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基于有限元应变能量信息致密砂岩储层裂缝甜点预测
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Abstract:
本文利用有限元法构建了致密砂岩储层的甜点预测方法。应变能量(U)能定量表征不同类型岩石介质内部微尺度破裂发生的概率。其具体步骤为：首先，建立低幅度构造区地质模型，以相控原则对岩石力学参数进行了赋值，通过边界施加载荷恢复了目的层在燕山期的古构造应力场；然后，根据能量守恒原理求取目的层的应变能量密度分布。U值的平面分布具有明显呈带状分布的特征。分析了应变能量密度与低幅构造区强非均质性致密砂岩储层产能之间的关系，符合率较高。高应变能量区为甜点区。本文基于U值定义的甜点主要是从岩体变形及破裂角度进行的分析。在实际勘探过程中，还应考虑储层物性及保存条件等地质因素。本文建立了一套系统的基于U值计算的甜点预测方法。该方法适用于鄂尔多斯盆地低幅构造区强非均质性致密砂岩储层。
In this paper, the finite element method is used to construct a sweet spot prediction method for tight sandstone reservoirs. Strain energy (U) can quantitatively characterize the probability of micro-scale fractures in different types of rock media. The specific steps are: first, establish a geological model of the low-amplitude structural zone, assign values to the rock mechanics parameters based on the phase control principle, and restore the paleo-tectonic stress field of the target layer in the Yanshanian period through the boundary load. Then, according to the principle of energy conservation, the strain energy density distribution of the target layer is obtained. The plane distribution of U value has obvious characteristics of band-like distribution. The relationship between strain energy density and productivity of tight sandstone reservoirs with strong heterogeneity in low-amplitude structural areas is analyzed, with a high coincidence rate. The high strain energy zone is the sweet spot. In this paper, the sweet spot defined by the U value is mainly analyzed from the perspective of rock deformation and fracture. In the actual exploration process, geological factors such as reservoir physical properties and preservation conditions should also be considered. This paper establishes a systematic dessert prediction method based on U value calculation. This method is suitable for tight sandstone reservoirs with strong heterogeneity in the low-amplitude structural area of the Ordos Basin.
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