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西山煤田构造-水文地质对煤层气成藏的控制作用

Controlling effects of structural-hydrogeological conditions on coalbedmethane accumulation in Xishan Coalfield

  • 摘要: 煤层气富集成藏受构造、沉积环境、水文地质条件、岩浆活动等多方面因素控制,为了研究西山煤田煤层气富集的主控因素及其成藏规律,通过资料收集整理、采样分析研究,发现西山煤田煤层气成藏的主控因素为构造及水文地质条件。利用多口西山煤田水文孔的资料,分别对太原组含水层及山西组含水层的水动力场和水化学场进行研究;利用煤层气井的含气量等资料,找出对煤层气有利的构造、水动力、水化学因素,提出3种构造-水动力成藏模式;最后基于前面的研究提出构造-水动力控制下的煤层气富集区识别标准,对研究区进行富集区识别。研究表明:①西山煤田煤系地层水动力场可以分为三部分地下水流动系统:西北部系统Ⅰ、中南部系统Ⅱ和东部系统Ⅲ;其中屯兰矿东曲矿南部、原相地区以及西部水峪贯向斜核部、杜儿坪断层附近,水动力活动相对较弱,有利于煤层气成藏;②有利于煤层气富集的水化学类型为重碳酸钠型;③提出构造-水动力作用有利于煤层气聚集成藏的3种模式:单斜-水动力成藏、向斜-水动力成藏、断层-水动力成藏;④对西山煤田进行煤层气富集区识别,识别出邢家社附近和杜儿坪南部2个富集区。用上述方法将构造-水文地质条件对煤层气成藏的控制作用定量化和标准化,有利于其他区块参考和利用。

     

    Abstract: Coalbed methane rich integration were controlled by many factors such as structure, sedimentary environment, hydro-geological conditions, magnetic activity. In order to study the main controlling factors of coalbed methane enrichment and its accumulation law in Xishan Coalfield, this paper collected and sampled the data, and found that the main controlling factors of the coalbed methane in Xishan Coalfield were structure and hydro-geological conditions. The hydro-dynamic and hydro-chemical fields of Taiyuan Formation aquifer and Shanxi Formation aquifer were studied the data of the hydro-logical pore from several Xishan Coalfield.And then the favorable structural, hydrodynamic and hydro-chemical factors for coalbed methane were found out by using the gas content of coalbed methane wells, and three structural-hydrodynamic reservoir-forming models were proposed. Finally, based on the previous studies, this paper proposed identification criteria of coalbed methane enrichment area under the structure-hydrodynamic control system to identify the enrichment area in the study area. The results show that: ①Xishan coalfield strata hydrodynamic field can be divided into: south-central systemⅠ, northwestern system Ⅱand east system Ⅲ; the hydrodynamic activity was relatively weak in the southern Yuanxiang,Dongqu coal mine,near Duerping fault and in the core of Shuiyuguan syncline, which was conducive to CBM accumulation. ②The water chemistry that was conducive to the enrichment of coalbed methane was sodium bicarbonate; ③Three modes of structure-hydrodynamics which were beneficial to coalbed methane accumulation and accumulation were proposed: monoclinic-hydrodynamic accumulation, syncline-hydrodynamic accumulation, fault-hydrodynamic accumulation.④The coalbed methane enrichment areas in Xishan Coalfield were identified:one was near Xingjiashe and the other was in the south of Duerping. The above method was used to quantify and standardize the control effect of structural-hydrological and geological conditions on coalbed methane accumulation, which was beneficial to reference and utilization of other blocks.

     

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