Method for quantitatively evaluating pore throat change degree in stress sensitive process

Abstract

The invention discloses a method for quantitatively evaluating the pore throat change degree in a stress sensitive process. The method comprises the following steps: taking a rock core used for an experiment, washing oil and drying, and measuring the porosity and the gas measured permeability of the rock core; preparing simulated formation water used for the experiment, wherein the simulated formation water reaches a formation water mineralization degree; selecting the displacement velocity of the simulated formation water; placing the rock core in a rock core clamping device; applying a confining pressure for displacing the rock core with the simulated formation water; calculating the water measured permeability according to the inlet pressure of the rock core and the displacement velocity, and measuring the nuclear magnetic resonance T2 spectrum under the confining pressure; gradually rising the confining pressure, and measuring the nuclear magnetic resonance T2 spectrums under different confining pressures; converting the nuclear magnetic resonance T2 spectrums under different confining pressures into pore throat radiuses r; drawing a pore throat radius distribution curve under different confining pressures, and measuring the pore throat change degrees under different confining pressures. According to the method, on-line measurement can be performed in real time; samples are not required to be unloaded and loaded repeatedly; the influence on pore throat change caused by the change of the confining pressure in the unloading and loading processes is avoided; therefore, the pore throat change degree in the stress sensitive process is quantitatively evaluated.

Description

technical field [0001] The invention relates to the technical field of oil and gas development experiments, in particular to a method for quantitatively evaluating the degree of pore-throat change in a stress-sensitive process. Background technique [0002] During the development of oil and gas reservoirs, the pore pressure continues to decrease while the pressure of the overlying rock remains unchanged, resulting in an increase in effective stress and a decrease in pore throats. The change degree of pore throats has important reference value for reducing the degree of stress sensitivity, taking corresponding measures, and then guiding the rational development of oilfields. In the existing research, patent CN103528934A, a cross-correlation technique for measuring the stress sensitivity of ultra-low permeability rock permeability. CN202066847U, a stress-sensitivity simulation test device for unconsolidated sandstone reservoirs and a special core holder thereof. CN102721636A...

AI Technical Summary

Problems solved by technology

[0003] Existing studies mainly analyze the change of pore throats before and after stress sensitivity through the change of permeability during the process of stress sensitivity or combined with mercury intrusion, cast thin section, scanning electron microscope and other means. The macroscopic reaction can only be evaluated qualitatively; the mercury intrusion, casting thin section, and scanning electron microscope analysis before and after stress sensitivity are not done on the same sample, and the conclusions obtained are open to question

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