ABSTRACT Tight oil siltstones are rocks with complex structure at pore scale and are characterized by low porosity and low permeability at macroscale. The production of tight oil siltstone reservoirs can be increased by hydraulic fracturing. For optimal fracking results, it is desirable to map the ability to fracture based on seismic data prior to fracturing. Brittleness is currently thought to be a key parameter for evaluating the ability to fracture. To link seismic information to the brittleness distribution, a rock physics model is required. Currently, there exists no commonly accepted rock physics model for tight oil siltstones. Based on the observed correlation between porosity and mineral composition and known microstructure of tight oil siltstone in Daqing oilfield of Songliao basin, we develop a rock physics model by combining the Voigt–Reuss–Hill average, self‐consistent approximation and differential effective medium theory. This rock physics model allows us to explore the dependence of the brittleness on porosity, mineral composition, microcrack volume fraction and microcrack aspect ratio. The results show that, as quartz content increases and feldspar content decreases, Young's modulus tends to increase and Poisson ratio decreases. This is taken as a signature of higher brittleness. Using well log data and seismic inversion results, we demonstrate the versatility of the rock physics template for brittleness prediction.

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用于脆性地震预测的致密油粉砂岩岩石物理模型

摘要 致密油粉砂岩是孔隙尺度结构复杂的岩石，宏观尺度上具有低孔低渗的特点。通过水力压裂可以增加致密油粉砂岩储层的产量。为了获得最佳压裂结果，需要在压裂之前根据地震数据绘制压裂能力图。脆性目前被认为是评估断裂能力的关键参数。要将地震信息与脆性分布联系起来，需要岩石物理模型。目前，还没有普遍接受的致密油粉砂岩岩石物理模型。基于松辽盆地大庆油田致密油粉砂岩孔隙度与矿物成分的观测相关性及已知微观结构，我们通过结合 Voigt-Reuss-Hill 平均、自洽近似和微分有效介质理论开发了一个岩石物理模型。这种岩石物理模型使我们能够探索脆性对孔隙度、矿物成分、微裂纹体积分数和微裂纹纵横比的依赖性。结果表明，随着石英含量的增加和长石含量的降低，杨氏模量趋于增大，泊松比减小。这被视为较高脆性的标志。使用测井数据和地震反演结果，我们证明了岩石物理模板用于脆性预测的多功能性。微裂纹体积分数和微裂纹纵横比。结果表明，随着石英含量的增加和长石含量的降低，杨氏模量趋于增大，泊松比减小。这被视为较高脆性的标志。使用测井数据和地震反演结果，我们证明了岩石物理模板用于脆性预测的多功能性。微裂纹体积分数和微裂纹纵横比。结果表明，随着石英含量的增加和长石含量的降低，杨氏模量趋于增大，泊松比减小。这被视为较高脆性的标志。使用测井数据和地震反演结果，我们证明了岩石物理模板用于脆性预测的多功能性。