary oil recovery from the Turner shale, similar to other shale oil plays, is very low, only about 5-8% of the oil in place in the drainage area of these horizontal shale wells. Thus there is a tremendous amount of oil remaining at primary production depletion that may be recovered via enhanced oil recovery (EOR) processes.
This paper describes the use of a compositional reservoir simulation model to assess two novel and proprietary shale oil EOR processes in a production history matched horizontal well producing from the Turner shale. The paper illustrates how these proprietary shale oil EOR processes may be implemented to significantly enhance oil recovery while reducing the cost per barrel of production.
These novel shale oil EOR methods, named SuperEOR and UltraEOR, utilize a triplex pump to inject a liquid solvent having a specific composition into the shale oil reservoir, and a method to recover the injectant at the surface for storage and reinjection. The processes are fully integrated with compositional reservoir simulation to optimize the recovery of residual oil during each injection and production cycle. These patented shale oil EOR processes have numerous advantages over cyclic gas injection – greater oil recovery in shorter time, lower cost than primary production, lower risk of interwell communication, optimization via integration with compositional reservoir simulation modeling, and lower environmental impact. If implemented early in the well life, their application may preclude the need for artificial lift, and may produce substantially more oil sooner, resulting in a shallower decline rate and greater recovery of reserves. The SuperEOR process has been proven successful in the Eagle Ford shale since late 2022, where it recovered 44% more oil than its prior cumulative recovery in the first 11 months of EOR operation.
Compositional reservoir simulation modeling of these novel processes in the modeled Powder River Basin Turner shale EOR project well indicates the SuperEOR and UltraEOR processes may increase oil recovery by more than 2X and 4X a wells' cumulative primary production in 40 years of operation, respectively.