北部湾盆地福山凹陷天然气成因与来源

GENESIS AND SOURCE OF NATURAL GAS IN THE FUSHAN DEPRESSION,BEIBUWAN BASIN

利用(1δ3C2-1δ3C3)-C2/C3(mol/mol)关系、“天然气曲线”和天然气C7-重烃三角图对海南福山凹陷天然气的成因和来源进行了研究,结果表明福山凹陷天然气主要为干酪根生烃高峰到湿气阶段的产物;天然气和该区原油同源,都来自流沙港组Ⅱ-Ⅲ型有机质;天然气没有遭受明显的次生变化,受运移效应的影响也较弱;花场地区天然气主要来自白莲次凹,而Hx4井和H 3-4井的天然气可能有来自皇桐次凹的贡献。认为(1δ3C2-1δ3C3)-C2/C3(mol/mol)关系图和“天然气曲线”是研究天然气成因与来源的有效方法。

By using （δ^13C2-δ^13C3） versus C2/C3 （mol/mol） plot and ＂natural gas plot＂, and the ternary diagram of C7-hydrocarbon of natural gas, this paper studies the genesis and source of the natural gas discovered in the Fushan depression, Hainan. It shows that the gaseous hydrocarbons in the Fushan depression are mainly generated by kerogen from the hydrocarbon generating peak stage to the wet gas stage. The gases and associated oils are derived from the same source kitchen of Liushagang formation, which is dominated by type Ⅱ - Ⅲ kerogens. The natural gases had not undergone significant secondary alteration and migration fractionation. The natural gas in the Huachang area is mainly derived from the Bailian sub-depression （sag）. The gas in HX4 and H3-4 wells, however, may be partly from the Huangtong sub-depression. The （δ^13C2-δ^13C3） versus C2/C3 （mol/mol） plot and ＂natural gas plot＂ are successfully applied to the study of genesis and source of natural gas in the Fushan depression.