鲁西地区奥陶系碳酸盐岩储集特征及主控因素

RESERVOIR CHARACTERS AND KEY CONTROLLING FACTORS OF THE ORDOVICIAN CARBONATE ROCKS IN WESTERN SHANDONG

应用薄片、铸体和阴极发光等室内分析技术,对鲁西隆起奥陶系碳酸盐岩及济阳坳陷潜山奥陶系钻井岩心样品进行了成岩作用及储集特征详细研究。奥陶系碳酸盐岩原生孔隙消失殆尽,次生成因的孔、洞和缝是主要储集空间。其中裂缝储集层在各层段均有发育,但白云岩段优于其它岩性段;构造缝主要分布在构造轴部和断裂带附近,溶蚀缝在不整合面附近较为发育。孔洞型储集层主要发育在白云岩层段,以晶间孔、晶间溶孔和晶内溶孔为主要储集空间;有少量有效孔隙分布在灰岩段,以铸模孔、粒内溶孔和粒内孔为主。马家沟组八陡段顶部发育溶蚀角砾岩、纹层状结晶灰岩,砾间缝、晶间缝和溶洞为主要储集空间。白云岩段是奥陶系碳酸盐岩主要储集层段,构造因素、岩性和成岩作用(尤其是胶结作用和溶蚀作用)是造成奥陶系碳酸盐岩储集层剖面分布差异性的主要控制因素。

The reservoir characteristics of the Ordovician carbonate rocks from cores in the Jiyang Depression and outcrops from the West Shandong Rise were studied systematically by means of techniques of casting,slicing and cathodoluminescencing, etc. The results showed that the primary porosity was almost lost, the secondary porosities and fractures were preponderant now. The fractures developed in all formations, but they were more prominently in dolomite formation than that in limestone. The tectonic fractures were most preponderant among all fracture types and they always occurred in the fold axis or nearby the fault belts, while the dissolution fractures were often discovered beneath the unconformities. The intracrystal porosity, intercrystal dissolution porosity and rugs were dominant reservoir space in the dolomite rocks. The reservoirs developed mainly in the sections of dolomite rocks of Majiagou Formation and a few in limestone, with types of reservoir space being mainly moldic, interparticle and dissolution po- rosities. The dissolution breccia and bedded crystallization limestone occurred in the top of Badou Member of Majiagou Formation, with major types of porosity being intragravel,intracrystal and rugs. It might be very important for exploring reservoir in dolomite rocks. Tectonics, lithology and diagenesis should be the key factors controlling the vertical distribution of reservoir of the Ordovician carbonate rocks in the Jiyang Depression and the West Shandong Rise.