Method for full-size characterization of unconventional tight reservoir pore diameter

Abstract

The invention relates to an unconventional tight reservoir aperture full-size characterization method. The method comprises steps of drying a rock core, dividing the rock core into two parts so as toavoid pore structure characterization errors possibly caused by heterogeneity of an unconventional tight reservoir, and carrying out a high-pressure mercury injection test and a low-temperature nitrogen adsorption test of a columnar rock core; based on a fractal method, dividing an aperture distribution area obtained by mercury intrusion testing into three parts, namely a mum- grade crack, a normal pore and a compressed nm-grade pore; calculating a compression coefficient of the rock core in combination with the low-temperature nitrogen absorption test result of the rock core, and correcting real pore size distribution of the compressed nm-level pores in the mercury injection test; drawing the corrected mercury intrusion test pore size distribution curve and the corrected low-temperature nitrogen absorption test pore size distribution curve in the same graph, finding out an intersection point, and obtaining full-size representation of the pore size of the unconventional tight reservoirby taking nanoscale pores obtained by a low-temperature liquid nitrogen absorption test as a benchmark. The method is advantaged in that the full-size distribution characteristics of the pore diameters of the unconventional tight reservoirs can be finely and effectively represented.

Description

Technical field [0001] The invention relates to the technical field of oil and gas development, in particular to a method for characterizing the full-size pore size of unconventional tight reservoirs. Background technique [0002] The proportion of unconventional oil and gas resources such as coalbed methane, tight sandstone gas, shale gas, and shale oil in the world’s energy structure has gradually increased. Unconventional oil and gas resources correspond to coal reservoirs, tight sandstone reservoirs, and shale reservoirs. The pore structure in tight reservoirs is complex, with both μm-level pores-fractures and nm-level pores developed. μm-level pores-fractures are conducive to the seepage of unconventional oil and gas, while nm-level pores are conducive to the adsorption of unconventional oil and gas. Therefore, through the full-scale fine characterization of μm-level pores-fractures and nm-level pores in unconventional tight reservoirs, the quantitative study of the ratio o...

AI Technical Summary

Problems solved by technology

[0004] The main problems mentioned above are: (1) Although the existing studies have adopted multiple methods for joint testing, they are mostly based on different test samples and analyze the pore size distribution characteristics measured by different testing methods, without considering the strong pressure of unconventional tight reservoirs. The heterogeneity of the pore structure may cause characterization errors; (2) when the existing research uses high-pressure mercury porosimetry to characterize the pore size distribution, the maximum test pressure reaches 170MPa, and the compressibility of the pores under high-pressure conditions (>10MPa) is not considered.

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