Title

Dynamic Propagation of Multiple Horizontal Fractures and Mutual Interference Between Induced Stresses

作者

张然李根生朱海燕

Authors

ZHENGRan LIGensheng ZHUHaiyan

单位

"油气资源与探测"国家重点实验室·中国石油大学(北京), 北京昌平 102249 "油气藏地质及开发工程"国家重点实验室·西南石油大学, 四川成都 610500

Organization

State Key Laboratory of Petroleum Resource and Prospecting, China University of Petroleum(Beijing), Changping, Beijing 102249, China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China

摘要

QA油田X储层埋深较浅，高角度天然裂缝发育，水力压裂后形成的水力裂缝形态较为复杂，压后效果时好时坏，给压裂设计及施工带来诸多困难，急需弄清该储层水力裂缝的形态，以确定合理的压裂施工方案。首先，采用三轴岩石力学测试系统对X储层岩石力学特征进行测试，观察天然裂缝形态。其次，建立砂泥岩相间的二维平面渗流-应力-损伤耦合有限元模型，采用二次应力起裂准则作为水力裂缝是否起裂的判断依据，以幂律流来表征流体在Cohesive单元内的流动。模拟了X储层水力压裂多裂缝交错延伸的裂缝形态，探究了水力裂缝几何形态及压裂液排量、地应力、压裂液黏度对缝间应力干扰的影响，揭示了复杂多裂缝交错扩展的干扰机理，发现该储层具有形成复杂裂缝的力学和工程地质条件，为该区域的压裂改造提供理论指导。

Abstract

The X-6 Formation is located at a depth of 500-700 m in the QA Oilfield and has low porosity and low permeability. Natural high-angle fractures exist in the formation. These conditions partially satisfy the requirements for a fracture network after hydraulic fracturing but may result in relatively complex fracture patterns and introduce difficulties to the fracturing design and treatment. Firstly, triaxial tests were carried out in this work to study rock mechanical properties. A two-dimensional seepage-stress-damage-coupled finite element model of the sand- and mudstone-interlayered formation was then established. Lastly, the propagation of multiple hydraulic fractures and the stress interference mechanism of the X-6 reservoir were simulated and the influences of the pumping rate, in situ stress, and fracturing fluid viscosity on the stress interference were studied. The interference mechanism of the interaction of the hydraulic and natural fracture was revealed. We found that the reservoir has complex fracture mechanical and engineering geological conditions for complex fracture generation, providing theoretical guidance for the hydraulic fracturing of the region.

关键词：

裂缝形态; 水平裂缝; 应力干扰; 交错扩展; 孔压单元;

Keywords:

fracture morphology; horizontal fracture; stress interference; fracture intersection; pore pressure element;

基金项目

DOI

10.11885/j.issn.1674-5086.2016.09.19.02

水平多裂缝交错扩展及其诱导应力干扰研究