鄂尔多斯盆地北部巴汗淖地区马五6段为风化壳型碳酸盐岩地层,岩性以鲕粒灰岩、晶粒白云岩为主,次生孔隙发育,是重要的油气储集层。采用Finnigan MAT252气体同位素质谱仪分别对该段碳酸盐岩进行C、O同位素测试,详细分析了巴汗淖地区马五6段碳酸盐岩成岩环境及孔隙演化条件。样品分析结果表明:埋藏高温成岩环境使得δ18O值与奥陶纪海水的δ18O值相比明显偏负,且白云岩δ18O值与灰岩δ18O值相比偏负,主要是埋藏白云石化作用的结果;δ13C值与奥陶纪海水δ13C值相当,极个别数值偏负,说明研究区马五6段在成岩作用过程中受有机碳影响较小,表明成岩作用发生在浅-中埋藏条件下。研究区孔隙度、渗透率的相关关系明显,主要是大气淡水成岩作用的改造,优化了孔隙及渗流通道,提高了储层的物性。 In the northern section of the Ordos Basin, the fifth member of Mahan-5 in the Bashan area is a weathered crust type carbonate rock. The lithology is dominated by oolitic limestone and crystalline dolomite. Secondary porosity is an important oil and gas reservoir. The Carbon isotopes and Carbon isotopes of the carbonate rocks were measured by Finnigan MAT252 gas isotope mass spectrometer. The carbonate rocks diagenetic environment and pore evolution conditions in the fifth and fifth member of the Brahmin region were analyzed in detail. The results of sample analysis show that the δ18O value is significantly negatively correlated with the δ18O value of Ordovician seawater and the δ18O value of dolomite is negatively correlated with the δ18O value of limestone, mainly due to burial dolomitization. The δ13C value is comparable to the δ13C value of Ordovician seawater and the extreme values ​​of the individual values ​​are negative, indicating that the M5 member of the study area is less affected by organic carbon during diagenesis, indicating that the diagenesis occurred under shallow-medium burial conditions. The correlation between porosity and permeability in the study area is obvious, mainly due to the reconstruction of atmospheric freshwater diagenesis, optimizing the pores and seepage channels, and improving the reservoir physical properties.