川西地区固井及完井过程中井漏原因分析及对策

CAUSES OF LOST CIRCULATION OCCURRED IN CEMENTING AND COMPLETION OPERATIONS IN WEST SICHUAN AREA AND CONTROL MEASURES

针对川西地区固井完井过程的井漏问题,分析其原因,并提出预防和处理措施。指出了应用堵漏技术从安全的角度考虑应注意的主要问题:①对长裸眼层段存在多压力系统发生井漏与溢流,应分析各层段的地层压力与承压能力,确定漏失层与气层,为制定堵漏与压井施工方案提供科学依据;②在钻井施工中进行堵漏作业,应认真分析漏失层岩性特征、漏失原因与机理,针对性地选择堵漏材料与堵漏工艺;③对喷漏同存的井,应将堵漏与压井进行综合考虑和有机结合,保持井内动态液柱压力始终高于漏层压力,即气层发生井漏实施吊灌技术;④若漏失层为非产层,在不构成伤害油气层前提下,可选择堵漏固化后强度高的永久性堵漏材料;若漏层为产层,确需堵漏则选择能最大限度保护产层的暂堵材料;⑤高含硫气井喷漏同存复杂条件下,固井与完井工艺选择要符合气田采气技术要求。

The causes of lost circulation occurred in cementing and completion operations in west Sichuan area are analyzed in this paper,and the corresponding preventive and control measures are put forward.The major concerns of lost circulation control include:① for loss occurred in open hole section with long length and multi-pressure system,the formation pressure and load bearing capability of each interval should be analyzed to locate the thief zone and the gas zone,providing scientific basis for plugging and well killing planning;② when conduct plugging during drilling operation,the lithological properties,the leaking causes and mechanism of the thief zone should be carefully studied,so as to select the proper LCM material and the proper plugging procedures;③ for wells with both loss and blowout,plugging and well killing should be considered comprehensively and combined properly,to keep the hydrodynamic pressure in the wellbore higher than the formation pressure of the thief zone;④ if the thief zone is not a pay zone,on condition no potential damage to the reservoir,the permanent LCM material with high strength after setting can be used,and protective LCM material shall be adopted if the thief zone is a pay zone;⑤ if the well is a high H2S well,and with both loss and blowout,the cementing and completion technology adopted shall meet the technical requirements for gas production.