The Research of Origin of Deep Natural Gas of Qianbei Sub-Sag in the South of Songliao Basin

Abstract

This paper analyses the origins of deep natural gas in Qianbei Subsag using a variety of analytical data such as the natural gas components, the isotope and the light hydrocarbon analysis combining with the development characteristics of hydrocarbon source rocks. The study results show as the following: The abundance of organic matter from hydrocarbon source rocks in Qianbei Subsag is high and dominated by humus type. Part of good hydrocarbon source rocks of Type II1 and Type II2 are developed in Yingcheng Formation and these are the major gas source rocks that is in the stage of postmaturity in evolution degree. The natural gas component is dominated by methane and non-hydrocarbon gas content is low. The isotope values of ethane are lighter and methane and ethane have an obvious phenomenon of carbon isotopic reversal. Parent material types of methane and ethane are from different sources. The sources of methane are biased to humic parent material while the sources of ethane are biased to sapropelic parent material.