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在 MTS 系统中模拟储层埋藏状态并于140 MPa/200℃(保持180min 和100MPa/120℃,393 min)条件下用状态差法研究了饱和水长石石英砂岩的结构变化。同常温常压条件相比,上述条件下,砂岩骨架颗粒和填隙物晶格主峰 d 值减少0.7%—0.24%,全部衍射峰 d/nm 值平均减小0.0266—0.0012,骨架颗粒间距减小5.3μm,骨架矿物粒度平均值减小16.8μm;岩石结构向紧密压缩状态变化;石英颗粒波状消光增加,电子致光性增强,其裂纹增加。砂岩的这种变化符合固体物质统计热力学规律。在≤140 MPa/≤200℃的条件砂岩呈弱塑性变形,其变形结果可以保持到常温常压下,因此常温常压下岩石结构特征可反映埋藏结构状态。可用状态差法研究埋藏结构。在本实验的温压及保持时间(最长393 min)条件下各种矿物特别是粘土矿物在物相上未发生变化。
The MTS system was used to simulate the burial status of the reservoirs and the structural changes of the saturated feldspathic quartz sandstone were studied by the state difference method under conditions of 140 MPa / 200 ℃ (180 min and 100 MPa / 120 ℃, 393 min). Compared with the normal temperature and normal pressure conditions, under the above conditions, the d value of the main lattice peak of the sandstone skeleton particles and interstitials is reduced by 0.7% -0.24%, the d / nm value of all the diffraction peaks is reduced by 0.0266-0.0012 on average, and the spacing of the skeleton particles is decreased 5.3μm, and the average grain size of skeleton minerals decreases by 16.8μm. The rock structure changes to the state of close compression. The wave extinction of quartz particles increases and the electrophotosensitivity increases, and the crack increases. This change in sandstone is consistent with the statistical thermodynamic laws of solids. Under the condition of ≤140 MPa / ≤200 ℃, the sandstone shows weak plastic deformation, and the deformation result can be kept at normal temperature and pressure. Therefore, the rock structure characteristics under normal temperature and pressure can reflect the burial structure. Burial structure can be studied by state difference method. Under the conditions of warm pressure and holding time (up to 393 min), all kinds of minerals, especially clay minerals, did not change in the phase.