苏丹红海中部地区沉积特征及成藏地质条件分析

Analysis of Sedimentary Feature and Petroleum Geological Conditions in the Middle Block of Sudanese Red Sea

评价区位于红海裂谷盆地中部,具有海水深、盐层厚度大等复杂地质条件,导致油气勘探及认识程度较低。区域地质、钻井及地震等资料综合分析表明,该区前裂谷期沉积地层相对不发育,沉积物主要为中、上新统同裂谷期和后裂谷期沉积的碎屑岩、蒸发岩和碳酸盐岩,纵向上形成盐上及盐下两套含油气系统。盐上含油气系统分布于Zeit组三角洲沉积体系中,有利勘探区受盐丘形态控制,范围较为局限。盐下含油气系统以中新统Rudeis组页岩为生油岩,储层主要为Belayim组砂岩或碳酸盐岩,盖层为Dungnab组厚层盐岩和石膏,储、盖配置条件有利,是该区最有利的勘探目的层系。不过由于资料少,地震成像质量较差,盐下源岩的分布范围及生烃规模、有利灰岩储层分布范围、以及盐下圈闭的真实构造形态等都需要进一步落实。

The studied Area was located in the middle of Red Sea rift basin and it had complex geologic conditions of deep water and thick salt distribution,by which low level of oil exploration and low understanding were induced.Based on the study of regional geologic,seismic and well drilling data,the research results indicate that the pre-rift sedimentary formation is not developed,the sediments are Miocene-Pliocene clastic carbonate and evaporate rocks which deposited in the Pre-Cambrian igneous and metamorphic rocks basement during Red Sea rifting and drafting periods and formed two sets of petroleum systems vertically.Above the salt,the petroleum system was developed in delta sedimentary system of Zeit Formation.The extent of Zeit Formation was mainly controlled by salt dome distribution and favorable exploration area was limited.Sub-salt petroleum system has more favorable oil-gas generation and accumulation conditions.The reservoir was mainly of sandstone and carbonate from Rudeis Formation.The cap-rock is thick salt and gypsum in Dungnab Formation,where favorable reservoir-sealing assemblage is formed,it is the most favorable target zone of the area.Because of lack of exploration data and poor seismic image quality,sub-salt source rock distribution scale and hydrocarbon generation extent,favorable grey rock reservoir distribution scale as well as the actual structural shape of the sub-salt traps in Belayim Formation,carbonate reservoir distribution extent and the real structural geometry of sub-salt traps are needed to be identified for further evaluation.