| Petroleum is an energy source that people often use in daily life.With the rapid development of the world economy,people's demand for oil is increasing.Therefore,the transmission and analysis of information in oil exploration and exploration work and in drilling work has become a hot spot in research and development.Research on drilling technology is also extremely important.The electromagnetic measurement while drilling technology mainly refers to a new type of measurement method that was researched in industrial application fields such as petroleum resource mining and coal resource mining in the 1980 s.The use of advanced electromagnetic wave transmission method is simple and easy to operate.During the measurement process,the demand for circulating drilling fluid and circulating medium is small,and it can be widely applied to air,foam or other materials.Therefore,this method has been widely used commercially.Due to the complexity of the stratum environment,it is necessary to choose an appropriate method to model the electromagnetic signal transmission model.For complex non-uniform problems,the transmission line-based method is currently widely used,but this method can only consider a one-dimensional model,and cannot consider the radial layered model and the detailed structure of the instrument.Therefore,this paper chooses to use the finite element method to carry out electromagnetic modeling of the "complete channel of electromagnetic wave transmission while drilling formed by the drill string,drilling fluid,casing,cement ring,and formation".First,the wave equation satisfied by the total field in the formation medium is derived from Maxwell's equations,and then the expression of the functional is obtained by simple variational principle,and then it is discretized and expressed as the integral on each subdivision unit sum.In order to better fit the model,a hexahedron is used as the basic unit for the division,and a mixed-order stacked vector function is used to describe the field at any point in the division unit,which reduces the unknowns and improves the solution speed.Using the above-mentioned finite element method,the electromagnetic modeling of the electromagnetic wave transmission channel formed by the drill string,drilling fluid,casing,and formation was carried out,and the drill pipe,casing,cement ring,drilling fluid,drilling fluid,etc.were studied and analyzed in detail.The influence of the stratum on the electromagnetic wave transmission while drilling has guided the parameter design of the prototype of the electromagnetic wave transmission principle while drilling.Specifically: Study and compare the effects of transmitting antenna and receiving antenna on the electromagnetic wave transmission while drilling at different positions of the casing,thereby optimizing the position layout of the relay antenna;Simulation analysis of wire antenna and solenoid The size of the antenna affects its receiving performance,and the design of these two receiving antennas is further optimized.The study investigated the receiving performance of the receiving antenna at different frequencies in different stratums and uneven stratums,so as to optimize the frequency to select the appropriate electromagnetic wave excitation frequency.In addition,through the above-mentioned simulation analysis,the downhole test of the instrument can be guided,and the scope of use and the environment of the use of the electromagnetic wave while drilling instrument can be evaluated.Finally,the prototype designed based on the method in this paper was tested in real well at Luntai,Xinjiang.The single section achieved a transmission distance of nearly 900 meters.The test results of the instrument and the simulation results were compared to further verify the method and simulation results of this paper.The correctness. |
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