Method for determining shale gas reservoir permeability

Abstract

The invention discloses a method for determining shale gas reservoir permeability. The method comprises the steps that (1) pore size distribution of shale core samples is obtained under laboratory conditions; (2) nuclear magnetic resonance pore size distribution is obtained; (3) the relation between permeability test data of the shale core samples and pore structure instruction parameter values isfitted, and a permeability model of a shale core is established; (4) the pore structure instruction parameter values of a shale gas reservoir are obtained based on nuclear magnetic resonance loggingdata; and (5) the pore structure instruction parameter values, obtained in the step (4), of the shale gas reservoir are substituted into the permeability model established in the step (3) in combination with shale lithofacies classification, and therefore the permeability of the shale gas reservoir is obtained. The method for determining the shale gas reservoir permeability effectively overcomes the dual defects that in the prior art, crack contribution estimation is insufficient, and nanometer organic matter pores cannot be effectively represented.

Description

technical field [0001] The invention relates to the technical field of oil and gas geophysics, and more specifically, relates to a method for determining the permeability of shale gas reservoirs. Background technique [0002] Shale gas refers to a kind of unconventional natural gas resource that occurs in organic-rich mud shale and other lithological interlayers in the form of free and adsorption. It is widely distributed around the world and has huge reserves. Mining and utilization prospects. [0003] The permeability of shale gas reservoirs is an important parameter in the exploration and development of shale gas. Permeability is not only a key parameter in gas reservoir engineering modeling, but also plays an important role in productivity evaluation. The production process is also critical. [0004] In terms of logging evaluation of shale permeability, foreign countries generally use the method of core calibration to establish regional empirical formulas or models to ...

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Problems solved by technology

There are two existing NMR-based permeability models, namely the Coates-bound water permeability model and the SDR-relaxation time permeability model. However, the above model has two shortcomings in shale. One is that the model treats fractures or micro-fractures only as large pores, which does not highlight the impact of fractures or micro-fractures on permeability. The second is that a large number of nano-organic pores are developed in shale gas reservoirs, and the pore size is usually smaller than that of clay pores. When using the above model, the nano-organic pores will be treated as bound fluids. Obviously, this is virtually ignored. The contribution of nano-organic pores to permeability

In addition, Xiao Liang et al. (Xiao Liang, Liu Xiaopeng, Mao Zhiqiang. Method for calculating reservoir permeability by combining NMR and capillary pressure data[J]. Acta Petroleum Sinica, 2009, 30(1):100-103; Xiao Zhongxiang, Xiao Liang. Calculation method of reservoir permeability based on NMR logging and capillary pressure [J]. Atomic Energy Science and Technology, 2008, 42(10): 868-871) proposed a method to calculate reservoir permeability by combining NMR and capillary pressure data method, however, this evaluation method relies on the determination of the geometric mean of the NMR transverse relaxation time, and does not give the specific construction method and steps of the pore structure parameters

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