松科二井轻烃组分垂向分布特征及其对深部油气的指示

Vertical distribution characteristics of light hydrocarbon components in Well SK-2 and its implications for deep oil and gas

松辽盆地深部油气已成为今后油气战略性接替领域的一个重要方向,松科二井连续取样的6042组103种单体的轻烃组分数据显示,轻烃组分垂向分布特征呈现明显的分段性,整体可划分为6个区段:Ⅰ段(井段470~1000 m)罐顶气峰面积小,出峰个数少,主要以甲烷为主,重烃较低,为浅层低熟油气段。Ⅱ段(井段1000~2800 m)罐顶气峰面积小,出峰个数多;甲烷含量中等,重烃含量普遍较高;有机质类型以Ⅰ型为主,处于成熟阶段,为常规油气段。Ⅲ段(井段2800~3320 m)罐顶气峰面积小,出峰个数较少、零散;甲烷含量整体较高,重烃含量与Ⅳ段相似,表明该段气源可能来源于Ⅳ段。Ⅳ段(井段3320~5940 m)罐顶气峰面积大,集中分布在3400~3800 m和5200~5400 m井段,明显高于Ⅲ段和Ⅴ段;为Ⅲ型烃源岩,处于高成熟-过成熟阶段。Ⅴ段(井段5940~6200 m)罐顶气峰面积、出峰个数低;甲烷和重烃含量较低。Ⅵ段(井段6200~7018 m)出峰个数、罐顶气峰面积低;甲烷含量较高,重烃含量中等,其总体特征与Ⅳ和Ⅴ段不同,推测深部可能存在气源。上述垂向分布特征反映了白垩系、侏罗系和前侏罗系在油气成因类型、成熟度和含气性及其油气来源等具有不同的特征,为松辽盆地深部非常规天然气探索拓展提供了重要依据。

With the maturation of oil and gas exploration and development in Songliao basin, it is urgent to expand strategic replacement areas for oil and gas storage and production. In this task,deep oil and gas seem to be an important direction. Roof gas logging with continuous sampling in the whole well section of Well SK-2 obtained 6042 groups of light hydrocarbon composition data containing 103 monomers,and fully demonstrated vertical variation characteristics of light hydrocarbon components in the deep part of Well SK-2,which shows obvious segmentation. As a whole, it can be divided into 6 sections: section Ⅰ(470-1000 m in well section), which has a small peak area, a small number of peak outfalls, and a low heavy hydrocarbon content, showing the characteristics of shallow and low-mature oil and gas;Section Ⅱ(well section 1000-2800 m) has a large peak area, a large number of peaks and a high heavy hydrocarbon content. It is a mature type Ⅰ source rock and a conventional oil and gas section dominated by oil generation;Section Ⅲ(2800-3320 m in well section) has fewer and scattered peaks, low content of heavy hydrocarbon and no hydrocarbon source rocks, which are characteristic of reservoirs;Section Ⅳ(3320-5940 m in well section) is the upper unconventional gas section of Shahezi Formation, with a large peak area and a large number of peak outputs, high content of heavy hydrocarbon, being Type Ⅲ source rocks with large thickness in the maturation-over-maturation stage, and sandstone interbeds can form various types of unconventional natural gas, suggesting an important section for future exploration;Section Ⅴ(5940-6200 m in well section) is the lower part of Shahezi Formation and Huoshiling Formation, and the peak area and peak number of roof gas are scattered within the section which is considered to be in the stage of over-maturation;Section Ⅵ(6200-7108 m in well section)is volcanic rock and basement segment, and the peak area and number of peaks are generally low. However, the peak area of top gas in 7000-7100 m well segment shows that the light hydrocarbon parameters are different from those of section Ⅴ, and it is inferred that there may be gas sources of type Ⅱ-Ⅲ organic matter in the deep part. These characteristics show that the vertical distribution of light hydrocarbon components reflects the different characteristics among Jurassic, Cretaceous and the basal formations in oil and gas formation, maturation, gas content and oil and gas sources. The results obtained by the authors reveal the potential of deep unconventional gas resource, and provide an important foundation for Songliao Basin’s exploration shift from conventional oil and gas exploration and tight conglomerate gas exploration at the edge of fault depression to deep trough zone for the exploration and expansion of unconventional natural gas.