川东南涪陵地区石炭系黄龙组地震异常特征及其意义

CHARACTERISTICS AND IMPLICATIONS OF THE SEISMIC ABNORMAL RESPONSES OF CARBONIFEROUS HUANGLONG FORMATION IN FULING AREA,SOUTHEASTERN SI-CHUAN BASIN

涪陵地区位于川东南探区北部,通过该区石炭系黄龙组地震剖面测线逐条解释,识别出了四种典型异常反射结构:①地震同相轴波峰、波谷均表现为中振幅～弱振幅;②地震同相轴下拉波峰振幅有强有弱,上部波谷反射呈现强振幅～中振幅;③地震反射同相轴明显下拉,同时下拉同相轴上部反射呈现中振幅～弱振幅、下部反射振幅减弱;④地震同相轴反射为弱振幅,近空白反射或弱波谷反射。基于岩溶单元发育理论模型及该区沉积特征,对四种典型地震剖面反射异常地质成因解释进行了地球物理正演模拟,结果显示了与实际典型地震反射结构相吻合的地震剖面特征。其分别代表了岩溶高地峰丛与浅洼发育;被泥质充填或半充填的溶洞或孔隙性非常高的储层发育;高泥质含量充填物,或低速度、未被完全充填的缝洞体发育;7 m～9 m及以下的黄龙组地层。同时,基于特殊剖面结构研究成果,对该区可能发育的新型储层类型进行了预测,有效地指导了该区下部油气有利储层的寻找。

Fuling area is located in southeastern Sichuan basin.Through carefully seismic interpretation of Huanglong formation of carboniferous in Fuling area,there are four typical seismic responses in reflecting structure as follows:①The amplitude of both peak and trough of seismic are medium to weak.②Peak amplitude with phase axis pulled down present as strong or weak,and above trough amplitude is high to medium.③Seismic phase axis is pulled down clear and the amplitude is medium to weak,and amplitude is weakens lower with the seismic phase axis pulled down clear.④Seismic amplitude is weak and close to nil trace.Based on the theoretical models of karst u-nits developing and sedimentary characteristics in this area,the four seismic responses in reflecting structure which we mentioned above probably means four differ-ent geologic origins,which respectively represented:A.developing of karst positive topography and karst negative topography;B.developing karst caves that are filled by mud completely or certain mud or developing high-porosity reservoirs;C.developing fissures and caves that are filled by much mud or not entirely filled that performances low speed in seismic profiles;D.identifier of Huanglong formation which is deposited seven to nine meters or the sediment thickness is less than that.Meanwhile,the seismic forward mod-eling for the four geologic origins is matching for the four typical seismic responses in reflecting structure well.All those study results based on specific struc-ture in seismic profiles can be used to predict the new type of reservoirs and effective to search for new alter-native exploration zones for more gas discovery in Ful-ing area.