柴达木盆地西部咸化湖相优质烃源岩地球化学特征及成藏意义

发布时间：2018-07-08 21:11

本文选题：咸化湖盆 + 优质烃源岩　；参考：《石油学报》2017年10期

【摘要】：传统上认为柴达木盆地西部地区咸化湖相烃源岩有机质丰度低,油气主要来源于"可溶有机质"。在柴达木盆地西部首次发现一定规模有机质丰度较高的优质咸化湖相烃源岩,其TOC值一般约在1%,最高可达4%以上;生烃潜量一般大于6 mg/g,最高可达40 mg/g;氢指数一般在500 mg/g(TOC)以上,最高可达900 mg/g(TOC)以上。有机质类型以I型和II1型为主,少量II2型,为倾油型有机质。而有机质丰度过低的样品(TOC0.5%),其类型也较差,所含的可溶有机质也较低,生烃潜力小,为无效烃源岩。优质烃源岩生物标志化合物中富含植烷、C28甾烷、伽马蜡烷和C35藿烷等指示咸水环境的化合物,同时具有高甾烷低藿烷、高C27甾烷低C29甾烷等特征,指示有机质主要来自于水生藻类。这些藻类中富含脂类化合物,被称为"油藻",在较低的成熟演化阶段可直接转化为烃类。咸化环境有利于藻类直接转化而成液态烃的保存,从而形成"未熟—低熟油"。柴达木盆地西部咸化湖相烃源岩中所含的"可溶有机质"明显高于淡水湖相烃源岩,这正是该地区在中浅层发现的一批"未熟—低熟油田"的重要物质来源。通过模拟实验证实,有机质在成熟演化阶段也具有较高的生油潜力,符合经典的油气生成模式。因此,对于深层来说,成熟的烃源岩形成的油气是主要的勘探对象。在该地区古近系深层优质烃源岩形成的油气具有2类成藏模式:(1)源外成藏,即通过油源断层将油气运移至浅部构造圈闭聚集成藏;(2)源内成藏,即在深部烃源岩附近的岩性圈闭中近源聚集。目前这2类油气藏勘探均已获得重大突破,发现了2个亿吨级储量区块,证实深部优质烃源岩形成的油气藏勘探潜力巨大。
[Abstract]:Traditionally, it is considered that the abundance of organic matter in the saline lacustrine source rocks in the western Qaidam Basin is low, and the oil and gas mainly come from "soluble organic matter". In the western part of Qaidam Basin, the high quality salted lacustrine source rocks with relatively high abundance of organic matter on a certain scale were first discovered. Their TOC values are generally about 1 and the maximum is above 4%, and the hydrocarbon generation potential is generally greater than 6 mg / g with a maximum of 40 mg / g, and the hydrogen index is generally above 500 mg/g (TOC). The maximum can be more than 900 mg/g (TOC). The types of organic matter are mainly type I and II 1, and a small amount of type II 2, which belong to the oil type. However, the samples with low abundance of organic matter (TOC 0.5%) are poor in their types, low in soluble organic matter and low in hydrocarbon generation potential, so they are ineffective source rocks. The biomarkers of high quality source rocks are rich in phytoalkane C 28 sterane, gamma wax alkane and C 35 cariane, and have the characteristics of high sterane low hopane, high C 27 sterane and low C 29 sterane, etc. Indicating that organic matter mainly comes from aquatic algae. These algae are rich in lipids, known as "oil algae", and can be converted directly into hydrocarbons at a lower stage of maturation and evolution. The salinization environment is favorable to the direct transformation of algae into the preservation of liquid hydrocarbons, thus forming "immature-low mature oil". The "soluble organic matter" in the saline lacustrine source rocks in the western Qaidam Basin is obviously higher than that in the freshwater lacustrine source rocks, which is an important material source of a group of "immature and low-mature oilfields" found in this area. Through simulation experiments, it is proved that organic matter also has high oil generation potential in the mature evolution stage, which accords with the classical oil and gas generation model. Therefore, the oil and gas formed by mature source rock is the main exploration object for deep layer. In this area, the oil and gas formed in the Paleogene deep layer and high quality source rocks have two types of reservoir forming models: (1) reservoir formation outside the source, that is, migration of oil and gas to shallow structural traps through oil source fault, and (2) accumulation of oil and gas in source. That is, near source accumulation in lithologic traps near deep source rocks. At present, the exploration of these two types of oil and gas reservoirs has made a great breakthrough, and 200 million tonnage reserve blocks have been found, which proves that the exploration potential of oil and gas reservoirs formed by deep high quality source rocks is great.
【作者单位】：中国石油勘探开发研究院;中国石油青海油田公司勘探开发研究院;
【基金】：中国石油天然气股份有限公司重大科技专项(2016E-0101)资助
【分类号】：P618.13

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