| Microseismic monitoring is very important for the development of low-permeability reservoirs,and its core technology is to locate the microseismic source.In recent years,with the development of microseismic monitoring theory,crack evaluation technology based on microseismic monitoring has become the most intuitive and reliable technology in the mining process of low permeability reservoirs.Based on the ground monitoring,the key technologies of microseismic monitoring,such as forward numerical simulation,velocity model construction and correction,microseismic positioning and three-dimensional microseismic monitoring visualization software,are studied.Velocity model is one of the key factors that affect the positioning accuracy of microseisms.When the initial velocity model and perforation data obtained from the combined logging curve are used to calibrate the velocity model,there is a problem that the starting time of perforation cannot be accurately obtained.In this thesis,the difference between the theoretical velocity model and the actual velocity model is described based on the double differential root mean square error of the first break time difference.In order to reduce the error of double difference root mean square error quickly,the minimum value of double difference root mean square error can be quickly obtained by using the very fast simulated annealing algorithm,and then the velocity model can be obtained.According to the obtained velocity model,the perforation relocation can improve the positioning accuracy.It is necessary to calculate the propagation time of seismic wave in the process of double difference root mean square error.In this thesis,based on ray tracing technology,the seismic wave forward simulation is carried out.The fast two-point ray tracing algorithm and the step-by-step iterative algorithm are used to calculate the seismic wave propagation time respectively.The accuracy and efficiency of the two algorithms are compared.Under the condition of ensuring the accuracy,the fast two-point ray tracing algorithm with high efficiency is selected.Source location is the core of microseismic monitoring.Based on the grid search algorithm,this thesis analyzes the factors that affect the positioning accuracy and concludes that:in addition to the speed model,the first arrival pick-up time of geophone is also the main factor that affects the positioning accuracy.Aiming at this problem,this thesis proposes a dispatch scheduling model based on the p-wave and s-wave time-difference analysis theory.Through this model,it is possible to select the detector data with relatively accurate and small error of the first arrival of the seismic wave before the source is located.In order to further constrain the error,the objective function is optimized by using the same principle at the same time of the same source to increase the probability of selecting a detector with a lower data error.Finally,using the selected geophone data to locate the seismic source can improve the positioning accuracy.This thesis develops a three-dimensional visualization software for microseismic monitoring,which integrates the calculation and drawing functions of Java,Matlab,Python and other languages.The processed microseismic data is imported into the calculation module,and the microseismic events are displayed in three dimensions through analysis and processing,which provides a convenient human-computer interaction tool for microseismic monitoring. |
