InterPore2026

Research on the Technology of Sediment Removal and Resumption of Production for Abandoned Coalbed Methane Wells

19 May 2026, 11:35

15m

Oral Presentation (MS16) Complex fluid and Fluid-Solid-Thermal coupled process in porous media: Modeling and Experiment MS16

Speaker

Xitu Zhang (Taiyuan University of Technology)

Description

During the development of coalbed methane and the process of hydraulic fracturing, due to the physical and chemical damage caused by the mechanical properties of the coal seam itself, stress mechanical failure, etc., it is prone to the production of sediment particles such as coal fines and clay minerals. These particles are washed away from the coal rock body by fluids, remaining and block in the propped fractures of the coal reservoir, which will reduce the gas production of coalbed methane wells, restrict the continuous and stable production of coalbed methane wells, and seriously lead to the well shutdown caused abandoned wells, hindering the high-quality development of coalbed methane industry. For the abandoned wells with sediment mainly coal fines, by establishing a mathematical model of coal fine retention in propped fractures - pore evolution - gas-liquid flow, the dynamic evolution mechanism of the porosity and permeability of propped fractures under the coupling of gas-liquid-solid was studied. And the influence law of the spatial-temporal distribution of coal fines on the gas-liquid flow in propped fractures was revealed, which achieved synchronous analysis of the microscopic pore evolution and macroscopic seepage characteristics of porous media. Based on the developed composite system of coal fine unblocking agent, the mechanism of the gas-liquid-solid three-phase dispersed foam unblocking agent system for coal fine transportation and unblocking was clarified. Then the "unblocking agent nitrogen bubble injection + forward and reverse circulation gas lift" cleaning and resumption production renovation technology was formed; for the abandoned wells with sediment mainly clay minerals, based on the law of clay minerals dissolution rate by acid corrosion and the alteration characteristics of pore structure, a mathematical model of the evolution of acid corosion unblocking of propped fractures under acid intervention was established. It revealed the dynamic feedback mechanism of acid concentration - particle size reduction - permeability evolution in the porous medium of propped fractures. And discovered that the higher the acid concentration, the larger the effective hydraulic radius of acid corrosion in the propped fractures, the lower the capillary acid liquid flow velocity, and the slower the acid corrosion reaction rate. An acid corrosion unblocking agent system targeting the removal of clay minerals was developed, analyzing the recovery effect of acid corrosion unblocking agents on the drainage capacity of propped fractures under different particle sizes and deposition amounts of clay minerals. The influence laws of unblocking parameters such as acid liquid sealing time and drainage conditions on the clay mineral discharge rate of abandoned wells was researched. Then a "retreat-style segmented fine cleaning + stepwise circulation forced drainage" acid corrosion unblocking renovation method for the deep blockage of abandoned wells was proposed. The above technical methods for cleaning and resuming production of abandoned coalbed methane wells with different sediment types based on targeted unblocking of clay minerals can provide technical demonstrations for reviving a large number of high-cost abandoned wells.