Research on the key performance evaluation and application of ultra-high temperature and pressure offshore coring tools
Deep and ultra-deep wells in offshore oil fields often suffer from ultra-high temperature,ultra-high pressure,narrow safety pressure window,and complex geological conditions,which leads to complex situations such as well leakage and sticking dur-ing drilling and coring operations.Moreover,the low coring efficiency via using conventional drilling and coring tools cannot meet the requirements of coring operations.Therefore,based on the analysis of the difficulties in coring technology for offshore ultra-high temperature and pressure wells,a set of ball-free drilling coring tools suitable for offshore ultra-high temperature and pressure wells was designed.Three key performance parameters,namely thread connection strength,water diversion joint and coring bit hydrody-namics,and suspension assembly friction,were evaluated.The results show that the thread strength of the coring tool can meet the industry standard requirements under both room temperature and ultra-high temperature(250℃)conditions.Reasonable structural design of water diversion joints and core drilling bits results in small pressure drop,low friction resistance of the suspension assem-bly,and relatively stable operation of the inner cylinder.The drilling and coring tools for offshore ultra-high temperature and pres-sure wells have been successfully applied in the coring operations of two ultra-high temperature and pressure wells in the Ledong block.The bottom hole temperatures of WC-9 and LS-2 wells are 205.2℃ and 212.3℃,and the pressure coefficients are 2.29 and 2.31,the coring recovery rates of both wells have reached 100％,and the core has good column forming performance.The coring bit is not significantly worn,achieves good on-site application results indicating good feasibility for promotion and application in off-shore similar ultra-high temperature and pressure wells.
ultra high temperature and pressure wellscoring toolskey parametersthread connection strengthhydrodynamicsfrictional resistance
NETL
NSTL
万方数据
