地洼区海相碳酸盐岩的生油气条件以湘中地区上古生界碳酸盐岩为例

湘中地区在印支运动以前是一个地台的一部分,中新生代强烈活化而成为地洼区。海相碳酸盐岩组成本区上古生界的主体,其有机碳丰度数据符合伽马分布,平均值较低。正常地温场和埋藏时间在印支运动以前是控制有机质演化进程的主导因素,但从印支运动以来,构造变动和岩浆活动对这一进程的影响十分明显。因为上古生界有机质的演化水平很高,地质工作的重点应该摆在气藏的普查勘探方面。近三年来,由于油气资源定量预测工作的需要,我们以中泥盆统棋梓桥组至下石炭统石磴子组的碳酸盐岩为重点,对湘中地区的上古生界(图1)进行了野外调查和室内研究。本文试图对控制本区上古生界碳酸盐岩油气生成过程的内因和外因,进行初步分析。

OCCURRENCE OF HYDROCARBONS IN THE PALEOZOIC CARBONATE ROCKS OF MARINE ORIGIN IN THE XIANGZHONG DEPRESSION

As a part of a platform before the Indo-Chinese Movement, the Xiangzhong region in the central part of Hunan province was reduced to a depressed area following the violent tectonic activities during the Meso-Cenozoic time. Marine carbonate rocks constitute the main body of upper Paleozoic rocks of the region, with the organic carbon content corresponding to gam-ma distribution and a fairly low average value. Before the Indo-Chinese Movement, the normal geothermal field and the time of burial were the principal factors that controlled the transformation of organic matter, but since then, tectonic deformation and magmatism played the dominant role. Due to the high level of evolution of organic materials in late Paleozoic, the authors propose that exploration of gas pools should be main objective of this region.