为了研究准南乌鲁木齐矿区低煤阶煤层气甲烷风化带特征及影响因素，规避勘探风险，降低开发成本。依据低煤阶煤层气含气量低、次生生物成因气与热成因气共存的特点，利用煤层含气量以及主要气体(CH4，CO2，N2)浓度测试数据，提出了甲烷风化带划分的新方法，以甲烷含量≥1 m3/t，N2体积分数≤20%分别作为判断甲烷风化带经济边界和地质边界的指标。进一步利用该方法对乌鲁木齐河东、河西矿区甲烷风化带深度进行了划分，讨论了构造、沉积以及水文地质对矿区甲烷风化带深度的影响，分析了造成两个矿区甲烷风化带深度差异的成因。结果表明，河东矿区甲烷风化带深度在370 m左右，河西矿区甲烷风化带深度在200 m左右。在构造抬升前，河东、河西矿区均生成了部分热成因甲烷，此时甲烷风化带较深。研究区经历了晚侏罗世与新生代两次地层抬升运动，河东矿区煤层顶板以砂岩为主，一方面易于地表水渗入，使研究区生成大量次生生物成因气，随着地下水滞留程度的增加，大量煤层气富集;另一方面，较差的顶板封盖条件也造成了一定量煤层气散失，导致河东矿区甲烷风化带深于河西矿区。而河西矿区的泥岩顶板隔水阻气能力好，构造抬升后，地表水渗入能力有限，生成小部分次生生物成因气，但是顶板泥质岩阻气能力强，使得绝大部分的煤层气得以保存，甲烷风化带较浅。

In order to study the characteristics and influencing factors of methane weathering zone of lowrank coalbed methane in Urumqi mining area,southern Junggar,avoid exploration risk and reduce development cost,based on the characteristics of low gas content and the coexisting of secondary biogenic gas with thermogenic gas in lowrank coal,a new method of dividing methane weathering zone was proposed by using the test data of gas content and concentration of main gases (CH4,CO2,N2).The methane content ≥1 m3/t and N2 concentration ≤20% were used as indicators to assess the economic boundary and geological boundary of methane weathering zone,respectively.The method was used to divide the depth of methane weathering zone of Hedong area and Hexi area in Urumqi,and the influence of structure,sediment and hydrogeology on the depth of methane weathering zone was discussed,and the cause of the depth difference of methane weathering zone in the two areas was analyzed.The results showed that the depth of methane weathering zone was about 370 m in Hedong and 200 m in Hexi.Before the tectonic uplift,part of thermogenic methane was generated in the two areas,the methane weathering zone was deeper.The study area experienced two strata uplift movements in Late Jurassic and Cenozoic.The roof of the coal seam in Hedong was mainly sandstone.On the one hand,it was easy for surface water to infiltrate,which generated a large amount of secondary biogenic gas in the study area.With the increase of groundwater stagnant degree,a large number of coal seam gas was enriched.On the other hand,the poor roof sealing also caused a certain amount of coalbed methane loss,resulting in the methane weathering zone in Hedong being deeper than that in Hexi.However,the mudstone roof in Hexi had a good ability to obstruct water and block gas.After the tectonic uplift,the infiltration ability of surface water was limited,resulting in the generation of a small part of secondary biogenic gas.Due to the mudstone roof had a strong ability to block gas,so that most of the coalbed methane could be preserved,and the methane weathering zone was shallow

1 区域地质概况

2 研究区气体分布特征

   2.1 含气量

   2.2 主要气体体积分数

3 甲烷风化带划分新方法

4 甲烷风化带的划分及影响因素分析

   4.1 甲烷风化带划分

   4.2 构造条件

   4.3 沉积环境

   4.4 水文地质条件

5 结论