河南平顶山矿区含煤地层沉积环境及其对煤系气成藏的控制^*

Sedimentary environment of coal-bearing strata and its control on accumulation of coal measure gas in Pingdingshan mining area,Henan Province

摘要

近几年来,河南省平顶山矿区煤系气勘探开发取得了新突破,采动井、采空井和预抽井的单井日抽采量分别达到40 500 m³、20 000 m³和4 500 m³。为了查明煤系气生成与赋存的沉积背景,本次工作采用地层学与沉积学的研究方法,开展了精细的地层、沉积特征和沉积序列以及气测录井资料分析,从而揭示出本区主要含煤地层山西组和下石盒子组中煤系气(煤层气、页岩气和致密砂岩气)生成与赋存的沉积环境,也就是潮坪上的泥炭沼泽(泥炭坪)、三角洲分流间湾沼泽和分流河道沉积环境控制了煤系气的成藏。基于地层沉积特征在垂向上的变化规律,划分出9种不同沉积环境的沉积序列类型,并在综合分析的基础上,提出了平顶山矿区山西组—下石盒子组煤系气赋存的沉积环境模式。研究还表明,区内煤系气含量变化及区域分布特征不仅与滨岸潮坪沼泽、三角洲分流河道砂体和分流间湾沼泽的时空变化密切相关,而且还与储集层厚度变化相关。该成果可为今后平顶山地区煤系气勘探开发井的设计、部署与施工提供科学依据。同时,对华北地区相同含煤地层的煤系气开发也具有重要借鉴意义。

Abstract

In recent years,a new breakthrough has been made in the exploration and development of coal measures gas in the Pingdingshan mining area of Henan Province. The daily production per well in mining area,goal area and unmining area reached 40 500 m³,20 000 m³ and 4 500 m³,respectively. To better understand the sedimentary background of coal measure gas generation and occurrence,this study applies stratigraphy and sedimentology research methods to conduct a detailed analysis of strata,sedimentary characteristics,and sedimentary sequences,along with gas logging data. This reveals the sedimentary environment controlling the generation and occurrence of coal measure gas(coalbed methane,shale gas,and tight sandstone gas)in the Shanxi Formation and Xiashihezi Formation. Specifically,the sedimentary environment of peat swamp(peat flat)on tidal flat,delta interdistributary bay swamp and distributary channel control the accumulation of coal measure gas. According to the vertical variation of stratigraphic and sedimentary characteristics,nine different sedimentary sequence types are classified,and the sedimentary environment model of coal measure gas occurrence in the Shanxi Formation and Xiashihezi Formation in Pingdingshan area is proposed. The study also shows that the content change of coal measure gas and its regional distribution characteristics are not only closely related to the spatio-temporal variation of coastal tidal flat marsh,delta distributary channel sand body and interdistributary bay marsh,and are also related to the variation of reservoir thickness. The results can provide a scientific basis for the future design,deployment and production of coal measure gas exploration and development wells in Pingdingshan area. Moreover,the findings offer important reference significance for the development of coal measures gas in the similar coal-bearing strata in North China.

关键词

煤系气开发 / 地质勘探 / 含煤地层 / 山西组 / 下石盒子组 / 平顶山矿区

Key words

coal measure gas development / geological exploration / coal-bearing stratum / Shanxi Formation / Xiashihezi Formation / Pingdingshan mining area

基金资助

*国家自然科学基金项目(编号: 42372198)与河南省高校创新团队(编号: 21IRTSTHN007)联合资助