Tight sandstone reservoirs basically have low porosity and permeability, a complex pore structure and a heterogeneous distribution of immiscible fluids. With the development of theoretical models, it is common to characterize rock properties, i.e., pore structure, microfractures, fluid type and saturation, etc., based on acoustic and electrical properties. We have taken four tight sandstone samples and performed X-ray diffraction and cast thin section analyses. We measure porosity and permeability as well as ultrasonic properties and electrical conductivity at different confining pressures and fluid saturations. These measurements show that the P-wave velocity, P-wave attenuation and conductivity strongly depend on the type and saturation of the fluid and the microstructure of the rock. We propose a combined acoustic-electrical model based on the concept of equivalent medium and on the double porosity, patchy saturation and squirt flow models. We then create rock physics templates calibrated with wellbore log data to estimate fluid saturation and equant and soft porosities, which are well corroborated by gas production reports. This work demonstrates the link between combined acoustic-electrical responses and rock properties and provides an effective approach for applications in reservoirs.

中文翻译：

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通过实验室测量验证的致密砂岩声电联合建模

致密砂岩储层基本具有低孔低渗、孔隙结构复杂、非混相流体分布不均匀的特点。随着理论模型的发展，基于声学和电学性质来表征岩石性质，即孔隙结构、微裂缝、流体类型和饱和度等已成为普遍现象。我们采集了四个致密砂岩样品，并进行了 X 射线衍射和铸件薄片分析。我们测量不同围压和流体饱和度下的孔隙度和渗透率以及超声特性和电导率。这些测量结果表明，纵波速度、纵波衰减和电导率很大程度上取决于流体的类型和饱和度以及岩石的微观结构。我们提出了一种基于等效介质概念和双孔隙率、斑片饱和度和喷射流模型的组合声电模型。然后，我们创建用井眼测井数据校准的岩石物理模板，以估计流体饱和度以及等孔隙度和软孔隙度，这些都得到了天然气产量报告的充分证实。这项工作证明了声电组合响应与岩石特性之间的联系，并为储层应用提供了一种有效的方法。