海上气田压力衰竭储层长水平段安全钻井控制技术

南海西部海域东方某气田Y平台采取浅层大位移水平井模式开发莺歌海组二段浅部气藏，储层埋深在井深1300m左右，最大水平位移为3783 m，最高水垂比为2.73。该气田经过十几年的开采，储层存在一定程度压力衰竭。同时，Y平台水平段穿过断层，钻进期间漏失风险高。在前期的一些开发井作业中，储层段钻进时曾多次发生井漏等复杂情况。因此，针对以往开发难题和结合Y平台的地层特点，进一步改良屏蔽暂堵无固相钻井液体系，配套环空ECD实时监测与精细控制工艺，成功解决了该区域储层漏失难题。Y平台实施的5口井提效显著，φ215.9 mm水平井段平均机械钻速为77.27 m/h，创造了东方区域类似浅部气藏大位移水平井的作业纪录。储层保护效果好，测试产量超油藏配产25%。 

Technology for Safe Drilling of an Offshore Well with Long Horizontal Section through Depleted Gas Reservoir

Extended reach horizontal drilling is used in developing the shallow gas reservoir buried in the 2nd segment of the Yinggehai Formation. The Y platform, where the horizontal wells were drilled, is located in an offshore gas field in the east of the Western South China Sea. The buried depth of the gas reservoir is about 1,300 m, the maximum horizontal length of the well is 3,783 m, with the maximum horizontal vertical length ratio of 2.73. After decades of production, the reservoir became depleted to some extent. The horizontal section of the wells drilled on the Y platform penetrated a fault zone, and the risk of mud losses during drilling existed. Mud losses in previous development well drilling have been encountered. A temporary plugging solids free drilling fluid was modified to address the mud loss problem based on the analyses of difficulties previously encountered and the characteristics of the formations around the Y platform. The temporary plugging solids free drilling fluid plus the technique of annular ECD real-time monitoring and precise controlling, successfully resolved the mud loss difficulty. Drilling efficiency of 5 wells drilled on the Y platform was obviously increased, the average rate of penetration (ROP) in drilling the φ215.9 mm horizontal section was 77.27 m/h, created a new record in extended reach horizontal shallow well drilling in the same area. The gas reservoir was well protected; the production rate tested was 25% higher than predetermined.