Significance of Rock Mineral Composition On Rock Mechanical Properties And Brittleness Evaluation of Roof And Floor of Broken Soft Coal Seam

Fracture of coal structure and low permeability were the main reasons for the “difficult to released gas” in broken soft coal seam. Exploration of horizontal well coalbed gas technology of roof and floor of broken soft coal seam provided a new technical way for coalbed gas development in broken soft coal seam. In this paper, taking Xinxie -1 drilling as an example, the evaluation method of fractured reservoirs in roof and floor of broken soft coal seam was improved. By systematic studied on mineralogy, petrology and engineering mechanics characteristics of top and bottom plates in broken soft coal seam, the influence of rock mineral composition on the rock mechanics properties of the roof and floor of coal seam was explored. In addition, By used correlation analysis and grey relational analysis, a brittle evaluation method of coal seam top and bottom plates based on mineral composition was established. The research results showed that: ①The main components of rock minerals in the top and bottom plates of broken soft coal seam were quartz and clay minerals, followed by plagioclase, siderite and pyrite. The main types of rock cementation were quartz enlargement and siderite cementation, and the pore damage caused by cementation was much greater than that of compaction; ②With the increased of rock particle size, compressive strength (CS) and elastic modulus (E) showed a gradual increase trend, Poisson's ratio (μ) showed a gradual decrease trend, other rock mechanical parameters had no obvious changes. The difference of mineral composition and cementation type was the key factor cause abnormal mechanical properties of rocks; ③Compared with clay minerals, the change of brittle mineral content such as quartz, plagioclase and siderite in rocks were sensitive to the mechanical properties of rocks. The sensitive minerals of compressive strength, shear strength, elastic modulus and softening coefficient were quartz, the sensitive minerals of compressive strength were plagioclase and siderite, and the sensitive minerals of Poisson's ratio are quartz and clay; ④The calculation results of the established mineral weight analysis method were more realistic. It could be concluded that the roof of 13-1 coal, 11-2 coal, 9-2 coal and 4-2 coal seams were more inclined to form fracture network during fracturing, which had guiding significance for the optimization of fracturing horizon.

A “full spectrum-domain-time” coalbed gas utilization model and its application in mining area

Coalbed gas (CBG) has been widely used as an important energy source. However, its utilization and allocation system is imperfect in mining areas. During the utilization process, a large amount of CBG is discharged into the air, causing environmental pollution. In this study, we proposed a “full spectrum-domain-time” CBG utilization model. In this model, by combining high methane concentration gas power generation, low methane concentration gas purification, and ultra-low methane concentration gas thermal storage and oxidation utilization, we were able to utilize CBG with full-spectrum of methane concentrations. In addition, by establishing CBG transportation and storage system in mining area, we were able to realize CBG supply in the entire network domain. Furthermore, based on the time series prediction algorithm, the CBG demand of different mining areas is predicted and regulatorily met by real time allocation. Through these three steps, an efficient “full spectrum-domain-time” CBG utilization system was formed and practically applied in Yangquan mining area. The application results showed that under the comprehensive control of “full spectrum-domain-time” CBG utilization model, CBG with methane concentration ≥0.2% could be used in the mining area and its utilization rate increased year by year, reaching the highest of 77.15%. Overall, our study provided a reference for the efficient CBG utilization in the mining area.

A “Full Spectrum-Domain-Time” Coalbed Gas Utilization Model and Its Application in Mining area

Background: As an important energy source, coalbed gas (CBG) has been widely used. However, the allocation system of CBG resources is not perfect. During the utilization process, a large amount of CBG is discharged into the air, causing environmental pollutionMethods: In this study, we proposed a “full spectrum-domain-time” CBG utilization model, including full spectrum CBG utilization technology and full domain CBG supply, In addition, based on time series algorithms, real-time prediction of the demand for CBG, grasp the characteristics of time changes in demand, and scientifically allocate resources, that is, “full-time” regulation. Taking Yangquan Coal Group, Shanxi Province, China, as a case study, introduced the application of the “full spectrum-domain-time” utilization model in the enterprise, and at last assessed the achievement of the model application. Results and Conclusions: The time series algorithm can be used to predict CBG demand in different regions of the mining area. Driven by this model, both the total CBG and low-concentration CBG utilizations in the Yangquan Coal Group increase year after year, making it promising to reach 77.15% of CBG utilization rate and indicating that application of the model has made great accomplishment.