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青海油田柴达木盆地涩北气田为第四系不成岩地层大型生物气田。该地层胶结疏松、成岩性差,地层岩性软,泥质含量高,易吸水膨胀,分散性强,严重影响井壁的稳定。钻井过程中易发生缩径、井漏及钻头泥包等复杂问题,且水平井段极易出现井壁坍塌、卡钻,起下钻抽吸等复杂情况。针对该地区地层特点,研究出了聚合物甲酸盐超低渗透钻井液。该体系主要利用聚合物的强包被性、甲酸盐的强抑制性稳定井壁,利用JYW-1在井壁岩石表面形成致密超低渗透封堵膜实现近零滤失钻井,达到安全钻井、防漏、堵漏和保护储气层的目的。现场应用结果表明,聚合物甲酸盐超低渗透钻井液具有强抑制性和封堵性能,较低固相含量和剪切稀释能力,提高了第四系不成岩地层钻井的速度,完全满足了水平井顺利钻井的要求;该体系能很好地提高井壁稳定性和岩心的渗透率恢复值,有利于保护储气层。
The Sebei gas field in the Qaidam Basin of Qinghai Oilfield is a large-scale biogas field of Quaternary immature diagenetic stratum. The formation of loose cement, poor diagenesis, lithology soft formation, high clay content, easy to water swelling, strong dispersion, seriously affecting the stability of the shaft wall. Drilling process prone to shrinking, Lost circulation and drill mud package and other complex issues, and the horizontal section prone to collapse of the borehole wall, stuck drill, drill down from the complex situation. According to the characteristics of the strata in this area, ultra-low permeability drilling fluid of polymeric formate has been developed. The system mainly utilizes the strong coating property of the polymer and the strong inhibitory stability of the formate wall to form a near-zero loss drilling by using JYW-1 to form a dense ultra-low permeable plugging film on the rock surface of the well wall to achieve safe drilling , Leak-proof, plugging and protection of the purpose of the reservoir. Field application results show that the ultra-low permeability drilling fluid of polymer formate has strong inhibition and plugging performance, low solid content and shear thinning ability, which improves the drilling speed of Quaternary immature diagenesis and fully satisfies Horizontal well smooth drilling requirements; the system can well improve the core wall stability and permeability of the recovery value, help to protect the gas reservoir.