The Seismic Techniques For Exploring Marine Facies Stratigraphic Hydrocarbon Entrapped In The Middle Uplift Of The South Yellow Sea

The exploration of carbonate hydrocarbon entrapped at Mesozoic—Palaeozoic depositing at South Yellow Sea started lately and corresponding seismic exploration technique development was poor, which prevented the development of seismic exploration.The remarkable improvement have been obtained on seismic exploration of marine stratigraphic depositing in the middle uplift of South Yellow Sea through resent studying on exploration theory, forward modeling and key prospecting techniques. The main studies included of seismic reflection research, maring acquisition technical research and practice, multiple mechanism and pressing research, modeling on seismic stacked velocity and fine velocity analysis and the key techniques applied to improve the poor quality of deep seismic reflection, as a result a series of techniques have been built applied to the exploration of marine stratigraphy depositing in Mesozoic—Palaeozoic in the middle uplift of South Yellow Sea.Four new innovations and techniques had been got through studying key project and making practices.1 The synthetic modeling techniques for analyzing seismic reflection charactersIt firstly used Zoeppritz function, Snell law and absorption attenuation regular of seismic wave propagating, full wave equation and seismic physical model experiment to make seismic reflection characteristics calculated theoretically, analogizing in digital and in physical, so the dominant factors controlling Mesozoic—Palaeozoic strata reflection had been summarized and it had been concluded that long layout and multiple coverage could be used to obtain better quality seismic acquisition data and correct stacked velocity could ensure improving the seismic section quality.2 The techniques for designing and evaluating marine seismic acquisition parametersThe relationship of wavelet character parameters, which was resulted from different optimum depth of air gun and streamer, dependent on penetrating power and propagation distance had been studied and analyzed. And then the every wavelet characters parameter, especially energy, dominant frequency, minimum safeguard frequency, maximum safeguard frequency and wavelet forms, should be considered according to different seismic prospect target to select suitable source wavelet.The acquisition parameters had been obtained for exploring marine stratigraphy through theory studying and marine testing to verify the theory modeling for seismic wavelet parameters correct. The parameters obtained were consisted by long layout, multiple coverage, deeper depth locating air gun and streamer. It had been resulted that the effective reflection could be acquired if the line was parallel or approximlately parallel to the trend of the structure.3 The technique for analyzing velocity basing on velocity character modelingThe seismic velocity and multiple mechanisms had been firstly modeled and analyzed through logging velocity calculation and analysis. The stacked velocity change regulars had been observed through studying abrupt velocity change and multiple generated in horizons. The high velocity formations and multiple generation and their effects on stacked velocity had been then analyzed to found that the refractions velocity induced at T2 interface is key for defining stacked velocity and reflection quality and multiple development. It was suggested that the T2 interface refraction velocity could be used to guide seismic velocity analysis. The workflow for velocity analysis, multiple pressing and DMO dip correction had been configured.4 The key processing technique for emphasizing deep poor reflection The factors influence on quality of seismic data acquired at Yellow South Sea had been analyzed. The key techniques for processing seismic data acquired at Mesozoic—Palaeozoic strata depositing at Yellow South Sea had been developed, which were consisted of multiple study and identification, multiple pressing developed by ourselves named high accuracy paracurve Radon transform, velocity analysis on velocity characters modeling, deep poor energy improvement and accurate imaging migration.The remarkable exploration improvement had been obtained through method study and production practice. The effective reflection from marine strata with clear wave group character and high ratio of signal to noise had firstly been acquired at the middle uplift, which had provided data base for marine strata hydrocarbon prospecting in Yellow South Sea.