塔里木盆地库车坳陷白垩系巴什基奇克组致密砂岩力学性质影响因素及其变化规律

Factors affecting the mechanical properties of tight sandstone and their patterns of variation in Cretaceous Bashijiqike Formation of Kuqa Depression in Tarim Basin

徐珂 鞠玮 张辉 梁艳 尹国庆 王志民 徐浩然 张玮 梁景瑞

XU Ke JU Wei ZHANG Hui LIANG Yan YIN Guoqing WANG Zhimin XU Haoran ZHANG Wei LIANG Jingrui

1. 中国石油天然气股份有限公司 塔里木油田公司, 新疆 库尔勒 841000; 2. 中国石油天然气集团有限公司 超深层复杂油气藏勘探开发技术研发中心, 新疆 库尔勒 841000; 3. 新疆维吾尔自治区 超深层复杂油气藏勘探开发工程研究中心, 新疆 库尔勒 841000; 4. 中国矿业大学 资源与地球科学学院, 江苏 徐州 221116; 5. 煤层气资源与成藏过程教育部重点实验室, 江苏 徐州 221008; 6. 山东省煤田地质局 第二勘探队, 山东 济宁 272100

1. PetroChina Tarim Oilfield Company, Korla, Xinjiang 841000, China; 2. Research and Development Center for Ultra-Deep Complex Reservoir Exploration and Development, CNPC, Korla, Xinjiang 841000, China; 3. Engineering Research Center for Ultra-deep Complex Reservoir Exploration and Development, Xinjiang Uygur Autonomous Region, Korla, Xinjiang 841000, China; 4. School of Researces and Geosciences, China University of Mining and Technology, Xuzhou, Jiangsu 221116, China; 5. Key Laboratory of Coalbed Methane Resources and Reservoir Formation Process (Ministry of Education), China University of Mining and Technology, Xuzhou, Jiangsu 221008, China; 6. The Second Exploration Team of Shandong Provincial Bureau of Coal Geology, Jining, Shandong 272100, China

为查明塔里木盆地库车坳陷白垩系巴什基奇克组致密砂岩力学特性，结合深层—超深层油气勘探开发的现场问题，采用三轴压缩实验定量研究了围压、流体和加载速率影响岩石力学性质变化的规律，并初步分析其原因。研究结果表明，砂岩试样最大主应力差、弹性模量均随着围压的增大而显著增大，其微观原因在于围压增大使岩石内部质点彼此之间距离缩短，增强了岩石的内聚力，颗粒之间不易离散；砂岩试样经历低围压脆性→脆—韧性转换→高围压韧性变形破裂演化的过程。与干燥砂岩试样相比，纯净水浸泡样、150 g/L溶液浸泡样、250 g/L溶液浸泡样和350 g/L溶液浸泡样弹性模量降低幅度分别为67.71%、61.45%、64.69%和57.32%，纯净水浸泡造成的降低幅度最大，流体矿化度的升高能够减弱岩石力学参数弱化的趋势；晶体表面结晶和双电层厚度变化是上述变化规律的重要控制因素。在较低的加载速率条件时，砂岩试样的最大主应力差、弹性模量和泊松比的值都较小，但随着加载速率的增大增速较快；当加载速率达到一定关键数值之后(本次实验为0.05 mm/min左右)，岩石力学参数值增速变缓。

To clarify the mechanical characteristics of tight sandstone in the Cretaceous Bashijiqike Formation of Kuqa Depression in Tarim Basin, and address field issues in deep and ultra-deep oil and gas exploration and development, triaxial compression experiments were used to quantitatively study the patterns of changes in rock mechanical properties influenced by confining pressure, fluid, and loading rate, with a preliminary analysis of their causes. The results showed that the maximum principal stress difference and elastic modulus of the sandstone samples increased significantly with confining pressure. The micro-reason was that the increase in confining pressure reduced the distance between particles inside the rock, enhancing the rock's cohesion and making particle dispersion less likely. Sandstone samples exhibited a progression from brittleness under low confining pressure to brittle-ductile transformation, and to ductile deformation under high confining pressure. Compared with dry sandstone samples, the reduction in the elastic modulus of samples soaked in pure water, 150 g/L solution, 250 g/L solution, and 350 g/L solution were 67.71%, 61.45%, 64.69%, and 57.32%, respectively, with pure water soaking causing the greatest reduction. Increasing fluid salinity could mitigate the weakening trend in rock mechanical parameters. Crystallization on crystal surfaces and changes in the electric double layer thickness were important controlling factors for these patterns. At lower loading rates, the values for maximum principal stress difference, elastic modulus, and Poisson’s ratio of the sandstone samples were smaller, but they increased faster with increasing loading rates. When the loading rate reached a certain critical value (around 0.05 mm/min in this experiment), the rate of increase in rock mechanical parameters slowed down.

https://doi.org/10.11781/sysydz202404823