南海西部乌石海域ø508 mm隔水导管简易井口稳定性研究

南海西部海域常规探井简易水上井口前期普遍采用ø762 mm×25.4 mm大尺寸隔水导管,作业成本较高。从隔水导管桩土承载力、海底土浅层破裂压力、极端海况下隔水导管强度等方面分析ø508 mm×25.4 mm隔水导管稳定性。结果表明:隔水导管最小入泥深度为45 m时,能满足井口承载1 000 kN要求; 极端海况下隔水导管能满足强度要求,在水面及泥线下2 m附近出现最大弯矩与应力,泥线以下10 m后应力较小。现场应用表明,乌石海域采用ø508 mm隔水导管可实现后续安全钻井作业,相比ø762 mm大尺寸隔水导管方案,可降低作业工期与费用。

Stability Study of a Simple Wellhead with 508 mm Riser in Wushi Sea Area,Western South China Sea

In the early stage of simple water wellhead of conventional exploration wells in the western South China Sea, the large-size riser with diameter of 762 mm× 25.4 mm was widely used with high operation cost. The pile-soil bearing capacity of the riser, the shallow rupture pressure of the seabed soil and the strength of the riser under extreme sea conditions were analyzed. The results show that when the minimum mud depth of riser is 45 m, it can meet the requirement of 1 000 kN bearing capacity of wellhead. Under extreme sea conditions, the riser can meet the strength requirements. The maximum bending moment and stress appear at the water surface and 2 m below the mudline, and the stress is smaller 10m below the mudline. The field application shows that the application of ø508 mm riser in Wushi sea area can realize the follow-up safe drilling operation. Compared with the ø762 mm large size riser, it can effectively reduce the operation period and cost.