Heterogeneity of Deltaic Reservoir Predicted from Modern Marine Brazos Delta, Texas, USA

Naofumi Sakuyama, Tomohisa Kawamoto, Masaru Nakamizu

Brazos Delta in Texas, which has been deposited since 1929 man-made diversion, is very young and active delta in Gulf of Mexico.

Detailed sedimentary processes of single delta lobe in study area is very well visualized based on dense core sampling, bathymetric survey and high resolution acoustic profiling survey in very shallow (surface to 25m) water area. The scale observed in modern marine delta should be used for describing heterogeneity of ancient deltaic sediments, because all of thick deltaic sequences are considered as an amalgamated delta lobes.

Sediments in Brazos delta lobe is classified into 14 lithological units based on core observation. Particle size distribution and mineral composition of each units were analyzed for characterizing their physical properties. Characterized properties were compared with sedimentary processes and the relationship of neighbored units are considered with several examples. The distribution of each lithological units suggests detailed heterogeneity of single delta lobe in a 3-dimensional view.

Additionally, for applying modern sediments into ancient rocks as an analogue, it is also important to understand evolution of sediments in burial process. In this study, porosity and permeability of each lithological units are predicted based on the experimental data (Beard and Weyl, 1973 and Pittman and Larese, 1991).

AAPG Search and Discovery Article #91020©1995 AAPG Annual Convention, Houston, Texas, May 5-8, 1995