Improving Oil Recovery while Helping to Achieve Net Zero Emissions from Shale Reservoirs

Abstract

Abstract Shale reservoirs will help to meet oil demand that is forecasted to continue increasing for several years. Oil recovery from shales is low and has been reported to range between 5 and 10%. The objective of this paper is to show how oil recovery from shale can be improved while simultaneously reducing CO2 emissions, contributing thus to the goal of a Net-Zero future. The proposed methodology shows how oil recovery from shales can be increased while simultaneously storing CO2 in undepleted (as opposed to depleted) shale oil reservoirs, and consequently contributing to a future with Net-Zero emissions. The methodology is developed with the use of reservoir simulation, and is achieved by performing the following procedure: (1) start huff 'n' puff CO2 injection, 2 or 3 years after the well goes on oil production; thus, the shale reservoir is undepleted, (2) store CO2 gradually in the shale reservoir during the huff periods, and continuously once the huff'n'puff project is finalized. The simulation model includes a history match period with actual production data from a pilot horizontal well, and a forecast period with huff 'n' puff CO2 injection. Two cases, one with diffusion and one without diffusion are carried out for evaluating the molecular diffusion effect. The initial pressure is never exceeded. Our literature survey indicates that the methodology proposed in this paper has not been considered previously in the geoscience of petroleum engineering literature. The proposed approach will help to achieve Net-Zero emissions by storing CO2 in undepleted shale reservoirs while simultaneously increasing oil production. This win-win combination, to the best of our knowledge, is novel.