Method for correcting natural gamma ray spectral logging of barite mud well

Abstract

The invention relates to a method for correcting natural gamma ray spectral logging of a barite mud well. At present, two methods, namely a five-energy window least square method and a three-energy window spectrum stripping method or a three-energy window matrix method for unfolding spectrums and solving the content of potassium, uranium and thorium of a formation are commonly adopted at home and abroad, and the precision of measuring the potassium, the uranium and the thorium is low. The method comprises the following steps of: 1) transferring logging to a lower level, namely when gamma ray (GR) is more than 85API and the layer thickness is more than 5m, performing five-energy window measurement; 2) performing three-energy window spectrum unfolding, and solving a two-low energy window correction coefficient by using the three-energy window spectrum unfolding; 3) lifting the logging, solving a five-energy window counting rate, and correcting a two-energy window correction coefficient; 4) determining whether the total GR is higher than 85 API or not, returning to the step (2) when the total GR is higher than 85 API and using the original coefficient for five-energy window spectrum unfolding when the total GR is lower than 85 API; and 5) acquiring K, U and Th of the formation by using the five-energy window spectrum unfolding. By the method, the formation lithology can be correctly determined, and the precision of measuring the potassium, the uranium and the thorium is high.

Description

technical field [0001] The invention relates to a method for log correction of barite mud well natural gamma ray energy spectrum. Background technique [0002] At present, two methods are commonly used at home and abroad to solve the spectrum to obtain the content of potassium, uranium, and thorium in the formation, that is, the five-energy window least square method; the three-energy window stripping spectrum method (or three-energy window matrix method) [0003] 1) Five-energy window least square method to solve the spectrum, [0004] The least square method is used to fit, and the content values ​​of formation K, U, and Th are solved to obtain: [0005] Y=(A T WA) -1 A T WN………………………(1) [0006] In the formula: [0007] The magnitude matrix of formation K, U, Th is: [0008] Y = K U Th ; ...

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Problems solved by technology

[0024] Barite reduces the count rate of low-energy windows in five-energy windows;

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