Stress sensitivity of coal samples in terms of anisotropy
Tóm tắt
The permeability and porosity of coal seams are anisotropic, and the variation of confining stress may induce deformation in coal samples. In order to study these characteristics, experiments and model analyses were conducted to understand the behaviors of anisotropic stress sensitivity of lean coal samples. The results showed as the closure of cleats and the generation of micro-cracks, the strong stress sensitivity of coal samples and the discrete changes in porosity were caused by confining pressure changes. In the compression period, the anisotropy trend first increased, and then decreased. In the direction perpendicular to the bedding plane, the permeability decrease rate and the irreversible damage rate were the highest. In the direction parallel to the cleats, permeability recovery rate was higher and the irreversible damage rate was lower along butt cleats. Compared to the cube root of permeability to porosity, a 1/6 power relationship was proved to be closer to the experiment results, the new relationship had the highest fit level in the face cleat direction, and the lowest fit level in the vertical direction.
Tài liệu tham khảo
Barton N, Bandis S, Bakhtar K, 1985. Strength, deformation and conductivity coupling of rock joints. International Journal of Rock Mechanics and Mining Sciences & Geomechanics, 22(3): 121–140.
Boit M A, 1941. General theory of three dimensional consolidation. Journal of Applied Physics, 12(2): 155–164.
Duan P J, Wang Z Y, 2012. Experimental investigation on mechanics properties and failure of coal in Hancheng. Coal Geology & Exploration, 40(4): 39–42.
Frank O A, Jones J, 1975. A laboratory study of the effects of confining pressure on fracture flow and storage capacity in carbonate rocks. Journal of Petroleum Technology, 27(1): 21–27.
Fu X H, Qin Y, Jiang B, Wang W F, Li G Z, 2001. Compress experiment of coal cleat and mathematical simulation of coal reservoir permeability. Journal of China Coal Society, 26(6): 574–577.
He Y L, Yang L Z, 2004. Testing study on variational characteristics of rock mass permeability under loading-unloading of confining pressure. Chinese Journal of Rock Mechanics and Engineering, 23(3): 415–419.
Jones S C, 1972. A rapid accurate unsteady-state klinkenberg permeameter. SPE Formation Evaluation, 12(5): 383–397.
Li T L, Wu X M, Tu H Z, 2000. The measurement and analysis and application on the mechanical property of coal seam. Geology and Prospecting, 36(2): 85–88.
Lin B Q, Zhou S N, 1987. Experimental investigation on the permeability of the coal samples containing methane. Journal of China University of Mining & Technology, (1): 21–28.
McKee C R, Bumb A C, 1988. Koenig R A. Stress-dependent permeability and porosity of coal. SPE Formation Evaluation, 3(1): 81–91.
Meng Z P, Hou Q L, 2012. Experimental research on stress sensitivity of coal reservoir and its influencing factors. Journal of China Coal Society, 37(3): 430–436.
Meng Z P, Tian Y D, Li G F, 2010. Theory and method of coalbed methane development geology. Beijing: Science Press, 69–70.
Peng Y W, Qi Q X, Deng Z G, Li Y H, 2008. Experimental research on sensibility of permeability of coal samples under confining pressure status based on scale effect. Journal of China Coal Society, 33(5): 509–513.
Seidle J P, Jeansonne M W, Erickson D J, 1992. Application of matchstick geometry to stress dependent permeability in coals. SPE Formation Evaluation, (5): 433–444.
Somerton W H, Soylemzoglu I M, Dudley R C, 1975. Effect of stress on permeability of coal. International Journal of Rock Mechanics and Mining Sciences, 12: 129–145.
Song C Z, Zheng R C, 2006. Stress sensitivity on low permeability gas reservoir and its impact on single well production. Petroleum Geology & Oilfield Development in Daqing, 25(6): 47–49.
Tang J P, Pan Y S, Li C Q, Shi Q, Dong Z X, 2006. Experimental study on effect of effective stress on desorption and seepage of coalbed methane. Chinese Journal of Rock Mechanics and Engineering, 25(8): 1563–1568.
Yang M P, Wang G, Xu S Y, Gao C, 2011. Steady flow productivity equation for stress sensitivity coalbed methane gas well. Nature Gas Geoscience, 22(2): 347–351.
Zhang S L, Li B F, 1996. Mechanism of coalbed cleat and its significance in evaluation of coalbed methane exploration and development. Coal Geology of China, 8(1): 72–77.
Zhu B C, Huang Y, Tang S H, 2010. Research on mechanical properties of water saturated coal samples under triaxial stress. //Coalbed Methane Exploration and Exploitation Theories and Techniques-National Coalbed Methane Symposium of 2010, Beijing: Petroleum Industry Press, 72–77.
Zhu J, Jiang Y D, Zhao Y X, Zhao Y X, 2010. Experimental study on permeability of coal samples under the simultaneous action of unloading and loading. Journal of China Coal Society, 35(1): 76–80.