Work

Micro-Nano Structure Characteristics and Gas Enrichment Mechanism of High-Rank Coals in the Southern Qinshui Basin

Year: 2025

Type: article

Abstract: As a clean unconventional natural gas resource, the exploitation and utilization of coalbed methane is of double strategic significance in alleviating the contradiction between energy supply and demand, reducing greenhouse gas emissions and realizing the goal of “double carbon”. However, the pore-fracture system of tectonic coal is characterized by strong heterogeneity and dynamic evolution, and its structural differences at the micro-nano scale directly affect the occurrence state and exploitation potential of methane. In this paper, the metamorphism, deformation, and pore-fracture structure of coal reservoirs in the southern Qinshui Basin were studied and analyzed by using Proximate analysis, Macro-micro observation, Low-temperature nitrogen adsorption and Mercury intrusion, etc., which elucidated the influencing factors on the permeability of coal reservoirs and revealed the mechanism of methane enrichment. The research shows that: the metamorphism degree of the coal reservoirs is generally characterized by a gradual decrease from south to north and from the margin to the interior; the deformation type is mainly dominated by brittle deformation and the deformation degree is relatively weak; the pore-fracture structure mainly consists of large matrix pores, cuttings and tectonic and fracture, indicating that the contribution of secondary pores and secondary fractures to the reservoir space is particularly significant. The metamorphism, deformation and pore-fracture structure of coal reservoirs are the main controlling factors affecting their permeability. The coalbed methane has experienced the dynamic enrichment process of ‘hydrocarbon generation to uplift and transformation to adjustment and enrichment’. Hydrodynamic conditions and tectonic activities are the main influencing factors for coalbed methane enrichment. Therefore, this study not only deepens the theory of multi-field coupled seepage in coal reservoirs, but also injects the core driving force for the efficient development of coalbed methane resources and the green low-carbon transformation.

Source: Energy & Fuels

DOI: 10.1021/acs.energyfuels.5c02981