CO 2 –Water–Rock Interaction and Its Influence on the Physical Properties of Continental Shale Oil Reservoirs

Sheng Cao, Qian Sang (), Guozhong Zhao, Yubo Lan, Dapeng Dong and Qingzhen Wang
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Sheng Cao: National Key Laboratory for Multi-Resources Collaborative Green Production of Continental Shale Oil, Daqing 163712, China
Qian Sang: School of Petroleum Engineering, China University of Petroleum (East China), Qingdao 266580, China
Guozhong Zhao: National Key Laboratory for Multi-Resources Collaborative Green Production of Continental Shale Oil, Daqing 163712, China
Yubo Lan: National Key Laboratory for Multi-Resources Collaborative Green Production of Continental Shale Oil, Daqing 163712, China
Dapeng Dong: National Key Laboratory for Multi-Resources Collaborative Green Production of Continental Shale Oil, Daqing 163712, China
Qingzhen Wang: National Key Laboratory for Multi-Resources Collaborative Green Production of Continental Shale Oil, Daqing 163712, China

Energies, 2024, vol. 17, issue 2, 1-20

Abstract: Shale oil resources are abundant, but reservoirs exhibit strong heterogeneity with extremely low porosity and permeability, and their development is challenging. Carbon dioxide (CO 2 ) injection technology is crucial for efficient shale oil development. When CO 2 is dissolved in reservoir formation water, it undergoes a series of physical and chemical reactions with various rock minerals present in the reservoir. These reactions not only modify the reservoir environment but also lead to precipitation that impacts the development of the oil reservoir. In this paper, the effects of water–rock interaction on core porosity and permeability during CO 2 displacement are investigated by combining static and dynamic tests. The results reveal that the injection of CO 2 into the core leads to reactions between CO 2 and rock minerals upon dissolution in formation water. These reactions result in the formation of new minerals and the obstruction of clastic particles, thereby reducing core permeability. However, the generation of fine fractures through carbonic acid corrosion yields an increase in core permeability. The CO 2 –water–rock reaction is significantly influenced by the PV number, pressure, and temperature. As the injected PV number increases, the degree of pore throat plugging gradually increases. As the pressure increases, the volume of larger pore spaces gradually decreases, resulting in an increase in the degree of pore blockage. However, when the pressure exceeds 20 MPa, the degree of carbonic acid dissolution will be enhanced, resulting in the formation of small cracks and an increase in the volume of small pores. As the temperature reaches the critical point, the degree of blockage of macropores gradually increases, and the blockage of small pores also occurs, which eventually leads to a decrease in core porosity.

Keywords: shale formation; CO 2 flooding; CO 2 –water–rock reaction; blocking action; dissolution reaction (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2024
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