Method for determining the relative content of shale clay and brittle minerals by low-field nuclear magnetic resonance

Abstract

The invention discloses a method for determining the relative content of shale clay and brittle minerals by low-field nuclear magnetic resonance, comprising steps: S1, drying the original shale sample; S2, measuring the nuclear magnetic resonance T of the saturated shale sample 2 Spectrum; S3, the measured NMR T of the shale sample after centrifugation 2 Spectrum; S4, Selected NMR T 2 Cut-off value, using NMR T of saturated shale samples 2 The integrated area within the range of 0.01-100ms of the spectrum minus the NMR T of the shale sample after centrifugation 2 Spectrum 0.01‑100ms integral area, denoted as A; using NMR T of saturated shale samples 2 Spectrum 0.01‑T 2 The integrated area of ​​the cutoff minus the NMR T of the shale sample after centrifugation 2 Spectrum 0.01‑T 2 The integral area of ​​the cut-off value is denoted as B; the relative content of clay minerals in shale is C=B / A*100%, and the relative content of brittle minerals in shale is F=100%-C. The reliability of the experimental results of the present invention is high.

Description

technical field [0001] The invention relates to a method for measuring the relative content of shale clay and brittle minerals by low-field nuclear magnetic resonance, belonging to the field of shale gas exploration and development. Background technique [0002] Low-field NMR technology is mainly used in the field of shale gas geology to identify pores, calculate pore size distribution, use fractal dimension to evaluate pore microscopic heterogeneity, measure porosity and permeability, and monitor water molecules in shale. Dynamic diffusion seepage, etc., have not been used to determine the relative content of shale clay and brittle minerals. The current general research results believe that the main inorganic mineral components in shale mainly include clay minerals and brittle minerals, and only a small amount of organic matter in the organic components. [0003] Conventional X-ray diffraction experiments need to grind the sample into powder, and the sample volume is only a...

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Problems solved by technology

[0003] Conventional X-ray diffraction experiments need to grind the sample into powder, and the sample volume is only about 20g when measuring, so the representativeness and convincingness of the results are poor, but the experimental results of NMR samples can be maximized without destroying the structure. Reducing the heterogeneity is more convincing. In addition, there is peak overlap in the conventional X-ray diffraction analysis method, and the human error is large when compared with the standard peak, while the low-field NMR analysis method is simple and the human error is small.

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