Reservoir Models for Meandering and Straight Fluvial Channels: Examples from the Travis Peak Formation, East Texas

DAVIES, DAVID K., David K. Davies and Associates Inc., Kingwood, TX, BRIAN P. J. WILLIAMS, University of Aberdeen, Aberdeen, Great Britain, and RICHARD K. VESSELL, David K. Davies and Associates Inc., Kingwood, TX

Reservoir models for meandering and straight channel systems have been developed from analysis of cores and logs using knowledge of channel style, depositional environment, and diagenesis. Predictions of reservoir dimensions in the Travis Peak Formation are based on geologic modeling and supported by production test data from Gas Research Institute staged field experiments. Two channel styles existed simultaneously during Travis Peak deposition: (1) high-sinuosity (meandering) channels and (2) low-sinuosity (straight) channels. Each was restricted to a specific geographic area of east Texas, a result of the long-term stability of the loci of sediment input into the ancestral Gulf of Mexico.

Reservoirs that developed in high-sinuosity channel systems consist of a volumetrically small compartment characterized by high permeability and low area (compartmentalized point bars, 10-150 ac) and a volumetrically large compartment characterized by low permeability and high area (overbank splays > 640 ac). Original depositional environment controls the number and distribution of megascale heterogeneities (dominantly shale breaks) and the overall reservoir quality of each compartment. Reservoirs that developed in low-sinuosity channel systems are lithologically homogeneous and lack internal, megascale heterogeneities. These reservoirs consist of one single, high-volume compartment (channel and splay sands) that covers large area (> 5000 ac). Because of extensive diagenesis, th s single reservoir compartment generally has low permeability.

Effective permeability to gas (KEG) is a function of porosity and specific depositional environment. For any given porosity, KEG is particularly sensitive to changes in depositional environment. A detailed knowledge of depositional environment and channel style is of critical importance in predicting economically viable reservoirs in fluvial sandstones.

AAPG Search and Discovery Article #91006 © 1991 GCAGS and GC-SEPM Meeting, Houston, Texas, October 16-18, 1991 (2009)