Shale gas saturation calculation method based on resistivity method

A technology of resistivity method and calculation method, which is applied in the fields of earth cube drilling, permeability/surface area analysis, suspension and porous material analysis, etc., to achieve the effect of broad application prospects

Pending Publication Date: 2020-09-04
CHINA UNITED COALBED METHANE
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Problems solved by technology

[0003] In view of this, the object of the present invention is to provide a shale gas saturation calculation method based on resistivity method, which can solve the problem of accurate calculation of free gas saturation in low resistivity shale gas

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  • Shale gas saturation calculation method based on resistivity method
  • Shale gas saturation calculation method based on resistivity method
  • Shale gas saturation calculation method based on resistivity method

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Embodiment

[0179] as attached figure 1 As shown, in the shale section below 2570 meters, the content of organic carbon is significantly higher, the density is lower, the neutrons are smaller, and the "mirror image" of neutron-density intersection in the gas layer is obviously increased, indicating that the gas-bearing layer is good, which is interpreted as Type I shale gas formation.

[0180] After being identified as a low-resistivity shale gas reservoir, it is necessary to conduct research on the low-resistivity shale gas reservoir model; taking the traditional "Archie model" as an example to illustrate the improved calculation model formula for low-resistivity shale gas reservoir saturation; Archie The model is as follows:

[0181]

[0182] in:

[0183] R t - rock resistivity, Ω.m;

[0184] POR—effective porosity, V / V;

[0185] m—the cementation index corresponding to the effective pores, dimensionless;

[0186] S w —water saturation, V / V;

[0187] n—saturation index, dimen...

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Abstract

The invention provides a shale gas saturation calculation method based on a resistivity method, and the method comprises the steps: adding an equivalent water conductivity item in an effective pore after a conventional calculation model formula, and obtaining an improved calculation model formula; wherein equivalent water conductivity items in the effective pores are expressed as the specification, wherein the parameters are described as follows: EPOR is the equivalent water porosity, V / V; m is the cementation index corresponding to the effective pores and has no dimension; a is a lithologic coefficient related to effective pores and has no dimension; b is a lithology saturation coefficient and has no dimension; Rw is formation water resistivity (omega*m). Compared with the prior art, themethod is based on the understanding of the low-resistance cause of the shale gas layer, achieves the high-conductivity correction of a conventional calculation model through supplementing equivalentwater conductivity items, obtains an improved calculation model formula, and can solve a problem of the accurate calculation of the saturation degree of the free gas in the low-resistivity shale gas.

Description

technical field [0001] The invention relates to the technical field of unconventional natural gas, in particular to a calculation method for shale gas saturation based on resistivity method. Background technique [0002] There are many models for calculating saturation by well logging. The traditional electrical saturation models include Archie, Waxman-Smith and Simendou models for shale correction. However, various traditional saturation models cannot solve the problem of accurate calculation of free gas saturation in low-resistivity shale gas. The degree model is based on the volume model. The smaller the porosity, the lower the conductivity. The low-resistivity shale gas layer has a non-Archie phenomenon in which the water saturation and conductivity do not match, and the clay content or clay-added conductivity also It is impossible to describe the high conductivity produced by a small amount of water or the network distribution of conductive minerals in micro-fractures;...

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G01N27/04G01N15/08E21B49/00
CPCG01N27/041G01N15/088E21B49/00
Inventor 金力钻周文革谢岚傅小康朱光辉王应斌史浩杜佳孙玉红程璐
Owner CHINA UNITED COALBED METHANE
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