西南非海岸盆地过渡期海相烃源岩有机相特征及其平面预测

海相烃源岩是全球油气的主要来源，在全球范围内广泛分布。目前关于海相烃源岩的研究主要偏重其生烃理论，缺乏紧密结合油气勘探生产的海相烃源岩识别、预测和评价方法研究。为了建立一套切实可行的、以有机相分析为手段的海相烃源岩评价关键技术组合，针对西南非海岸盆地过渡期主力海相烃源岩，综合利用沉积相、古生态相、有机地化相以及地震相对其进行“四相合一”综合有机相分析，从而对该套烃源岩进行系统分析。研究认为，该套烃源岩为海陆混源型烃源岩，且从陆向海可依次划分4个有机相带：滨海陆源型有机相A、内浅海混源型有机相B、外浅海混源型有机相C和上坡折带内源型有机相D。总体来说，研究区平面上呈现“内侧倾气、外侧倾油”的特点。

ORGANIC FACIES AND SPATIAL DISTRIBUTION OF TRANSITIONAL MARINE SOURCE ROCKS IN WESTERN SOUTH AFRICAN COASTAL BASIN

Marine source rocks contribute a lot to oil and gas generation in the world and are widely distributed on the earth. So far, the research on marine source rocks mainly focuses on its hydrocarbon generation mechanism, but lacks the research on its identification, prediction and evaluation technology in particular in the exploration and production stage of an oil field. In order to establish a set of feasible technical methods for marine source rock evaluation by organic facies analysis, this paper selected the Western South African Coastal Basin as a case. Comprehensive organic facies analysis of the main marine source rocks has been carried out by integrated analysis of sedimentary facies, paleoecologicalfacies, organic geochemical facies and seismic facies, or so called "four facies integrattion", and then the main marine source rock in this basin is systematically evaluated. The marine source rock consists of mixed terrestrial and marine organic matters. It can be further subdivided into four organic facies zones from the land to the sea, i.e.the coastal terrestrial organic facies A, the inner shallow sea mixed organic facies B, the outer shallow sea mixed organic facies C, and the upper slope autochthonous organic facies D. In a plane view, the distribution of hydrocarbon is characterized by a pattern of "inner part gas-prone and outer part oil-prone" in the basin.