摘要
目前水力压裂起裂压力的预测模型均针对螺旋射孔的情形,忽略套管对井周应力场的影响,已不适用于定向射孔水力压裂起裂压力的预测。定向射孔时,井周未产生微环隙,以此建立了套管井井周应力的解析模型。以渤海BZ25-1油田A1井为例,将该井周应力解析模型与有限元模型进行对比,其最大误差仅为2.3%。同时,结合Hossain模型和最大拉应力准则,建立了套管井定向射孔时孔眼的起裂压力和起裂角的预测模型。考虑流体渗流和套管的共同作用,采用水力压裂的渗流与变形耦合的数值计算方法进行验证,该模型得到的起裂压力与数值计算的误差仅为2.9%,表明该模型准确可靠,可以用于指导定向射孔水力压裂的设计。
Current prediction models for the hydraulic fracture initiation pressure are all applicable to spiral perforation, in which the casing effect on circumferential stress field can be ignored, however, they are not suitable to the prediction of the hydraulic fracture initiation pressure in oriented perforation. An analytical model was established for circumferential stress distributions of cased boreholes based on the effect of the micro-annulus of the first or second interface between the pipe, cement sheath and res- ervoir rock in oriented perforation. Taking the A I well of the BZ25 1 oilfield as an example, this circumferential stress model was compared with the finite element model and the maximum error is only 2.3%. At the same time, combined with the Hos- sain＇ s model and the maximum tension criterion, a prediction model for the fracture-initiation pressure and angle in oriented per- foration of cased boreholes was built. A numerical method coupled with hydraulic fracture seepage and rock deformation was adopted to verify this prediction model for the fracture initiation pressure when co functions of liquid seepage and casing were taken into con- sideration. The result showed that compared with the numerical calculation method, the prediction error of this model for the frac- ture-initiation pressure is only 2.9%, indicating the credibility of this model and its feasible application in guiding the hydraulic frac- turing design of oriented perforation.
出处
《石油学报》
EI
CAS
CSCD
北大核心
2013年第3期556-562,共7页
Acta Petrolei Sinica
基金
国家自然科学基金项目(No.51174219)和国家自然科学基金创新群体项目(No.51221003)资助
国家重大科技专项(2011ZX05009-005)
关键词
定向射孔
水力压裂
起裂压力
井周应力
模型
oriented perforation hydraulic fracturing fracture initiation pressure circumferential stress~ model
