致密油藏原油与压裂液乳化的液阻效应及其对采油的影响实验  

Experiment on fluid lock effect of tight reservoir oil emulsification with fracturing fluid and its impact on oil recovery

作　　者：李诗豪 钟立国[1] 高大鹏 贾磊磊 孙红宇 张海龙[3] 林庆祥[3] 何剑[3] 张明伟[3] LI Shihao;ZHONG Liguo;GAO Dapeng;JIA Leilei;SUN Hongyu;ZHANG Hailong;LIN Qingxiang;HE Jian;ZHANG Mingwei(Unconventional Petroleum Research Institute,China University of Petroleum(Beijing),Beijing 102249,China;Oilfield Development Department of PetroChina Daqing Oilfield Co.Ltd.,Daqing 163453,China;Downhole Service Company of PetroChina Daqing Oilfield Co.Ltd.,Daqing 163453,China)

机构地区：[1]中国石油大学(北京)非常规油气科学技术研究院,北京102249 [2]中国石油大庆油田有限责任公司开发事业部,黑龙江大庆163453 [3]中国石油大庆油田有限责任公司井下作业分公司,黑龙江大庆163453

出　　处：《大庆石油地质与开发》2024年第6期163-174,共12页Petroleum Geology & Oilfield Development in Daqing

基　　金：中国石油天然气股份有限公司重大科技专项“难采储量有效动用技术研究与试验”(2016E-0210)。

摘　　要：致密油藏在压裂改造过程中易发生压裂液侵入,投产后存在产能恢复速度慢和产能低等问题。为了明确致密油藏压后产能低的影响因素,通过核磁共振(NMR)和扫描电镜(SEM)分析研究了致密油藏孔隙结构特征,基于原油乳化前后的流变性和界面张力测定及乳化相态显微分析,研究了压裂液与原油的乳化规律,结合天然岩心驱替实验与微观刻蚀模型驱替实验模拟,研究了压裂液侵入与原油采出过程。结果表明,压裂液侵入后与原油原位乳化,形成的大乳滴、聚集排列的小乳滴以及多重乳滴流经狭窄的孔喉时会产生强烈的液阻效应,阻碍原油采出。压裂液侵入后原油采出的过程可分为3个阶段:第Ⅰ阶段为侵入区压裂液的返排;第Ⅱ阶段为乳状液缓速排出;第Ⅲ阶段为纯原油的采出。附加阻力计算结果显示,当孔喉半径小于或等于0.20μm时,乳滴通过孔喉所需的压力梯度大于0.02965 MPa/m,原油乳液流动难度大。研究成果能够从乳化及其液阻效应的角度理解致密油藏压裂液侵入伤害机制。During hydraulic fracturing stimulation of tight oil reservoirs,issues such as fracturing fluid invasion and slow or low post-fracturing production recovery rates often arise.To elucidate the factors causing reduced post-fracturing production in tight oil reservoirs,pore structure characteristics are studied via NMR and SEM analysis.Emulsification behavior between fracturing fluid and oil is investigated through rheology and interfacial tension measurements before and after emulsification.The processes of fracturing fluid invasion and oil production are simulated through combining natural core displacement experiment and micro-etching model displacement experiment.The results show that fracturing fluid invasion causes in-situ emulsification with oil,and the formed large emulsion droplets,clustered small emulsion droplets and multiple emulsion droplets lead to significant fluid lock effect as they pass through narrow pore throats.This hinder oil production.Oil production process after fracturing invasion is divided into 3 stages:StageⅠinvolves flowback of invading fracturing fluid,StageⅡis slow release of emulsion,and StageⅢcorresponds to pure oil production.Additional resistance calculation reveals that,when throat radius is≤0.20μm,the pressure gradient required for emulsion droplets to pass through the throats is>0.02965 MPa/m,making it difficult for oil emulsion to flow.The research provides insights into invasion damage mechanism of tight oil reservoirs from the perspective of emulsification and its fluid lock effect.

关 键 词：致密油藏 压裂液侵入 乳化 液阻效应 原油采出 

分 类 号：TE355[石油与天然气工程—油气田开发工程]