【摘要】 潮汕坳陷是中生界地层为主的沉积坳陷,是南海油气勘探突破的重要领域.LF35-1-1钻井证实了潮汕坳陷存在大套中生代海相地层,但未获油气发现,在钻至目标层前钻遇了侵入岩体,凸显了中生界钻前预测的重要性.本文对收集到的一条穿越潮汕坳陷长排列地震测线资料进行了多次波压制和AVO反演处理,获得了清晰的剖面反射特征,识别了两个中生界AVO异常带.研究区中生代速度普遍较高,但折射波速度计算表明这两个异常带中生界纵波速度低于背景速度,可能具有有利储集物性条件,因此作为AVO分析的选择区.但是AVO反演的纵波速度反射率剖面上显示为很大的数值,因此异常带成岩程度较高,可能不是油气成因的异常.地震偏移剖面也显示异常区受到切穿海底的高角度断裂影响,下部反射模糊杂乱,可能还有岩体侵入的影响,都不利于油气储集.更多还原

【Abstract】 Located in the northern South China Sea,Chaoshan Depression is an important area for gas and oil exploration as a relict Mesozoic basin.Well LF35-1-1 is the only one so far drilled in northern Chaoshan Depression,which has drilled thick Mesozoic marine deposits,but without any oil show.It has drilled intruded granite before the predicted reservoir.The case further necessitates the pre-drill reservoir analysis.The Mesozoic strata here feature too high velocity as excellent reservoir rocks.Extensive multiple suppression and AVO inversion are done on a new available seismic survey line run through the northwest of Chaoshan Depression.The seismic line is of 6 km long streamer and full of refraction phases from the top of Mesozoic strata.Two zones where the refraction velocities of the top Mesozoic strata are lower than neighboring areas and remarkable AVO anomaly shows are chosen for AVO analysis.However,various AVO attributes over the zones,e.g.,P-wave reflectivity,Poisson’s ratio and AVO cross plot,show as large positive values,possibly due to high lithification,not hydrocarbon infill.Further,from the migrated profiles,the zones are found with dense high-angle faults cut through from deep to seabed,weak and chaotic reflection pattern in deep which might be magmatic intrusion.Thus,the analyzed features are unfavorable to reservoir over the worked seismic line.更多还原