Optimization of triple-alternating-gas (TAG) injection technique for enhanced oil recovery in tight oil reservoirs

Abstract

After single-gas (SG) injection operations in tight oil reservoirs, a significant amount of oil is still unrecovered. To increase productivity, several sequencing gas injection techniques have been utilized. Given the scarcity of research on multiple-gas alternating injection schemes, this study propose an optimized triple-alternating-gas (TAG) injection for improved oil recovery. The performance of the TAG process was demonstrated through numerical simulations and comparative analysis. First, a reservoir compositional model is developed to establish the properties and composition of the tight oil reservoir; then, a suitable combination for the SG, double alternating gas (DAG), and TAG was selected via a comparative simulation process. Second, the TAG process was optimized and the best case parameters were derived. Finally, based on the oil recovery factors and sweep efficiencies, a comparative simulation for SG, DAG, and TAG was performed and the mechanisms explained. The following findings were made: (1) The DAG and TAG provided a higher recovery factor than the SG injection and based on recovery factor and economic advantages, CO2 + CH4 + H2S was the best choice for the TAG process. (2) The results of the sensitivity analysis showed that the critical optimization factors for a TAG injection scheme are the injection and the production pressures. (3) After optimization, the recovery factor and sweep efficiency of the TAG injection scheme were the best. This study promotes the understanding of multiple-gas injection enhanced oil recovery (EOR) and serves as a guide to field design of gas EOR techniques.

New Trends in Biosurfactants: From Renewable Origin to Green Enhanced Oil Recovery Applications

“…Solar-generated steam in EOR is another method that uses concentrating solar power technology to produce steam. Gas injection methods, which serve as a main EOR method in fractured-vuggy carbonate reservoirs, involve injecting gases like carbon dioxide or nitrogen into the reservoir to increase pressure and displace oil [ 87 ]. In terms of environmental impact, chemical-microbial EOR methods can pose challenges due to potential groundwater contamination.…”

“…Thermal EOR methods also face environmental challenges, such as cyclic fluctuations in steam injection rate associated with sunlight hours and seasonal variations, which challenge this technology from becoming a standalone solution [ 84 ]. Gas injection methods have been shown to provide major contributions during EOR, including crude-oil viscosity reduction, thermal expansion, and crude oil vaporization [ 87 ].…”