中国石化江苏油田页岩油开发，面临着投资高、产量低的问题。油田开发已近45年，废弃老井数量多，利用老井眼侧钻的方式开发页岩油能降低钻井成本。2022年在花庄地区开展利用老井侧钻水平井，采用小井眼钻井方式的探索。针对小井眼钻具柔性大、轨迹控制难、钻速慢、间隙小、环空压耗大、固井质量差、井控风险高等难题，探索大套管开窗、井眼轨迹优化、高效钻头+螺杆+LWD地质导向钻井、泡沫固井、油基钻井液堵漏、窄间隙井控等技术，形成页岩油井小井眼高效钻井技术体系。应用表明：苏北盆地花庄地区H2CHF井实钻机械钻速最快达5.0 m/h，与邻井常规井眼钻速相当，比实施新井方案钻井投资降低50 %，节约投资1 500万元，为页岩油低成本开发提供了重要思路。

The shale oil development in Sinopec Jiangsu Oilfield is facing the problems of high investment and low production. After 45 years of development, there are a lot of abandoned old wells. Developing shale oil by old borehole side drilling can reduce drilling costs. In 2022, the sidetracking slimhole horizontal drilling in old wells is carried out in Huangzhuang. The slimhole drilling tools have the problems of large flexibility, difficult track control, slow drilling speed, small clearance, large air pressure consumption, poor cementing quality and high well control risk. In order to solve these problems, a system of efficient sidetracking slimhole horizontal drilling technology system is formed by the applications of large casing windowing, well track optimizations, high-efficiency drill bit+screw+LWD geosteering drilling, foam cementing, oil-based drilling fluid plugging, narrow gap well controlling, small hole coring, etc. A test application in H2CHF well shows that the actual drilling speed is up to 5.0 m/h, which is equivalent to the conventional drilling speed in adjacent wells, and the total drilling cost is reduced by 50 %, saved by 15 million. The new development and test would provide important ideas and reference for future development of shale oil in Jiangsu Oilfield.