低活度强抑制封堵钻井液研究与应用

济阳坳陷沙河街组地层油泥岩黏土矿物含量高，以伊/蒙混层、伊利石为主，且微裂缝发育，钻井过程中易发生坍塌、掉块等井壁失稳问题，为此进行了低活度强抑制封堵钻井液研究。利用油泥岩的半透膜作用，根据活度平衡理论，通过优化活度调节剂的加量来降低钻井液的活度，通过优选抑制剂来提高钻井液的抑制性，并利用"钻井液全固相粒度优化+多元协同封堵"技术优选封堵剂提高钻井液的封堵性，形成了低活度强抑制封堵钻井液。室内性能评价结果表明，低活度强抑制封堵钻井液的常规性能满足钻井要求，其活度低于油泥岩的活度，抑制性能与油基钻井液接近，封堵性能良好，动滤失速率在10 min时显著降低，60 min后逐渐趋于平缓。10余口井的现场应用表明，低活度强抑制封堵钻井液的常规性能满足钻井要求，钻井过程中油泥岩和泥页岩井段未发生坍塌、掉块等井壁失稳问题。这表明，低活度强抑制封堵钻井液可以减缓油泥岩、泥页岩的吸水膨胀和水化分散，实现微裂缝的有效封堵，能够解决水平井段油泥岩、泥页岩坍塌、掉块等井壁失稳问题。 

Research and Application of Plugging Drilling Fluid with Low-Activity and High Inhibition Properties

With their high clay mineral content,oil-bearing mudstone in Shahejie Formation are dominated by illite/smectite formation and illite.Due to development of micro-fractures,drilling operations in these formations are perplexed by collapsing,chipping and other problems related to instability of sidewalls.To eliminate these problems,low-activity plugging drilling fluids with high inhibition performances were developed.In accordance with the theory of activity equilibrium and by using the semi-permeable membrane properties of oil-bearing mudstone,the activity of drilling fluids was reduced by adjusting volume of activity regulators.At the same time,optimal inhibitors were deployed to enhance inhibition performances of the drilling fluids.In addition,plugging performances of the drilling fluids were enhanced through optimization of solid granularity and collaborative performances of multiple plugging agents to generate plugging drilling fluids with low activity and high inhibition properties.Lab tests showed the innovative plugging drilling fluids with low activity and high inhibition properties had activities lower than those of oil-bearing mudstone,whereas inhibition performances of the drilling fluids were similar with those of oil-based drilling fluids.In addition,the newly-developed drilling fluids had outstanding plugging performances with dynamic filtration losses reduced significantly at 10 min and gradually leveled off after 60 minutes.Generally speaking,the performances of the plugging drilling fluids with low activity and high inhibition properties were sufficient to satisfy demands of drilling operations with no collapsing,chipping or other sidewall instability incidents observed in oil-bearing mudstone and shale mudstone intervals.Research results showed that plugging drilling fluid with low-activity and high inhibition properties could effectively alleviate water absorption expansion and hydration dispersion of oil-bearing mudstone and shale to plug micro-fractures effectively.In this way,collapsing,chipping and other problems related to instability of sidewalls during drilling of horizontal intervals in mudstone and shale formations could be eliminated effectively.