Method for evaluating thickness of water film after water-phase imbibition flowback of gas reservoir rock containing expansive clay

Abstract

The invention discloses a method for evaluating the thickness of a water film after water-phase imbibition flowback of gas reservoir rock containing expansive clay. The method comprises the following steps: determining the porosity of a rock core sample according to a pressure pulse method, and performing vacuum pressurization on the rock core sample to saturate absolute ethyl alcohol; performing nuclear magnetic resonance testing on the rock core sample to obtain a T2 map, performing inversion, and determining pore structure distribution data; drying the rock core sample, and carrying out a water phase imbibition flowback experiment on the dried rock core sample; performing a nuclear magnetic resonance test on the rock core sample after the water phase imbibition flowback experiment to obtain a T2 map, performing inversion, and determining the volume fraction of the water phase after imbibition flowback; and finally, determining the water film thickness after the water phase imbibition flowback according to the porosity of the rock core sample, the pore structure distribution data and the volume fraction of the water phase after the imbibition flowback. According to the method, ethanol is adopted as a saturated medium to measure the pore structure of the rock sample, hydration of clay minerals can be avoided, the pore structure of the rock is not damaged, the test cost is low, and operation is convenient, safe and efficient.

Description

technical field [0001] The invention relates to a method for evaluating the thickness of a water film after water-phase imbibition and flowback of a gas reservoir containing expanded clay, and belongs to the technical field of laboratory experiments of petroleum geology and oil-gas field development. Background technique [0002] Hydraulic fracturing is an important technical measure for increasing the production of oil and gas wells and water injection wells. It is not only widely used in low-permeability, tight and shale gas reservoirs, but also has achieved good results in the stimulation of medium-high permeability gas reservoirs. . Hydraulic fracturing injects a large amount of fracturing fluid into the reservoir, and more than 90% of the fracturing fluid is water, which is easy to seep into the reservoir rock. Most gas reservoir rocks are hydrophilic, so the fracturing fluid still partially remains in the gas reservoir rock pores after flowback measures are implemente...

AI Technical Summary

Problems solved by technology

Water-phase saturated cores will cause hydration, expansion, dispersion, migration, or precipitation of clay minerals, blocking or even blocking oil and gas flow channels, which cannot effectively reflect the real pore structure state of reservoir rocks, and will also affect subsequent rock water-phase imbibition and return. Row experiments make an impact

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