The Study On The Logging-while-drilling Electromagnetic Wave Resistivity Tool Based On Direct Digital Frequency Synthesis

With the development of worldwide petroleum industry,more and more high technology apply to drilling engineering.In order to exploit oil reservoir which is smaller,thinner and worse,deviated holes,branch holes and horizontal wells are widely used in exploration.Logging while drilling technology has such a lot of advantages,it's replacing wireline well logging technology gradually.Electromagnetic wave propagate resistivity logging technology is the critical technology that are used in real time formation evaluation and geo-steering drill.It can measure surrounding formation resistivity which is very important in formation hydrocarbon content evaluation.This thesis introduces the basic theory of electromagnetic wave logging technology,proposes four transmitter,two receivers symmetric compensation antenna array which is originated from three antenna system and antenna structure design.The environmental impacts in resistivity logging while drilling is introduced in the paper.And the relation plate which can convert the phase difference resistivity and the amplitude ratio resistivity into apparent resistivity is proposed.This thesis introduces direct digital frequency synthesis technique,which is applied to the resisitivity instrument's transmitting signal generator.The whole circuit system is studied according to the system requirement and design specification.The electric system include: power supply circuit,transmitter circuit,receiver circuit,analog to digital converter circuit,real time clock circuit,memory interface circuit,serial interface with upper PC circuit,ethernet interface circuit,frequency shift keying modulation circuit.The experiment showed that all circuit modules performed stable and reliable.The output signal precision meets the overall system design requirement.Instrument has been calibrated,functional tested in workshop and field tested has been performed on rig.After many field test and verification,this thesis can provide design reference and technical implementations for resistivity instrument development which can work under harsh condition.