泡沫钻井液井壁稳定性评价研究

泡沫流体的结构特点虽能缓解泥页岩地层自吸水的能力,但不能阻止泥页岩地层水化的趋势,随着钻井时间的增加,泥页岩水化加剧,进而引发井壁失稳问题。因此,采用合适的评价方法寻求性能优越的抑制剂配方,成为人们普遍关注的重点。通过对泡沫流体引发井壁失稳过程进行分析可知,在对泡沫钻井液进行性能评价时应从两方面入手,即泥页岩自吸水能力以及泥页岩抑制能力。泥页岩自吸水是引发泥页岩水化的先决条件,通过泥页岩自吸水测试,可以筛选出具有一定封堵或减缓泥页岩吸水速度的泡沫钻井液配方。对于泥页岩抑制能力测试可以将膨润土抑制性测试、滚动回收实验以及硬度测试相结合,这样便于优选出抑制能力强且具有持久抑制作用的泡沫钻井液配方。

Evaluation study on wellbore stability of foam drilling fluid

The self-absorption water ability of shale formation can be reduced because of foam structure,but it can't stop the trend of shale hydration which increases over time and finally causes the wellbore instability.Therefore,adopting appropriate evaluation methods to seek the excellent shale inhibitors becomes the focus of people's attention.Through analyzing the wellbore instability process caused by foam fluid,the performance evaluation of foam fluid should consider two aspects,shale self-absorption water ability and shale inhibition.The process of shale self-absorption water is the necessary prerequisite to shale hydration,and the shale self-absorption water test contributes to optimize foam drilling fluids which have good sealing capacity or slow the self-absorption water speed.Bentonite inhibition,hot rolling dispersion test and bulk hardness test are best choice used in shale inhibition evaluation,and help to select the foam drilling fluid that has strong and permanent shale inhibition in shale hydration.