塔里木X区古近系膏泥岩层力学性质分析

Analysis of Cream Mudstone's Mechanical Properties in Tarim X Area

对塔里木X区古近系膏泥岩进行取样,镜下鉴定表明其主要成分为硬石膏和泥质.进行室内声波测试和力学测试,结果表明：85℃范围内波速的温度效应可以忽略不计；硬石膏泥岩的波速值比膏质泥岩大（约1.4倍）；但泥质含量高的膏质泥岩在有效围压不断增加过程中波速平均增量约为硬石膏泥岩的2倍；膏泥岩动模量变化规律与波速类似.泊松比变异系数为21.7％,离散度高,各阶段增减变化比较杂乱；但变化量级较小.单轴条件下膏泥岩为脆性变形,三轴条件下为弹-塑性变形,硬石膏泥岩的抗压强度、静弹性模量及静泊松比都比膏质泥岩大得多.温度条件对两类岩性岩石力学参数的影响程度不大.岩样抗张强度与三轴抗压强度线性正相关,内聚力和内摩擦角与波阻抗线性正相关.通过动静参数对比,表明两种岩性服从相似的变化规律,可以对整体进行拟合.最后计算出该区正常压实关系式；并根据Eaton法与相关地层压力测试对比计算出古近系地层压力系数.结果表明古近系压力系数大约在1.1～1.2左右变化,该压力系数表明膏泥岩层的压力梯度变化要大于一般压实层.按此压力系数近似计算该区古近系剩余压力在3.5～7.2 MPa左右.该研究可以为深入分析古近系膏泥岩层力学性质、制定合理钻井液密度、高效钻探及制定完井方案等方面提供一些参考.

By sampling of the cream mudstone in Tarim X area, making indoor acoustic and mechanics test, it shows：the effect of wave velocity within 85 qC can be neglected;wave velocity value of hard gypsum mudstone is about 1.4 times bigger than cream mudstone,but in the process of effective confining pressure increasing the aver- age wave velocity increment of high argillaceous content cream mudstone is larger, about 2 times of hardened gyp- sum mudstone ; the changing rule of cream mudstone＇ dynamic modulus is similar with the wave velocity ; poisson ra- tio＇variation coefficient was 21.7%, the discrete degree is high, but the changing order of magnitude is small; study statics parameters such as the compressive strength, elastic modulus, poisson＇s ratio, cohesion and internal friction angle and the change rule between movement parameters, finally calculate the normal compaction equation, and according to the Eaton method of the research in formation pressure, the results show that the paleogene system pressure coefficient is about 1.1 - 1.2, the pressure coefficient shows that cream mudstone layer of pressure gradi- ent change than general compaction layer, according to the pressure coefficient of the approximate calculation in this area, the residual stress is around 3.5 -7.2 MPa.