Study of geometry footprints origin from the physical modeling data

Abstract

Introduction Acquisition footprint is a new concept of seismic noise, which appears in 90s of last century when seismic exploration has carried out in complex area. It was called “Acquisition artifacts” firstly (Gulunay, 1994). Its impacts are found in marine streamer survey and complex surface survey on land. Marine plume cable and surface obstacles will make spatial sampling of receiver irregular, which causes uneven properties distribution among underground panels. When data is applied 3D DMO or 3D pre-stack migration, this impact will be enhanced. This has been thought of the reason for acquisition footprint. However, with improving of seismic imaging resolution in the lithologicalreservoirs and subtle reservoirs, people find that regular 3D geometry and spatial sampling will produce acquisition footprints also, which have bad influence on the high-precision imaging quality of target zone, so this problem has been a focus of 3D seismic exploration. Acquisition footprints include geometry acquisition footprints and non-geometry acquisition footprints. Most of the latter are irregular, caused by the equipment, complex surface, weather etc., which have been considered by the routine processing. Now attentions are on the geometry acquisition, and because it is relative with geometry, its rules can be cognized. During last few years of 20th century, many papers about this problem have appeared and can be divided into two parts. One is theory analysis, using numerical simulation and physical modeling simulation to study the feature and origin of footprints and optimize geometry design. Another part is application, whose aim is attenuation and even removal of acquisition footprints to improve imaging quality. There are not many good results in numerical analysis because of its large computation. If we apply 3D wave equation with field design 3D geometry on the layered models to analyze acquisition footprints, computer skill cannot meet the capacity now. To this point, physical modeling study shows its advantages. In recent years, CNPC Key Laboratory of Geophysical Exploration where the author is has carried out some 3D seismic physical modeling simulation experiments with different 3D geometry. This paper chooses 2 physical models with three kinds of geometries to analyze footprints features. On the basis of Xiong’s results, the author defines two new concepts: static acquisition footprints and dynamic acquisition footprints. And then shows their features and origin separately.