复合岩盐层井眼蠕变缩径的数值模拟

盐岩在深部高温高压环境下具有很强的蠕变特性,在岩盐层钻井经常出现井眼缩径、卡钻等复杂事故。目前关于岩盐层井段安全钻进泥浆密度的计算方法主要适用于均匀地应力的情况,难以在非均匀地应力条件下应用。为此研究建立了三向地应力作用下盐岩和砂泥岩相互交错的复合岩盐层井眼蠕变缩径的三维有限元模型,并以塔里木油田羊塔克地区深井为例,研究了非均匀地应力条件下,复合岩盐层井眼随时间变化的蠕变缩径规律,得出了一定泥浆密度下岩盐层井眼在不同时刻的井径值。计算结果表明,安全泥浆密度有限元模拟值与羊塔克地区岩盐层井段实际采用的安全泥浆密度非常接近,验证了所建数值模型的合理性和计算结果的可靠性,研究成果为岩盐层井段的安全钻进提供了技术支撑。

NUMERICAL SIMULATION OF HOLE CREEP SHRINKAGE FOR COMPOSITE ROCK SALT LAYERS

Salt rocks have very strong creep behaviors in HTHP environment in deep formations, complex accidents such as hole shrinkage, drill pipe sticking, etc. occurring frequently. Current methods to calculate the safe drilling mud density are mainly used in circumstances of homogeneous earth stress. The 3-D finite element analysis （FEA） model of borehole creep shrinkage concerning salt rock and sand shale was established in this paper under triaxial earth stress. On the basis of deep wells of Yangtake in Tarim, laws of borehole creep shrinkage vs time were studied under the condition of heterogeneous earth stress, and values of borehole diameter in different times are obtained when the mud density is specified. Results calculated are very close to the safety drilling mud density field used in rock salt layers, thus verifying the reasonableness and reliability of the model established in the paper. Research results can provide technical support for safe drilling in rock salt layers