川西雷口坡组不稳定地层长水平段白油基钻井液技术

White oil-based drilling fluid technology for long horizontal section of unstable formation in Leikoupo Formation,western Sichuan

川西雷口坡组四段地层破碎、坍塌压力高于孔隙压力、水基钻井液体系易发生失稳掉块导致阻卡严重,难以满足长水平段安全钻井。从井壁失稳机理分析入手,明确井壁失稳的主要原因。为此开发适用于不稳定地层的白油基钻井液体系,通过关键处理剂的研选,构建白油基钻井液体系,完成关键性能的室内评价分析。在PZ4-4D井和PZ5-4D井三开雷四段地层应用,解决井壁失稳和酸液污染难题,保障川西气田长水平段安全钻井。

As the 4th member of Leikoupo Formation in western Sichuan is characterized by the fractured formation,the collapse pressure being higher than the pore pressure,and the water-based drilling fluid system being prone to instability and slough(possibly serious sticking),it is difficult to meet the requirements for safe drilling in a long horizontal section.From the analysis of wellbore wall instability mechanism,we made clear the primary reasons of wellbore wall instability.For this purpose,a white oil-based drilling fluid system suitable for the unstable formation was developed.Through the research and selection of key treatment agents,the white oil-based drilling fluid system was established to complete the indoor evaluation and analysis of key properties.It was applied in the 4th member of Lei Formation during the third spudding in well PZ4-4D and PZ5-4D to address the problems of wellbore wall instability and acid pollution and ensure the safe drilling of a long horizontal section in the gas fields of western Sichuan.