吐哈煤田艾丁湖一区煤炭地下气化地质评价体系

Underground coal gasification in the Aidinghu mining area,Turpan-Hami coalfield:Geological evaluation system and the selection of the optimal coal seam

【目的】煤炭地下气化(underground coal gasification,UCG)是传统采煤技术的革新,系统的地质评价体系构建和科学的地质选层是UCG成功的先决条件。【方法】以吐哈煤田艾丁湖一区煤储层为研究对象,采用层次分析法、变异系数法和逼近于理想值的排序方法(TOPSIS法)等数学分析方法,从煤岩煤质、煤层赋存、含水层与围岩、地质构造、有害元素、地质勘查程度等方面进行了系统分析,深入探究了吐哈煤田艾丁湖一区UCG的可行性,同时构建了UCG地质选层资源评价体系并进行了气化炉址的地质选层。【结果和结论】结果表明:研究区煤的煤阶较低,煤层水分灰分较低、挥发分适中,煤层较多,煤体结构和煤层地质构造较简单,煤层埋深适中,顶底板岩性多为泥岩和粉砂岩、细砂岩,断层不发育,煤炭储量丰厚,煤层有害元素含量低,地质勘查程度较高,适宜进行UCG工作;优选出煤种、煤层埋深、顶底板岩性、煤炭储量等23个地质因素作为二级评价指标,通过合理的数理统计和科学的定量化转化,计算出了其综合权重并进行了分级处理,建立了适用于研究区的UCG多层次地质选层资源评价体系;基于该评价体系,运用加权求和法和TOPSIS法优选出的艾丁湖一区UCG有利煤层前3位均为8上>11号>7-3号煤层,最终确定8上号煤层为研究区UCG工作的最有利煤层。研究结果可为该区后续的地下气化工作实施提供科学依据,也对其他地区UCG地质选层具有借鉴意义。

[Objective]Underground coal gasification(UCG)is an innovation in traditional coal mining technology.The prerequisites for successful UCG include developing a systematic geological evaluation system and scientifically selecting the optimal coal seam.[Methods]Using mathematical analysis methods such as analytic hierarchy process(AHP),coefficient of variation method,and technique for order preference by similarity to ideal solution(TOPSIS),this study systematically analyzed the coal quality,coal seam occurrence,hydrology,surrounding rocks,geological structures,hazardous elements,and geological exploration degree of coal reservoirs in the Aidinghu mining area,Turpan-Hami coalfield.Accordingly,this study deeply explored the feasibility of UCG in the Aidinghu mining area,constructed the resource evaluation system for selecting the optimal coal seam for UCG,and determined gasifier sites.[Results and Conclusions]The results indicate that the study area exhibits coals with low ranks and simple structures.The coal seams in the area display low moisture and ash contents,moderate volatile constituents,substantial quantity,simple geological structures,and moderate burial depths.The roofs and floors of the coal seams consist largely of mudstones,siltstones,and fine-grained sandstones,with faults being underdeveloped.Furthermore,the study area boasts abundant coal reserves,low hazardous element contents in the coal seams,and a high geological exploration degree.All these render the study area suitable for UCG.The second-level evaluation indices consist of 23 geological factors such as coal type,the burial depth of coal seams,the lithology of coal seam roofs and floors,and coal reserves.Using reasonable mathematical statistics and scientific quantitative transformation,this study determined the comprehensive weight and grades of these indices and established a multi-level resource evaluation system for selecting the optimal coal seam for UCG applicable to the study area.Using this evaluation system,as well as the weighted sum method and TOPSIS,this study determined that the top three coal seams favorable for UCG in the Aidinghu mining area are the upper part of the No.8 coal seam,the No.11 coal seam,and the No.7-3 coal seam sequentially.Finally,the upper part of the No.8 coal seam was identified as the most favorable coal seam for UCG in the study area.The results of this study provide a scientific basis for the subsequent UCG implementation in the study area and serve as a reference for selecting the optimal coal seam for UCG in other areas.