Method and system for simultaneously obtaining low-frequency elastic property and density of reservoir rock

Abstract

The invention provides a method and system for simultaneously obtaining low-frequency elastic property and density of reservoir rock. The method comprises the steps of: obtaining a reservoir rock sample S to be measured, a first standard sample Al and a second standard sample Lu with known elastic properties, wherein the compression coefficient and the density of the first standard sample are kappaal and Rhoal, the compression coefficient and the density of the second standard sample are kappalu and Rholu; measuring and obtaining a volume Val of the first standard sample and a volume Vlu of the second standard sample as well as a volume Vs of the reservoir rock sample to be measured; measuring and obtaining a resonance frequency f0 of an acoustic resonance cavity of a difference resonance acoustic spectrum device; measuring resonance frequencies in N positions in the difference resonance acoustic spectrum device: fal, i(i=1, 2...N), flu, i(i=1, 2...N) and fs, i(i=1, 2...N); and by using the parameters, simultaneously obtaining the compression coefficient and the density of the reservoir rock to be measured, which are respectively kappas and Rhos, by using a least square method nonlinear inversion method. According to the method, the high-precision low-frequency elastic property and the high-precision density of the reservoir rock can be simultaneously obtained.

Description

technical field [0001] The invention relates to the field of oil and gas exploration, in particular to a method and system for simultaneously obtaining low-frequency elastic properties and densities of reservoir rocks. Background technique [0002] The laboratory measurement of petrophysical properties is a basic research work in geophysical applied research. Due to the complexity of underground rocks, it is generally believed that the petrophysical properties of rocks change with the frequency. Accurately measuring the petrophysical properties in the field application frequency range in the laboratory is very important for using seismic exploration and acoustic logging data to understand underground rocks. It is of great significance to study the change characteristics of seismic phase and logging phase with frequency. [0003] There are several important methods in the experimental measurement of rock physics at home and abroad. The first type is the ultrasonic transmiss...

AI Technical Summary

Problems solved by technology

Using differential resonance acoustic spectrum measurement technology to obtain the elastic properties of materials at frequencies below kHz, there are some important limitations and shortcomings in the measurement technology and elastic modulus estimation technology involved in the existing known technology, as shown in: 1) measurement When measuring multiple points in the cavity, only the measurement information of the center point of the cavity is used for modulus estimation; 2) There are too many approximations in the algorithm, so that only the elastic modulus (or acoustic properties) of relatively soft materials can be accurately estimated ; 3) Poor repeatability of sample elastic properties measurement

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