Effective Sand Prediciton Method On Thin Sand With High Velocity In Continental Facies

In the continental facies strata with good consolidation,sand velocity is usually higher than shale velocity,and the velocity of effective sand is between that of shale and sand.Due to the impact of complex structural background,sedimentary environment and diagenism,the information of effective reservoir is always concealed by non-reservoir information.The accuracy of effective reservoir prediction decides the risk and cost of the subtle oil&gas exploration and development.Aiming at Dai 1 formation on abrupt slope in southern Gaoyou Sag,based on petrophysics-geologic modeling-seismic forward modeling,reservoir and non-reservoir elements were studied.Under the guidance of geologic contributing factors,effective reservoir information was acquired,and effective sand prediction technique series was set up.The outcome is as follows:(1)According to the importance for seismic response,ranking of reservoir and non-reservoir factors is: impaction and solidation,sedimentary cycle,lithology,porosity and fluid(former are more important).(2)Integrated with petrophysical forward modeling and practical drilling data,the impact of lithology,porosity,fluid,depth and sedimentary cycle on rock elastic parameters was quantitatively analyzed,and reservoir parameter interpretation templates for different sand groups were established.(3)Integrated with seismic forward models and practical seismic data,the relation between reservoir parameters and seismic amplitude,phase,frequency and waveform were analyzed,and sensitive seismic attribute was confirmed.(4)Aiming at the lateral facies variation and uneven well distribution,the process of facies controlled-log constrained inversion was established to make the inversion results in accordance with geological rules.(5)Aiming at problems of multiple sedimentary cycles,big depth variation,sand-shale velocity overlap,the step by step petrophysical interpretation technique was set up to get rid of non-reservoir information and predict reservoir parameters quantitively.(6)Optimize the geostatistics inversion process,thus the method could adapt to exploration area with few well control,and could improve the vertical resolution of the reservoir prediction.(7)Aiming at different geologic and seismic condition,subtle oil pools such as Xiao15,Zhou64,Shao23 and Huang166 were discovered.