南海西部油田表层隔水导管稳定性分析技术

TECHNOLOGY USED TO ANALYZE STABILITY OF CONDUCTOR RISER AT WESTERN SOUTH CHINA SEA OILFIELD

南海西部W油田是中海油重要的原油生产基地,该油田拟新增调整井以进一步挖掘产能和提高产量,同时,为持续降本增效,新增调整井计划简化井身结构,将隔水导管尺寸从原Φ762mm优化为Φ508mm,为避免采用小尺寸隔水导管而可能产生的井口失稳风险,并克服表层钻进易井漏失返的难题,亟需开展隔水导管稳定性研究。对此创新提出了横向力学、纵向力学及水力学“三位一体”的隔水导管稳定性综合分析思路和方法,首先运用有限元建模分析并推荐采用了钢级K55、壁厚14.3mm的Φ508mm隔水导管,其次通过分析计算海底土承载力和浅层破裂压力,优化得到隔水导管最佳入泥深度为50m。现场应用结果表明,W油田新增调整井表层作业过程中始终保持了井口稳定,且未发生井漏、井口失返等复杂情况,确保了现场作业安全顺利,缩短作业周期近3d,降本增效显著。

It’s planned to build more adjustment wells for more production and output at W oilfield of western south China sea,which is an important crude oil production base of CNOOC.In order to continually reduce cost and increase efficiency,Φ508mm-size conductor riser shall be used instead of Φ762mm-size conductor riser to simplify the casing program of additional wells.It’s necessary to make a research about conductor riser stability in order to overcome wellbore unstability after conductor riser minimized and lost circulation during surface drilling.Thus a conductor riser stability analysis idea combining transverse mechanics,vertical mechanics and hydraulics has been adopted.First,a Φ508mm conductor riser with steel grade K55 and 14.3 mm-size thickness has been recommended by finite element analysis.Second,the driving depth of conductor riser has been optimized to 50 meters after analysis of the ultimate load-bearing capacity and fracture pressure of shallow formation.The oilfield application shows that the riser pipe of additional adjustment wells in W oilfield always remain stable and no lost circulation happened,a safe and smooth operation ensured.Over two million RMB investment has been saved and nearly three days of operation time has been saved.The cost is decreased and efficiency increased markedly after conductor riser stability analysis used.