Visual system and method for starting migration of pulverized coal in fracture induced by gas-water two-phase flow

Abstract

The invention belongs to the technical field of coal bed gas development, and discloses a gas-water two-phase flow induced crack pulverized coal starting migration visualization system and method, and the visualization system comprises a micro-flow unit and a crack width adjusting device. The micro-flow unit is a cuboid coal rock slice containing an artificial fracture, the periphery of the micro-flow unit is wrapped with a silicon rubber layer, and the artificial fracture is prepared by adopting a three-point bending method; the seam width adjusting device is composed of a rock clamping device and a spiral positioner. The width of the artificial fracture is adjusted through the spiral positioner, a complex rock core clamping system is not needed, operation is easy and convenient, and cost is low; by means of a laser confocal microscopic imaging technology, visual characterization and quantitative analysis of the starting migration behavior of the pulverized coal in the gas-water two-phase flow induced fracture can be realized; the micro-flow unit provided by the invention can be repeatedly used, so that research on the influence rule of gas and liquid phase apparent velocity, two-phase flow pattern, crack width, pulverized coal size fraction and pulverized coal type on the pulverized coal starting migration behavior is facilitated, and the experiment system has more powerful functions.

Description

technical field [0001] The invention belongs to the technical field of coal bed gas development, and in particular relates to a visualization system and method for starting and migrating pulverized coal induced by gas-water two-phase flow in coal seam fissures. Background technique [0002] At present, coal rock has the characteristics of hard texture, but brittle and easy to break. Its compressive / tensile strength is low and Poisson's ratio is large. Minimal stress disturbance will induce changes in coal rock structure and lead to coal dust particles. During the drainage process of coalbed methane wells, coal powder starts-migrates with the fluid, which will not only block the seepage channels (cleats / cracks and support fractures), damage the permeability of coal seams, but also induce wellbore blockage, buried pumps, stuck pumps, Problems such as pump leakage have seriously damaged the continuous, stable and efficient drainage of coalbed methane wells. Field tests show th...

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Problems solved by technology

[0005] (1) In the prior art, it is difficult to restore the surface properties of natural cracks in the coal seam based on artificial cracks made of glass plates, and it is impossible to truly simulate the start-migration behavior of coal powder, and the accuracy of relevant information obtained is poor;

[0006] (2) In the prior art, the start-migration visualization experiment of coal powder is carried out based on the natural fractures in the coal sample. Although the start-migration behavior of coal powder can be truly reproduced, it is difficult to realize the reuse of natural cracks, so it cannot be carried out. Research on the influencing factors of pulverized coal start-up-migration behavior, the function of the experimental system is relatively simple;

[0007] (3) In the prior art, a core clamping device with a relatively complex structure is mostly used to adjust the width of artificial or natural cracks, and the experimental process is cumbersome and costly

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