吐哈油田胜北区块地层特性及钻井液技术对策

吐哈油田胜北区块钻井过程中遇到壁失稳引起的下钻遇阻、划眼、卡钻等井下复杂情况，制约了钻井提速提效。以胜北508H为代表井，对不同层位岩屑样品的矿物组成及理化性能进行了测定，进而分析了上部地层和下部地层的主要特性和井壁失稳机理。研究表明，地层中普遍存在泥岩，泥岩中粘土矿物含量较高且其组成主要以伊蒙混层和伊利石为主，同时也含有蒙脱石，这些是导致井下发生复杂情况的地层因素。针对上部地层泥岩易水化分散造浆、缩径，提出了采取聚合物强化包被性能以及复合盐强化抑制性能的钻井液技术措施，优化后钻井液的滚动回收率高达88.40%，膨胀率为1.17%。针对下部地层泥岩易剥落掉块、坍塌，提出了通过微-纳米全尺寸封堵并结合复合盐的活度控制及聚胺强化抑制性能的钻井液技术措施，优化后钻井液的平衡压力时间大幅延长，达160 h。钻井液活度低于0.76，钻井液72 h浸泡泥岩岩心的强度降幅减小。优化后的钻井液在胜北区块SH5s21-2和SH5s13-2两口井应用中取得了良好的效果，钻井过程中未发生复杂事故，实现了维持井壁稳定、提高钻井时效的目的。

Formation characteristics and the drilling fluid technology countermeasures of the Shengbei block in Tuha oilfield

During the drilling process in the Shengbei block, there are complex downhole situations such as wellbore instability caused by tripping obstacles, reaming, and sticking, which have restricted the speed and efficiency of drilling. Taking the Shengbei 508H as a representative well, the mineral composition and physicochemical properties of rock debris samples from different layers were measured, and the main characteristics and wellbore instability mechanism of the upper and lower strata were analyzed. Research has shown that mudstone is commonly present in the strata. The clay mineral content in mudstone is relatively high, and its composition is mainly composed of illite and illite mixed layers, as well as montmorillonite, which are geological factors that lead to complex underground situations. A drilling fluid technology measure has been proposed to enhance the coating performance of polymers and the inhibition performance of composite salts in response to the easy hydration, dispersion, slurry making, and diameter reduction of upper formation mudstone. After optimization, the rolling recovery rate of the drilling fluid is as high as 88.40%, and the expansion rate is 1.17%. In response to the tendency of mudstone in the lower strata to peel off and collapse, a drilling fluid technology measure was proposed that combined micro nano full size sealing with activity control of composite salts and polyamine enhanced inhibition performance. After optimization, the equilibrium pressure time of the drilling fluid was significantly extended to 160 hours. The activity of drilling fluid is lower than 0.76, and the strength decrease of mudstone core soaked in drilling fluid for 72 hours decreases. The optimized drilling fluid has achieved good results in the application of two wells, SH5s21-2 and SH5s13-2, in the Shengbei block. No complex accidents occurred during the drilling process, achieving the goal of maintaining wellbore stability and improving drilling efficiency.