强交变热载荷下页岩气井水泥环完整性测试  

Integrity tests of cement sheath for shale gas wells under strong alternating thermal loads

作　　者：林元华[1] 邓宽海[1] 易浩[2] 曾德智[1] 唐亮 韦奇 LIN Yuanhua;DENG Kuanhai;YI Hao;ZENG Dezhi;TANG Liang;WEI Qi(State Key Laboratory of Oil&Gas Reservoir Geology and Exploitation//Southwest Petroleum University,Chengdu,Sichuan 610500,China;Research Institute of Petroleum Engineering,Sinopec Northwest Oilfield Company,Urumqi,Xinjiang 830011,China;Chongqing Xinyu Pressure Vessel Manufacturing Co.Ltd.,Chongqing 402560,China)

机构地区：[1]“油气藏地质及开发工程”国家重点实验室·西南石油大学,四川省成都市610500 [2]中国石化西北油田分公司石油工程技术研究院 [3]重庆欣雨压力容器制造有限责任公司

出　　处：《天然气工业》2020年第5期81-88,共8页Natural Gas Industry

基　　金：国家自然科学基金项目“交变温度、压力及其耦合作用下套管-水泥环-地层完整性研究”(批准号:51904261);中国博士后科学基金(批准号:2019M653478)。

摘　　要：页岩气井大规模水力压裂过程中,因井筒内的温度、压力波动及持续变化、循环加卸载引发的水泥环完整性问题将威胁到井筒的完整性。为了弄清强交变热载荷下水泥环完整性失效机理、避免页岩气水平井大规模压裂过程中水泥环屏障失效,基于自主研发的实验装置对全尺寸实物“生产套管—水泥环—技术套管”组合体在强交变热载荷作用下的密封完整性和力学完整性进行了测试及评价,获得了2种全尺寸水泥环(普通水泥环和高强度水泥环)在3种强交变热载荷作用下(出现间断CO2气泡的循环次数分别为4次和14次,出现连续气泡的循环次数分别为5次和15次,交变热载荷分别为30~120℃和30~150℃)的完整性实验结果。研究结果表明:①交变热载荷对水泥环完整性具有显著的负面影响,并且随着交变温度及温差的增大,表征水泥环密封完整性的热循环次数急剧减少;②表征水泥环与套管间的剪切力、轴向与径向结合强度等界面力学性能指标均随交变温度增加而下降;③水泥环微环隙主要是由套管与水泥环材料之间的不协调变形所致,而交变热载荷诱导的水泥石自身力学性能衰退及损伤在一定程度上加剧了水泥环密封完整性失效。结论认为,该研究成果可以为深部页岩气水平井大规模压裂施工设计提供参考。During large-scale hydraulic fracturing in shale gas horizontal wells,a cement sheath easily loses its integrity due to the fluctuation and continuous change of wellbore temperature and pressure and the cyclic loading and unloading,which will threaten wellbore integrity.In order to figure out the failure mechanism of cement sheath integrity under strong alternating thermal loads and prevent the failure of cement sheath barriers during large-scale hydraulic fracturing in shale gas horizontal wells,this paper adopted the independently developed experimental device to test and evaluate the sealing integrity and mechanical integrity of the full-scale combination of production casing,cement sheath and intermediate casing under strong alternating thermal loads.And the integrity experimental results of two kinds of fullscale cement sheaths(conventional and high-strength cement sheaths)under three kinds of strong alternating thermal loads(cycle number for the occurrence of discontinuous CO2 bubble:4 and 14;cycle number for the occurrence of continuous CO2 bubble:5 and 15;alternating thermal load:30-120℃and 30-150℃)were obtained.And the following research results were obtained.First,alternating thermal load has a significant negative impact on the integrity of cement sheath,and with the increase of alternating temperature and temperature difference,the thermal cycle number characterizing the sealing integrity of cement sheath reduces sharply.Second,the interfacial mechanical property indicators that characterize the shearing force between cement sheath and casing and the axial and radial bonding strength decrease with the increase of the alternating temperature.Third,the micro annulus in cement sheath is mainly caused by discordant deformation between the casing and the cement sheath materials,and the mechanical degradation and deterioration of the set cement induced by the alternating thermal load aggravate the failure of the sealing integrity of cement sheath to a certain degree.In conclusion,the research results ca

关 键 词：页岩气井 强交变热载荷 水泥环完整性 温差 生产套管-水泥环-技术套管 全尺寸实物测试 界面力学性能 

分 类 号：TE377[石油与天然气工程—油气田开发工程]