Method using nuclear magnetic resonance to measure rock porosity

Abstract

A method using nuclear magnetic resonance to measure rock porosity includes: machining rock with dissolution pores into a core column, and removing organic substances attaching to the core column; filling the dissolution pores of the core column with flexible water-absorption substances; submerging the core column into water under the pressure of 2-5MPa for 24-72 hours; taking out the core column, removing the water on the surface of the core column, and using a film to wrap the core column; performing a nuclear magnetic resonance experiment on the core column to obtain the porosity. The method has the advantages that the water-absorption substances are used to fill the dissolution pores of the rock so as to constrain the water in the dissolution pores, the water in the dissolution pores does not flow out of the dissolution pores during the nuclear magnetic resonance experiment, and the measured rock porosity is accurate.

Description

technical field [0001] The invention relates to the technical field of rock analysis, in particular to a method for measuring rock porosity by nuclear magnetic resonance. Background technique [0002] NMR measurement of rock porosity is to measure the nuclear magnetic relaxation signal of hydrogen-containing fluid in rock pores, and finally obtain rock pore structure and total porosity through the response of hydrogen ions in pores of different sizes. Carbonate rocks often have relatively large dissolved pores and caves due to dissolution, but conventional measurement methods often cannot accurately measure the pore system in the rock, because the water in the large pores is lost to the surrounding rock during the measurement process , resulting in an overestimation of bound water and water in pores. [0003] In recent years, nuclear magnetic resonance instruments have become more and more popular in the measurement and analysis of rock pores. Rocks with relatively small po...

AI Technical Summary

Problems solved by technology

Carbonate rocks often have relatively large dissolved pores and caves due to dissolution, but conventional measurement methods often cannot accurately measure the pore system in the rock, because the water in the large pores is lost to the surrounding rock during the measurement process , resulting in overestimation of bound water and water in pores

[0003] In recent years, nuclear magnetic resonance instruments have become more and more popular in the measurement and analysis of rock pores. Rocks with relatively small pore diameters can be measured more accurately when they are saturated with water. The main problem is: after the rock with large pores is saturated with water, the water in the large pores is very easy to lose during the plastic film wrapping process, so that the final measured porosity is too small; during the NMR measurement process, The water in the large pores is easy to seep into the film, so that the proportion of small-diameter pores measured by nuclear magnetic resonance increases, and the proportion of large-diameter pores decreases, resulting in inaccurate evaluation of the pore structure of large pores by nuclear magnetic resonance.

Images