苏20K-P1储气库井超低压砂岩地层随钻堵漏技术

苏20K-P1井是华北油田苏20储气库的一口四开水平井,目的层为砂泥岩互层,地层压力系数仅为0.18,而且为防止泥岩垮塌,钻井液设计密度为1.10g/cm3,防漏、堵漏难度大.室内实验从邻井苏20井的地质资料出发,利用渗透率公式计算出目的层平均孔隙直径为18μm,根据“四球相接理论”,选择粒径为0.125～0.180mm的砂床进行堵漏模拟实验,优选出了随钻堵漏钻井液配方,用其污染苏20井岩心后渗透率降低率达76％,堵漏材料侵入深度为1cm左右,可酸化解堵.现场应用表明,优选出的随钻堵漏材料,配合使用成膜防塌聚合物,可在封堵层表面形成致密的封堵层,阻隔液柱压力传导,达到防漏堵漏的目的,但应注意机械钻速不能过高,必须保证随钻堵漏材料有充足的时间形成封堵层；该随钻堵漏技术能够保证超低压砂岩地层的顺利钻进,具有推广应用前景.

Technology of Mud Loss Control While Drilling in Ultra-low Pressure Sandstone Formation of Gas Storage WellSu20K-Pl

The well of Su20K-P 1 is a gas storage horizontal well with four intervals in Huabei oilfield, and the target formationis interbeded of sandstone and mudstone with the formation pressure coefficient is only 0.18.To prevent mudstone sloughing,the designed drilling fluid density is 1.10 g/cm3, so it is very difficult to prevent and control mud loss.In laboratory, basedon the geology information, using calculating formula of permeability, the average density of target formation is obtained of18 urn, and according to the Four Balls Touching theory, the sand bed of 0.125-0.180 mm is chosen to simulate lostcirculation.The experimental results show that after contaminated by LCM drilling fluid, the reduced penetration rate ofthe offset well cores is 76%, and the invasion depth is only 1cm that can be broken down easily.The application of thistechnology of mud loss control while drilling is very successful, which the formed plugged zone is tight so as to stop thepressure transmission, however, the ROP must be controlled in reasonable range to make the LCM has enough time to sealthe thief zone.