Quantitative characterization and microscopic occurrence mechanism of pore water in shale matrix

被引：0
|
作者：
Li J. [1 ]
Lu S. [1 ]
Zhang P. [2 ]
Li W. [1 ]
Jing T. [3 ]
Feng W. [1 ]
机构：
[1] School of Geosciences, China University of Petroleum, Qingdao, 266580, Shandong
[2] College of Earth Science and Engineering, Shandong University of Science and Technology, Qingdao, 266590, Shandong
[3] Huaneng Clean Energy Research Institute, Beijing
来源：
Shiyou Xuebao/Acta Petrolei Sinica | 2020年 / 41卷 / 08期
关键词：
Content distribution; Evaluation method; Evaluation theory; Pore water; Shale gas; Shale matrix;
D O I：
10.7623/syxb202008007
中图分类号：
学科分类号：
摘要：
The water-bearing capability of shale matrix is one of the important geological factors affecting the enrichment and migration of shale gas. However, there is no mature theory and method of quantitative characterization for the water of different states (adsorption state and free state) in the matrix pores and the mechanism of microscopic occurrence is not clearly understood. Based on the fact that adsorbed water and free water coexist in the pores, this paper proposes two theoretical models of adsorption ratio equation and liquid state equation. The former can calculate the mass ratio of adsorbed water in the pores of saturated shale matrix, and the latter can be used to describe the occurrence state of pore water in saturated shale and evaluate adsorption parameters (density and thickness of adsorbed water). Furthermore, using nuclear magnetic resonance technology (NMR), this paper establishes a quantitative evaluation method for pore water in (un)saturated shale matrix based on NMR T2 spectrum, and applies it to the marine shale in Wufeng-Longmaxi Formation in the southeastern Sichuan Basin. The research results show: (1) under laboratory conditions (20℃, atmospheric pressure), the mass ratio of adsorbed water in matrix pores of the shale saturated with distilled water (i.e., adsorption ratio) is 26.8%-62.9%, with an average of 45.5%; the saturation of adsorbed water is 19.19%-52.36%, with an average of 35.71%; the average density and average thickness of adsorption water are about 1.54 g/cm3 and 0.65 nm, respectively. (2) In the NMR T2 spectrum, the adsorbed water is mainly distributed in the interval of small T2 values, and it is the opposite for the free water, and there is an overlap between the two. (3) There is a critical size for pores; with the pore size smaller than the critical value, the pores will be completely filled with adsorbed water; with the pore size greater than the critical value, the pores have both adsorbed water and free water. As the pore size increases, the saturation of adsorbed water gradually decreases and the saturation of free water gradually increases. In general, the absorbed water is mainly distributed in pores with the diameter <50 nm, and the free water is distributed in pores with the diameter >50 nm. (4) In the same shale core, under different water content, the content and distribution of adsorbed water change slightly; as the water content decreases, the content and distribution of free water changes greatly; the content and amplitude gradually decreases. © 2020, Editorial Office of ACTA PETROLEI SINICA. All right reserved.
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页码：979 / 990
页数：11
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共 55 条
  • [1] MAHADEVAN J, SHARMA M M, YORTSOS Y C., Evaporative cleanup of water blocks in gas wells[J], SPE Journal, 12, 2, pp. 209-216, (2007)
  • [2] ZHOU Shangwen, LIU Honglin, YAN Gang, Et al., NMR research of movable fluid and T<sub>2</sub> cutoff of marine shale in South China, Oil & Gas Geology, 37, 4, pp. 612-616, (2016)
  • [3] FANG Chaohe, HUANG Zhilong, WANG Qiaozhi, Et al., Cause and significance of the ultra-low water saturation in gas-enriched shale reservoir, Natural Gas Geoscience, 25, 3, pp. 471-476, (2014)
  • [4] CHENG Peng, TIAN Hui, XIAO Xianming, Et al., Water distribution in overmature organic-rich shales:implications from water adsorption experiments[J], Energy & Fuels, 31, 12, pp. 13120-13132, (2017)
  • [5] LI Jing, CHEN Zhangxing, LI Xiangfang, Et al., A quantitative research of water distribution characteristics inside shale and clay nanopores, Scientia Sinica Technologica, 48, 11, pp. 1219-1233, (2018)
  • [6] HU Zhiming, DUAN Xianggang, HE Yabin, Et al., Influence of reservoir primary water on shale gas occurrence and flow capacity, Natural Gas Industry, 38, 7, pp. 44-51, (2018)
  • [7] LIU Honglin, WANG Hongyan, Ultra-low water saturation characteristics and the identification of over-pressured play fairways of marine shales in south China, Natural Gas Industry, 33, 7, pp. 140-144, (2013)
  • [8] CHALMERS G R L, BUSTIN R M., The organic matter distribution and methane capacity of the Lower Cretaceous strata of Northeastern British Columbia,Canada[J], International Journal of Coal Geology, 70, 1, pp. 223-239, (2007)
  • [9] LI Jing, LI Xiangfang, WANG Xiangzeng, Et al., Water distribution characteristic and effect on methane adsorption capacity in shale clay[J], International Journal of Coal Geology, 159, pp. 135-154, (2016)
  • [10] TANG Xu, RIPEPI N, VALENTINE K A, Et al., Water vapor sorption on Marcellus shale:measurement,modeling and thermodynamic analysis[J], Fuel, 209, pp. 606-614, (2017)
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