绒囊暂堵转向压裂裂缝转向能力及其力学机理分析  

Analysis on the fracture diverting capacity and mechanical mechanisms of fuzzy-ball temporary plugging, diverting and fracturing technology

作　　者：薛亚斐 温哲豪[2,3] 沈云波 王乐 梁凌云[1,2] XUE Yafei;WEN Zhehao;SHEN Yunbo;WANG Le;LIANG Lingyun(Oil and Gas Technology Research Institute, Changqing Oilfield Branch Company of PetroChina, Xi’an 710018, Shaanxi, China;National Engineering Laboratory for Exploration and Development of Low-Permeability Oil & Gasfields, Xi’an 710018, Shaanxi, China;The Business Department for Gas Field Development, Changqing Oilfield Branch Company of PetroChina, Xi’an 710018, Shaanxi, China;China University of Petroleum (Beijing), Beijing 102249, China)

机构地区：[1]长庆油田分公司油气工艺研究院 [2]低渗透油气田勘探开发国家工程实验室 [3]长庆油田分公司气田开发事业部 [4]中国石油大学(北京)

出　　处：《石油钻采工艺》2018年第5期633-640,共8页Oil Drilling & Production Technology

基　　金：国家高技术研究发展计划( 863 计划)"致密砂岩气高效钻井与压裂改造关键技术"(编号: 2013AA064801 )

摘　　要：现场已用绒囊转向剂实施造缝转向,其转向力学机理尚未研究。室内利用7枚?25 mm致密砂岩天然岩心人工造缝模拟压裂后初始裂缝,选择其中3枚注入绒囊转向剂实施封堵,利用三轴试验机测量7枚岩心径向应力-应变曲线,计算绒囊转向剂封堵后岩心水平应力差值5.33MPa,相对未封堵岩心水平应力差值8.57 MPa下降37.81%。绒囊转向剂封堵后岩心脆性系数0.45降至0.16,下降64.44%。实验表明,利用绒囊转向剂封堵裂缝可提高岩石整体强度,降低岩石水平应力差,为重复压裂后新缝转向提供力学环境。室内以300 mm×300 mm×300 mm大尺寸岩心模拟地层,在真三轴压裂模拟系统中利用胍胶压裂形成初始裂缝后,注入绒囊转向剂实施暂堵,再注入胍胶模拟二次压裂。测试二次压裂破裂压力相对初次压裂升高约10 MPa,剖开岩心定性观察暂堵后二次压裂岩心中新缝与初始裂缝方向差异明显,未封堵岩心中新缝与初始裂缝方向重合。研究认为,绒囊转向剂通过提高含裂缝岩石破裂压力,降低地层水平应力差值,增大新缝起裂角度,促使裂缝转向。Fuzzy-ball diverting agent has been applied on site for fracture initiation and diverting,but its mechanical mechanisms of diverting have not been studied yet.In this paper,7natural cores(Ф25mm)of tight sandstone were adopted in laboratory to simulate the postfrac initial fractures by using artificial fractures.And fuzzy-ball diverting agent was injected into3cores to plug the fractures.The radial stress-strain curves of7cores were measured by means of the triaxial testing machine.The horizontal stress differential of the cores after they were plugged with fuzzy-ball diverting agent was calculated,and it is5.33MPa,which is37.81%lower than that of the plugged cores,i.e.,8.57MPa.And the brittleness coefficient of the cores plugged with fuzzy-ball diverting agent drops by64.44%from0.45to0.16.It is indicated that to adopt fuzzy-ball diverting agent for plugging fractures can increase the overall strength of rock and decrease the horizontal stress differential of rock,so as to provide the mechanical setting for the diverting of new fractures after refracturing.In laboratory,large-size cores of300mm×300mm×300mm were used to simulate the strata.In the true triaxial fracturing simulation system,the initial fractures were created by using guar,fuzzy-ball diverting agent was injected for temporary plugging and then guar was injected again to simulate the secondary fracturing.The fracturing pressure of secondary fracturing was tested and it is about10MPa higher than that of primary fracturing.Finally,the cores were split for qualitative observation.It is shown that the orientation of new fractures created by secondary fracturing after temporary plugging is obviously different from that of initial fractures while the orientation of new fractures in unplugged cores is coincident with that of initial fractures.In conclusion,fuzzy-ball diverting agent can increase the fracturing pressure of rocks with fractures,decrease the in-situ horizontal stress differential and increase the fracture initiation angle of new fractures so

关 键 词：重复压裂 转向压裂 转向剂 绒囊流体 水平应力差值 脆性系数 破裂压力 

分 类 号：TE357[石油与天然气工程—油气田开发工程]