Research and engineering application of pre-stressed cementing technology for preventing micro-annulus caused by cyclic loading-unloading in deep shale gas horizontal wells
Research and engineering application of pre-stressed cementing technology for preventing micro-annulus caused by cyclic loading-unloading in deep shale gas horizontal wells
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DOI：
10.1016/j.petrol.2021.108359
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发表时间：
2021-05
影响因子：
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通讯作者：
Yan Xi;Wei Lian;L. Fan;Q. Tao;Xueli Guo
中科院分区：
文献类型：
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作者：
Yan Xi;Wei Lian;L. Fan;Q. Tao;Xueli Guo
页岩气勘探开发保持了良好的势头，但同时也存在一些亟待解决的问题，如持续的套压问题，带来了很多安全问题，缩短了油井的使用寿命。通过一系列的实验研究和数值研究，分析了采用预应力固井技术前后套管-水泥环-地层组合体中第二界面微环宽度的变化规律。通过三轴压缩试验、CT扫描和累积塑性应变试验，评价了循环加卸载和围压共同作用下的残余应变。通过全尺寸水泥环实验，定量确定了多级压裂开始漏气时微环宽度临界值。建立了实际深部页岩气井全尺寸水泥环物理模拟装置和预应力固井工艺的数值模型。分析了不同因素组合对微环距变化和压裂段数耐压能力的影响。分析了套管内压、预应力荷载、水泥环力学参数等一系列因素的影响。研究结果表明，减小套管压力，增加预应力荷载，有利于保持水泥环密封的完整性。可以通过降低弹性模数和提高泊松比来降低微环风险。对8口深水平页岩气井进行了预压固井。实际应用结果表明，多级压裂前后均未出现SCP现象，证明了该方法的有效性。
Shale gas exploration and development maintained good momentum, but it has some problems at the same time urgently need to be solved, such as sustained casing pressure (SCP), which brought a lot of safety issues and shortened the well service lifetime. A series of experimental investigations and numerical studies were carried out to analyze the development of the micro-annulus width of the second interface in the casing-cement sheath-formation assembly before and after using the pre-stressed cementing technology. Triaxial compression tests computed tomography scanning and accumulated plastic strain tests were conducted to evaluate the residual strain under the combined action of cyclic loading-unloading and confining pressure. Full-size cement sheath experiments were performed to quantify the width critical value of the micro-annulus when gas leakage began during multistage fracturing. The corresponding numerical models of the full-size cement sheath physical simulation facility and pre-stressed cementing technology of a real deep shale gas well were developed. Different combinations of factors were analyzed to quantify the variation of micro-annulus and tolerance ability of fracturing section numbers. The influence of a series of factors, including casing inner pressure, pre-stressed loading, and mechanical parameters of the cement sheath, were analyzed. The result of the research showed that the reduction of casing pressure and increase of pre-stressed loading could help to maintain the seal integrity of the cement sheath. Micro-annulus risks can be reduced through lowering elasticity modulus and raising Poisson's ratio. Eight deep horizontal shale gas wells were cemented with pre-stressed loading. The practical application results showed there was no SCP in prior and post-multi-stage fracturing, which proved the effectiveness of this method.