The Research Of Seismic Data Refraction Static Correction Methods

The heterogeneous variations of thickness and velocity of the weather zone in near-surface layers is the reaseon for the non-uniform delay of seismic wave travel time in seismic exploration. As a result, the observed travel times of reflection wave are distorted, which greatly affect the imaging in stacked sections and even cause false structural interpretation. The static correction is an important work to remove the influence caused by the complex variation in near-surface layers. Solving the long wave-length static problem and the short wave-length static problem orderly is needed. The long wave-length static problem leads to the false structual interpretation while the short wave-length static problem may cause a poor imaging in stacked sections.The common used seismic data refraction static correction methods are the key research in this paper, which includes main contents as follows: The study of the relation between offset and travel time of refraction wave in the condition of single horizontal layer, multiple horizontal layers, single tilt layer and curved layer. The research of theories of refraction static methods like AB Method, Generalized Reciprocal Method (GRM), Generalized Linear Inversion (GLI), Delaye time Decompose Method and Interactive Iteration Method. Analysis of the performance of several inversion algorithms like Simultaneous Itreration Reconstruction Technique (SIRT), Conjugate Gradient (CG) and Least Square QR decomposition (LSQR). Put forward a method of first break auto picking constrained by space varied time windows. Furthermore, a software is programmed to solve the long and short wave-length static correction problems, in which there are several functions like management and analysis of seisimic data, first break auto picking, long wave-length static correction processing and short wave-length static correction processing.This paper has drawn some conclusions in the base of doing research of refraction static correction methods in detail: (1) In order to solve the static correction problems better, not only the ability to identify the effects caused by the comlex near-surface acqusition condition in seismic data is needed, but also the work of doing research of kinds of static correction methods and getting to know geology conditions in the explored area is inevitable. (2) In the condition of stable refraction layer existing in the whole area and first break information obtained precisely, comprehensive refraction static correction method can solve both long and short wave-length static problems. (3) That the results of refraction static correction is good or not depends on the choice of parameters and the input information. (4) The method of first break auto picking constrained by space varied time windows is proved to be a simple and useful technique. (5) Making use of near-surface information obtained by field work can help to improve the results of static correction processing.