摘要
优化设计水力喷射分段压裂施工方案时,需要较为准确地预测不同位置的起裂压力。基于Westergaard理论,建立了考虑裂缝诱导应力场的水力喷射分段压裂起裂模型,分析了受第一条裂缝诱导应力影响的后续裂缝起裂压力,并与现场实际压裂数据进行对比;同时,分析了不同裂缝高度、裂缝净压力、原地最小水平主应力和与第一条裂缝的距离对第二条裂缝起裂压力的影响。计算结果显示,模型计算值与压裂试验数据吻合较好。在实际施工参数条件下,裂缝面净压力每增大5 MPa,后续压裂起裂压力增大3 MPa;第一条裂缝高度每增加10m,后续裂缝起裂压力增加2 MPa,诱导应力场影响范围增加30m;与第一条裂缝距离越近,后续裂缝起裂压力越高,最大增幅可达21%;原地最小水平主应力增大,诱导应力场的影响范围并不会增大。研究结果对优化设计水力喷射分段压裂施工方案具有一定的指导作用。
It is necessary to accurately predict the fracture initiation pressure at different positions when a staged hydraulic jet fracturing program is designed and optimized.In this paper,therefore,a fracture initiation model which takes the induced stress field into consideration is established for the staged hydraulic jet fracturing on the basis of Westergaard theory.The effect of the induced stress of the first fracture on the following initiation fracture was investigated and compared with the actual fracturing data.In addition,an analysis was conducted to determine the effect of fracture height,net fracture pressure,minimum horizontal in-situ principal stress and fracture spacing from the first to the second one on the initiation pressure of the second fracture.The calculated results showed that the model calculations and the test values were maintained identical.In situations with practical parameters,the following initiation pressure increased by 3 MPa if the net pressure at the fracture plane increased by 5MPa.It increased by 2MPa,and the influential range of induced stress field enlarged by 30 mif the height of first fracture increased by 10 m.The following initiation pressure increased with the shortening of the spacing to the first fracture,with maximum increase ratio 21%.The minimum horizontal in-situ principal stress had no effect on the influential range of induced stress field.It was shown that the fracture initiation model established in this paper was better accordant with the field testing data.The following fracture initiation pressure was significantly affected by the net fracture pressure,the fracture height and the spacing to the first fracture,but was hardly affected by the minimum horizontal in-situ principal stress.The research results in this paper played an instructive role for the design and optimization of staged hydraulic jet fracturing programs.
出处
《石油钻探技术》
CAS
CSCD
北大核心
2015年第5期31-36,共6页
Petroleum Drilling Techniques
基金
国家自然科学基金重大项目"多重耦合下的页岩油气安全优质钻井理论"(编号:51490652)资助
关键词
水力喷射压裂
起裂模型
起裂压力
诱导应力
hydraulic jet fracturing
fracture initiation model
fracture initiation pressure
induced stress
