AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Seismic-Sedimentologic Interpretation of Fluvial Sedimentary Architectures: We Should Focus More on Development Scale
(1) Georesource and Information School, China University of Petroleum, Dongying, China.
(2) Bureau of Economic Geology, University of Texas at Austin, Austin, TX.
When people focus on exploration of thin beds, problems in developments of thick fluvial reservoirs require more attention. “Homogeneous” thick sandstone on exploration scale are heterogenetic on reservoir development scale. This study shows why and how we make seismic-sedimentologic characterization of thick fluvial reservoir architectures.
Seismic forward modeling and outcrop study with ground penetrating radar (GPR) are employed to study the reflection characteristics of different fluvial architectures. Thickness and sedimentary architectures of sandstone are considered. And then the results from outcrop study and seismic forward modeling are used in the well-seismic integrated fluvial reservoir characterization in Tiger Shoal, Gulf of Mexico. What stratal slices tell us and how to identify real geological information from seismic data are focused in the real seismic data study.
The characterization of point bar complex in Tiger Shoal shows (1) two phases of river depositions developed in the study unit, (2) a wide distributed thin shale layer deposited between them, (3) lateral migration and reconstruction of rivers make depositions of each sedimentary phase complex.
It can be concluded that (1) thickness, sedimentary architecture and seismic frequency are the three important factors influencing on reservoir’s seismic reflections in fluvial thick reservoirs; (2) stratal slice tells us more sedimentary information than what seismic sections do; (3) for the same sand body, seismic reflection geometries may change with frequencies. What seismic data we need in seismic-sedimentologic interpretation is not the one with highest main frequency but the one with ‘proper’ frequency; (4) stratal slice is not a picture of reservoirs as what satellite images is for modern deposition. So it needs a different interpretation method. It is important to identify real information from the fake like shadow channels on slice.