惠民凹陷南坡煤型气有效供气中心分析

Analysis of Effective Generation Center of Coal-Formed Gas in South Slope of Huimin Sag

惠民凹陷南坡石炭 -二叠系煤层分布广泛、厚度较大 ,为一套以潮坪 -泻湖沉积为主的海陆交互相地层 ,其有机质属浅沼森林有机相和深沼芦苇有机相。生气模拟实验表明 ,太原组和山西组煤岩生气潜力分别达 15 0mL/g有机碳和 110mL/g有机碳。煤型气源岩经历了复杂的热演化过程 ,其有效二次生气时期为早第三纪至今 ,门限温度 135℃ ,对应的埋深为 4 0 0 0m。有效供气中心位于济阳地堑东部和曲堤地垒东段 ,生气强度一般达到 (2 0～ 4 0 )× 10 8m3 /km2 。

Coal beds occur in a wide area and developed with big thickness in south slope of Huimin Sag. These coal beds are sediments of marine terrestrial interface which deposited under environments of tidal flat and lagoon. It is shown by gas generation simulation experiments that the gas generation potential of the Taiyuan and Shanxi Formation are 150mL/g and 110mL/g organic matter respectively. The source rock of coal formed gas has a very complex thermal evolution process. The second gas generation occurred from the Early Tertiary to the Quaternary, with a threshold tempreture of 135℃ and corresponding depth of 4000m. The effective gas generation center is located in eastern of the Jiyang Graben and Quti Horst. The gas generation intensity is about 20×10 8m 3/km 2 to 40×10 8m 3/km. Therefore, eastern parts of Quti Horst is the main target of exploration.