摘要
塔中隆起寒武系碳酸盐岩储层油气资源丰富,然而由于复杂的构造地质背景,油气来源和天然气类型还存在较大争议。通过详细分析ZS1井、ZS1C井和ZS5井寒武系不同层段中凝析油和天然气的组成、碳同位素等特征,并结合寒武系-下奥陶统与中、上奥陶统烃源岩地球化学特征,对其油气来源和天然气成因类型进行了判别。研究结果表明,该区天然气为典型的腐泥型干酪根裂解气,其中寒武系肖尔布拉克组天然气干燥系数大于0.98,N2含量介于2.5%~4.0%,为过成熟干气,且凝析油族组分与和饱和烃单体烃碳同位素偏重,nC_9—n C20碳同位素介于-28.8‰^-26.3‰,表明油气来源为寒武系-下奥陶统烃源岩。而寒武系阿瓦塔格组和吾松格尔组天然气干燥系数介于0.63~0.78,N2含量介于0.2%~0.8%,为低成熟湿气,且凝析油族组分和饱和烃单体烃碳同位素相对较轻,nC_9—nC_(23)碳同位素介于-37.25‰^-32.56‰,表明油气来源为中、上奥陶统烃源岩。
The Cambrian carbonate reservoirs of Tazhong uplift is rich in oil and gas. However, there are different opinions on the origin and genetic types of oil and gas in this area due to the complex tectonic setting. In this paper, we studied the origin and genetic types of oil and gas through a detailed analysis of the composition and carbon isotope data of condensate oil and gas in different intervals of the Cambrian in ZS1, ZS1C and ZS5 wells and the geochemical characteristics of the Cambrian-Lower Ordovician and Middle-Upper Ordovician source rocks. The results indicate that the Cambrian gas in the Tazhong uplift is typical cracking gas of sapropelic kerogen. Gas in the Xiaoerbulake Formation is typical over-mature dry gas with a drying coefficient of higher than 0.98 and N2 content of 2.5 % - 4.0 %. The carbon isotopes of group composition and individual n-alkanes of condensate in the Xiaoerbulake Formation are relatively heavy. The carbon isotope of C9 -C20 n-alkane are -28.8‰- -26.3‰. These geochemistry characteristics indicate that the condensate oil and gas in the Xiaoerbulake Formation originated from the Cambrian-Lower Ordovician source rocks. While the natural gas in the Awatage and Wusonggeer Formations is low-mature wet gas with a drying coefficient of 0.63 - 0. 78 and N2 content of 0. 2 % - 0. 8 %. The carbon isotope of group composition and individual n-alkanes of condensate in the Awatage and Wu- songgeer Formations are relatively light. The carbon isotopes of C9 - C23 n-alkane are - 37.25‰ - 32.56‰. These geochemistry characteristies indicate that the condensate oil and gas in the Awatage and Wusonggeer Formations originated from the Middle-Upper Ordovician source rocks.
出处
《石油与天然气地质》
EI
CAS
CSCD
北大核心
2017年第2期302-310,共9页
Oil & Gas Geology
基金
国家科技重大专项(2011ZX05007)
