鄂尔多斯盆地靖边气田马家沟组五段白云岩沉积微相测井识别与评价

Well logging identification and evaluation of depositional microfacies in dolostones from the 5th Member of the Ordovician Majiagou Formation in the Jingbian gas field,Ordos basin

通过岩芯和薄片观察,结合常规、成像测井和试气等资料,对鄂尔多斯盆地靖边气田奥陶系马家沟组马五段白云岩沉积特征进行了研究。结果表明马五5-马五10亚段白云岩储层为典型相控型储层,储层类型主要是白云岩晶间孔及晶间溶孔型。其沉积相分为开阔台地和局限台地两类,且开阔台地主要发育滩间海及台内滩亚相,局限台地则发育潮坪及颗粒滩亚相,其中砂屑滩、台内滩、云坪等是优质储层发育的有利沉积微相带。通过对不同微相的常规测井曲线和成像测井图像对比分析,建立起一套适用于马五5-马五10亚段台地相的成像测井沉积微相识别模式,包括块状模式、条带模式、层状模式、线状模式、斑状模式和暗斑-线状组合模式等6种成像测井相模式。通过常规、成像测井组合特征实现了单井纵向上沉积微相的连续识别与划分。结合测井解释结论及生产试气资料,进一步验证了有利沉积微相对储层有效性的控制作用,深化了奥陶系马五段碳酸盐岩沉积相成像特征及有利储层的认识,对马家沟组碳酸盐岩天然气的勘探开发具有指导意义。

Drilled cores,thin sections,well logs,image logs and gas testing results were analyzed to systematically study the sedimentary and image characteristics of carbonate platform from the 5 th Member of the Ordovician Majiagou Formation in the Ordos basin.The results show that there are two sedimentary facies named "open platform"and "restricted platform"in the research area.The open platform can be classified into interbank sea and intra-plateform subfacies.The restricted platform can be classified into tidal flat and grain bank subfacies.It is possible that grain bank,intra-plateform,dolomitic flat and dolomitic bank microfacies could be favorable reservoir layers.A set of sedimentary facies recognition model image logs,suitable for the platform facies of the 5 th Member of the Ordovician Majiagou Formation,was established by comparing the conventional log data with image logs of different depositional microfacies,including block mode,strip mode,layered mode,linear mode,patch mode and dark patch-linear combination mode.This formed the basis for continuous identification and division of the depositional microfacies in a single well.Combined with logging interpretation results and gas test data,the controlling effect of favorable sedimentary microfacies on reservoir effectiveness was further verified.The resulting in-depth understanding of sedimentary facies features and characterisation of favorable reservoirs in the Ordos basin has significance for the exploration of the Lower Paleozoic carbonate reservoirs.