Abstract
Abstract Tight-oil reservoirs have low porosity and permeability, with microcracks, high clay content, and a complex structure resulting in strong heterogeneities and poor connectivity. Thus, it is a challenge to characterize this type of reservoir with a single geophysical methodology. We propose a dual-porosity-clay parallel network to establish an electrical model and the Hashin-Shtrikman and differential effective medium equations to model the elastic properties. Using these two models, we compute the rock properties as a function of saturation, clay content, and total and microcrack porosities. Moreover, a 3D elastic-electrical template, based on resistivity, acoustic impedance, and Poisson’s ratio, is built. Well-log data is used to calibrate the template. We collect rock samples and log data (from two wells) from the Songliao Basin (China) and analyze their microstructures by scanning electron microscopy. Then, we study the effects of porosity and clay content on the elastic and electrical properties and obtain a good agreement between the predictions, log interpretation, and actual production reports.
Highlights
Tight-oil reservoirs are widely distributed around the world (e.g., [1, 2]) and become a new prospect of hydrocarbon exploration and development [3, 4]
We propose a dual-porosity-clay parallel network to establish an electrical model and the Hashin-Shtrikman and differential effective medium equations to model the elastic properties
We superimpose the elastic and electrical attributes on the 3D template and use a grid searching method to estimate the reservoir properties at Wells A and B
Summary
Tight-oil reservoirs are widely distributed around the world (e.g., [1, 2]) and become a new prospect of hydrocarbon exploration and development [3, 4]. Tight-oil rocks exhibit low porosity and permeability, a complex pore structure, and higher clay content [5,6,7]. By using a single-scattering model and the spectral-ratio method, Ma and Ba [28] estimated the coda and intrinsic attenuation of tight-oil siltstones and analyzed the effects of saturation, pore structure, and mineral content on wave attenuation. Jensen et al [37] related elastic and electric attributes by using differential effective medium (DEM) theories He calibrated this approach with core samples and well-log data. The Gassmann equation [51] yields the elastic modulus of the saturated rock These models allow us to analyze how the elastic and electrical properties are affected by water saturation, total and microcrack porosities, and clay content. The results are compared with the log interpretation and actual production reports
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