Research On Response Characteristics Of Resistivity Logging In Defective Casing

Logging technology plays an important role in oil and gas exploration.At the same time,it plays an indispensable role in the discovery of oil and gas reservoirs and the accurate description of oil and gas storage.Casing wells work after a long time,the metal casing is in the harsh environment such as high temperature、high pressure、high strength corrosion and so on.The casing may produce different defects such as holes,cracks,distortion,corrosion,and even fracture.The existence of defective casing will cause the production wells to work in bad condition,which will affect the measurement,and it will make the production wells scrapped,resulting in a waste of oil and gas resources,and it will cause serious economic loss to the oil field exploitation and cause great pollution to the environment at the same time.Therefore,it is necessary to know the dynamic defects of the casing well,and to be able to identify the characteristics of the defect casing,and to detect the casing defect so as to evaluate the use of the casing in real time.In the cased hole resistivity logging,the power supply A is located in the borehole axis,and the electric field can be divided into three zones: the near,the intermediate and the far zones.Within the intermediate zone,casing well logging response can be obtained.By using the COMSOL finite element analysis software,casing model,such as the uniform corrosion of the inner and outer walls,collar casing well,casing fracture and conductivity change of casing was built and computed,loading the steady current field to carry on the simulation solution.In the study of response characteristics of resistivity logging in defective casing,the potential distribution,the electric field distribution and the second derivative of the potential distribution in the casing wells with different defects were studied.And the distribution characteristic curve was drawn to study the correspondence between casing defect and logging response.Based on the study of the response characteristics of resistivity logging in the defect casing,it provides the theoretical basis for quantitative explanation and evaluation of well logging response curve.At the same time,it provides technical support and guarantee for the design of casing resistivity logging tool and the analysis of logging response.