Geological characteristics and exploration breakthroughs of coal rock gas in Carboniferous Benxi Formation,Ordos Basin,NW China  

作　　者：ZHAO Zhe XU Wanglin ZHAO Zhenyu YI Shiwei YANG Wei ZHANG Yueqiao SUN Yuanshi ZHAO Weibo SHI Yunhe ZHANG Chunlin GAO Jianrong 

机构地区：[1]PetroChina Research Institute of Petroleum Exploration&Development,Beijing 100083,China [2]Research Institute of Exploration and Development,PetroChina Changqing Oilfield Company,Xi’an 710018,China

出　　处：《Petroleum Exploration and Development》2024年第2期262-278,共17页石油勘探与开发（英文版）

基　　金：Supported by the PetroChina Science and Technology Major Project(2023ZZ18-03);Changqing Oilfield Major Science and Technology Project(2023DZZ01)。

摘　　要：To explore the geological characteristics and exploration potential of the Carboniferous Benxi Formation coal rock gas in the Ordos Basin,this paper presents a systematic research on the coal rock distribution,coal rock reservoirs,coal rock quality,and coal rock gas features,resources and enrichment.Coal rock gas is a high-quality resource distinct from coalbed methane,and it has unique features in terms of burial depth,gas source,reservoir,gas content,and carbon isotopic composition.The Benxi Formation coal rocks cover an area of 16×104km^(2),with thicknesses ranging from 2 m to 25 m,primarily consisting of bright and semi-bright coals with primitive structures and low volatile and ash contents,indicating a good coal quality.The medium-to-high rank coal rocks have the total organic carbon(TOC)content ranging from 33.49%to 86.11%,averaging75.16%.They have a high degree of thermal evolution(Roof 1.2%-2.8%),and a high gas-generating capacity.They also have high stable carbon isotopic values(δ13C1of-37.6‰to-16‰;δ13C2of-21.7‰to-14.3‰).Deep coal rocks develop matrix pores such as gas bubble pores,organic pores,and inorganic mineral pores,which,together with cleats and fractures,form good reservoir spaces.The coal rock reservoirs exhibit the porosity of 0.54%-10.67%(averaging 5.42%)and the permeability of(0.001-14.600)×10^(-3)μm^(2)(averaging 2.32×10^(-3)μm^(2)).Vertically,there are five types of coal rock gas accumulation and dissipation combinations,among which the coal rock-mudstone gas accumulation combination and the coal rock-limestone gas accumulation combination are the most important,with good sealing conditions and high peak values of total hydrocarbon in gas logging.A model of coal rock gas accumulation has been constructed,which includes widespread distribution of medium-to-high rank coal rocks continually generating gas,matrix pores and cleats/fractures in coal rocks acting as large-scale reservoir spaces,tight cap rocks providing sealing,source-reservoir integration,and five types of effici

关 键 词：coal rock gas coalbed methane medium-to-high rank coal CLEAT Ordos Basin Carboniferous Benxi Formation risk exploration 

分 类 号：P618.13[天文地球—矿床学]