松辽盆地南部德惠断陷深层天然气地球化学特征及成因

A STUDY ON GEOCHEMICAL CHARACTER AND ORIGIN OF DEEP NATURAL GAS IN DEHUI FAULT DEPRESSION OF THE SOUTHERN SONGLIAO BASIN

德惠断陷已有40余年的勘探历史,20世纪90年代以来,油气勘探一直没有大的突破。通过对德惠断陷深层天然气的组分及其碳同位素组成的分析并结合具体地质条件研究后表明:德惠断陷二氧化碳组分主要为有机成因;农安气田埋深相对较浅的干气形成除与母质类型有关外更主要的是天然气纵向运移过程中的分馏作用和泉三段的泥岩超压所致,而营城组和沙河子组天然气较干主要是因为来源于高过成熟生烃母质;德惠断陷天然气可以划分为油型气、混合气、煤成气和生物成因气4种类型,但以煤成气为主。认为德惠断陷深层营城组和沙河子组既聚集了部分未曾调整破坏的正常成熟气,又聚集了大量高过成熟阶段的天然气,油气源丰富,有望形成较大规模气藏,是勘探的有利层位。

Dehui fault depression has been made since 1990s ,so it is signifi been explored for more than forty years, while less breakthrough has cantly to deep understand the geochemical character and origin of deep natural gas to the next exploration. Studying on its components and carbon isotopes , with the research on geological condition, show that. carbon dioxide is organic origin, shallow dry gases in Nongan gas field are formed correlating with fractionation duing vertical migration and overpressure in Quan No. 3 interval in mudstone besides parent materials, but dry gases from the Yingcheng and Shahezi formations origin from high mature source rock, gases can be subdivided into petroliferous gases, coal derived gases, hybrid gases and biogenic gases according to the types of parent material and the second one is the major part. It iS also believed that part normal mature gas which has not been destroyed and abundant high mature gas accumulate in the Yingcheng and Shahezi formations ,and large-scale gas reservoir may be formed in these formations for their enough hydrocarbon source.