Static Corrections Study And Its Application In Deep Sahara Desert

For land seismic exploration for hydrocarbons, Static Corrections for seismic reflexion data has long been one of the hottest and yet to be properly solved research and application issues, and might be the top, sophisticated and frustrating issue for oil companies. As the near-surface conditions grow more complicated for exploration, the issue becomes more important than ever. CNPC's risky exploration concession in deep Sahara desert in Niger is one of areas. A good estimate of statics in these areas facilitates the imaging of reflexions, and may avoid mis-interpretations of geological structures. Therefore the study to resolve the statics problem is of great importance.(a) The dissertation is funded by CNPC's exploration and research project in Niger, mainly for the reflexion illumination problems in the newly acquired and the vintage seismic data in the area. Statics contributes a major part to the problem, among other reasons. After careful investigation of the static corrections methods available, the near-surface structure and the characteristics of the problematic seismic data, a systematic study of constrained tomostatics method and other static corrections methods is conducted, through which the following are achieved: based on the study of the constraints for tomostatics, a combined constraints involving uphole data, logging data, surface and LVL bottom correlation data in some areas, and even gravity data is proposed to control the tomographic inversion, and successful application is seen;(b) The first statics and near-surface model database is proposed and established, and plays a dominant role in the successful processing of the vintage data, the effective application is coducted;(c) The serious statics and imaging problems of the massive vintage data in the area are tackled with satisfactory results, which relives these vintage data to service the new round of exploration;(d) A new Sand dune curve method for static corrections incorporating realsurveying data, uphole data and many near-surface model data is proposed and applied to the new and vintage seismic data in the area, and proves successful;(e) Some research on and analysis of the impacts of statics on the phase and frequency of seismic signals are also carried out, and the inspection and verification of static corrections scenario for practical use is presented.Real application shows that the methods and approaches proposed and studied in this dissertation are suitable and effective for the statics and also the imaging problems presented in both new and vintage seismic data in this deep desert area in Sahara. And they might be useful for tackle the same problems in similar area with complex surface and subsurface conditions.