Research On Analog Circuit System Of Seismoelectric Logging In Wellbore

Seismoelectric logging is the technology that uses the seismoelectric effect to perform exploration of oil and gas resources.Artificial sound sources are used as the excitation sources to generate acoustic waves that propagate in different media within the wellbore containing the fluid.When the acoustic wave propagates in the wellbore rock,the electric double layer structure formed in the rock medium will vibrate,and thus generates an electric field accompanying the elastic wave,which is the seismoelectric signal.The application of seismic logging technology in LWD logging not only can effectively avoid the influence of collar waves,but also can identify cracks and oil-water interfaces in the formation.The effective acquisition and processing of seismoelectric signals by the seismoelectric logging tools can further analyze the parameters of the formation such as permeability and porosity,and it can also provide guidance for the exploration of oil and gas resources.However,there are currently no mature or practical seismic logging tools within wellbore on the market,and the relevant circuit systems are less studied.The main reason comes from two aspects.On the one hand,the seismoelectric signal generated by the seismoelectric effect is extremely weak,only the microvolt level,or even smaller.On the other hand,the lack of similar scientific experimental instruments has hindered the deeper research on the phenomenon of seismoelectric effect,which in turn has further affected the development of circuit systems or experimental instruments.Therefore,it is more and more important to investigate the seismoelectric logging circuit system or instrument,especially the study on the circuit system that can effectively deal with extremely weak signals,which has become the key and difficulty for the research of such logging instruments.In the absence of reference studies,this thesis completed the design of circuit system of the seismoelectric logging within wellbore.Firstly,according to the principle of seismic logging and the technical indicators of the acquisition system as well as the requirements of the actual project,the design of acquisition system of the seismoelectric logging within wellbore was proposed.Secondly,considering the complexity of the logging environment,the space of the circuit board,low power consumption requirements of the circuit system,requirements for signal multi-path measurement and extremely weak characteristics of the seismic signal,eight acquisition circuit system boards of seismoelectric signal and one circuit board with expanding circuit functionality that can meet the requirements have been designed.Finally,the debugging of the circuit system was completed,and an experimental test platform for seismic logging circuit system within the wellbore has been built.The thesis has completed the experiment of the system in different porous media,and examined the parameters of the seismoelectric signal.Through analyzing and summarizing the experimental data,the performance of circuit system of the seismoelectric logging within wellbore has been verified and met the technical specifications.The research results about the acquisition system of the seismoelectric signal can provide good technical support for the development of the seismoelectric logging instruments in the later period.