KCl-有机盐聚合物钻井液在川西双鱼石区块的应用

川西地区双鱼石区块目的层埋藏深，完钻井深在7 000 m以深，上部φ444.5 mm、φ333.4 mm井眼主要采用“空气钻”提速，空气钻井转钻井液如何保证井壁稳定至关重要，在“高效PDC+螺杆”提速方式下优质的钻井液性能也尤其重要。为此，KCl-有机盐聚合物钻井液在KCl、有机盐的共同作用下抑制能力强，能够抑制岩石组分水化分散、膨胀，封堵防塌剂可以快速形成致密泥饼，减少滤液侵入井壁地层，防止“空气钻”后干燥井壁“吸水”引起的井塌；抑制钻屑水化分散，钻井液流变性能稳定、波动小、易调控、现场维护处理简单；钻井液强抑制性、低黏度和切力可提高钻头水马力，减少钻屑在钻头上的吸附，防止钻头泥包现象，减少钻井液中微米、亚微米粒子，有助于提高机械钻速。双探8井等现场应用表明，KCl-有机盐聚合物钻井液确保了“空气钻”井段井壁稳定，顺利钻过沙溪庙组下部（沙一段）、凉高山组、自流井组及须家河组易垮塌地层，井眼畅通、井壁稳定、井径规则、电测顺利、井下安全、钻速较高，满足工程、地质录井需要。 

Application of KCl Organic Salt Polymer Drilling Fluid in Upper Section of Wells Drilled in Block Shuangyushi,West Sichuan

The target zones in the block Shuangyushi in west Sichuan are buried deep, and wells drilled in that block have completion depth of at least 7 000 m. Air drilling is generally adopted in drilling the upper φ444.5 mm and φ333.4 mm in an effort to drill fast. It is critical to convert air drilling fluid to liquid base drilling fluids, and so is the performance of drilling fluids used in drilling with "high efficiency PDC bit + PDM". KCl organic salt polymer drilling fluid, under the synergistic effect of KCl and organic salts, performs much better in inhibiting the hydration, dispersion and swelling of shaly formations. Plugging agents, on the other hand, quickly form dense mud cakes on the borehole wall, thereby reducing invasion of mud filtrate into formations and preventing the dry borehole wall generated in air drilling from collapsing because of water (mud filtrate) absorption. By minimizing hydration and dispersion of drilled cuttings, mud rheology becomes stable and is easy to maintain. A drilling fluid with good inhibitive capacity, low viscosity and gel strength is helpful in enhancing bit hydraulics and minimizing adsorption of drilled cuttings on drill bit, thereby avoiding bit balling. Reduction in the concentration of micron-sized particles and submicron-sized particles is helpful in ROP enhancement. Field application of the drilling fluid in well Shuangtan-8 showed that the use of KCl-organic salt polymer drilling fluid ensured the borehole stability of the air drilling section, helped drilling through the bottom of the Shaximiao formation (Shayi member), Lianggaoshan formation, Ziliujing formation and Xujiahe formation successfully. During drilling operations, tripping of drilling string was smooth, borehole wall was stable, electric wireline logging was conducted favorably, no downhole problems took place, and penetration arte was satisfactory. The use of the KCl-organic salt polymer drilling fluidhas satisfied the needs of engineering and mud logging.