东海某气田 φ311.15 mm井段主要使用低自由水钻井液体系,总体作业顺利,但是由于地层存在大量的泥岩和砂泥岩互层,导致前期钻井作业过程中存在一定的起下钻遇阻和憋扭矩问题.后期该气田钻井更多地采取了大斜度井方式开发,由于井斜角大、裸眼段长,井壁稳定和井眼清洁问题更加突出.依据泥岩地层失稳机理,通过在低自由水钻井液体系中引入氯化钠,降低体系的活度和增强体系的抑制性,减少了滤液侵入和地层泥岩膨胀.现场应用结果显示,在加入氯化钠后,优化后的低自由水钻井液体系性能更加稳定,现场钻进过程中钻井液性能变化较小,井壁稳定,实现了直接起下钻,提高了起下钻效率,很好地解决了东海大斜度井泥岩段的钻进问题,缩短了钻井工期,提高了钻井时效,为东海类似井型和岩性地层的钻井提供了良好的技术支持.%Low free water drilling fluid was required to drill the φ311.15 mm hole section in a gas field in East China Sea. The drilling operation was successful, but the existence of interbedded mudstone and sandstone has resulted in high friction when RIH and excessive torque in the early stage of development. In later stage development of the oilfield, more and more highly deviated wells were drilled, borehole wall instability and borehole cleaning were becoming increasingly urgent because of high well angle and long open hole. In dealing with these problems, sodium chloride was introduced into the low free water drilling fluid to reduce the activity of water base and to enhance the inhibitive capacity of the drilling fluid. Other measures taken included reducing filtration rate to minimize shale swelling. Field operation showed that after the introduction of sodium chloride, the property of the low free water drilling fluid became more stable, and the stability of wellbore was improved, realizing smooth tripping of drill pipes. With these measures, problems in drilling high angle well section through thick shale formation have been resolved, drilling time saved, and the efficiency of drilling operation increased. The technology has provided good technological support for drilling wells with similar borehole profile through formations of the same rock type in East China Sea area.
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