陕甘宁盆地奥陶系源岩及碳酸盐岩生烃的有关问题讨论  

Carbonate Source-Rocks of the Ordovician in Shan-Gan-Ning Basin and Discussion on the Hydrocarbon Generation of Carbonates

作　　者：陈安定[1] 

机构地区：[1]江苏石油勘探局地质科学研究院

出　　处：《沉积学报》1996年第A00期90-99,共10页Acta Sedimentologica Sinica

基　　金：八五国家重点攻关项目

摘　　要：陕甘宁盆地中部气田是目前中国陆上最大的气田。气源研究确认，该气田奥陶系天然气主要来源于奥陶系的一套低丰度碳酸盐。本文在介绍这套源岩地球化学背景基础上，探讨了用于碳酸盐源岩工业性评价用的有机碳丰度指标．同时，通过隐藻碳酸盐、钙藻碳酸盐等五种相环境源岩的对比分析，提出氧化—还原条件等是影响早古生代碳酸盐岩石有机质丰度、性质、产烃能力的最直接的因素。The carbonate source-rocks of the Ordovician are relatively poor in organic matter (Corg 0.24% ). According to the result on gas/source-rock correlation, it could be suggested that the carbonates with mean over 0. 2% organic carbon content at stage of over maturity should be able to form largescale oil-gas accumulation. Furthermore, this paper proposed in the carbonates with mean over 0. 15% organic carbon content the expulsion, migration and accumulation of hydrocarbons can happen based on fluorescence thin-section observation.The paper had listed the carbonate source-rocks from five kinds of sedimentary environments which have the different content of organic matter and original potential of hydrocarbon generation, and put stress on the comparison of calcareous alga-bearing carbonates with cryptalgal-bearing carbonates as well. The Cryptalgal-bearing carbonates are main sourcerocks of natural gases in the central gas-field. Finally this paper suggested following views:(1) The carbonates, rich in non-skeleton algae or other organic-shell living bodies, are good source rocks.(2) The content of organic matter in carbonates mainly depends on the oxidationreduction condition of deposition, shallow burial and the content of mudstone.(3) The oxidation-reduction condition also influences original properties of kerogen. In reduction system there is a high residual ratio to bio-remains, and original lipid properties of kerogen could be protected because oxidization not only reduces the content of organic matter,but also damages lipid properties of primary kerogen and decrease the potential of the kerogens. Although almost all kerogen in the Early Palaeozoic Period originated from precursers such as algae, plankton and palaeo-bacteria etc., they may have different potential. Based on analysis and calculation, generally, the carbonate with lower organic carbon content was merely medium potential (IH0=250±) of hydrocarbons generation, however, it might have high efficiency of expulsion of hydrocarbons.

关 键 词：碳酸盐岩 源岩 生烃 奥陶纪 

分 类 号：P588.245[天文地球—岩石学]