Research And Application Of Micro-motion Exploration Technology In Geothermal Exploration Of Middle And Deep Layers

With the increasing emphasis on energy development and utilization in our country,geothermal energy,as a new renewable clean energy,has been greatly developed in its exploration and utilization.Conventional geophysical exploration methods include magnetotelluric,artificial seismic,etc.When working in towns or construction areas,these commonly used methods have certain limitations,or have poor anti-interference ability,or high cost,or shallow exploration depth,thus unable to achieve the exploration purpose of geothermal energy.At this time,fretting exploration breaks into people's field of vision.This method is a type of natural source surface wave exploration.It uses weak vibrations that naturally exist on the earth as a signal source.Therefore,when using its operation,it has no special requirements for the geophysical prospecting environment and has relatively high With strong anti-interference ability,the exploration depth can reach hundreds of kilometers,and the exploration cost is relatively low,so it has more prominent advantages when applied to geothermal exploration.This article expounds the basic theory of micro-motion exploration technology,researches and discusses the processing and inversion methods of micro-motion data,conducts further research through field experiments,conducts spectrum analysis of the collected data and picks up the dispersion curve,and uses the relevant The initial model is established from the data,and the genetic algorithm is used to perform inversion to obtain the corresponding velocity structure.Based on this,the corresponding micro-motion profile is drawn,and then the geological structure is explored,and the relevant data is compared for analysis and research.The main research results are as follows:(1)Through the collection of relevant data in the study area,the study and analysis show that the deep geothermal geology in Fanxian area is Cambrian-fractured zone thermal reservoir,and the geothermal genesis type is sedimentary basin conduction type and fault structure convection type.(2)The influence of different physical parameters(P-wave velocity,S-wave velocity,density,layer thickness)on the dispersion curve is studied through micro-motion experiments,and it is obtained that the shear-wave velocity is the parameter that has the greatest influence on the dispersion curve,followed by the layer thickness and the longitudinal wave.The speed effect is small,and the density has almost no effect.(3)The data processing software uses Geogiga software,and the dispersion curve extraction methods used include spatial autocorrelation(SPAC)and extended spatial autocorrelation(ESPAC).A more detailed description of the processing flow provides a reference for quickly determining site properties,accurately extracting dispersion curves,and reasonably determining stratum structure;comparative analysis of the two methods shows that in deep geothermal exploration,the ESPAC method has a better application effect,Which is more consistent with geological data and has higher accuracy.(4)The apparent shear wave velocity profile is obtained by data processing.It is considered that the anomaly of the apparent shear wave velocity value of the profile is less than 800m/s as the reflection of the Quaternary system,and the apparent shear wave velocity value of 800?1700m/s is the reflection of the Neogene;the results of geological interpretation are the same as the previous regional geology.The data are in good agreement and are in line with the actual geological conditions.The distortion section of the apparent shear wave velocity contour at stake number1827?2400m is inferred and interpreted as F1 reflection,with a fault distance of about225 m and an inclination angle of 70°,passing through the bottom of the geothermal well.This shows that the geothermal well The final hole is located in the F1 fault zone,combined with previous data,it is inferred and interpreted as Baiyige fault(F1),a trunk branch of the Liaolan fault,with a fault distance greater than 3000 m.(5)Combined with the previous results of gravity and earthquake,the results of micro-motion results are analyzed,and the data are in good agreement.The study believes that the combination of gravity and micro-zoological exploration methods can better solve the problem of urban deep geothermal resource exploration.