湖南湘中坳陷泥盆—石炭系的生油地球化学特征及找油气方向

THE GEOCHEMICAL FEATURES OF OIL GENERATION IN DEVONIAN-CARBONIFEROUS OF XIANG-ZHONG DEPRESSION, HUNAN, AND THE DIRECTION IN OIL AND GAS EXPLORATION

陈正辅

Chen Zhengfu

地质部石油地质中心实验室

Central Laboratory of Petroleum Geology, Ministry of Geology

湘中坳陷是雪峰古陆东侧石油普查的重点地区之一。在大地构造上属南华准地台的一部分。加里东运动回返后,在几乎整个晚古生代,是一个相对稳定沉降的坳陷。中泥盆统棋梓桥组(D2q)、上泥盆统佘田桥组(D3s)及锡矿山组(D3x)、下石炭统岩关阶(C1y)及大塘阶(C1d),以碳酸盐岩为主的海相沉积厚达3000—5000米。见油气苗及井下气显示多处,反映了地史发展过程中有过油气的生成及一定的成油地质条件。印支运动使上古生界及中下三迭统产生褶皱,印支、燕山构造运动和岩浆活动,对油气聚集、再分配及加剧油气演化,都有明显的影响。

Xiang-Zhong was an area of relatively stable and secular depression in Late paleozoic. It is thousands of metre thick with marine facies carbonate rocks as the bulk of the sedimentation which was possessed of certain oil forming geological conditions. In this paper, the abundance, type and evolution of organic matter are studied through the analysis of organic carbon,gaseous hydrocarbons, GR/G chloroform extracts, group compositon of the extracts, GC of saturated hydrocarbons, infrared and ultraviolet spectra of aromatic hydrocarbons; and the vitrinite reflectance, elemental composition, paramagnetic spectra,scanning electron microscopic observation thermal-thermogravimetric analysis of kerogen. Meanwhile, as well as computer simulation using the relationship of time versus temperature,the history of the formation of oil-gas is inferred.The basic suggestions are: The Middle Devonian Qiziqiao Formation and Lower Carboniferous of Xiang-Zhong depression; and the Upper Devonian Shetianqiao Formation of Xin Hua depression are the major horizons of oil generation. The evolution of oil-gas has reached a stage of overmature and the prospecting has to be focussed on natural gas. The Middle-Late Carboniferous and Permain were the main stage of oil formation. Around the episoda of the Indosinian movement there came the prosperous stage of the formation of natural gas. Therefore, the structure of early Indosinian and pre-Indosinian, and the Devonian-Carboniferous reef-bank facies provided favourable condition for forming pools. So, it should be a prior target for oil prospecting.

https://doi.org/10.11781/sysydz198104245