苏丹M盆地下白垩统泥岩标志层的发现及意义

DISCOVERY OF LOWER CRETACEOUS SHALE MARKER IN M BASIN OF SUDAN AND ITS SIGNIFICANCE

Muglad盆地位于苏丹中南部Darfur省境内,是中国石油天然气集团公司海外合作油气勘探开发的区块之一。为搞清该区重要的稀油与天然气产层——Muglad盆地六区Fula坳陷下白垩统Abu Gabra组上段的生储盖组合以及油气富集规律,通过对地震、钻井、测井等资料的综合分析,并结合地层划分对比研究结果,发现在Abu Gabra组上段顶部地层中具有3段泥岩对比标志层且该标志层在Fula坳陷区域内稳定分布。进而认识到:Abu Gabra组上段三角洲前缘砂岩储集体与泥岩标志层构成了有利的自储自盖组合(油气来自下部地层);3段泥岩既是Abu Gabra组重要的区域地层对比标志,又是油气藏的重要盖层;若缺失顶部第一泥岩标志层,则就会因缺失盖层而使得油气藏不复存在。因此,泥岩标志层的有效识别对该区油气藏组合的清晰认识具有重要意义。

The Muglad Basin,located in Darfur province in central south of Sudan,is one of CNPC's oversea petroleum exploration and development areas.In order to study the source-reservoircaprock assemblages and the patterns of hydrocarbon accumulation in the upper member of the Lower Cretaceous Abu Gabra Formation in Fula depression of the Muglad Basin which is an important light oil and gas producing layer in the study area,a comprehensive analysis of seismic,drilling and logging data,in combination with stratigraphic division and correlation,shows that 3 shale correlation markers with stable distribution occur in the top interval of the upper member of Abu Gabra Formation in the study area.The delta front sandstone reservoir and the shale markers in the upper member of Abu Gabra Formation constitute favorable reservoir-seal combinations,in which the hydrocarbons are sourced from the lower formations.The 3 shale layers are both important geologic correlation markers of the Abu Gabra Formation and important seals of the oil and gas pools in the study area.If the top shale marker had been absent,the oil and gas pools would not have been formed for lack of seals.Therefore,identification of these shale markers is of great significance to the understanding of the oil and gas reservoir combinations in the study area.