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

Mvomo Ndzinga Edouard,Nguu D Muchiri,Chinedu J Okere,Pingchuan Dong,Fame N Jacques,Gao Xiaodong,Abakar Y Adoum,Samba K Prosper,Luc Y Nkok

doi:10.1007/s13202-021-01369-x

Mvomo Ndzinga Edouard, Nguu D Muchiri + Show 7 more

Open Access

https://doi.org/10.1007/s13202-021-01369-x

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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.

Highlights

The ever-increasing world population has resulted in a corresponding rise in global energy consumption (Alina et al 2019)
The ratio 3:1 provided the most efficient oil recovery, which can be attributed to the theory that explains that gases have relatively high mobility compared to oil; breakthrough of gases will occur
After optimization, the recovery factor for TAG, double alternating gas (DAG), and SG was 84.74%, 78.61%, and 63.14%, respectively. This implies that the TAG injection enhanced oil recovery (EOR) process increased the percentage oil recovery factor of the DAG and SG by approximately 8% and 34%, respectively

Summary

Introduction

The ever-increasing world population has resulted in a corresponding rise in global energy consumption (Alina et al 2019). Journal of Petroleum Exploration and Production Technology and 22%) remained, in that order, the top three sources of global energy supply. All this huge amount of energy had impacted negatively on the environment and has resulted in global warming due to CO2 emissions (Sher et al 1998). Notwithstanding, several studies have projected that fossil fuels will remain dominant in the future global energy supply (Alina et al 2019; Okere et al 2020; 2021a, b; He et al 2021). To meet the global demand for fossil fuels ( crude oil), efficient enhanced oil recovery (EOR) techniques are necessary (Tawfik and Mukaila 2019; 2021; Okere et al 2020)

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