南堡凹陷馆陶组火山事件及其油气地质意义
VOLCANIC EVENTS AT THE STAGE OF GUANTAO FORMATION IN NANPU SAG AND ITS PETROLEUM GEOLOGICAL SIGNIFICANCE
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摘要: 南堡凹陷新近系馆陶组地层沉积时期凹陷内火山活动剧烈。通过测井分析及地震解释表明,火山喷发物的岩性以玄武岩为主,形成于新近系早期。平面分布上具有东北薄、西南厚,纵向上具有多期叠置发育的特点。综合分析认为,大量的火山物质改变了凹陷的地貌形态,影响了后继河流相沉积地层的空间分布,在西部地区形成大量的地层圈闭。由于火山事件的热作用,改变了凹陷内的地温场分布,导致烃源岩的异常热演化,对凹陷内油气生成具有重要促进作用。火山岩体的封隔作用可以形成多种类型的圈闭,对后期油气的运移、聚集及分布等方面具有重要的影响。Abstract: The volcanic eruption was intensive and frequent in the Nanpu Sag during the period of Neogene when the Guantao Formation was deposited. Through logging and seismic interpretation, it is revealed that the volcanic rocks were mainly basalt in lithology formed in the early Neogene. The volcanic sequence is thicker in the southwest and thinner in the northeast, and formed by multi-stage eruption. The comprehensive study suggests that the eruption of huge amount of volcanic materials changed the geomorphology of the Sag, that influenced the spatial distribution of the fluvial strata deposited later on. Many stratigraphic traps were formed in the west of the Sag. The volcanic activities also brought changes in the geothermal field in the Sag, which led to the abnormal evolution of source rocks, and greatly accelerated the hydrocarbon generation process within the Sag. Acting as an effective sealing, volcanic bodies could be the cover of many types of traps. The significance of the volcanic rocks should never be underestimated in hydrocarbon migration, accumulation, and distribution.