疏松砂岩储层微压裂机理与应用技术研究  

Microfracturing mechanisms and techniques in unconsolidated sandstone formations

作　　者：林伯韬 LIN Botao(State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum-Beijing,Beijing 102249,China;College of Petroleum Engineering,China University of Petroleum-Beijing,Beijing 102249,China;College of Artificial Intelligence,China University of Petroleum-Beijing,Beijing 102249,China)

机构地区：[1]中国石油大学(北京)油气资源与探测国家重点实验室,北京102249 [2]中国石油大学(北京)石油工程学院,北京102249 [3]中国石油大学(北京)人工智能学院,北京102249

出　　处：《石油科学通报》2021年第2期209-227,共19页Petroleum Science Bulletin

基　　金：国家自然基金重大项目“天然气水合物储层力学特征及多场耦合工程响应机制”(编号:51991362)资助。

摘　　要：疏松砂岩储层在改造及注水施工中表现出与致密储层压裂迥异的力学变形特征,亟需特定的力学机理解释其宏微观变形行为,从而为现场施工提供理论指导。针对疏松砂岩质地松软、塑性强、渗透率高的岩土力学性质,本文引入土力学的理念,介绍微压裂这一储层改造与增注技术,深入分析该类储层在微压裂过程中的扩容及微裂缝起裂机理。在理清微压裂力学机理的基础上,总结归纳已有的储层微压裂效果评价方法,包括室内实验、解析分析和数值计算方法,阐明各类方法的必要性和优缺点。基于力学机理和计算方法,讨论了微压裂技术在超稠油储层改造、井筒解堵和人工干预地应力场中的应用方法和工程案例。最后,以超稠油储层改造为例,提出微压裂效果自动化评价技术。研究发现微压裂为综合孔隙弹性、塑性和断裂多种力学变形的复杂力学机制,在不同的应用场合实现的功能各异,但普遍体现为扩容至微裂缝起裂这一过程的局部至全部特征;分析微压裂作用效果应当考虑多尺度效应,结合多类数值计算方法开展实际工程案例评价。超稠油储层微压裂改造以井周产生微裂缝、井间储层发生孔隙扩容为主,加强井间热对流效应,加速井间连通。微压裂应用于井筒解堵时提供了反洗冲砂、井周扩容与造微裂缝恢复流体通道的作用,从而延长解堵效果。此外,微压裂亦可应用于致密储层,通过人工干预井周、井间、段簇间有效地应力场,使其利于预期造缝目标。未来的技术攻关应集中在完善自动化、进而发展智能化的微压裂技术,逐步取代人工决策及控制。Unconsolidated sandstone formations display specific mechanical deformation behavior in their stimulation or injection,which is distinct from that of tight formations upon hydraulic fracturing.In this regard,the mechanical mechanisms must be revealed to interpret the macro and micro-scale deformation,therefore providing theoretical guidance for field practices.Given the characteristics of an unconsolidated sandstone formation such as soft texture,great plasticity,and high permeability,this article brings in soil mechanics to introduce the formation stimulation and injection augmentation technique known as microfracturing,then delves into the dilation and microfracture initiation mechanisms during microfracturing in such a type of formation.Based on the microfracturing mechanisms,assessment methods of microfracturing efficiency,including laboratory experiments,analytical solutions,and numerical approaches,are discussed,and summarized on their necessity as well as advantages and disadvantages.Based on the mechanical mechanisms and the calculation methods,the applications of microfracturing in the stimulation of ultra-heavy oil formation,plugging-removal in wellbores and artificial interference of the geostress field,are discussed with respect to the detailed approaches and successful case studies.Finally,the automatic evaluation technique of microfracturing efficiency is proposed using ultra-heavy oil formation stimulation as an example.It is found that microfracturing is a complex mechanism that combines the theories and techniques of poroelasticity,plasticity,and fracture mechanics.It demonstrates various functionalities in different engineering scenarios,but generally shows a series of features of the process from dilation to microfracture initiation.It is believed that the analysis of its stimulation efficiency in realistic practices must consider multiscale effects and use multiple numerical approaches.Microfracturing in an ultra-heavy oil formation is mainly characterized by the microfracture generation surro

关 键 词：疏松砂岩 微压裂 扩容 裂缝 解堵 地应力 智能 

分 类 号：TE31[石油与天然气工程—油气田开发工程]