松辽盆地南部浅层气成藏条件分析

松辽盆地南部浅层天然气主要赋存于晚白垩纪地层中。气样组分分析表明,该区天然气属甲烷型生物成因气。有机地球化学分析表明,生物气气源层具强-较强的还原环境,同时具有较高的有机质丰度、较好的有机质类型。持续沉降、快速沉积作用和有利的沉积环境是生物气形成的重要地质条件。良好的储盖条件有利于浅层气的聚集和保存,该区储气层以细砂为主,由于埋藏浅、时代新、岩石疏松、未固结成岩,构成了良好的储集层。本区白垩系泉头组至嫩江组沉积时期,是大型沉积坳陷形成和发展的全盛时期。坳陷期在盆地中部形成了湖区或沉积中心,湖区范围大于8万平方公里,沉积了松辽盆地最有利的生烃层,同时也为良好的区域盖层。

Reservoir formation condition of shallow gas in the Songliao basin

The shallow gas in the south of Songliao basin mainly existes in late Cretaceous strata. According to component analysis, it is methane type biogas . Organic geochemical shows that the biogas source bed has strong or relatively strong reducing environment and rich, good- typed organic matter. The continuance sedimentation, speedy sediment and good sedimentary environment are the important geology factors to forming shallow gas. Favorable reservoir and seal conditions are conductive to its congregation and conservation. The favorable reservoir rock layer in this area is mainly built up by fine sandstone, and it has the character of shallow concealed, new era, loose and unconcretion. The deposition time from Quantou Formation to Nenjiang Formation in the Cretaceous strata is the heyday of large-scale depos-its hollowly's formation and development. In the depression term, lake areas and deposit centers form in the centre of thebasin. The lake area is more than 80 thousand square kilometers, where deposits the most favorable hydrocarbon layer of Songliao basin and as well as a good regional cap rock.