Method for obtaining pure inelastic scattering gamma-ray energy spectra in stratum element well logging

Abstract

The invention provides a method for obtaining pure inelastic scattering gamma-ray energy spectra in stratum element well logging. The method includes the following steps that the inelastic scattering gamma-ray energy spectra and capture gamma-ray energy spectra of a target stratum are obtained according to well logging materials, wherein the inelastic scattering gamma-ray energy spectra include the capture radiation reaction influence; the inelastic scattering gamma-ray energy spectra including the capture radiation reaction influence are segmented by the adoption of the feature of the elements in the known stratum and the feature of the capture gamma rays, and corresponding deduction coefficients are arranged for all the energy spectrum segments; according to the deduction coefficients of all the energy spectrum segments and the deduction amount determined by the product of the capture gamma-ray energy spectra of the corresponding energy spectrum segments, the influence of the capture radiation reaction is deducted from the inelastic scattering gamma-ray energy spectra of the corresponding energy spectrum segments so as to obtain the pure inelastic scattering gamma-ray energy spectra of the target stratum. By means of the method, the more pure inelastic scattering gamma-ray energy spectra can be obtained.

Description

Technical field [0001] The invention relates to the technical field of geophysical logging, in particular to a method for acquiring net inelastic scattering gamma energy spectrum in formation element logging. Background technique [0002] Formation element logging is to measure the gamma energy spectrum produced by the reaction of neutrons emitted by the neutron source to the formation and the formation element nucleus, and use the spectral analysis method to obtain the relative yield of the formation elements, and then convert the relative yield of the elements into element content , It can describe the formation more finely, and provide an effective means for logging evaluation of complex reservoirs and unconventional oil and gas reservoirs. [0003] The formation element logging technology (such as Schlumberger's ECS and Halliburton's GEM) that captures the gamma spectrum can be used to obtain the Si, Fe, Ca, S, Ti, Gd and other elements of the formation. However, for the key f...

AI Technical Summary

Problems solved by technology

At present, the research on the acquisition method of net inelastic scattering gamma energy spectrum mainly includes the fixed deduction coefficient method and the hydrogen subtraction peak method, but they are all aimed at the carbon-oxygen ratio logging.

In the net inelastic scattering gamma energy spectrum obtained by the current technology, a deduction coefficient is used for the entire energy spectrum, and there is too much deduction in the energy spectrum that should not be deducted from the impact of captured radiation or insufficient deduction in the energy spectrum that should be deducted. As a result, the correlation between the obtained net inelastic scattering gamma energy spectrum and the theoretical net inelastic scattering gamma energy spectrum is too low, and the accuracy of element content obtained by energy spectrum analysis is not enough

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