A Study And Assessment Of 3D Seismic Acquisition Geometry Based On Ray Theory In Layer Models

Nowadays, increasing complication of the exploration objects results in thehigher precision demands in modern oil exploration. 3D seismic exploration is beingused more and more widely to improve the image effect in industry. The rationality ofthe 3D acquisition geometry has the direct relationship with the quality of thesubsurface' image. How to design a 3D exploration geometry is a very important issuein modern seismic exploration.Double-focus acquisition evaluation is based on WRW model and guided byprestack imaging quality of target points. WRW model divides the seismic wavepropagation as five independent process, which are: sources explode, seismic wavepropagates downward, seismic wave reflection at the subsurface, seismic wavepropagation upward and receivers acquisition. Detector focus beam and source focusbeam are defined. The former one is got by focusing the seismic wave field with focalsource operator and then downward continuing the result to image subsurface. Thelatter one is got by focusing the seismic wave field with focal detector operator andthen downward continuing the result to image subsurface. They reflect the influenceon the image resolution of the object from detector and source. Double focus beam isthe product of the two beams.This dissertation simplifies the double-focus resolution algorithm based onseismic ray theory. First, the response of the target point at the surface is calculatedaccording to seismic ray theory, which is called CFP gather. Then the CFP gather isfocused to the target layer by downward extrapolating, getting the focus beam. Thismethod is proved to be effective and accurate by theory and actual models, and hassignificance in practical application.The examples of this dissertation shows that the image result would be better andthe side lobe would be suppressed when the detectors and the sources of theacquisition geometry is dense. If there is a geologic structure with dip angle, theenergy around the target object would drift toward the tendency of the structure. Thisregular would be more significant with the acquisition geometry more sparse.