Time-domain Seismic Beam-forming Based On Receiver Array

When noise is strong or seismic exploration is used in the complex area, SNR ofthe obtained seismic data is usually unable to meet the demand. Research shows thatstimulate directional seismic waves by the phased source system (PAVS, Phased ArrayVibrator System) can significantly improve signal to noise ratio of seismic records,which can form directional seismic beam, was developed.However, PAVS application process has a new problem in recent years. Becauseof the need for multiple source simultaneously, it is difficulty in handling and highcost. Since the non-uniformity between the source affects the seismic directionalprecision of PAVS，SNR improvement is difficult to meet the requirements for targets;and it requires multiple PAVS experiments to explore the case of unknownunderground area for the low efficiency，because of the seismic experimental datacollected by PAVS only improving the signal quality in one direction Meanwhile.These factors restrict the PAVS application and promotion.In order to solve the problems that exist in earthquake beamforming technologyof the source, this paper presents the seismic beamforming method of receiver-Time-domain Seismic Beam-forming Based on Receiver Array（TSBBRA） to extractthe data from the beam directional seismic exploration targets and improve receptionObjective data quality. TSBBRA method can extract any direction of seismic waves,and when the parameters of direction are consistent with the reflected wave directionfrom exploration targets, it can effectively improve the quality of seismic data atlower cost to achieve the same application effect as the seismic source beamforming.This paper focuses on the theory, methods, numerical simulation, observationsystem optimization design and field experiments, and expands research contents forTSBBRA methods，the main research work are as follows:First, this paper expounds the working principle of TSBBRA. We derivedseismic wave field intensity distribution and the direction factor of TSBBRA methodtheoretically from the Forming principle of beam, and analyze the main characteristicsof synthetic seismic beams: the main beam direction, the main beam width, beam zeroposition and beam sidelobes；also analyze the main parameters affecting of theseismic beam characteristics: source number, source spacing, seismic wave velocityand delay parameters. And we do some research for the effects of various parameterson the formation of the earthquake beam， and propose the similarities anddifferences earthquake beamforming methods of seismic source and TSBBRA from atheoretical point, and analyze the strengths of TSBBRA methods.Then, methods, combined with TSBBRA theory we propose (NSTSBBSFD),Numerical Simulation of Time-domain Seismic Beam-forming Based onStaggered-mesh Finite difference), which is applied to numerical simulation ofTSBBRA. We establish the wave equation and staggered-mesh finite differencescheme of single source point, and give the other limited factors, including the stability conditions, boundary conditions and the source function. NSTSBBSFD givesTSBBRA seismic wave field data synthesis equation, including data synthesisequation of TSBBRA wave field synthesis snapshots, TSBBRA shot record datasynthesis equation and TSBBRA direction characteristic data synthesis equation.Secondly, we study the TSBBRA seismic response in a typical velocity model atnumerical simulation. According TSBBRA numerical simulation method, illustratethe TSBBRA method can achieve seismic beam orientation by comparing the singlecontrolled source and TSBBRA simulation results in a homogeneous medium models.For the complex problems of TSBBRA beam shape in complex media conditions, westudy TSBBRA seismic response in typical medium model, Including horizontallayer media model, tilt media models anticline,syncline media model,high-speedmodel and low-speed model. In several media model, we give TSBBRA synthesizedwave field snapshots,directional characteristics and shot record. By comparison with asingle controlled source, we demonstrate the effectiveness of TSBBRA conditions incomplex media, and that improve signal to noise ratio of seismic records isfeasibility. We propose the concept of angle domain energy density distribution，conducted a seismic wave field angle domain decomposition, analysis the angledomain energy distribution of seismic wave field, and measure changes of the mainbeam direction of the reflected wave in different media. In addition, compare ofdifferent velocity model, and based on the simulation results, we describe a methodTSBBRA application methods for different types of exploration targets.Again, in the observation system optimization design, Achieve optimizationdesign of TSBBRA delay parameter for three different bit depth of the target reflectorlayer in tilt mining model, and demonstrate the effectiveness of the delay parameteroptimization to further improve the quality of the reflected wave data. We proposethe optimal delay parameter design principles based on the strongest energy andenergy density in the receive array，and give the design method. Using single sourcedata Synthesis directivity TSBBRA data, We analyze the reflected wave seismogramsat different TSBBRA delay for different reflective layers，and obtain optimal delayparameter is applied to different target layers by plotting the receiving array reflectedwave energy(Curve Fitting). Analysis the seismic wave field at TSBBRA optimaldelay parameter, quantitatively calculate the main beam direction at optimal delayparameter for different reflective layer, and quantitatively analyze the delay parameteroptimization to improve the signal to noise ratio and resolution of reflected wave.Finally, we utilize self-development electromagnetic vibrator in filedexperiments with method of TSBBRA in the aspect of field experiments.The resultsshow that the stacked section of shot record in a signal controlled source and usingdifferent delay time with TABBRA method in the same exploration area. Compared itwith signal controlled source, we find that the TSBBRA method improves the qualityof seismic records, and increase the depth of exploration with appropriate delayparameters. From a practical point of view, we prove the effectiveness of TSBBRAmethod.Summary, papers from theory, numerical simulation and practical perspectiveillustrates the importance of TSBBRA method of improving SNR of seismic records. Review of that based on seismic studies around doing the receive array beamformingmethod has the following major achievements in several areas:1) Through theoretical research, we prove the feasibility of TSBBRA methodthat the receiving end to realize the seismic beam directed and study the seismic mianbeam characteristics and analyze the parameters that affect the characteristics of themain beam.2) We elaborate the working method of TSBBRA, and give a synthetic methodof that snapshot of the wave field TSBBRA method, single recording data anddirectional characteristics of a single shot.3) Through numerical simulation, we get6typical methods of seismic datawhich from simple to complex velocity models of TSBBRA. Analysis of the wavefield snapshot of different models of seismic data, shot records and directionalcharacteristics of the data.We elaborated the TSBBRA application methods fordifferent types of exploration.4) According the needs of the observation system design, we aim at tilt miningmodel for different target horizons, we optimize the design of methods for TSSBBRAdelay parameters.We study the the energy distribution of receiving array seismic afteroptimized delay parameters, and the angle domain of seismic wave field.We alsoquantily analysis of the TSBBRA ways to improve SNR of the reflected signal intarget horizon.5) Completed a field test using the method of TSBBRA, the method ofTSBBRA proves the effectiveness that the realization of the seism from thedirectional beam and improve the SNR of seismic records.The main innovtion of the paper:1) Theoretically prove the feasibility of TSBBRA method at receiving end torealize the orientation of seismic beam, and analysis of the seismic beamcharacteristics and influencing factors.2) We propose a method of numerical simulation, and realize the forming ofdirectional data in a simulation region.And elaborate the TSBBRA applicationmethods for different types of exploration.3) We propose that using the directional characteristics of seismic wave fielddiagram,and anlaysis the directional characteristics of seismic wave propagation indifferent media.4) We propose a selecting principle that using the combination of the strongestreflected wave energy density of receving array and the blance of energy density.Forthe target layers at different depths, we optimize the delay parameter of TSBBRAmethod. And we also quantily analysis of the TSBBRA ways to improve SNR ofthe reflected signal in target horizon.