关键词: 致密砂岩, 储层特征, 岩石力学特征, 微地震, 压裂改造, 裂缝网络, 鄂尔多斯盆地

Abstract: Tight sandstone reservoirs are characterized by poor petrophysical properties, strong heterogeneity and complex sandbody connectivity. Volumetric fracturing in horizontal wells is the primary technique for the efficient development of such reservoirs. A comprehensive evaluation of reservoir quality, spatial distribution of hydraulic fractures, fracture-network connectivity and stimulated reservoir volume is critical for determining single-well productivity. In this study, downhole microseismic monitoring was used to monitor fracture development during the entire fracturing process of six wells in three blocks in the mid-eastern Ordos basin. Continuous production performance tracking was carried out to comprehensively evaluate the stimulation effectiveness of gas wells. The results show that the scale of hydraulic fracturing controls the stimulated reservoir volume, and the increasing fracturing scale is positively correlated with fracture propagation. When the fracturing scale reaches a certain level, an obvious marginal effect occurs in the fracture network. Under the same fracturing stimulation scale, the larger the scale of high-quality sandbodies, the better the hydraulic fracturing effectiveness. Fracturing cluster spacing should be designed according to the mechanical properties of reservoir rocks. A higher the reservoir brittleness index requires a larger designed cluster spacing. When cluster spacing is uniformly distributed, a complex fracture network with interacting fractures can be formed after fracturing. A better match between high-quality reservoir conditions and fracturing stimulation scale leads to higher the single-well productivity.

Key words: tight sandstone, reservoir characteristics, rock mechanical characteristics, microseismic, fracturing stimulation, fracture network, Ordos basin