基于成像测井和岩性扫描测井的沉积相研究——以柴达木盆地黄瓜峁地区为例

柴达木盆地黄瓜峁地区储集层岩性混杂,既有碳酸盐岩、碎屑岩,又有砂、泥、碳酸盐矿物混积的岩性,储集层厚度小,利用常规测井曲线无法有效识别岩性。利用地层微电阻率扫描成像(FMI)测井和岩性扫描(LS)测井可以较好识别出岩石的矿物成分和结构构造,进而确定储集层岩石类型。利用钻井岩心、LS测井、FMI测井和常规测井综合刻度,识别出4种沉积微相类型,并总结了不同微相的测井响应特征:藻席在LS测井上碳酸盐矿物含量一般大于80%,FMI测井具有高亮杂乱或絮状反射特征,常规测井表现为超低自然伽马和低自然电位;灰云坪在LS测井上碳酸盐矿物含量大于50%,FMI测井为弱—强层状,常规测井表现为低自然伽马、低自然电位和中—高电阻率;砂坪在LS测井上长英质矿物含量大于50%,FMI测井为块状结构,常规测井表现为低自然伽马和低—中电阻率;泥灰/云坪矿物成分复杂,砂、泥、碳酸盐矿物互层,LS测井曲线齿化严重,FMI测井为强层状,常规测井表现为中—高自然伽马,曲线呈齿状。基于测井相对黄瓜峁地区沉积微相的空间展布开展刻画,其研究结果对明确该区有效储集层展布有指导性作用。

Study on Sedimentary Facies Based on FMI logging and LS logging:A Case Study of Huangguamao Area,Qaidam Basin

There are three types of lithologies such as carbonate rock,clastic rock and mixtite in Huangguamao area of Qaidam basin and conventional logging curves can't be used to effectively identify the lithologies because the reservoirs in the study area are very thin.By using lithoScanner logging (LS) and imaging logging (FMI),mineral compositions and structures of the rocks can be identified,and then the reservoir rock type can be determined.Based on the well core,LS logging,FMI logging and comprehensive calibration of conventional logging,this paper identifies four categories of sedimentary microfacies and summarizes the corresponding logging characteristics of different microfacies.Firstly,for alga mat,LS logging shows that the calcite content of the alga mat is generally more than 80%,FMI logging is characterized by highlight and disorder or flocculent reflections and the conventional logging curve has the characteristics of ultra-low GR and low SP.For calcareous dolomitic flat,LS logging shows that its carbonate mineral content is more than 50%,FMI logging indicates that it is a weak-strong layer,while the conventional logging exhibits low GR,low SP and medium-high resistivity.For sand flat,LS logging shows that its felsic mineral content is higher than 50%,FMI logging indicates it has a blocky structure and the conventional logging exhibits a feature of medium-low GR and medium-low resistivity.The mineral compositions of marlstone (dolomite) flat are very complex,sandstone and marl are interbedded with each other,for this microfacies,a serious toothed LS logging curve is noted,FMI logging shows a strong stratification and the toothed conventional logging curve exhibits a feature of medium-high GR.Based on the logging facies analysis,detailed characterization is carried out for the spatial distribution of the sedimentary microfacies and the study results can be a guidance for the determination of the effective reservoir distribution in the area.