碱探1井超高温水基钻井液技术

碱探1井是位于柴达木盆地中央鼻隆带碱山构造的一口重点风险探井，钻探的主要目的是探索碱山构造基岩含气性，该井完钻井深为6343 m，实测井底最高温度达到235℃，为目前国内陆上钻井井底温度最高记录之一。该区块地层存在裂缝发育、长段膏泥岩层、高压盐水层、高浓度CO₂、高地温梯度，施工过程中井塌、井漏、溢流、膏泥岩层蠕变缩径等复杂因素相互交织。室内通过开展超高温稳定性能、流变性能以及超高温下的滤失性控制等方面的技术攻关，在有机盐钻井液的基础上，通过对国内外超高温降滤失剂、封堵防塌剂、润滑剂、热稳定剂等的筛选及优化，形成碱探1井抗240℃超高温有机盐水基钻井液的最终配方。该配方钻井液在老化72 h后，高温高压滤失量保持在10 mL以内、润滑系数小于0.1、砂床侵入深度小于12 cm。另外，该井四开、五开钻遇微裂缝及基岩风化壳，裂缝多次发生漏失，优选耐温性能良好的刚性、柔性及胶质封堵材料，形成了碱探1井超高温堵漏技术配方，漏失井段承压能力逐步提高，为超深井段的井壁失稳和井漏的预防治理发挥了关键作用，顺利完成了柴达木盆地第一超高温井碱探1井的钻探保障任务。 

Ultra-High Temperature Drilling Fluid Technology for Drilling Well Jiantan-1

The well Jiantan-1 is a key exploratory well of PetroChina located in the Jianshan structure of the central rhinoplasty belt in the Chaidamu Basin. The main purpose of this 6343 m well is to explore the gas reserves in the base rocks of the Jianshan structure. The highest bottom hole temperature measured is 235℃, one of the highest bottom hole temperatures encountered in onshore drilling. The formations drilled in this area have fractures that are fully developed, long sections of gypsum and mudstones, high pressure saltwater zones, high CO₂ concentrations and high geothermal gradient. Borehole wall collapse, mud losses, overflow, creeping and tight hole in the gypsum/mudstone formations are downhole troubles encountered and sometime intertwined with each other during drilling. To deal with these problems, laboratory study was conducted on several aspects of the drilling fluid used, which are high temperature stability, rheology and high temperature filtration control. An organic salt drilling fluid was formulated with additives specially selected, such as ultra-high-temperature filter loss reducers, anti-collapse additives with plugging capacity, lubricants and thermal stabilizers etc. This drilling fluid is able to resist high temperatures up to 240℃. After aging for 72 hours, the HTHP filtration rate was maintained with 10 mL, the coefficient of friction was less than 0.1, and the invasion depth on a sand-bed less than 12 cm. In addition, the fourth and fifth intervals of the well penetrated formations with micro-fissures and a basal rock weathered crust, and mud losses occurred many times into the fissures. A lost circulation material slurry for the well Jiantan-1 was then developed with choice rigid, flexible and gel-like plugging additives which are suitable for use at elevated temperatures. Using this mud loss control slurry, the pressure bearing capacity of the formations into which mud losses have occurred was finally enhanced. The organic salt drilling fluid and the mud loss control slurry played a major role in preventing and controlling borehole wall collapse and mud losses, ensuring the success of the drilling of the first ultra-high temperature Jiantan-1 well in Chaidamu Basin.