Logging Evaluation Of Water Flooded Layer In Guantao Formation Of Bohai Block P With Low Resistivity

As the largest Neogene oilfield group in the Bohai Bay Basin,Bohai Block P is rich in reserves.After more than 20 years of development and production,the comprehensive water cut of some well areas has reached more than 80%,and has entered a period of high water cut.The development difficulty is increasing,and the exploitation and development of remaining oil in the reservoir has gradually become the focus.However,the lithology of the reservoir is complex.There are a large number of low resistivity oil layers in Guantao Formation.The log response difference between the low resistivity oil layer and the water flooded layer is not obvious,and the water flooded condition is complex.Moreover,due to the mixed logging while drilling and wireline logging series in this area,the logging data is not matched,and the basic research is weak.Therefore,it is difficult to carry out the evaluation of the flooded layer.At first,this paper has conducted a full investigation of the sedimentary and structural characteristics of the study block,in-depth study of the basic characteristics of the target block reservoir,and on this basis,carried out the "four-character relationship analysis" of the reservoir,to establish a geological basis for the subsequent evaluation of the flooded layer;Secondly,the genetic mechanism of low resistivity oil layers in Guantao Formation of the research block is systematically analyzed,and the main reasons for the development of low resistivity oil layers are analyzed from the macro and micro perspectives by using a large number of petrophysical experimental data and combining with geological conditions;By amplifying the difference in conventional logging response,nuclear magnetic resonance logging,gas logging and other data of low resistivity oil layer and water flooded layer,the qualitative identification chart of water flooded layer with multiple deep detection resistivity and various sensitive parameters is established,and the qualitative identification of low resistivity oil layer and water flooded layer is combined with gray relational analysis and extreme learning machine algorithm;Combined with the characteristics of the reservoir in the study block,the genetic mechanism of the low resistivity reservoir,and the experimental data of rock physics,the quantitative evaluation model suitable for the shale content,porosity,permeability,water saturation,water production rate,oil displacement efficiency and other parameters of the target block is established using the core data as the scale.The resistivity and residual oil saturation of the mixed solution after water flooding are calculated by using the material balance method and Improved Simandoux formula inversion iteration,On the basis of these parameters,the identification and classification criteria of the flooded layer are established.The method proposed in the paper is used to study the water flooded layer in the Bohai P area,which has achieved good application results and improved the coincidence rate of logging interpretation of the water flooded layer.