Nuclear magnetic resonance spectrum coefficient based method for calculating saturation of irreducible water

Abstract

The invention discloses a nuclear magnetic resonance spectrum coefficient based method for calculating saturation of irreducible water, and belongs to the field of reservoir evaluation. The method comprises the following steps: first conducting nuclear magnetic resonance (NMR) standard T2 test experiment on the core to obtain a core NMR T2 distribution spectrum, and using a weighing method to calculate actual irreducible water saturation STURE of a rock specimen; determining undetermined coefficients under different aperture components by using NMR T2 spectrum and irreducible water saturation STURE of the rock specimen through a least squares method; establishing and calculating a new model of irreducible water saturation; and finally acquiring the calculated irreducible water saturation of the rock specimen. The present invention realizes determination of reservoir irreducible water saturation by using nuclear magnetic resonance spectrum coefficient method; by comparing the calculation result of the new model, the reservoir irreducible water saturation can be obtained more accurately and more reliably; and the method provides reliable reservoir parameters for oil exploration and reservoir development evaluation.

Description

technical field [0001] The invention relates to the field of reservoir evaluation and the field of reservoir bound water saturation evaluation, in particular to a method for calculating bound water saturation based on nuclear magnetic resonance spectral coefficient method. Background technique [0002] It is particularly important to calculate the irreducible water saturation of reservoirs by using nuclear magnetic resonance logging, which directly or indirectly affects the calculation accuracy of reservoir parameters such as effective porosity, permeability, and free fluid saturation. There are two main methods of water saturation: T 2 Cutoff value method and spectral coefficient method. [0003] T 2 The cut-off value method is currently the most commonly used method, and the calculation model is as follows: [0004] S B V I = ∫ ...

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Problems solved by technology

[0011] T 2 The model of the cut-off value method is simple, and the regional dependence of the cut-off value varies greatly, and the accuracy of the calculation results in specific areas is difficult to meet the requirements, especially in heavy oil reservoirs. The calculation results are too large; The reservoir calculation results are often too small, and the weight coefficient model needs to be improved

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