Research On The Response Characteristics Of Cracks In Electromagnetic Remote Detection

Carbonate oil fields are the most important part of global oil fields,and their oil and gas storage spaces mainly exist in the form of fractures.Fractured reservoirs are already an important area for increasing reserves and production in the 21 st century.In China,the number of fractured reservoirs is more prominent.Based on the COMSOL finite element simulation software,this paper constructs a model for electromagnetic remote detection of cracks,and uses its multi-component electromagnetic signal sensitivity and long detection range to study the spatial position,crack opening,crack azimuth and cracks of the electromagnetic remote detection instrument.The pitch angle,the dip angle of the fault,the fault distance and the thickness of the fault logging response characteristics,the three-dimensional description of the fractured reservoir characteristics in the formation.The following are the main research contents and results.The first part is the numerical simulation of cracks in electromagnetic remote detection based on COMSOL software.In view of the characteristics of conventional fractured reservoirs,electromagnetic remote detection instruments are selected for response analysis,and three models of fractured reservoirs are determined.At the same time,the COMSOL software was used to perform numerical simulation verification in a uniform formation.The results show that the relative error of the numerical solution and the analytical solution of the T-R1 double-coil system structure and the T-B2-R2 three-coil system structure of the remote detection instrument are less than 1 %,in line with the requirements of instrument detection accuracy.The second part analyzes the response characteristics of the electromagnetic remote detection tool through the well fracture,and studies the influence of the fracture length,the fracture opening degree and the fracture conductivity of the well fracture.The effective apparent conductivity values in the three directions of XX,YY,and ZZ can be obtained.When the instrument rod moves in space,the unique and definite apparent conductivity value can be obtained for different crack lengths,crack opening degrees or crack conductivity.At the same time,the T-R double-coil system structure can measure the relative position of the instrument bar from the crack,and the T-B2-R2 three-coil system structure can determine the relative direction of the instrument bar and the crack.The third part analyzes the response characteristics of the side-well fracture of the electromagnetic remote detection instrument,and studies the influence of the fracture opening degree,the fracture azimuth angle,the fracture pitch angle of a single side-well fracture,and the fracture opening degree of multiple side-well fractures.A single well-side fracture can obtain effective apparent conductivity values in five directions: XX,XZ,YY,ZX,and ZZ,and the spatial position of different fractures and the opening degree of the fractures can obtain a unique and definite apparent conductivity value.When researching the azimuth angle of the crack or the pitch angle of the crack,it is necessary to combine the apparent conductivity values of the two coils of the ZX direction coil to determine the azimuth angle or the range of the pitch angle of the crack,and the apparent conductivity values of the coils in the other directions to determine the crack Stay away or close.When there are multiple well-side fractures,parallel well-side fractures only have effective apparent conductivity values in the XX,YY,and ZZ directions,while vertical well-side fractures can obtain effective apparent conductivity values in nine directions,and the apparent conductivity values of different fracture openings If the value is different,the position of the fracture can be judged by the response curve of the cross-coil.Compared with the single-well side fracture,the number of fractures and the relative direction of the fractures can be judged indirectly.The fourth part analyzes the fault response characteristics of the electromagnetic remote detection instrument,and studies the influence of the dip,distance and thickness of the fault.The effective apparent conductivity values in the five directions of XX,YY,YZ,ZY,and ZZ can be obtained.When the instrument stick is moved in the fault,the inclination angle,fault distance or layer thickness of different faults can get a unique and definite apparent conductivity value.However,the boundary between the upper and lower reservoirs of the fault is affected by the skin effect and the surrounding rock.As the instrument rod passes through,the influence diminishes.