页岩气水平井多因素耦合套变分析

Mult-factor coupling casing deformation for shale horizontal wells

乔磊 田中兰 曾波 杨恒林 付盼 杨松1

中国石油集团工程技术研究院有限公司，北京 102206 中国石油西南油气田分公司，四川 成都 610051

Engineering Technology R＆D Company Limited, CNPC, Beijing 102206, China Southwest Oil ＆ Gasfield Company, PetroChina, Chengdu 610051, China

大型体积压裂过程中的套变问题已成为制约页岩气大规模高效开发的技术瓶颈，通过对影响页岩气水平井套管强度主控风险因素的分析和评价，提出了多因素耦合套变机理模型。研究结果表明，环空流体收缩、套管弯曲、套管摩阻、井筒降温、高压流体注入是影响页岩气套管强度设计的主要风险因素。其中，环空流体收缩占套管抗内压强度影响权重的94%，管外超高地层压力占套管抗外挤强度影响权重的53%。另外，井眼狗腿度与套管三轴抗内压强度基本呈线性关系，当井眼狗腿度为10°/30 m时，套管抗内压强度降低5.8%，抗外挤强度降低7.50%。通过WY201￣H1井实例分析发现，若水泥环中存在虚空段，压裂时温度大幅下降引起虚空段内的流体收缩，再耦合套管弯曲应力、套管摩阻等载荷，可引起套管抗内压失效。

The problem of casing deformation in large-scale volumetric fracturing has become a bottleneck that restricts the large-scale and efficient development of shale gas. Through the analysis and evaluation of the main risk factors that affect the casing strength of shale gas horizontal wells, a multi-factor coupling casing deformation mechanism model was proposed. The results indicate that the annulus fluid shrinkage, casing bending, residual casing friction, wellbore cooling, and high pressure fluid injection are the main risk factors affecting shale gas casing strength design. The impact weight of the annular bound fluid accounts for 94% of the internal compressive strength, and the extra-high formation pressure of the external formation for 53% of the impact resistance. In addition, there is a linear relationship between the dog′s leg height and the triaxial resistance to internal pressure. When the dog′s leghole is 10°/30 m, the resistance to internal pressure is reduced by 5.8% and the resistance to external extrusion is reduced by 7.50%. Analyzing the case of WY201-H1 Well, if there is a void section in the cement ring, the temperature in the fracturing will drop significantly and the fluid in the void section will shrink. After the casing is coupled with bending stress, casing friction resistance and other loads, it can cause failure of casing to internal pressure.

10.6056/dkyqt201901024