摘要
随着储层改造复杂性的增加,研究者已认识到,水力压裂多裂缝现象与早期砂堵、施工压力升高等现象密切相关,但是,目前还没有完整的横向多裂缝模型来描述裂缝延伸压力与闭合应力的同时增加。为此,通过建立计算裂缝端部应力强度因子的不连续位移法,来考虑裂缝轨迹的变化、多条转向裂缝之间闭合应力的相互影响程度;同时结合物质平衡原理与压力平衡原理来描述多裂缝之间的流量动态分流;最后结合裂缝壁面滤失规律的变化、三维裂缝的延伸规律,来模拟不同方位处或同方位处起裂的多条裂缝同时延伸时,流动压力的变化。计算实例表明,与单条裂缝相比,多条裂缝同时延伸时,裂缝净压力升高、裂缝长度变短;不同方位起裂的多个裂缝,由于转向轨迹与应力场的不同,离理想方位越远则流动阻力越大。此模型为现场施工提供了依据。
With the increasing complexity of the reservoirs,it is commonly recognized that the formation of multiple fractures during hydraulic fracturing is closely related with early sand plug and increasing operation pressure.However,there is not a complete multiple-transverse-fracture model up to now to describe the simultaneous increase of fracture extension pressure and the closure stress.By means of the displacement discontinuity method to calculate the stress intensity coefficient at the fracture end.this study took into consideration the transformation of the fracture track,and the interaction between the closure stresses of multiple turning fractures.And through combining the material balance principle and the pressure balance principle,it described the dynamic flow distribution between the multiple fractures.Finally according to the rules of leak-off on fracture faces and the extension rules of 3D fractures,this study simulated the flowing pressure changes which normally occured when multiple fractures originated at different or same azimuths extend simultaneously.After analysis on a few calculation examples,this study found out that compared with single fractures,when multiple hydraulic fractures extended at the same time the fracture net pressure was increasing while its length was becoming shorter;and due to the variety of turning track and stress field,as for the multiple hydraulic fractures originated from different azimuths,the farther the fracture from the ideal direction was,the higher the flow resistance would be.This model will provide references for field operation works.
出处
《天然气工业》
EI
CAS
CSCD
北大核心
2007年第10期75-78,共4页
Natural Gas Industry
基金
新疆石油管理局重点项目<提高复杂裂缝油气藏压裂效果的裂缝模拟
工艺技术研究>的资助
关键词
完井
水力压裂
酸化压裂压裂裂缝
数学模型
completion,hydraulic fracturing,acidizing fracturing,fracture,malhematic model
