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四川盆地西北部广元－－旺苍地区二、三叠系主要为碳酸盐岩沉积。本对已取心的五个二、三叠系构造共七个层组的所有岩心和区内部分露头剖面，系统采集有机碳样品260个。经综合分析、对比人为，除下三叠统飞二、飞三段不具备生烃条件下，区内主要目的层均属有效烃源岩（碳酸盐岩有机碳下限取0.20%,泥页岩取0.50%），其中P2d、P2ω、P1m有机碳平均值均在0.40%以上（分别为4.60%、0.40%、0.58%),P2c为0.35%。有机碳含量与沉积相、地层时代密切相关。水体深度对有机碳影响最大，其次为生屑含量。按地层时代，有机碳含量最高的硅质岩是P2d，其次分别为P1m、P2ω及P2c。生屑灰岩也属有效烃源岩，若含硅质或属深水沉积（海槽），则有机碳含量较高（如P1m）。从有机质类型、成熟度以及天然气的组成、碳同位素和浓缩烃等初步判识，河湾场构造二叠系气藏属自生自储，天然气主要来自液态烃的高温裂解；飞仙关组气藏甲烷具煤成气特征，重烃（C2^ ）具油型气特征，可能属混合气。

Evaluation of Hydrocarbon Source Rocks in Permian and Triassic at Guangyuan-Wangcang Region in Northwest Sichuan Basin and a Primary Discussion on Gas Source

The Permain and Triassic at Guangyuan Wangcang region in Northwest Sichuan Basin are mainly composed of carbonate rocks.Through analyzing,contrasting and studying up 260 organic carbon samples collected from the cores of 7 strata belonged to Permian and Triassic in 5 structures and from partial outcrops within this region,it is considered that except T 1 f 2 and T 1 f 3,the other principal target zones are belonged in effective hydrocarbon source rocks (the organic carbon cutoff is 0.20% for carbonate rocks and 0.50% for mudstones and shales),in which the average values of the organic carbons in P 2 d ,P 2 w and P 1 m are more than 0.40%,being 4.60%, 0.40 % and 0.58% respectively and the average value in P 2 c is 0.35%.Organic carbon content is closely related to sedimentary facies and stratigraphis era.The influence of the water depth on the organic carbon is the greatest,then the biodetritus content.According to stratigraphic era,the organic carbon content of the silicalite is the largest in P 2 d ,then in P 1 m ,P 2 w and P 2 c resectively.Bioclastic limestone is also belonged in the effective hydrocarbon source rock and if it contains silicon or is belonged in deepwater deposit (trough),its organic carbon content is higher (e.g.P 1 m ).In light of the type and muturity of organic matters and the composition,carbon isotope and concentrated hydrocarbon of natural gas,it is primarily identified that the Permian gas reservoir in Hewanchang structure is belonged in self generating and self storing reservoir and natural gas in it mainly originated from liquid hydrocarbons' being cracked at high temperatures;and natural gas in Feixianguan Formation reservoir may be belonged in a mixed gas,because its methane is of the properties of coal formed gas and its heavy hydrocarbons (C 2+ ) have the characteristics of oil formed gas.