Study on the Propagation Law of CO 2 Displacement in Tight Conglomerate Reservoirs in the Mahu Depression, Xinjiang, China

Long Tan, Jigang Zhang, Jing Zhang, Ruihai Jiang, Jianhua Qin, Yan Dong, Zhenlong Deng, Ping Song, Chenguang Cui, Wenya Zhai and Fengqi Tan ()
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Long Tan: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Jigang Zhang: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Jing Zhang: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Ruihai Jiang: College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
Jianhua Qin: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Yan Dong: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Zhenlong Deng: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Ping Song: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Chenguang Cui: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Wenya Zhai: Research Institute of Exploration and Development, PetroChina Xinjiang Oilfield Company, Karamay 834000, China
Fengqi Tan: College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing 100049, China

Energies, 2025, vol. 18, issue 4, 1-15

Abstract: To achieve the efficient utilization of low-permeability tight sand and gravel reservoirs with strong heterogeneity in the Mahu oil area of Xinjiang, CO 2 injection is used to improve oil recovery. The sweep pattern of the injected gas is closely related to the development of reservoir pores and throats. Firstly, a three-dimensional model of the average pore-throat radius was established based on complete two-dimensional nuclear magnetic resonance scanning data of the target layer’s full-diameter core in the Wuerhe Formation. Subsequently, an online NMR injection CO 2 continuous oil displacement experiment was conducted using tight conglomerate rock cores to clarify the rules of CO 2 oil displacement in each pore-throat interval. Finally, the three-dimensional pore-throat model was combined with microscopic utilization patterns to quantitatively characterize the reservoir utilization rate of the CO 2 displacement oil and guide on-site dynamic analysis. The research results indicate that the reservoir space of the Wuerhe Formation is mainly composed of residual intergranular pores, accounting for 40.9% of the pores, followed by intragranular dissolution pores and shrinkage pores. The proportion of pore-throat coordination numbers less than 1 is relatively high, reaching 86.3%. The average pore-throat radius calculation model, established using online NMR data from the continuous coring of full-diameter cores, elucidates the characteristics of the average pore-throat radius in the Wuerhe Formation reservoir. Based on gas displacement experiments that explored the pore-throat behavior at the microscale, the calibrated CO 2 injection oil recovery rate was determined to be 43.9%, and the proportion of reserves utilized within the main range during CO 2 displacement amounted to 60.77%. The injection pressure is negatively correlated with the maximum pore-throat radius of the gas injection well group, and negatively correlated with the proportion of the 0.9~2 μm distribution of large pore throats in each gas injection well group.

Keywords: Mahu Depression; CO 2 displacement; full-diameter core; online magnetic resonance scanning; average pore-throat radius (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: 2025
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