According to Novi Labs, a well data analytics company, as of April, 2022, 94,000 horizontal shale oil wells had been placed into production in the 5 major US shale oil basins. Oil production from these wells is characterized by high initial rates and steep declines, with well lives of 9 to 16 years. Oil recovery factors, as a percentage of oil in place, range from 2.5 to 8 percent, leaving the vast majority of oil resources unrecovered. Shale oil EOR is in its infancy, with only 49 permitted projects involving a few hundred wells. 36 of these EOR projects are in the Eagle Ford shale. Prior publications have provided information on this activity, almost all of which involve cyclic injection of natural gas, or Huff-n-Puff EOR. Incremental recoveries have been projected to range from 10% to 80% of primary EUR.
Our objective is to describe two novel shale oil EOR methods that may provide superior incremental shale oil recovery of 100 to 200% of primary EUR in the DJ Basin Niobrara shale. We have developed two superior shale oil EOR methods that utilize a triplex pump to inject a liquid solvent mixture into the Niobrara shale reservoir, and methods to fully 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.
Compositional reservoir simulation modeling of the processes in a production and pressure history-matched horizontal DJ Basin Niobrara well indicates recoveries of 180% to 360% of primary EUR may be achieved. These processes have numerous advantages over cyclic gas injection - shorter injection time, faster and greater oil recovery, lower risk of interwell communication, lower cost of production, elimination of the need for artificial lift, and lower GHG emissions and water costs. These processes should work in all US shale oil plays, and have been successfully field tested in some. If implemented early in the well life, their application may enable recovery of more oil, faster, and preclude the need for artificial lift, resulting in shallower decline rates and much greater reserves. The processes also emit less GHG emissions and have lower water costs per barrel than primary recovery.