南海西部浅层大位移水平井钻井关键技术与实践

Key drilling technologies and practices of shallow extended reach well in western South China Sea

南海西部海域莺歌海盆地油气资源丰富,具有埋深浅、成岩性差、资源分布零散特点。现多采用大位移水平井方式挖潜老油气田周边剩余油气,作业中存在表层桩管鞋窜漏、浅层泥岩段出泥球憋漏地层、目的层压力亏空易漏导致储层伤害、技术套管下入摩阻大及固井压力作业窗口窄易漏失等难题。结合前期区域钻井作业经验,通过加深表层桩管下深至入泥95 m,降低桩管鞋窜漏风险;分段优化技术井段钻井液体系,解决浅层泥岩段起泥球、憋漏地层难题;优选液体润滑剂复配组合,配合漂浮接箍下套管工艺,确保技术套管顺利下入到位;优化无固相有机盐钻井液体系暂堵剂粒径复配,提供良好封堵承压能力,解决压力亏空易漏导致储层伤害难题;通过加深表层套管下深,使用动态当量循环密度控制固井技术,提高固井作业安全及质量,最终形成了一套浅层大位移水平井钻井关键技术。该技术成功应用于莺歌海盆地5口浅层大位移水平井,整个作业过程未发生起泥球、井漏及井下复杂情况,技术套管下入顺利,气井生产测试中的表皮系数为0.5。该系列技术为区块类似油气田的高效开发提供了技术支持。

Yinggehai basin in western South China Sea is of abundant hydrocarbon resources and is characterized by shallow reservoir buried depth,poor diagenesis and scattered resource distribution.Extended reach wells are widely used to tap the remaining oil and gas around the old oil and gas fields,but there are many difficulties during the operation,such as leakage of surface casing shoes,mud ball and formation leakage in shallow mudstone section,reservoir damage due to pressure depletion and leakage of the target stratum,large friction in technical casing running and narrow pressure window for cementing,etc.Based on the previous regional drilling experience,the risk of surface casing shoe leakage was reduced by deepening the surface casing depth to 95 m into the mud;the drilling fluid system of the technical well section was optimized in segments,solving the problems of mud ball formation and formation leakage in the shallow mudstone section;the optimal combination of liquid lubricants was selected,combined with the floating collar casing running technology,ensuring the smooth running of the technical casing;the particle size of the temporary plugging agent in the solid-free organic salt drilling fluid system was optimized,providing good sealing and pressure-bearing capacity,and solving the problem of reservoir damage caused by pressure depletion and leakage;the surface casing depth was deepened and the dynamic equivalent circulating density control cementing technology was used,improving the safety and quality of the cementing operation.Therefore,a set of key drilling technologies for shallow extended reach wells were formed finally.These technologies were successfully applied to five shallow extended reach wells in Yinggehai basin,and no mud ball,downhole-loss circulation or downhole complications occurred during the whole operation process.The technical casing was run smoothly,and the skin factor of the gas well production test was 0.5.These technologies have provided technical support for the efficient development of similar oil and gas fields in the block.