Study On Kirchhoff Pre-stack Time Migration With Rugged Topography

With the improvement in the level of exploration, the complex area of oil and gasexploration has become the main objective of the geophysical workers. Western China hasbecome a very important resource-replaced area of our country. But in this area, weencountered lots of difficulties and problems in exploration because of its special geologicalconditions and its complex surface and subsurface structures. What the situations we have toface are: rugged topography with serious noises contained in seismic wave, continuouschange of main propagation direction, uneven illumination of the oriented structure, irregulargeometry and high near-surface velocities. All these caused the tough problems that we meet,like the low signal to noise ratio of original single shot data, stack problems of differentphases, and bad resolution of structure interpretation. Among these, problems of low seismicdata S/N and bad structure interpretation resolution are two key technologies that we shoulddevelop, and these two are the main research direction of methods in western seismicexploration. We do migration on the rugged topography based on the method of topographicalKirchhoff pre-stack time migration.Normal post-stack migration processing technologies have taken a leading role inexploration and development of many oil fields all over the word. However, post-stackmigration cannot meet the ever-increasing needs of fine structure imaging and reservoirdescription, because of more and more difficulties and costs in oil exploration anddevelopment. Pre-stack time migration is one of seismic pre-stack imaging methods, whichcan not only solve the problems of blurring common reflection points, uncertain stack incomplex structures with sharp dips and incorrect imaging with the combination of DMO andpost-stack migration, but also provide common imaging gathers with betteramplitude-preserving adaptable to AVO/AVA lithologic analysis and inversion. Compared to pre-stack depth migration, pre-stack time migration also has advantages of lower cost, shorterprocessing periods, easier realization and lower influence by man-made factors of geologicknowledge. With the wide application of computer and pc-cluster of high performance,pre-stack time migration has been becoming an indispensable flow in pre-stack imagingprocessing. First, this paper summarizes various kinds of pre-stack time migration. In order toenhance the imaging accuracy, on the base of straight ray, consider the theory of curved raythat calculates the travel-time. Adding the concept of weight function, improve the capabilityof Amplitude-preserving.Along with the complexity of the surface conditions and the needs of production, weneed a better and more universal set of pre-stack time migration process (including the levelof surface and undulating surface). First, this paper introduces and discusses the level surfaceKirchhoff pre-stack time migration, including its methods and principles. It also introducesthe key technologies used to improve the imaging quality of the pre-stack time migration.Based on the previous studies of level surface pre-stack time migration imaging approach, thispaper focuses on irregular surface Kirchhoff pre-stack time migration methods to search amore suitable method for handling complex surface condition seismic data.