Rock heterogeneous quantitative evaluation method based on magnetic resonance imaging

Abstract

The invention discloses a rock heterogeneous quantitative evaluation method based on magnetic resonance imaging. Three-dimensional space orientation of rock can be realized by layer selection pulse, phase coded pulse and frequency coded pulse. An imaging signal can be obtained by applying a spin-echo sequence, and optimization selection of imaging experimental parameters can be carried out through experimental scale. On the basis, a nuclear magnetic imaging signal obtained by experimental measurement is subjected to digital image processing so as to generate a pseudo color graph. By means of the relationship between the porosity and nuclear magnetic imaging signal intensity of a stand sample, the total porosity and porosity and distribution spectrum of a single layer can be obtained. Multi-layer imaging results are compared and a porosity heterogeneous coefficient is defined, so that the longitudinal porosity distribution characteristic and heterogeneity of rock can be obtained. In addition, by applying a first-order spherical variation function model and a grid search method, characteristic parameters of a variation function can be obtained. Heterogeneous coefficients and relative heterogeneous coefficients can be defined to realize longitudinal and horizontal heterogeneous quantitative characterization of rock.

Description

technical field [0001] The invention belongs to the fields of petrophysical experiments and petroleum exploration, and in particular relates to a method for quantitatively evaluating longitudinal and transverse heterogeneity of rocks using nuclear magnetic resonance imaging data. Background technique [0002] With the further development of international energy demand, oil and gas exploration is developing from conventional to low porosity, low permeability and tight reservoirs. Low porosity and low permeability, poor physical properties, complex pore structure, and strong heterogeneity in tight reservoirs lead to complex logging response characteristics and difficult oil and gas evaluation, which greatly restricts the success rate of oil and gas drilling. [0003] Heterogeneity evaluation is an important content of petrophysical experiments and logging evaluation for low porosity, low permeability and tight reservoirs. At present, the evaluation methods of rock heterogenei...

AI Technical Summary

Problems solved by technology

X-CT scanning, casting thin sections, and scanning electron microscopy are common methods for laboratory research on microscopic heterogeneity of rocks, but because they can only be studied and analyzed on small-scale samples, it is difficult to achieve supporting analysis with formation rocks; The observation method has strong empirical requirements for researchers, and most of them are mainly qualitative descriptions, and it is difficult to make quantitative evaluations; the logging identification method mainly displays the structure of downhole rocks through new technologies such as imaging logging and dipole acoustic logging. Features, and quantitative characterization of rock heterogeneity through image processing technology, which is affected by detection depth, instrument response and logging environment

In addition, the quantitative characterization method of logging heterogeneity can only realize the heterogeneity characteristics of a certain layer of rock.

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