四川盆地元坝气田钻井液转化为完井液的工艺技术

四川盆地元坝气田超深、高温、高压、高含硫化氢等特殊复杂地质条件,导致试气测试工作一直存在着诸多技术难题,特别是测试工作液长期高温静置后易出现降解或固化现象,引起测试管柱、安全阀等工具失效,既造成非生产时效增加,又伤害储层,甚至导致井下事故频发。为此,通过大量室内模拟实验,以降本增效为原则,对现有钻井液进行调整,进而转换为试气测试用完井液,后者具有配伍性好、抗高温稳定性强、储层保护性好、成本低等优点;配套形成的钻井液转换为完井液工艺技术,具有工艺简便、操作性强、易推广的特点;在此基础上,提出了一套适合元坝气田的完井液技术评价方法及技术性能指标。通过元坝气田超深水平井的现场应用,在160℃条件下静置250 d后性能保持稳定,完井液上、下层密度差小于0.03 g/cm~3,满足了该气田超深水平井衬管完井的工艺要求。

Technology of transforming drilling fluid into completion fluid in the Yuanba Gasfield,Sichuan Basin

Special and complex geologic conditions like ultra depth, high temperature, high pressure and high H2S contents in the Yuanba Gasfield, Sichuan Basin, often bring about many technical problems in the course of formation test for gas, especially, after sitting quietly at high temperatures for a long time, the test fluid is prone to degradation or solidification, and thus resulting in the failure of tools like test strings and safety valves, which not only increases the downtime, but also damages the reservoir, even triggers frequent downhole accidents. For this reason, based on multiple lab simulation experiments under the principle of cost reduction and efficiency improvement, the existing drilling fluid was adjusted and then transformed into completion fluid used in the formation test for gas, which has the advantages like good compatibility, high temperature resistance, strong stability, good protection to reservoir, and low cost; the technology of transforming drilling fluid into completion fluid formed accordingly is characterized by simple process and strong operability. On this basis, this paper presents a set of completion fluid technology assessment methods and technical performance indicators suitable for the Yuanba Gasfield. Field application in the ultra-deep horizontal wells there shows that after sitting quietly at 160℃ for 250 d, the completion fluid is stable in properties, with a differential density between the upper and lower layers of less than 0.03 g/cm³, meeting the technological requirements of liner completion of ultra-deep horizontal wells in this gas field.