Effects of miscible degree and pore scale on seepage characteristics of unconventional reservoirs fluids due to supercritical CO2 injection

Hao Chen, Xiliang Liu, Chao Zhang, Xianhong Tan, Ran Yang, Shenglai Yang and Jin Yang

Energy, 2022, vol. 239, issue PC

Abstract: Supercritical CO2 (ScCO2) injection is a potential way to enhance oil recovery (EOR). The displacement effect varies significantly with the difference of miscible degree and pore scale. However, studies in this field are rarely reported. In this paper, relative permeability curves of three miscible types are firstly measured. Interestingly, the ultimate oil recovery of near-miscible flooding is found to be comparative with that of miscible flooding due to the obvious decrease of gas relative permeability under higher residual oil saturation. On this basis, four main zones in the vicinity of oil-ScCO2 contact are divided in view of the multiple contact miscibility mechanism. A new threshold pressure gradient (TPG) considering both pressure sensitivity and oil properties, is proposed as the indicator of the seepage capacity for the reservoir fluids. The seepage resistance of different cores is greatly reduced due to the ScCO2 injection, especially for the permeabilities less than 5 × 10−3 μm2. The modified TPGs decreased exponentially with the increase of mobility indicating that the seepage capacity of reservoir fluids can be enhanced significantly by strong and sufficient interactions of ScCO2 and oil. Thus, CO2 soaking-alternating-gas (CO2-SAG) flooding is proposed and evaluated to verify the importance of contact time and mass transfer.

Keywords: Miscible degree; Near miscible flooding; Pore scale effect; ScCO2 injection; Tight reservoir (search for similar items in EconPapers)
Date: 2022
References: View references in EconPapers View complete reference list from CitEc
Citations: View citations in EconPapers (7)

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Persistent link: https://EconPapers.repec.org/RePEc:eee:energy:v:239:y:2022:i:pc:s0360544221025354

DOI: 10.1016/j.energy.2021.122287

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