鄂尔多斯盆地富县地区天然气地球化学特征及其成因

在对鄂尔多斯盆地富县地区奥陶系天然气地球化学特征研究的基础上,将其组分、烷烃气碳同位素、氦同位素、氩同位素等与盆地中部主要气田进行了对比,并结合区域地质背景综合分析了天然气的成因类型.指出该地区奥陶系天然气具有"干燥系数大、二氧化碳含量高、烷烃气碳同位素组成轻、热演化程度高"的特点,与靖边气田奥陶系天然气地球化学特征非常接近.应用国内学者建立的甲烷碳同位素与镜质体反射率关系方程式计算了富县地区奥陶系天然气的Ro约为3.33%,处于过成熟演化阶段.利用天然气成因判别图版综合分析,认为富县地区奥陶系天然气为油型气和煤成气的混合气体,且以油型气为主.

Geochemical characteristics and genesis of the natural gas in Fu County area, Ordos Basin

There is abundant Palaeozoic natural gas resource in Ordos Basin.The recent exploration and research are mainly focused in the middle and the north of the basin,but hardly in the south of it.The chemical composition,the carbon isotope of alkane gas,the isotope of helium and the isotope of argon in Ordovician natural gas in the area of Fu County in southern Ordos Basin are compared with those in the natural gas in the main gas fields in the middle of the basin based on the study on the geochemical characteristics of the Ordovician natural gas,and the genetic types of the natural gas are comprehensively analyzed based on the regional geology background.It is held that the Ordovician natural gas is of the features of high drying coefficient,high carbon dioxide content,light carbon isotope of alkane gas and high thermal evolution degree,these features are approach to those of the Ordovician natural gas from Jingbian Gasfield.The vitrinite reflectance of the Ordovician natural gas in the area of Fu County is calculated by using the relation equation between methane carbon isotope and vitrinite reflectance established by domestic scholars,and it is about 3.33%.This shows that the natural gas is in overmature evolution stage.According to the identifying chart of natural gas genesis,the Ordovician natural gas in the area of Fu County belongs to the mixture of oil-formed gas and coal-formed gas,and oil-formed gas is main component in the Ordovician gas.