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Exploration of Subtle Reservoir on the Wing of Central Structure Ridge in Huanghekou Depression, Bohai Bay Basin, Eastern China


The Huanghekou depression located in the southern coast of Bohai Bay Basin, was an important exploration area. As the exploration extent advances on the wing of central structure ridge in Huanghekou depression, the structural traps could be smaller and the object for exploration began from structural trap to lithologic -structural trap, then to subtle trap. Furthermore the subtle trap exploration has become increasingly important. This study focuses on Neocene lower Minghuazhen formation layer in the north of Huanghekou depression. We depicted one of the main sand bodies combined with a variety of geophysical methods, comprehensive analysis of the fine sequence stratigraphy and extremely shallow delta sand body over the same period in the area. In order to discuss the petroliferous property of those sand bodies, we had been comprehensively analyzed the oil-water relationship with drilling. Then found the abnormal oil-water relationship was that water in high position of structural and oil-water layer in lateral positions. So we were predicting that maybe a small hidden fault existed between high and lateral in the sand. we confirmed the faults by using of the application of coherence technique, pre-stack time migration technique and 90°phase shift technique. Because of this fault segmenting the oil-water relationship in the same sand, it formed the complex oil-water relationship. Based on the interlayer faults identification technology, geophysical prospecting hydrocarbon detection technique, the more mature coupling technology of faults- sand, the regularity of hydrocarbon migration and accumulation in study area, we believed that the petroliferous property of this sand was very high. Drilling practice confirmed the sand depositing oil, and the recoverable reserve was 7.5MMBOE. Using this kind of methods we have revealed multiple lithologic traps which has been achieved a good exploration results.