Study On Imaging Method And Electromagnetic Modeling Of High Resolution Micro-resistivity Imaging Tool For Oil-based Mud

The impact of petroleum resources on the economic and political landscape of today’s world is of great importance,and the exploration and exploitation of oil has important and important strategic significance.Before the exploitation of oil and gas resources,it is necessary to find out the recoverable reserves of oil and gas resources and the geological characteristics around oil and gas reservoirs through logging,and analyze the potential of oil and gas resources.Micro-resistivity imaging logging technology,by which high-resolution images can be obtained,can collect a large amount of data from the formation around the wellbore,and is suitable for measurement of various complex formations,and has unique advantages in exploration of fractured reservoirs and reservoirs with complex lithology.With the discovery of abundant oil and gas resources in the South China Sea continental shelf in recent years,the resistivity of the seabed formation is often low,and imaging is difficult.Therefore,it is of great significance to study and improve the high-resolution oil-based mud micro-resistivity scanning imaging logging imaging method in low-resistance formation environment.Facing all these problems mentioned above,in this paper,the electromagnetic model of micro-resistivity imaging logging model in oil-based mud environment has been established by finite element method(FEM)and the electromagnetic modeling and research of two main structure logging models of oil-based mud micro-resistivity scanning imaging instrument are carried out.The differences of measurement results,resolution and detection depth between the two structure instruments are compared and analyzed.The influence of the change of the electrode area of the instrument loop on the logging response is also studied when the measured resistivity is relatively low.The equivalent circuit model and correction method for dual-frequency correction have been studied comprehensively.The validity of the equivalent circuit model is studied by comparing the impedance of the equivalent circuit model with that of electromagnetic model at different measurement frequencies.The influence of mud electrical parameters,correction frequency and measurement error on the correction results is also studied in this paper.In the study of dual-frequency correction equivalent circuit model and imaging method,it is found that the circuit parameters in the equivalent circuit model is affected by the measured frequency.Therefore,in this paper,the equivalent circuit parameters of formation and mud at different measuring frequencies are calculated accurately by electromagnetic modeling,and the relationship between parameters of dual-frequency equivalent circuit model and frequency is determined.By taking into account the relationship between equivalent circuit parameters and measurement frequency,in this paper,a new three-frequency correction equivalent circuit model and three-frequency correction method for mud micro-resistivity imaging in oil-based are proposed and the sensitivity of correction results in low resistivity formation to resistivity variation is improved.The new equivalent circuit model and imaging method are investigated and improved.