Fluvial Sandstone Reservoirs of Travis Peak (Hosston) Formation, East Texas Basin

Robert S. Tye

Gas production (7.2 billion ft³) from low-permeability sandstones in the Travis Peak Formation, North Appleby field, Nacogdoches County, Texas, is enhanced through massive hydraulic fracturing of stacked sandstones that occur at depths between 8,000 and 10,000 ft. Stratigraphic reservoirs were formed in multilateral tabular sandstones owing to impermeable mudstone interbeds that encase blocky to upward-fining sandstones. Pervasive quartz cement in the sandstones decreases porosity and permeability and augments the reservoir seal.

Subsurface data indicate that much of this 2,000-ft thick section represents aggradation of alluvial-valley deposits. Multiple channel belts form a network of overlapping, broad, tabular sandstones having thickness-to-width ratios of1:850 (8-44 ft thick; widths exceed 4-5 mi). Six to eight channel belts, each containing 80-90% medium to fine-grained sandstone, can occupy a 200-ft thick interval. In a vertical sequence through one channel belt sandstone, basal planar cross-bedding grades upward into thinly interbedded sets of planar cross-beds and ripple cross-lamination. Clay-clast conglomerates line scoured channel bases. Adjacent to the channels, interbedded mudstones accumulated in well-drained swamps and lakes. Poorly sorted sandstones represent overbank deposition (crevasse splay and lacustrine deltas). During Travis Peak deposition, fluvial styles evolved from dominantly braided systems near the base of the formation to more mud-rich, meandering systems at the top.

Sandstone geometry, continuity, and internal heterogeneity influence reservoir performance and well-to-well communication. Small-scale bed forms, biogenic structures, clay drapes, and scour surfaces create fluid-flow barriers and segment reservoirs. Best quality reservoir sandstone exists in wide bands oriented parallel to depositional dip. Quality decreases at channel margins (levees) and tops (abandoned channel) and in interchannel areas (shadow zones behind longitudinal bars) where siltstones and mudstones accumulated.

AAPG Search and Discovery Article #91022©1989 AAPG Annual Convention, April 23-26, 1989, San Antonio, Texas.