乍得BS油藏沉积微相特征及对油气分布的控制作用

结合区域沉积背景,应用BS1-1取心井资料进行泥岩颜色、岩石组合、沉积结构、构造、粒度分布、沉积韵律等相标志分析,对BS油藏沉积微相特征进行了深入研究,分析了沉积微相对油气分布的控制作用。BS油藏PI油层组为扇三角洲前缘远端沉积,水下分流河道分布范围有限,仅在断层附近发育,河道前端受湖浪作用改造明显,前缘席状砂发育,偶见远砂坝,河道间微相不发育。沉积微相类型控制了储层类型及其展布方式和储集性能,沉积微相展布对油气分布具有明显的控制作用,水下分流河道生储盖组合良好,为油气有利富集相带。

Sedimentary microfacies and their controls on the hydrocarbon distribution in the BS oil reservoirs in the Bongor Basin, southwestern Chad

The BS oil reservoirs are hosted to the GB oil field, Bongor Basin, southwestern Chad. Combined with regional sedimentary background and core data for the BS1-1 well, the present paper focuses on the mudstone colour, rock association, sedimentary texture and structure, grain size distribution, sedimentary rhythms, sedimentary microfacies and their controls on the hydrocarbon distribution in the BS oil reservoirs. The PI pay set in the BS oil reservoirs is interpreted as the fan delta front distal deposits. The subaqueous distributary channel deposits occur only around the faults. The other deposits include the well developed frontal sheet sands, minor amount of distal bar deposits, and less developed interdistributary channel deposits. The sedimentary microfacies types have exercised a major control on the type, distribution and quality of the reservoirs and hydrocarbon distribution. The subaqueous distributary channel microfacies is delineated to be the favourable facies zone for the hydrocarbon accumulation owing to the excellent source-reservoir-seal associations in the BS oil reservoirs.