Abstract
According to the characteristics of the paleostress field and tectonic features at the key moments during tectonic movement after the formation of the no. 3 coal seam, the superimposed areas of different folding zones in the southern section of Shizhuang in central and southern Qinshui Basin were divided. The reservoir permeability of the coal in different superimposed areas was obtained by integrating a laboratory in situ measurement technique, geological strength indices, and multiple parameter fitting of acoustic logging data. The maximum and minimum horizontal principal stresses in different superimposed areas were gained through analysis of the fracturing curve and acoustic logging data. Thus, the relationships between ground stress and permeability in different superimposed areas were revealed. The results show that the relationships between different stresses and permeability were not obvious without considering multistage tectonic superposition. The relationships between the varying stresses and permeability in the same superimposed areas were exponential. The deformation of coal seams in the superimposed areas on the wings of fold belts striking north-central direction was relatively weak, and its permeability was the highest. The permeability in the superimposed areas of the wings of different fold belts in a southeasterly direction was lower than that in the superimposed areas of the wings and the cores of folds. The permeability is the worst in the superimposed areas by the cores and wings of the folds. The results can provide a reference for the study of the heterogeneous deformation of coal reservoirs.
Highlights
Tectonic movement is one of the necessary conditions for the formation of coal seams, which affects the thickness and form of a coal seam and affects the current stress regime
In recent years, existing studies have found the permeability of coal seams by using methods including laboratory or in situ measurement, acoustic well logging, and integrated in situ well measurements [1,2,3] and estimated stresses by numerical simulation based on ANSYS with calculation of hydraulic fracturing pressure curves, strain gauge measurement [4,5,6], etc
With multiple tectonic movements and the relatively complicated geological structural conditions in most of China [11,12,13,14,15], there may be superimposed areas of “the cores of different synclines, the wings and the cores of different synclines, the cores of different anticlines, the wings and the cores of different anticlines, different wings of the folds” involved in the deformation of coal seams due to the differences in the directions of the principal stresses during multistage tectonic movement; Geofluids this changes the stress state, and the same formula may not be suitable for illustrating the relationship between permeability and ground stress
Summary
Tectonic movement is one of the necessary conditions for the formation of coal seams, which affects the thickness and form of a coal seam and affects the current stress regime. In recent years, existing studies have found the permeability of coal seams by using methods including laboratory or in situ measurement, acoustic well logging, and integrated in situ well measurements [1,2,3] and estimated stresses by numerical simulation based on ANSYS with calculation of hydraulic fracturing pressure curves, strain gauge measurement [4,5,6], etc. Based on the relationship between permeability and ground stress, the changes in permeability are exponentially related to the change in ground stress [7] According to this relationship, a high-permeability zone was predicted [8, 9]. The results of this study provide a reference for the prediction of permeabilities in superimposed zones under multistage tectonic movement
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