Abstract: 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.