非常规油气井压裂过程中水泥环完整性实验评价

Experimental Evaluation on the Cement Sheath Integrity of Unconventional Oil and Gas Well During Large-scale Hydraulic Fracturing

关志刚 邓宽海 吴彦先 林志伟 林元华

GUANZhigang DENGKuanhai WUYanxian LINZhiwei LINYuanhua

中国石油新疆油田公司工程技术研究院, 新疆 克拉玛依 834099 油气藏地质及开发工程全国重点实验室 · 西南石油大学, 四川 成都 610500

Research Institute of Petroleum Engineering, Xinjiang Oilfield Company, PetroChina, Karamay, Xinjiang 834099, China National Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu, Sichuan 610500, China

非常规油气井大规模压裂使水泥环处于极端服役环境，极易导致水泥环屏障失效，而避免水泥屏障失效的关键在于弄清压裂诱导的交变压力下水泥环完整性失效机理。因此，采用自主研发的实验装置模拟井筒环境开展了全尺寸“生产套管普通（高强度）水泥环技术套管”两种组合体在交变压力下的密封性能和界面力学性能测试及评价，利用密封失效循环次数和界面胶结强度分别表征了水泥环密封性能和界面力学性能，获取了普通水泥环在4种交变压力（0↗30↘0，0↗50↘0，0↗60↘0和0↗70↘0 MPa）、高强度水泥环在5种交变压力（0↗30↘0，0↗50↘0，0↗60↘0，0↗70↘0和0↗80↘0 MPa）下的完整性实验结果，分析了交变压力峰值及循环次数对水泥环完整性的影响规律，揭示了水泥环完整性在交变压力作用下的失效机理及过程，明确了水泥环密封性能和界面力学性能之间的相关性，发现了高强度水泥环耐交变压力的密封/抗窜能力及界面力学性能均明显优于普通水泥环。研究成果可为非常规油气井水泥浆体系的优选及压裂施工参数的优化提供重要依据。

Large-scale hydraulic fracturing of unconventional oil and gas wells will put the cement sheath in an extreme service environment, which is easily lead to the failure of the cement sheath barrier. The key to avoid the failure of the cement barrier is to investigate and understand failure mechanism of cement sheath under the alternating pressure induced by fracturing. Therefore, a self-developed experimental device is used to simulate the wellbore environment to carry out the physical test and evaluation of the sealing performance and interface mechanical performance of the full-scale“production casing- normal/high cement sheathintermediate casing” under alternating pressure. The sealing performance and interface mechanical performance of cement sheath were characterized by the number of seal failure cycles and interfacial bond strength, and the sealing performance results of ordinary cement sheath under four alternating pressures(0↗30↘0, 0↗50↘0, 0↗60↘0, 0↗70↘0 MPa) and high strength cement sheath under five alternating pressures(0↗30↘0, 0↗50↘0, 0↗60↘0, 0↗70↘0 and 0↗80↘0 MPa) are obtained. The influence of alternating pressure peak and cycles times on cement sheath integrity is analyzed, the failure mechanism and process of cement sheath integrity under alternating pressure are revealed, and the correlation between cement sheath sealing performance and interface mechanical performance is clarified. It is found that the sealing/channeling resistance and interface mechanical properties of high-strength cement sheath are obviously better than those of ordinary cement sheath. The results can provide an important basis for the optimization of cement slurry system and fracturing construction parameters in unconventional oil and gas wells.

10.11885/j.issn.1674-5086.2021.10.16.01