The Application Research Of Well-Ground CT For Shallow Velocity Distribution Surveying

Geological anomaly area has always been human want to solve one of the potential geological disaster, it exists serious threat to the safety of mineral mining,highway, railway engineering construction and people’s life and property.Want to remove these potential threats, the spatial location, buried depth, shape, and so on and so forth have enough understanding is that we must do.Conventional seismic reflection method to detect anomaly reflection interfaces are based on the continuous uniform, smooth, and the existence of abnormal area,often makes reflection interface is damaged, and the complexity of topography and geology, the size, scope, the anomaly can not be intuitive.Tomographic imaging using seismic data inversion of the underground structure of the material properties, in determining the formation of internal fine structure and local inhomogeneity has obvious advantages.Tomographic inversion of surface low velocity zone is also important basis of complex surface calculating statics, this paper mainly studied the application of wellbore formation tomography technology to detect anomaly area.On the basis of summarizing the predecessors’ research, this paper analyzes the geophysical characteristics of anomaly area, summarized the seismic wave propagation law and the basic principle of tomographic imaging, positive inversion algorithm.Selection method based on shortest path and SIRT inversion algorithm,numerical simulation of the forward modeling, respectively, two groups of Wells to anomaly model is established.First analysis of the abnormal body position of certainty for tomographic inversion, and the accuracy of the analysis of the multiple well joint inversion;In the final analysis the factors influencing the effect of tomography.Is obtained by analyzing the model of data processing of the following two conclusions:wellbore formation on a small scale photoacoustic imaging detection effect is better in the abnormal area, abnormal area for the inversion results have a certain influence,multiwell joint inversion in fine detecting abnormal body position, size of the effect is better.This paper take the well to seismic data of harmony county in guizhou and your port gangbei district in guangxi as examples, by tomographic imaging technology, it has beenbetter verified the accuracyin low velocity inversion and shallow anomaly detection.