三塘湖盆地石炭系埋藏溶蚀型凝灰岩致密油成藏特征

Accumulation Characteristics of the Carboniferous Tuff Tight Oil Formed by Burial Dissolution in the Santanghu Basin

凝灰岩致密油藏作为一种特殊的油藏类型,已受到高度关注,但前人对埋藏成岩阶段形成的凝灰岩致密油藏研究很少。通过对三塘湖盆地石炭系哈尔加乌组埋藏溶蚀型凝灰岩致密油成藏条件进行研究,明确了成藏主控因素,并建立了成藏模式。结果表明:哈尔加乌组烃源岩有机质丰度较高,有机质类型较好,并处于成熟演化阶段,油源对比表明埋藏溶蚀型凝灰岩油藏中原油来自哈尔加乌组内部烃源岩;埋藏溶蚀型凝灰岩物性较好,溶蚀孔隙为上部烃源岩在演化过程中产生的大量有机酸对储层的溶蚀作用而形成;埋藏溶蚀型凝灰岩油藏的形成主要受哈尔加乌组成熟烃源岩分布、卡拉岗组大套烃源岩下部物性较好的凝灰岩储层及圈闭条件的控制,形成“下部成熟烃源岩供烃、上部有机酸溶蚀形成物性较好凝灰岩储层及有效圈闭存储”多项成藏条件有利配置下的成藏模式。研究结果将对其他地区埋藏溶蚀型凝灰岩油藏的分布与预测提供借鉴。

As a special type of reservoir,tuff tight reservoir has attracted much attention.However,previous studies on the tuff tight reservoir formed in the burial diagenetic stage are few.The accumulation characteristics of the Carboniferous Haerjiawu Formation tuff tight oil formed by burial dissolution were studied to determine the main controlling factors and to establish the model of reservoir formation.The results show that the source rocks of the Haerjiawu Formation are of high organic matter abundance,good organic matter types,and are in the stage of mature evolution.Oil-source correlation shows that the crude oil of the tuff reservoirs formed by burial dissolution is mainly from source rocks in the Haerjiawu Formation.The dissolution pores are formed by dissolution of a large amount of organic acids produced from the upper source rocks.The formation of tuff reservoir caused by burial dissolution is controlled by the distribution of Haerjiawu Formation source rocks,the physical properties of the tuff reservoir formed by burial dissolution and the trap condition.The hydrocarbon accumulation model of“the mature source rocks in the lower part supply hydrocarbons,the organic acids in the upper part dissolve to form tuff reservoirs with good physical properties and effective traps storage hydrocarbons”is formed under favorable configuration of several accumulation conditions.The research results could be considered a reference regarding the distribution and prediction of tuff tight oil formed by burial dissolution in similar situations in other parts of the world.