库车山前大尺寸套管固井技术

针对库车山前大尺寸套管环空带压的问题，结合现场资料和室内试验评价，分析了大尺寸套管环空带压产生的原因，并在此基础上，通过强化井筒，提高管柱居中度，增加浆体摩阻级差和壁面剪应力，严格要求水泥浆稠化、过渡和起强度时间，细化憋压候凝程序等措施，形成了快速封固、全程压稳的大尺寸套管固井技术。研究发现，分级固井方式对复杂工况的处置有限，顶替和压稳措施针对性不强，导致大尺寸套管固井窜槽严重，未压稳地层高压流体，造成一次固井质量差，从而引起库车山前大尺寸套管环空带压。大尺寸套管固井技术在库车山前成功应用6井次，整体固井顶替效率达到95%以上，水层段固井质量合格率大于90%，固井质量良好，具有一定的推广应用价值。 

Cementing Technologies with Large-Size Casing in the Kuqa Piedmont

Aiming at solving the problem of sustained casing pressure in large-size casing in the Kuqa Piedmont, the reasons for sustained casing pressure in large-size casing were investigated by using field data analysis and laboratory test evaluation methods. On this basis, the cementing technologies with large-size casing, featuring quick sealing and whole-process stable pressure, were formed by the measures such as strengthening wellbore, improving pipe string centering, increasing slurry friction difference and wall shear stress. Further, it was necessary to institute strict controls over the thickening, transition, and the developing time for strength in cement slurry. More detailed procedures for pressure holding before cement setting were designed as well. It was found that factors such as the limited staged cementing control in handling complex situations, and poor displacement and pressure stabilization measures led to severe channeling in cementing with large-size casing, which failed to stabilize the high-pressure fluids in formations. All of these resulted in poor-quality of primary cementing, which further caused the sustained casing pressure in large-size casing in the Kuqa Piedmont. The developed technologies were successfully applied to six wells in the Kuqa Piedmont, and achieved overall cementing displacement efficiency of more than 95% with a pass rate of more than 90% for the cementing quality in water-bearing sections. The good cementing performance shows that the technologies are worth of promotion and application.