Quantitative evaluation of free gas and adsorbed gas content of Wufeng-Longmaxi shales in the Jiaoshiba area, Sichuan Basin, China

Abstract

Quantitative analysis of free gas and adsorbed gas content in shale reservoirs is great significance for efficient exploration and development of shale gas. Based on the isothermal adsorption experiment of shale samples from Wufeng Formation to Longmaxi Formation of JYA well in Jiaoshiba area and Langmuir volume model, the relationship between shale adsorption capacity and temperature, pressure, organic carbon content, quartz and clay mineral content is analyzed. Besides, the key parameters such as Langmuir volume and Langmuir pressure are dynamically calibrated by combining grey correlation method. A new model for calculating adsorbed gas and free gas is established, which takes fully into account the formation temperature, pressure, TOC and shale mineral components. The results showed that the gas content of shale calculated by the new dynamic modified model is in good agreement with the actual gas content characteristics of shale reservoirs. The new model fully takes into account the vertical and horizontal heterogeneity of mineral components and its influence on shale adsorption capacity. That is suitable not only for the tectonic stability area but also for the analysis of gas content in the area with strong tectonic movement. It is concluded that the modified calculation model can effectively predict the adsorbed gas, free gas and total gas content of shale reservoirs under formation conditions, which can be used as an indicator for the analysis and prediction of the exploration and development potential of shale gas wells.

Cited as: Gou, Q., Xu, S. Quantitative evaluation of free gas and adsorbed gas content of Wufeng-Longmaxi shales in the Jiaoshiba area, Sichuan Basin, China. Advances in Geo-Energy Research, 2019, 3(3): 258-267, doi: 10.26804/ager.2019.03.04

References

Ambrose, R.J., Hartman, R.C., Campos, M.D., et al. New pore-scale considerations for shale gas in place calculations. Paper SPE 131772 Presented at the SPE Unconventional Gas Conference, Pittsburgh, Pennsylvania, USA, 23-25 February, 2010.

Cai, J.C., Lin, D.L., Singh, H., et al. Shale gas transport model in 3D fractal porous media with variable pore sizes. Mar. Pet. Geol. 2018, 98: 437-447.

Cai, J.C., Lin, D.L., Singh, H., et al. A simple permeability model for shale gas and key insights on relative importance of various transport mechanisms. Fuel 2019, 252: 210-219.

Chalmers, G.R.L., Bustin, R.M. The organic matter distribution and methane capacity of the Lower Cretaceous strata of Northeastern British Columbia, Canada. Int. J. Coal Geol. 2007, 70(1-3): 223-239.

Curtis, J.B. Fractured shale-gas systems. AAPG Bull. 2002, 86(11): 1921-1938.

Dai, J.X., Zou, C.N., Dong, D.Z., et al. Geochemical characteristics of marine and terrestrial shale gas in China. Mar. Pet. Geol. 2016, 76: 444-463.

Gasparik, M., Bertier, P., Gensterblum, Y., et al. Geological controls on the methane storage capacity in organic-rich shales. Int. J. Coal Geol. 2014, 123(2): 34-51.

Gou, Q.Y., Xu, S., Hao, F., et al. Characterization method of shale pore structure based on nano-CT: A case study of Well JY-1. Acta Petrolei Sinica 2018, 39(11): 1253-1261.

(in Chinese) Gou, Q.Y., Xu, S., Hao, F., et al. Full-scale pores and micro-fractures characterization using FE-SEM, gas adsorption, nano-CT and micro-CT: A case study of the Silurian Longmaxi Formation shale in the Fuling area, Sichuan Basin, China. Fuel 2019a, 253: 167-179.

Gou, Q.Y., Xu, S., Hao, F., et al. A comprehensive evaluation index of gas-bearing property of shale reservoirs based on grey relation and its application: A case study of Jiaoshiba area, Sichuan Basin. Natural Gas Geoscience 2019b, 30(7): 1045-1052. (in Chinese)

Guo, T.L. The Fuling Shale Gas Field-A highly productive Silurian gas shale with high thermal maturity and complex evolution history, southeastern Sichuan Basin, China. Interpretation 2015, 3(2): 25-34.

Guo, T.L. Discovery and characteristics of the Fuling shale gas field and its enlightenment and thinking. Earth Science Frontiers 2016, 23(1): 29-43. (in Chinese)

Guo, X.S. Enrichment Mode and Exploration Technology in Jiaoshiba Area of Fuling Shale Gas Field. Beijing, Science Press, 2014. (in Chinese)

Guo, X.S., Hu, D.F., Wei, X.F., et al. Main controlling factors on shale fractures and their influences on production capacity in Jiaoshiba area, the Sichuan Basin. Oil & Gas Geology 2016, 37(6): 799-808. (in Chinese)

Hao, F., Guo, T.L., Zhu, Y.M., et al. Evidence for multiple stages of oil cracking and thermochemical sulfate reduction in the Puguang gas feld, Sichuan Basin, China. AAPG Bull. 2008, 92(5): 611-637.

Hao, F., Zou, H.Y. Cause of shale gas geochemical anomalies and mechanisms for gas enrichment and depletion in high-maturity shales. Mar. Pet. Geol. 2013a, 44: 1-12.

Hao, F., Zou, H.Y, Lu, Y.C. Mechanisms of shale gas storage: Implications for shale gas exploration in China. AAPG Bull. 2013b, 97(8): 1325-1346.

Haydel, J.J., Kobayashi, R. Adsorption equilibria in methane-propane-silica gel system at high pressures. Ind. Eng. Chem. Fundam. 1967, 6: 564-554.

Ji, W.M., Song, Y., Jiang, Z.X., et al. Geological controls and estimation algorithms of lacustrine shale gas adsorption capacity: A case study of the Triassic strata in the southeastern Ordos Basin, China. Int. J. Coal Geol. 2014, 134: 61-73.

Jiang, Z.X., Tang, X.L., Li, Z., et al. Pore structure and gas-bearing properties of typical marine and continental shale reservoirs in China. Beijing, Science Press, 2018.

(in Chinese) Jin, Z.J., Nie, H.K., Liu, Q.Y., et al. Source and seal coupling mechanism for shale gas enrichment in upper Ordovician Wufeng Formation-Lower Silurian Longmaxi Formation in Sichuan Basin and its periphery. Mar. Pet. Geol. 2018, 97: 78-93.

Kim, J., Kim, D., Lee, W., et al. Impact of total organic carbon and specific surface area on the adsorption capacity in Horn River Shale. J. Pet. Sci. Eng. 2017, 149: 331-339.

Langmuir, I. The adsorption of gases on plane surfaces of glass, mica and platinum. J. Am. Chem. Soc. 1918, 40(9): 1361-1403.

Lewis, R., Ingraham, D., Pearcy, M., et al. New evaluation techniques for gas shale reservoirs. In: Schlumberger Reservoir Symposium, Denver, Colorado, July 29-20, 2004.

Li, A.F. Reservoir Physics. 3nd Ed. Dongying, China University of Petroleum Press, 2015. (in Chinese)

Li, J., Wu, Q.Z., Lu, J., et al. To quantitatively determine the adsorption and free methane volume content in shale gas core based on NRM technique. Well Logging Technology 2018, 42(3): 315-320. (in Chinese)

Li, W.G., Yang, S.L., Xu, J., et al. A new model for shale adsorptive gas amount under a certain geological conditions of temperature and pressure. Natural Gas Geoscience 2012, 23(4): 791-796. (in Chinese)

Ma, Y., Zhong, N.N., Li, D.H., et al. Organic matter/clay mineral intergranular pores in the Lower Cambrian Lujiaping Shale in the north-eastern part of the upper Yangtze area, China: A possible microscopic mechanism for gas preservation. Int. J. Coal Geol. 2015, 137: 38-54.

Qi, Y., Ju, Y.W., Huang, C., et al. Influences of organic matter and kaolinite on pore structures of transitional organic-rich mudstone with an emphasis on S2 controlling specific surface area. Fuel 2019, 237: 860-873.

She, X.Y., Chen, J., Zhang, S.W., et al. Tectonic characteristics and their shale gas geological significance of the Mesozoic-Paleozoic in Jiaoshiba area, the Sichuan Basin. Oil & Gas Geology 2016, 37(6): 828-837. (in Chinese)

Standing, M.B., Katz, D.L. Density of natural gases. Trans. AIME 1942, 146: 140-149.

Tang, H.M., Wang, J.J., Zhang, L.H., et al. Testing method and controlling factors of specific surface area of shales. J. Pet. Sci. Eng. 2016, 143: 1-7.

Tang, Y., Li, L.Z., Jiang, S.X. A logging interpretation methodology of gas content in shale reservoirs and its application. Natural Gas Industry 2014, 34(12): 46-54.

(in Chinese) Wang, F.Y., Guan, J., Feng, W.P., et al. Evolution of overmature marine shale porosity and implication to the free gas volume. Pet. Explor. Dev. 2013, 40(6): 819-824.

Wang, F.Y., He, Z.Y., Meng, X.H., et al. Occurrence of shale gas and prediction of original gas in-place (OGIP). Natural Gas Geoscience 2011, 22(3): 201-510.

(in Chinese) Yang, F., Ning, Z.F., Zhang, R., et al. Investigations on the methane sorption capacity of marine shales from Sichuan Basin, China. Int. J. Coal Geol. 2015, 146: 104-117.

Yang, W.X., Li, J.Q., Gou, Q.F. Experiment study on shale adsorption properties for Jiaoshiba shale, Sichuan Basin. Natural Gas Geoscience 2017, 28(9): 1350-1355. (in Chinese)

Zhang, T.W., Ellis, G.S., Ruppel, S.C., et al. Effect of organic-matter type and thermal maturity on methane adsorption in shale-gas systems. Org. Geochem. 2012, 47(6): 120-131.

Zhang, X.M., Shi, W.Z., Shu, Z.G., et al. Calculation model of shale gas content and its application in fuling area. Earth Science 2017, 42(7): 1157-1168. (in Chinese)

Zhao, H., Givens, N.B., Curtis, B. Thermal maturity of the Barnett Shale determined from well-log analysis. AAPG Bull. 2007, 91(4): 535-549.

Zhao, J.Z., Shen, C., Ren, L., et al. Quantitative prediction of gas contents in different occurrence states of shale reservoirs: A case study of the Jiaoshiba shale gasfield in the Sichuan Basin. Natural Gas Industry 2017, 37(4): 19-25. (in Chinese)