A Study on the Heterogeneity Characteristics of Geological Controls on Coalbed Methane Accumulation in Gujiao Coalbed Methane Field, Xishan Coalfield, China

Abstract

Commercial exploration and exploitation of coalbed methane (CBM) in Gujiao coalbed methane (CBM) field, Xishan coalfield, have rapidly increased in recent decades. The Gujiao CBM field has shown strong gas distribution heterogeneity, low gas content, and wide distribution of wells with low production. To better understand the geological controlling mechanism on gas distribution heterogeneity, the coal reservoir evolution history and CBM accumulation process have been studied on the base of numerical simulation work. The burial history of coal reservoir can be classified into six stages: shallowly buried stage; deeply buried stage; uplifting stage; short-term tectonic subsidence stage; large-scale uplifting stage; and sustaining uplifting and structural inversion stage. Mostly, coal seams have experienced two-time thermal metamorphisms with twice hydrocarbon-generation processes in this area, whereas in the southwest part, the coal seams in there suffered three-time thermal metamorphisms and hydrocarbon-generation processes. The critical tectonic events of the Indosinian, Yanshanian, and Himalayan orogenies affect different stages of the CBM reservoir accumulation evolution process. The Indosinian orogeny mainly controls the primary CBM generation. The Yanshanian orogeny dominates the second and third gas generation and migration processes. The Himalayan orogeny mainly affects the gas dissipation process and current CBM distribution heterogeneity.

Evaluation of Favorable Area for Coalbed Methane Development Based on Local Variable Weight Theory

“…During the evaluation of favorable area for CBM development, the selection of main controlling factors must follow the principle of ‘selecting the main geological parameters, and each parameter is independent of others’. 37 Geological parameters utilized in the evaluation of favorable areas for CBM development include direct parameters (e.g., gas content, permeability, burial depth, reservoir pressure, critical desorption pressure, etc.) and indirect parameters (e.g., hydrogeological condition, crustal stress, and tectonic characteristics, etc.…”

“…Based on the production conditions and the degree of geological exploration in the study area, combined with the results of our previous research, 37 the following nine factors were selected as the main controlling factors ( Table 1 ).…”

“…The Weibei CBM field is located in the southeast margin of the Ordos Basin (Figure 1), which has shown great potential for CBM exploitation with a total gas-bearing area of up to 1530 km 2 . 37,38 Tectonically, the Weibei CBM field is a monoclinic tectonic structure, which gently tilted to the northwest as a whole (i.e., from the basin margin to the center). Three overthrust faults of F1, F2, and F3 (Figure 1) developed in the center part, which runs across the study area in W-E to NW-SE direction, and divided the Weibei CBM field into several structural domains.…”

“…The Weibei CBM field is located in the southeast margin of the Ordos Basin (Figure ), which has shown great potential for CBM exploitation with a total gas-bearing area of up to 1530 km 2 . , …”

MIC-GDM Coupled Quantification Model: A New Data-Driven Approach to CBM Reservoir Potential Evaluation

“…CBM resources are abundant in the Gujiao mining area, but the reservoir pressure, gas content, groundwater flow field and other parameters have obvious spatial distribution heterogeneity (Yan et al, 2021;Li et al, 2021). It is reported that the tectonic type, roof lithology, burial depth and groundwater dynamic conditions have significant effects on the reservoir .…”