Exploring pore-scale production characteristics of oil shale after CO2 huff'n'puff in fractured shale with varied permeability
Tianhan Xu1
Jian Wang1
Yuhao Lu1
Danling Wang2
Li Yu3
Ye Tian4
1.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,Sichuan,China2.Research Institute of Shenzhen Branch of CNOOC(China)Co.,Ltd,Shenzhen 518000,Guangdong,China3.PetroChina Huabei Oilfield Company,Cangzhou 062552,Hebei,China4.State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation,Southwest Petroleum University,Chengdu 610500,Sichuan,China;Institute for Carbon Neutrality,Southwest Petroleum University,Chengdu 610500,Sichuan,China
摘要：Recent studies have indicated that the injection of carbon dioxide(CO2)can lead to increased oil recovery in fractured shale reservoirs following natural depletion.Despite advancements in understanding mass exchange processes in subsurface forma-tions,there remains a knowledge gap concerning the disparities in these processes between the matrix and fractures at the pore scale in formations with varying permeability.This study aims to experimentally investigate the CO2 diffusion behaviors and in situ oil recovery through a CO2 huff'n'puff process in the Jimsar shale oil reservoir.To achieve this,we designed three matrix-fracture models with different permeabilities(0.074 mD,0.170 mD,and 0.466 mD)and experimented at 30 MPa and 91 ℃.The oil concentration in both the matrix and fracture was monitored using a low-field nuclear magnetic resonance(LF-NMR)technique to quantify in situ oil recovery and elucidate mass-exchange behaviors.The results showed that after three cycles of CO2 huff'n'puff,the total recovery degree increased from 30.28％to 34.95％as the matrix permeability of the core samples increased from 0.074 to 0.466 mD,indicating a positive correlation between CO2 extraction efficiency and matrix permeability.Under similar fracture conditions,the increase in matrix permeability further promoted CO2 extrac-tion efficiency during CO2 huff'n'puff.Specifically,the increase in matrix permeability of the core had the greatest effect on the extraction of the first-cycle injection in large pores,which increased from 16.42％to 36.64％.The findings from our research provide valuable insights into the CO2 huff'n'puff effects in different pore sizes following fracturing under varying permeability conditions,shedding light on the mechanisms of CO2-enhanced oil recovery in fractured shale oil reservoirs.
机标关键词：permeabilitycharacteristicsproductionshaleafterhuffpuffwith
论文发表日期：2024-02-28
在线出版日期：2025-08-15（本平台首次上网日期，不代表文献的发表时间）
页数：10( 194-203 )
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