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通过对天然气基本地球化学特征、成因与来源的系统分析,结合油气藏特征与油气地质条件,对兴隆台油气田的天然气成藏机理和成藏模式进行了系统的研究。天然气可以分为A和B2大类。A类天然气总体埋藏深度较小,甲烷含量高,甲烷、乙烷碳同位素组成偏轻,主要来自沙一段、沙二段和沙三段上部烃源岩生成的生物—热催化过渡带气;B类天然气埋藏深度变化大,甲烷含量变化范围大,甲烷、乙烷碳同位素组成偏重,丙烷碳同位素组成变化范围大,部分碳同位素组成明显偏重的天然气分布在较浅部位,主要与细菌的氧化降解作用有关。B类天然气主要与埋藏较深、演化程度较高的沙三段烃源岩有关。气藏和气顶中天然气主要来自原油溶解气的出溶。因大断裂的存在,浅层的构造高部位聚集了较多的B类天然气,其两侧主要聚集A类天然气。在其他中深部有油藏分布的地区,其浅层部位应该也存在原油溶解气出溶的天然气聚集,是浅层气勘探的重要领域。
By systematically analyzing the basic geochemical characteristics, origin and origin of natural gas, combining with the characteristics of oil and gas reservoirs and the geologic conditions of oil and gas, the natural gas accumulation mechanism and reservoir forming model in Xinglongtai oil and gas field are systematically studied. Natural gas can be divided into A and B2 categories. Class A natural gas has a lower total burial depth, a higher methane content, and a lighter carbon isotope composition of methane and ethane, mainly due to the bio-thermal catalytic transitional gas generated from upper source rocks of Sha-1, Sha-2 and Sha-3 Member. Class B Natural gas burial depth varies greatly, methane content changes a wide range, methane, ethane carbon isotope composition heavier, propane carbon isotope composition of a wide range of changes, part of the carbon isotope composition significantly more heavily distributed natural gas distribution in shallow parts, mainly with the bacterial oxidative degradation related. Type B natural gas is mainly related to the deeper source rocks of the 3rd member of the Shahejie Formation, which have a higher degree of evolution. Natural gas in gas reservoirs and gas cap mainly comes from the dissolution of crude dissolved gas. Due to the existence of large faults, more B-type natural gas is accumulated in the upper part of the shallow structure, and A-type natural gas is mainly gathered on both sides. In other areas where there are deep oil reservoirs, there should also be natural gas dissolved in the crude oil dissolved gas in shallow areas, which is an important area for shallow gas exploration.