胜科1井盐膏层段套管安全可靠性分析

Casing Safety Reliability Analysis in Salt and Gypsum Formation of Well Shengke-1

胜科1井为东部油田第一口井深超7 000 m的科学探井。三开井段有两组流变性较强的软泥岩和盐膏层段,邻井郝科1井因盐膏层的蠕变导致244.5 mm套管挤毁变形而被迫完钻。从套管柱强度设计、套管磨损与剩余强度和套管安全下入3个方面分析了盐膏层段套管的安全可靠性。分析与现场实践均表明:济阳坳陷东营凹陷深层盐膏层套管抗挤毁强度设计中,计算套管外挤力时管外压力应按上覆岩层压力计算,管内压力应按全漏失面计算;按缺陷套管推导出的磨损后套管剩余强度计算模型是可行的;为保证套管柱下至设计井深,应根据盐膏层的蠕变速度选择钻井液密度,以减少钻井过程中可能出现的各种井下复杂情况。

Well Shengke-1 is the first scientific exploratory well completed over 7000m in the East China oilfields.In the third hole section,there were two series of soft gypsum mudstone and saltbed stone with strong creep behavior.Neighboring Well Haoke-1 was forced to complete due to the collapsing deformation of φ244.5 mm casing string caused by the creep of salt stone.The reliability of the casing safety were analyzed from casing strength design,casing wear and remaining strength,and safety casing running.The analysis and field application indicate that,during the design of casing strings anti-collapse in deep salt-bed rock in Dongying sag of Jiyang depression,the outer dynamic load should be calculated using overlying strata pressure and internal pressure by using drilling fluid losing level;the mathematic model for calculating the casing remaining strength using defect casing empirical formula is advisable;for the purpose of running casing strings to designed depth,the drilling fluid density was supposed to be calculated using the creep speed of gypsum and salt stones to reduce possible complex cases occurred during drilling operation.