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A New Method for Assessment of Directional Permeability in Carbonate Formations Using Electrical Resistivity Measurements
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The assessment of directional permeability in carbonate formations is challenging due to their complex pore structure and anisotropic pore-network properties. Previous studies have shown that permeability is controlled by the conducting pore network; which is the portion of the connected pore system that contributes to both fluid and electric current flow in the formation. Conventional permeability assessment techniques attempt to quantify the conductive pore network volume fraction using well-log-based estimates of acoustic or non-shale porosity. However, these porosity estimates do not represent the anisotropic conducting pore network as they fail to account for the directional pore-network connectivity in carbonate rocks. As a result, conventional well-log-based permeability assessment techniques are unreliable for quantifying directional permeability in carbonate formations. This thesis introduces a method for depth-by-depth assessment of the directional conducting pore network volume fraction and directional permeability using combined interpretation of well logs and pore-scale images from carbonate formations. The proposed method takes advantage of the similarity between electric current and fluid flow paths in the rock-fluid system to estimate depth-by-depth directional conducting pore network volume fraction and permeability. In the field example presented, water saturation estimates were used to correct the electrical resistivity for the effect of hydrocarbon saturation. Then, well-log based rock classification was performed to identify different petrophysical rock types in the formation. Three-dimensional pore-scale images were obtained from each rock type using an X-ray micro computed tomography scanner. Then pore-scale simulations of electrical current and fluid flow were conducted to develop conducting pore-network and permeability models for each rock type. Finally, these pore-scale models were applied for depth-by-depth assessment of directional conducting pore-network volume fraction and directional permeability. The proposed method was applied in the pore-scale and well-log domain. In pore-scale domain, the method was used for the assessment of directional permeability in three carbonate rock types with complex pore structure. The pore-scale directional permeability estimates were cross-validated using permeability estimates obtained from a Lattice Boltzmann fluid flow simulator. In the well-log domain, the proposed technique was used to estimate permeability in the Canyon Reef formation of the SACROC oil field. The permeability estimates were cross-validated using available core measurements. The results showed a significant improvement using the proposed permeability assessment technique in both the pore-scale and well-log-scale domains. I observed a 52% and 34% decrease in the relative error associated with pore-scale and well-log domain permeability estimates, as compared to conventional porosity-permeability models.
Oyewole, Emmanuel O. (2015). A New Method for Assessment of Directional Permeability in Carbonate Formations Using Electrical Resistivity Measurements. Master's thesis, Texas A & M University. Available electronically from