Genetic Mechanism And Distribution Of Low Resistivity Oil Layers In Caofeidian Oilfield, Bohai Bay Basin

The sand body of Guantao Formation in Caofeidian oilfield in the Bohai Bay Basin has entered the stage of production decline since its exploitation in 2004,and the comprehensive water cut of conventional reservoir is as high as 85%.The discovery of low resistivity reservoirs plays a vital role in increasing oil reserves and production.However,due to the characteristics of low resistivity oil reservoirs with diverse genetic mechanisms,difficult identification and unclear distribution rules,it is difficult to evaluate and develop them.Therefore,in-depth study of its main control factors and spatial distribution characteristics will help guide the exploration and development of low resistivity oil reservoirs in similar layers and achieve the purpose of increasing reserves and production.This thesis takes the low resistivity oil layer in the upper of the third section of Guantao Formation of Caofeidian oilfield as the research object,integrates the regional geological background,logging,seismic,coring,analysis and test data,summarizes the basic characteristics of the low resistivity oil layer,analyzes the genetic mechanism of the low resistivity oil layer in this area,and establishes the logging and logging identification chart suitable for this area.Finally,through seismic attribute extraction and sedimentary microfacies characterization and other means to clarify the spatial distribution of low resistivity reservoirs.The results show that the low resistivity reservoir in Caofeidian oilfield has fine grain size and high shale content,and the reservoir belongs to medium-porosity-medium-high permeability type.The formation of low resistivity oil layer is controlled by the sedimentary environment macroscopically,located at the top of the sedimentary cycle longitudinally,with poor physical properties,and is mainly controlled by high bound water saturation,complex pore structure,and high cation exchange capacity of clay minerals microscopically.The intersection map method,logging curve overlap method,gas logging,and nuclear magnetic resonance logging methods are comprehensively applied to identify single wells of low resistivity oil layers,and the NE-SW distribution characteristics of low resistivity oil layers are predicted based on plane seismic attributes.This study has clarified the genetic mechanism and spatial distribution rules of low resistivity oil layers in this area,guiding the adjustment of oilfield exploration and development plans,and has important significance for the discovery of similar oil layers.