Method for accurately measuring shale porosity by adopting low-field nuclear magnetic resonance

Abstract

The invention discloses a method for accurately measuring shale porosity by adopting the low-field nuclear magnetic resonance. The method comprises the following steps: as for a saturated water column-shaped shale sample, conducting nuclear magnetic porosity measurement in different echo time and waiting time; conducting helium porosity measurement; comprehensively comparing and analyzing the porosity results of the two methods; optimizing the optimal echo time and waiting time for testing to facilitate the accurate testing of follow-up samples. The method solves the problems of how to set reasonable parameters to measure the shale porosity by adopting the low-field nuclear magnetic resonance, and solves the problem that in the actual testing, the nuclear magnetic porosity obtained in different echo time and waiting time is in great disparity, and the comparability of the nuclear magnetic porosity and the helium porosity is relatively poor; compared with the prior art, by adopting the method, the shale porosity can be quickly and nondestructively measured, the accuracy and precision of the shale porosity measurement can be improved, and the operation is convenient.

Description

technical field [0001] The invention relates to a method for measuring the physical properties of rock formations in the detection mining field, in particular to a method for accurately measuring the porosity of shale by using low-field nuclear magnetic resonance. Background technique [0002] Porosity reflects the ability of medium pores to accommodate fluid. Shale porosity is one of the important parameters in the study of shale reservoir physical properties, and is the basic physical property parameter for oil and gas reservoir evaluation and reserve calculation. With the rapid development of shale oil and gas in the global energy field, accurate measurement of shale porosity is of great significance to the exploration and development of shale oil and gas. However, most of the conventional porosity tests use helium porosimeters. Although the reliability is high, the shortcomings such as cumbersome testing process are difficult to realize the application in the exploration...

AI Technical Summary

Problems solved by technology

[0004] However, there is no uniform standard for the echo time and waiting time used in the measurement of shale porosity by low-field NMR technology at present, and most of the measurement results are still based on the conventional reservoir measurement parameters, that is, the echo time is 0.6 ms and the waiting time is 5 s. As a result, the porosity obtained by using conventional NMR parameters is not the true value of shale porosity. In actual tests, the shale NMR porosity measured under different echo time and waiting time conditions is not only different, but also different from that of helium gas. The contrast of porosity is also poor

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