Response characteristics of the resistivity and water content during the imbibition process in remolded coal without gas

Abstract

The water content distribution in a coal body is closely related to the gas distribution. It is difficult to directly determine the water content distribution in the process water imbibition. To retrieve the water content by the resistivity value and establish a relationship between the resistivity and water content, the response characteristics of the resistivity and water content of remolded coal formed under different loads are studied by a self‐designed resistivity experimental system. The results show that the resistivity of the remolded coal decreases over time during the imbibition process, including a rapidly decreasing stage and a slowly decreasing stage. The resistivity of the remolded coal is related to the water in the macropore in the rapidly decreasing stage. In the slowly decreasing stage, the resistivity is related to the contact between coal particles. The pressing load, imbibition range, and imbibition speed are negatively correlated with porosity. The resistivity of the steady state is also negatively correlated with the water content and pressing load. The relationship between the resistivity of the steady state and the water content fit a power function. This study reveals the law of resistivity and the water content during the imbibition process and provides an effective methodology to bridge the gap for measuring water content distribution during the imbibition process.

Estimation of Geotechnical Parameters for Coal Exploration from Quasi-3D Electrical Resistivity Measurements

“…The probable source of the saturated zone in the shale matrix of resistivity less than 200 Ωm around a depth of 24 m is a pond near the second ERT. When coal comes in contact with water, its resistivity decreases [55]. The electrical section of profile 2 shows a lower resistivity of the coal, probably because of the saturated coal.…”

“…This may be due to more loose sediments between 140 and 280 m of shale. The reduction of the salinity of irrigation water with depth may cause a gradual change in resistivity [55]. The coal seam starts at around 20 m depth and is approximately 60 m × 30 m in size, as interpreted at the center of the profile.…”

Measurement and Modeling of Spontaneous Capillary Imbibition in Coal

“…Wang and Jiang found that the imbibition process of static water could enhance coalbed methane recovery. High-energy sites can be easily occupied by water molecules under the action of oxygen-containing functional groups in the coal matrix and hydrogen bonds in water molecules . To summarize, the spontaneous imbibition of external water can lead to four effects, namely, accelerating methane desorption, decreasing the coal seam gas content, eliminating the danger of coal and gas outbursts, and increasing the production of coalbed methane (CBM).…”