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苏丹1/2/4区块上部地层主要为易水化、易造浆的泥岩与胶结性较差的砂岩互层,中部地层是以石英、蒙脱石及高岭石为主的大段泥岩层,油层岩性为砂岩,胶结疏松、孔隙度大。某些井地层水钙离子含量高,钻井液钙侵较为严重,但没有大段膏岩层。地层压力梯度均衡。复杂情况主要出现在中部泥岩地层,泥岩遇水膨胀,井壁不稳定,缩径,造成大段划眼和卡钻。针对该地层特点,选用了不同的钻井液体系。
The upper strata in Block 1/2/4 of Sudan are mainly hydratable and easy-to-mudstone interbedded with poorly cemented sandstone. The middle strata are large mudstones dominated by quartz, montmorillonite and kaolinite Layer, reservoir lithology sandstone, loose cement, porosity. Some wells have high levels of calcium ions in the formation water and more severe calcium infiltration in the drilling fluid, but no large gypsum rock layers. Stratum pressure gradient equilibrium. The complicated situation mainly occurs in the middle mudstone formation. Mudstone swelled with water and the borehole wall was unstable and constricted in diameter, resulting in large sections of planktonic eyes and stuck pipes. For the characteristics of the formation, choose a different drilling fluid system.