压裂液滤失对裂缝萌生及动态闭合过程的影响机理  

Influence mechanism of fracturing fluid filtration on fracture initiation and dynamic closure process

作　　者：周彤[1] 王海波[1] 李凤霞[1] 何柏 周涛[3] 李宁[1] ZHOU Tong;WANG Haibo;LI Fengxia;HE Bo;ZHOU Tao;LI Ning(SINOPEC Exploration&Production Research Institute,Beijing 100083,China;Institute of New Energy and Low-Carbon Technology,Sichuan University,Chengdu,Sichuan 610065,China;College of Safety and Ocean Engineering,China University of Petroleum,Beijing 102249,China)

机构地区：[1]中国石化石油勘探开发研究院 [2]四川大学新能源与低碳技术研究院 [3]中国石油大学(北京)安全与海洋工程学院

出　　处：《天然气工业》2023年第3期91-101,共11页Natural Gas Industry

基　　金：中国石油化工股份有限公司科技部项目“页岩气藏体积压裂模拟技术及软件研发”(编号:P21039-3)。

摘　　要：水力压裂技术已成为致密油气开发的主要措施之一,然而目前业内对储层改造过程中的裂缝动态闭合规律认识还不够深入,导致裂缝形成机制的研究理论难以满足生产实际需要。为此,为增强裂缝网络复杂性和沟通更多储集空间,基于拟三轴实验,从压裂液黏度和储层基础物性的角度构建了不同滤失行为模型,提出了根据储层实际物性来调控压裂液黏度的思路,以明确滤失行为对裂缝萌生机制的影响,揭示其动态闭合规律。研究结果表明:(1)随径向应力增大岩样破裂峰值强度和轴向应变增强,即出现较明显的应变软化特征,导致储层临界破裂压力更大;(2)水力压裂过程中压裂液黏度与储层基础物性构建的滤失体系,是导致裂缝萌生机制和动态闭合规律不同的主要原因之一;(3)页岩—低黏压裂液的中滤失程度体系易开启弱层理面,出现二次破裂,缝宽曲线呈双峰型,闭合程度为38%~71%;页岩—高黏压裂液体系滤失程度较低,裂缝开启后仅略微闭合,缝宽曲线呈平台型;而砂岩—高黏压裂液体系由于滤失程度较高,裂缝开启后压裂液在其壁面快速发生滤失行为,注入压力迅速下降,难以达到二次破裂条件,缝宽曲线呈单峰型,闭合程度为47%~94%。结论认为,现场压裂过程中应考虑上覆岩层压力,并结合储层实际基础物性,调控压裂液黏度,以期形成较为复杂的裂缝网络,该认识可以为致密油气现场压裂方案的制定和油气增产提供技术指导。Hydraulic fracturing technology has become one of the main measures for the development of tight oil and gas reservoirs.At present,however,the dynamic fracture closure laws in the process of reservoir stimulation are not understood deeply,so the research theory of fracture formation mechanism can hardly meet the needs of the actual production.In order to increase the complexity of fracture networks and connect more reservoir spaces,this paper establishes different filtration behavior models from the perspective of fracturing fluid viscosity and basic reservoir physical properties based on pseudo triaxial experiments.Then,the idea of controlling fracturing fluid viscosity according to actual reservoir physical property is put forward.Finally,the influence of filtration behavior on fracture initiation mechanism is clarified,and the dynamic closure laws are revealed.And the following research results are obtained.First,with the increase of radial stress,the peak fracturing strength and axial strain of the rock sample increase,i.e.,obvious strain softening characteristics occur,which results in higher critical reservoir fracturing pressure.Second,the filtration system formed during hydraulic fracturing due to fracturing fluid viscosity and basic reservoir physical properties is one of the main reasons for the differences in fracture initiation mechanisms and dynamic closure laws.Third,the medium filtration system of shale-low viscosity fracturing fluid can easily open the weak bedding surface,leading to secondary fracturing.The fracture width curve is bimodal,and the closure degree is 38%-71%.The shale-high viscosity fracturing fluid system has a lower filtration degree,so the fracture is only slightly closed after opening,and the fracture width curve is platform-shaped.The filtration degree of sandstone-high viscosity fracturing fluid system is higher,so the fracturing fluid presents filtration behavior rapidly on the wall after fracture opening.As a result,the injection pressure drops quickly,and the secondary frac

关 键 词：致密油气 径向应力 应力—应变曲线 压裂液黏度 裂缝萌生 裂缝开启 动态闭合 滤失行为 

分 类 号：TE357.12[石油与天然气工程—油气田开发工程]