摘要
CO2驱酸化溶蚀作用对储层会产生一定程度的伤害。为揭示这种伤害作用对原油采收率的影响机理,选取6块同级别渗透率的岩心样品,在地层温度、压力条件下进行物理模拟实验,通过核磁共振技术评价酸化溶蚀作用对原油采收率的影响机理。实验结果显示,驱替产出流体的pH值低于原始地层水,且通过离子浓度变化发现驱替过程中有长石和碳酸盐矿物发生溶蚀;岩心的渗透率在驱替结束后出现一定程度降低,且反应时间越长,渗透率的降幅越大;岩心样品的最终采收率与反应时间呈反比,反应时间为240 h的岩心样品相比反应时间为0 h的岩心样品,其最终采收率降幅达到27.31%。综合分析认为,CO2驱长时间的酸化溶蚀反应产物及脱落的黏土颗粒会堵塞孔喉,导致储层渗流能力下降,进而影响CO2驱的驱油效率及最终采收率。
The acidification of CO2 can cause damage to the reservoir to a certain extent.In order to reveal the influence mechanism of acidification on oil recovery,six core samples with the same level of permeability were selected for CO2 flooding tests under the conditions of reservoir temperature and pressure,and then the influence mechanism of acidification on oil recovery was evaluated by NMR technique.The results show that the pH value of the displaced fluids is lower than that of the original formation water,and the change of the ion concentration before and after CO2 flooding reflects the dissolution of feldspar and carbonate minerals.The permeability of the core samples decreased after CO2 flooding,and the longer the reaction time,the greater the decrease of permeability.The ultimate recovery factor of the core sample is inversely proportional to the reaction time.The core sample with a reaction time of 240 h was reduced by 27.31%compared to the core sample of 0 h.Comprehensive analysis shows that the long-term acidification and corrosion reaction products of CO2 flooding and the exfoliated clay particles will block the pore throat,resulting in the decline of reservoir seepage capacity,which in turn affects the displacement efficiency and ultimate recovery factor of CO2 flooding.
作者
孙会珠
朱玉双
魏勇
高媛
SUN Huizhu;ZHU Yushuang;WEI Yong;GAO Yuan(State Key Laboratory of Continental Dynamics,Northwest University,Xi'an 710069,China;Department of Geology,Northwest University,Xi'an 710069,China;School of Petroleum Engineering,Xi'an Shiyou University,Xi'an 710065,China;Fengcheng Oilfield Operation Area,PetroChina Xinjiang Oilfield Company,Karamay 834014,Xinjiang,China;Shaanxi Gas Group Co.,Ltd.,Xi'an 710016,China)
出处
《岩性油气藏》
CSCD
北大核心
2020年第4期136-142,共7页
Lithologic Reservoirs
基金
陕西省教育厅重点实验室项目“鄂尔多斯盆地陆相页岩储层微—纳米孔隙结构特征研究”(编号:17JS115)
陕西省自然科学基础研究计划资助项目“致密砂岩微纳米级多孔介质在CO2-原油混相体系下的尺度演化机制及动态预测模型研究”(编号:2019JQ-808)
陕西省教育厅科研计划项目“CO2-原油混相体系沉积颗粒在致密砂岩微—纳米级多孔介质中的流动规律及影响因素”(编号:19JK0670)联合资助。
关键词
CO2驱
酸化溶蚀作用
核磁共振技术
影响机理
采收率
CO2 flooding
acidification
nuclear magnetic resonance
influence mechanism
oil recovery
