山西沁水盆地广志区煤层气藏地质特征研究

Study on geological characteristics of coalbed methane reservoir inGuangzhi area,Qinshui Basin,Shanxi Province

沁水盆地煤层气田是中国第一个开展煤层气开发的热点地区,广志区位于沁水盆地复向斜东翼中段,盆地构造演化的主导作用导致煤层气成藏过程复杂。为揭示广志区中—高煤阶煤层气成藏富集规律及地质特征,依据该区以往测试实验成果资料和勘探成果资料,采用定量和定性分析分析相结合的方法,对该区主力煤层15号煤的煤层厚度、埋藏深度、煤岩煤质、储层物性、含气性、等温吸附特征、煤岩热演化程度等条件进行分析,建立煤层气成藏模式。结果表明:广志区煤层气成藏条件较好,主力煤层为15号煤层全区发育,厚度4.7 m,煤层含气量14.20 m~3/t;煤岩热演化程度较高,保存条件完好,具备良好煤层气成藏基础;煤层气成藏主要受构造特征、沉积特征及煤变质作用控制,次级背斜构造高部位为富集高产区。

The coalbed methane field in Qinshui Basin is the first hot spot of coalbed methane development in China.The Guangzhi area is located in the middle part of the east wing of the Qinshui Basin syncline.The leading role of the tectonic evolution of the basin leads to the complicated process of coalbed methane accumulation.In order to reveal the accumulation and geological characteristics of coalbed methane reservoirs in the middle and high coal ranks of Guangzhi District,based on previous testing and exploration results in the area,by combining quantitative and qualitative analysis,the coal seam thickness,burial depth,coal rock and coal quality,reservoir physical property,gas bearing property,isothermal adsorption characteristics,thermal evolution degree of coal rock and other conditions of the main coal seam No.15 in this area are analyzed,and the coalbed methane accumulation model is established.The results show that the coalbed methane reservoir formation conditions in Guangzhi District are good,with the main coal seam being the No.15 coal seam,which is fully developed in the area,with a thickness of 4.7 meters and a gas content of 14.20 m^(3)/t.The degree of thermal evolution of coal and rock is relatively high,with good preservation conditions and a good foundation for coalbed methane reservoir formation.Coalbed methane accumulation is mainly controlled by structural characteristics,sedimentary characteristics and coal metamorphism.The high part of secondary anticline structure is rich and high production area.