三塘湖盆地马朗凹陷石炭系火山岩系油气成藏主控因素及模式

三塘湖盆地马朗凹陷石炭系主要发育两套烃源岩,分别为哈尔加乌组上段和哈尔加乌组下段,油气藏形成的源控作用十分明显。通过烃源岩和原油地球化学的分析以及油源对比,发现不同类型原油的形成与分布严格受控于对应源岩的分布范围。分析表明,马朗凹陷石炭系火山岩系油气成藏的主控因素是优质烃源岩、强充注油源断裂和有利火山岩相带的合理配置。根据烃源岩与储层的配置关系,石炭系油气藏的形成可以概括为两种模式:一种为风化壳型成藏模式,油气聚集在石炭系火山岩顶部受风化淋漓作用改造的优质储层中,其中的油气来自下部烃源岩,运移通道为与烃源岩相沟通的油源断裂;另一种模式为内幕型成藏模式,储层为流体溶蚀改造的储层,其中聚集的油气来自邻近火山喷发间歇期沉积的炭质泥岩。

Main Controlling Factors and Models of Carboniferous Volcanic Hydrocarbon Accumulation in the Malang Sag, Santang Basin

There are two sets of source rocks in Carboniferous in the Malang sag, namely upper Haerjiawu Formation and lower Haerjiawu Formation. And source control effect is obvious on reservoir formation in this area. It is found that the formation and distribution of different types of crude oil are strictly controlled by the distribution of the corresponding source rocks using the geochemical comparative analysis of the source rock and crude oil as well as the oil source correlation. Our analysis indicates that the main controlling factor of hydrocarbon accumulation is the reasonable configurations of high quality source rock, strongly recharging of hydrocarbon into faults connecting source rock and reservoir, and favorable volcanic rock facies belt. There are two models of the carboniferous reservoir formation based on the configuration relations between the source rock and reservoir. One is weathering crust type hydrocarbon accumulation model, in which oil and gas from the below source rock accumulate in the high quality reservoirs of carboniferous volcanic top which is transformed by weathering and leaching, and migration channels are faults connecting source rock and reservoir. The other is inner hydrocarbon accumulation model, in which the reservoir is reconstructed by fluid dissolution and the oil and gas are derived from the nearby carbonaceous mudstone deposited during the volcano eruption break.