靖边气田北部下奥陶统马五_4~1段古岩溶储层特征及其控制因素

CHARACTERISTICS AND CONTROL FACTORS OF PALAEOKARST RESERVOIR OF THE MAJIAGOU FORMATION OF LOWER ORDOVICIAN IN NORTHERN JINGBIAN GAS FIELD OF ORDOS BASIN

通过钻井岩心、铸体薄片、扫描电镜、阴极发光观察及岩石孔渗测定等方法对鄂尔多斯盆地靖边气田北部马五41段古岩溶储层研究表明:晶间孔、溶孔(洞)、溶缝及铸模孔是最主要的储集空间类型;其孔隙度最大15.91%,最小0.22%,孔隙度平均值约为3.73%,渗透率最大为79.13×10-3μm2,最小为0.001 3×10-3μm2,平均渗透率为1.24×10-3μm2,储层可分为溶孔、晶间孔-溶缝型、晶间孔型、微孔-溶缝型和微孔型4种;沉积相是储层形成的基础,成岩相决定了最终储集空间的保存情况,而古岩溶地貌从宏观上控制着储集空间的发育程度和储层的保存状况,三者有利区叠合部位是油气勘探的重点区域。

The Characteristics of palaeokarst reservoir of O1m541 of lower Ordovician in northern Jingbian gas field of Ordos Basin are investigated by the analysis of core,cast thin section,SEM,CLM,porosity and permeability test.It is showed that intergranular pore,dissolved pore,dissolved fracture and moldic pore are the main primary pore types with the porosity between 15.91% and 0.22%,average 3.73%,with the permeability ranging from 79.13×10-3 μm2 to 0.001 3×10-3 μm2,average 1.24×10-3 μm2.The pore structures are divided into 4 types： dissolved pore-intergranular pore-dissolved fracture type,intergranular pore type,micropore-intergranular pore-dissolved fracture type,and compact micro-pore type.The development of reservoir is influenced by microfacies,diagenetic facies and karst palaeogeomorphology,with the sedimentary facies of the basis of its development.Diagenetic facies controls final reservoir space and palaeogeomorphology controls the degree of reservoir development and conservation.The composite parts of the three favorable areas are the key target for oil and gas exploration.