神狐隆起珠江组一段下钙质层分布特点及主控因素

Distribution and controlling factors of calcareous layer on the lower section of the first member of Zhujiang formation in Shenhu uplift

为明确神狐隆起新近系珠江组一段下储集层钙质干层分布规律及控制因素，结合沉积矿物学、岩石学、测井学等，从沉积相带、古环境、钙质层与泥岩成岩演化及油气充注的关系分析钙质层成因及分布控制因素．结果表明：钙质干层具有低伽马、高电阻、高密度、低声波时差特点，不同沉积相带钙质干层厚度、层数、频率不同，三角洲前缘、三角洲前缘与浅海过渡区、浅海相钙质层依次呈现减薄、层数及频率变低；古地貌构造位置越高，地层含砂率越高，形成钙质层厚度越厚；碳、氧同位素w（δ^13c）为-3．32‰、w（δ^18O）为-4．69‰，形成的古地温约为40℃，为早中成岩阶段的成岩碳酸盐胶结，钙质干层在砂岩中部相对砂泥岩界面受到泥岩成岩演化排出的流体溶蚀较小，含量较高；原油充注只有使储层含油饱和度增加到一定值（40%）以后，才对地层水流动抑制明显，控制晚期碳酸盐矿物的沉淀；本区含油饱和度在0～40％为弱的正相关性，铁白云石与总的碳酸盐胶结物含量随含油饱和度增加略有升高，含油饱和度在40％～80％为负相关性。碳酸盐胶结物含量随含油饱和度增加而降低．

In view of the fact that there few researches on calcareous dry layer distribution and controlling factors on the lower section of the first member of neogene Zhujiang formation in Shenhu uplift,we focus on the sedimentary facies,ancient environment and the relationships between calcareous layer and diagenetic evolution,also and hydrocarbon filling.Combined with sedimentary mineralogy,petrology, and well logging,the calcareous dry layer is identified as dense calcareous sandstone with low gamma, high resistance,high density and low acoustic slowness features.The calcareous dry layer becomes thinner and the less from the delta front to shallow marine facies,also the thicker as the high of structural position in the paleoand form and sand rates.The late calcareous layer was inferred from the paleogeotemperature at 40℃ from the isotopes ofδ13C is-3.32‰、δ18 O is-4.69‰,that is the thicker in the middle of sandstone than the neighbor interface between sandstone and mudstone.When the oil saturation at least 40% in this area,it is a negative correlation between oil saturation and the content of carbonate cements.