Method for representing anisotropy of shale pore structure based on small-angle neutron scattering

Abstract

The invention provides a method for characterizing anisotropy of a shale pore structure based on small-angle neutron scattering. The method comprises the following steps: preparing a shale sample to be detected; performing a small-angle neutron scattering experiment on the sample to obtain an ellipsoidal anisotropic two-dimensional scattering profile; dividing the two-dimensional scattering profile into integral regions, calculating the scattering intensity on each azimuth angle, and drawing a non-uniform distribution diagram of the scattering intensity relative to the azimuth angles; selecting a maximum scattering intensity region and a minimum scattering intensity region, and obtaining a corresponding one-dimensional scattering curve; correcting and fitting the one-dimensional scattering curve to obtain pore structure information of the sample; the anisotropy of the pore structure is represented by comparing pore structure information in two different directions. The brand-new method for characterizing the anisotropy of the pore structure of the shale is provided, the anisotropy of the pore structure is quantitatively characterized on the basis of the small-angle neutron scattering experiment, an effective means is provided for exploring an oil-gas migration dominant channel, and the method has important significance on fine evaluation and effective exploitation of an oil reservoir.

Description

technical field [0001] The invention relates to the technical field of unconventional oil and gas geology experiments, in particular to a method for characterizing the anisotropy of shale pore structure based on small-angle neutron scattering. Background technique [0002] Natural gas has become an effective alternative energy source for coal and crude oil due to its low carbon emission characteristics. At present, due to the rapid growth of shale gas production, unconventional natural gas is becoming more and more important. However, as a source rock, shale, with its complex pore structure, ultra-low porosity and permeability, encounters many challenges in the process of reservoir development. Among them, the nanoscale pore structure in the shale matrix is ​​crucial for predicting long-term natural gas production. The anisotropic pore structure of shale not only affects the adsorption capacity of natural gas, but also directly affects the diffusion capacity of gas in the ...

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Problems solved by technology

[0003] In recent years, small-angle neutron scattering, as a kind of ray detection method, has been effectively applied in shale. It can measure the nanoscale pore structure of shale samples without damage to the samples. An ellipsoidal scattering cross-section is encountered, which means that the sample has significant anisotropy, that is, the pore structure has obvious orientation, but this anisotropy is ignored in the processing process, and the data is directly averaged radially. The effect on isotropic samples is small, but there will be large errors on anisotropic samples, and the data of the anisotropy of the sample pore structure cannot be obtained

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