干气中浓缩轻烃分析及应用——以川东北、川东区天然气气/源对比研究为例

ANALYSIS AND CONCENTRATION OF LIGHT HYDROCARBONS IN DRY NATURAL GAS AND ITS APPLICATION——A CASE STUDY ON GAS-SOURCE ROCKS CORRELATIONS IN THE EAST AND NORTHEAST OF SICHUAN BASIN

该文简要介绍了干气中轻烃富集、分析方法,并对四川盆地川东区、川东北区共计9口钻井天然气进行了轻烃富集与分析,获得了9个气样浓缩轻烃的气相色谱图。在此基础上,通过浓缩轻烃结构组成(系列)对比、C7烃(nC7、MCC6、DMCC5)组成、C6+7脂族烃组成、庚烷值(H)、异庚烷值(Ⅰ)、Mango参数(K1、K2)、甲基环已烷指数等一系列反映轻烃的特征和参数进行了气/气对比,探讨了天然气的成因类型、热演化程度,并与研究区的烃源岩进行了对比。对比结果表明,川东北区的气源相对单一,主力气源层系可能为二叠系;川东建南气田石炭系产层天然气为源自下古生界原油的二次裂解水溶气,二叠系、三叠系产层天然气为源自二叠系过成熟裂解气与源自下古生界原油二次裂解水溶气的混合气。

The way of analysis and concentration of light hydrocarbons in dry natural gas is briefly introduced in this article. After the analysis and concentration of nine natural gas samples from the East and the Northeast of Sichuan basin, their chromatographic diagrams are attained. Based on the above experimental results, some properties and parameters of light hydrocarbons in the dry natural gas are studied, which include correlations of light hydrocarbons chemical compositions, relative contents of nC_(7)?MCC_(6) and DMCC_(5) in C_(7)-light hydrocarbons, lipoid compositions of C_(6+7)-light hydrocarbons, value of heptane(H) and isoheptane(I), Mango parameters(K_(1)?K_(2))and so on. The genetic types and maturity of the natural gas are discussed in term of these characteristics and parameters. Gas-gas and gas-source rock correlations are also studied. It is supposed that the natural gas of the northeast of Sichuan Basin mainly origin from the Permian source rocks. On the contrary, at Jiannan gas field in the east of Sichuan Basin, the origin of gas is complex. The natural gas from Carboniferous is the secondary cracking gas dissolved in the groundwater, whose source rocks are Silurian and Cambrian. The natural gas from the Permian and Triassic can be described as the mixture of thermogenic gas from Permian source rocks and gas dissolved in groundwater from secondary cracking of oil derived form Silurian and Cambrian source rocks.