Quantitative Evaluation for the Threat Degree of a Thermal Reservoir to Deep Coal Mining

Abstract

Taking the Suiqi coalfield located in North China as the object, where the coal seam burial depth is more than 1100 m, the water abundance of the roof pore thermal storage aquifer is better than average, the ground temperature is abnormally high, and hydrogeological data are relatively lacking, this paper selects and determines eight index factors that influence the mining of the coalfield. Based on the analytic hierarchy process (AHP), the index factor weight is defined, and then, the threat degree of the roof thermal storage aquifer to the coal mining is quantitatively evaluated and divided by using the fuzzy variable set theory. The evaluation results show that the threat degree of the roof in the eastern region is generally greater than that in the western region and that the closer it is to the coal seam outcrop line, the higher the threat degree is; near the boreholes, in the areas Qs1,Qs5, Qs8, Sx1, Tk5, Zc4, and Zc7, which are close to the hidden outcrop line of the coal seam, the classification characteristic value of the threat degree is greater than 3.5, which is in the high-threat zone for disasters caused by roof thermal storage aquifers during coal seam mining. The area above the medium-threat zone accounts for 71.82% of the total study area, indicating that deep coal mining is affected by multiple factors and that roof water and heat disasters are more likely to occur.

Integrated Waterflooding Effect Evaluation Methodology for Carbonate Fractured–Vuggy Reservoirs Based on the Unascertained Measure–Mahalanobis Distance Theory

“…Furthermore, originating from fuzzy mathematics, the evaluations can be transferred qualitatively to quantitatively via the FCEM by using the theory of membership degrees. The FCEM first identifies the influencing factors and evaluation grades of the reservoir waterflooding development effect, then it determines the weight of the influencing factors and the membership degree vectors to obtain the evaluation matrix; the evaluation matrix and the weight vector of the influencing factors are fuzzy-calculated and normalized to obtain the comprehensive evaluation results of the reservoir waterflooding development effect in the final step [15]. In addition, based on the reservoir numerical model, and incorporated with the interwell tracer technology, Guo et al [16] evaluated the balanced displacement effect during the reservoir waterflooding development process, according to the interwell areal sweep efficiency estimated by the tracer types and their monitoring amounts in the injection wells, and enabled the rapid assessment of the offshore reservoir waterflooding development effect.…”

Evaluation of Water Isolation Capability of Coal Floor Rocks Based on ArcGIS Vulnerability Index Method

“…The floor water-filled aquifers affecting the mining of J 16-17 coal are the L 2 , L 6-7 limestone aquifers of the Carboniferous Taiyuan Formation and the Cambrian limestone aquifers (Figure 2). The average thickness of the L 2 aquifer is 6.5m, the unit water inflow is0.0001-0.0043L/s•m, the permeability coefficient is 0.0189-0.0003m/d, and the water richness is poor; the average thickness of the L 6-7 limestone aquifer is 7.3m, and the unit water inflow is 0.075-0.019L/s•m, permeability coefficient 0.335~0.528m/d, weak water richness; the distance between Cambrian aquifer and J [16][17] coal is between 80-90m, the average thickness is greater than 200m, and the unit water inflow is 2.27-26.62L/s•m, permeability coefficient 1.092-7.47m/d, strong water richness but uneven distribution.…”

“…13 coal mine include geological characteristics, archaeological and engineering geological conditions and mining layout. The main control factors can be selected by analyzing the existing exploration data and underground mining exposure information and referring to the achievements of others [17].…”

Quantitative Identification of the Water Resistance Capacity of Composite Strata in Mining Coal Seam Floors

“…That is, the comprehensive weight can effectively combine the subjective and objective weights, and its weight distribution is more scientific and reasonable. According to the existing index factor data with reference to the existing research results [37], the water-insulation capacity of the composite strata in the coal seam floor can be divided into five grades, namely, extremely weak (I), weak (II), medium (III), strong (IV), and very strong (V).…”