碳酸盐岩孔洞型储层分层次储集空间表征--以鄂尔多斯盆地大牛地中奥陶统马家沟组马五_(7)为例

Reservoir space characterization of vuggy carbonate reservoirs with multiple scales:a case study of Ma 5-7 interval,Middle Ordovician Majiagou Formation,Daniudi area,Ordos Basin

碳酸盐岩具有多尺度、多成因的储集空间,储集空间和储集物性的表征是难点。鄂尔多斯盆地大牛地奥陶系马家沟组马五_(7)储层发育毫米—微米—纳米级储集空间,为研究其储集空间和储集物性,分层次、多尺度对该储集空间进行了表征,并结合测井曲线,建立了孔、洞的计算模型。研究表明:①对于发育多尺度储集空间的碳酸盐岩储层,采用岩心拓片提取溶蚀孔洞(>1 mm)、铸体薄片提取晶间孔(>2μm)、氩离子抛光—扫描电镜进行亚微米—纳米孔(<2μm)研究相结合,可以较准确地表征其储集空间;②在多尺度储集空间表征的基础上,对声波孔隙度和中子—密度孔隙度进行约束,可以建立对应的晶间孔孔隙度计算模型和溶蚀孔洞孔隙度计算模型,该模型具有更高的计算精度。

The reservoir space of carbonate rocks is of multiple scales and genesis mechanisms,and it is difficult to accurately demonstrate the reservoir space as well as physical properties.Millimeter-,micro-and nano-scale reservoir spaces were all developed in the Ma 5-7 interval(the 7 th sub-member of the 5 th member)of the Ordovician Majiagou Formation in Daniudi area,Ordos Basin.In order to study the storage space and physical properties,the storage space was characterized in layers at multiple scales,and combined with the approach of logging curves,a calculation model was established for the description of pores and caves.Several conclusions were made as follow.(1)For carbonate rock reservoirs with storage space of multiple scales,we can accurately describe their storage space by the means of core rubbing for dissolved pores(>1 mm),case thin section for intercrystalline pores(>2μm),and argon ion polishing-scanning electron microscope for submicron and nano pores(<2μm).(2)On the basis of multi-scale reservoir space characterization,the acoustic porosity and neutron-density porosity can be constrained,and the corresponding intercrystalline pore porosity calculation model and dissolved pore porosity calculation model can be established,which have higher calculation accuracy.