Abstract
This study examined the petrographically classification, petrological and petrophysical characteristics by taking a vast range of carbonate reservoir rock from Asmari and Bangestan group Formations in southern Iran basins. Implications of these characteristics were also studied to estimate the pore volume compressibility of the carbonate reservoirs. In the current study, a method is developed to classify the carbonate reservoir rocks based on the dominant factors involved in elastic properties of pore volumes. For classification, several 3702 thin sections were studied. Then, the pore volume compressibility of 200 core plugs corresponding to the range of classification parameters was obtained and quantified by a pre-proven equation. Based on the studied classification, the results clearly show an acceptable narrow bandwidth between the upper and lower bound of estimations. Furthermore, the analysis of the pore compressibility–stress relationship was in good agreement with the experimental observations. Also, the study shows that integrating the routine petrophysical properties is helpful for the estimation of stress-related properties of pore volumes into carbonate reservoir rocks.
Highlights
Hydrocarbon production operations can cause reservoir compaction due to reduction in pore fluid pressure and subsequent changes in external effective stress (Geertsma, 1957)
To turn the attention to the validity of the proposed model for prediction where the experimental Pore volume compressibility (PVC)-stress data is not available, 12 arbitrary samples were collected with porosity-permeability in the range of the frequent categories and 3 out-of-range data
We have used the petrophysical properties of rock including porosity and permeability and lithological description of samples to find out the empiricaltheoretical-based correlation between PVC and stress for different cases
Summary
Hydrocarbon production operations can cause reservoir compaction due to reduction in pore fluid pressure and subsequent changes in external effective stress (Geertsma, 1957). In order to evaluate the accuracy of the PVC models previously published by Hall (1953) , van der Knaap (1959), Horne (1997) and Jalalh (2006b), in an experimental study da Silva et al (2015) have investigated the petrophysical properties of carbonate rocks from North America from three distinctive geologic backgrounds. In a different way, Liu et al (2009) have derived two universal theoretical formulations for pore and bulk compressibilites of rocks using a novel conceptualization of the heterogeneous rock into two distinct parts, which one part follows a natural-strain-based Hooke’s law, and the other part obeys an engineering-strain-based Hooke’s law They proposed a universal exponential equation for the PVC-stress relationship as follows; Where, Cpc is the pore compressibility, is the pore compressibility, σ is the hydrostatic confining stress, Φ0 is unstressed initial porosity, and C∞pc, y, and K are constants which can be evaluated by fitting of the equation on experimental data points. Comparisons were made between these experimentally driven constants as full description indices of volumetric changes due to stress change, and rock classification
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