A method for calculating irreducible water saturation based on NMR spectral coefficient method

Abstract

The invention discloses a method for calculating bound water saturation based on nuclear magnetic resonance spectral coefficient method, which belongs to the field of reservoir evaluation. The method comprises: firstly performing a nuclear magnetic resonance standard T2 test experiment on the rock core, obtaining the core nuclear magnetic T2 distribution spectrum, measuring and calculating the actual bound water saturation STURE of the rock sample by using the weighing method; using the nuclear magnetic resonance T2 spectrum and the actual bound water saturation of the rock sample Saturation STURE uses the least square method to determine the undetermined coefficients under different pore components, establishes a new model for calculating irreducible water saturation, and finally obtains the irreducible water saturation calculated from rock samples. The invention realizes the determination of the irreducible water saturation of the reservoir by using the nuclear magnetic resonance spectral coefficient method, and by comparing the results calculated by using the new model, the irreducible water saturation of the reservoir can be obtained more accurately and reliably, and it is useful for oil exploration and reservoir development Evaluation provides reliable reservoir parameters.

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] [0005] In the formula: S BVI is the bound water saturation, T 2min for T 2 distribution minimum, T 2max for T 2 Distribution maximum value, φ is T...

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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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