Theoretical Study And Numerical Simulation Of Seismoelectric Logging While Drilling

With the development of the world economy,the shortage of oil and gas has become the main restricting factor of economic and social development.And the oil and gas are mainly stored in the porous media.So the application of seismoelectric effects in the exploration of oil and gas is very promising,especially in the search of “remaining oil".Logging while drilling is not only low cost,but also can save the detection time,and gets more accurate geological information.But the acoustic logging while drilling cannot groove to block the drill collar interference wave,in order to ensure the drill collar has enough strength.The drill collar is thick metal cylindrical shell now and the influence of instrument wave on the acoustic field can not be ignored.So it has become very urgent to search a new logging method in order to avoid the interference of drill collar waves.When the acoustic field propagates in the porous medium,the electromagnetic wave can be induced by the seismoelectric effects which can be used in the logging.Seismoelectric logging not only has the advantages of purely acoustic logging and traditional electromagnetic logging and overcome their defects,for example,it is not easy for acoustic logging to distinguish the oil and water,and the detection distance and resolution of electromagnetic logging is limited.At the same time,it has the advantage of sensitivity to the formation parameters and we can get rich information of stratum.In this paper,we establish the mathematic model and study the seismoelectric wave field excited by the monopole source and the multipole source with different center frequency,it provides theoretical guidance for the selection of excitation source and sound source frequency.We deduce the formulations of the acoustic and electromagnetic field of the liquid in the well,and give the acoustic and electromagnetic boundary conditions between the driller collar and the log liquid,when the driller collar is added.We also compare and analyze the amplitudes and phases of each component of the seismoelectric field,and study the influence of different receiving position,which provides theoretical guidance for the design and installation of the receiving antenna.We analysis the influence of the formation parameters on the seismoelectric wave field,It is proved that the seismoelectric wave field is sensitive to the variation of the formation parameters,and the more logging information can be obtained.In this paper,we investigate the detective depth of the seismoelectric logging,which proves the electromagnetic field is produced by the electro seismoelectric effect,and get the velocity dispersion characteristics of the acoustic and electromagnetic field through the multiple filter technique(MFT).Then this paper studies the effect of drill collars on seismoelectric field,and analyzes the influence of the formation parameters,such as porosity and permeability,on the dispersion characteristics of the acoustic field and electromagnetic field.Through the simulation we know the seismoelectric logs can avoid the interference of drill collar wave,when excited by the monopole source.