岩溶型碳酸盐岩储层中缝洞复合体及其油气地质意义

大中型溶洞和溶蚀裂缝是塔河油田岩溶型碳酸盐岩储层的主要储集空间,但是沿碳酸盐岩裂缝还发育一系列溶蚀孔洞,形成了良好的油气渗流通道和储集空间,本文中称其为缝洞复合体。根据露头、岩心和测井等资料,对碳酸盐岩缝洞复合体的分布与成因进行分析。结果表明,它们在岩溶型碳酸盐岩中广泛分布,且成因类型不同:在表层岩溶带沿着节理或裂缝发育,在渗流岩溶带沿着构造裂缝发育,在径流岩溶带沿着溶洞周围环状和放射状裂缝发育,在断层周围沿着诱导裂缝发育;节理和裂缝是岩溶水流的通道,在节理或裂缝交叉处、以及穿越岩溶带的可溶性较高的岩层处形成溶蚀孔洞,以致缝洞复合体形成。缝洞复合体在岩溶储层内是连接不同储集空间的桥梁,也被认为是大中型岩溶缝洞的雏形,对它的识别和评价有助于岩溶型储层的深入认识。

Identification of fracture-vug complex from karsted carbonates and its significance in petroleum geology

Medium to large scale fractures and caves are important reservoir spaces in karsted oilfields, which has been proven by petroleum exploration and production in Tahe Oilfield. However, a great number of small vugs or caves distributed along fractures have been found in outcrops of the Ordovician carbonates and the cores from Tahe Oilfield. These small caves are connected by fractures to form very good hydrocarbon storages and seepage channels, which are referred to as fracture-vug complex. By investigations on outcrops, drilling-cores and well-loggings, our study shows that the fracture-vug complexes are distributed widely in karsted carbonates including surface karst zone, vadose karst zone and runoff karst zone, as well as among the fault induced fractures. Four genetic types of fracture-vug complexes can be recognized. Formation of the fracture-vug complexes are recognized that carbonate fractures or joints were enlarged by atmospheric water leaching, and caves were formed at cross of fractures or joints and at easy corroding lithologies so that resulted in small caves distributing along fractures and along easy corroding beddings. Identification of fracture-vug complex helps to predict and evaluate reservoir spaces in karsted carbonate rocks.