查干改造型凹陷下白垩统储层及油气分布特征

查干凹陷下白垩统主要发育碎屑岩和火山岩两种储层,以碎屑岩储层为主。碎屑岩储层具有成分与结构成熟度均低、高岩屑与高填隙物含量、多填隙物组分与多胶结类型的总体地质特征。碳酸盐胶结物的“选择性”溶蚀与火山岩层对其下砂岩压实作用的抑制共同作用使部分砂岩段在总体为低孔低渗碎屑岩储层中形成较发育的次生溶蚀孔隙并成为有效储层;火山岩储层主要为溢流相的玄武岩,未被完全充填的气孔、岩石次生蚀变及构造动力产生的裂缝,形成缝洞型火山岩储层。已发现的构造岩性复合低产油气藏的油层分布受有利相带砂体展布及碳酸盐胶结物晚成岩作用次生孔隙发育段的控制,同时良好的油质是物性较差储层能够储集油气的重要原因。

CHARACTERS OF LOWER CRETACEOUS RESERVOIRS AND OIL-GAS DISTRIBUTION IN CHAGAN REFORMED DEPRESSION

Lower Cretaceous in Chagan Depression developed mainly volcanic and clasticrock reservoirs.The clasticrock reservoirs are characterized by low maturities of composition and texture,high contents of rock debris and filling materials,multi-compositon of filling materials and multi-type cemention.The selective soultion of carbonate cement and compacting of volcanic rocks resulted in the development of secondary pores,thus forming available reservoirs in some sections of low porous and low permeable clastic rocks.Volcanic rock reservoirs are mainly formed by overflow basalt,incompletely filled pores,fractures and holes in it and they are favourable reservoir spaces.The distribution of oil layers in the reservoirs is controlled by the sandbody distribution of favourable facies zones and the sections where secondary pore developed.At the same time,high quality oil is an important reason for oil accumulation in reservoirs with poor reservoir physical properties.