Abstract: Fractured Reservoir Analysis of a Horizontal Well Completion: Viola Ls, Marietta Basin, Oklahoma

Magell P. Candelaria, Brian P. Roux

Analysis of Viola Ls production in Marietta Basin of Jefferson and Carter Counties, Oklahoma is indicative of strong fracture control on reservoir performance. A horizontal well was drilled to test fracture susceptibility and productive capacity from the lowermost 100-150 feet of Viola Ls in Marietta Basin. Reservoir potential of the basal Viola was considered favorable due to abundant secondary silica content which is conducive to brittle deformation. Matrix permeability within the basal Viola is very low (<0.001 md), however due to the siliceous nature of this zone it was thought to be fracture prone along faults and flexures.

A horizontal well was completed openhole with approximately 1000 feet of borehole open to reservoir in the basal Viola. Production data and reservoir performance analysis from the horizontal well was modeled with a dual porosity reservoir simulator. The reservoir model was calibrated to match actual well performance. As predicted, production on pump remained constant until the fracture system was depleted. Matrix permeability was inadequate to feed the fracture network and sustain economic production rate.

Reservoir properties fundamental to successful horizontal Viola completions are fracture spacing, fracture aperture, vertical and lateral fracture extent, and adequate matrix permeability to sustain flow to the fracture network. Simulator results and production forecasts indicate the majority of production will be made very early in the history of a fractured reservoir completion. Thus, critical elements to a successful horizontal well completion are minimizing drilling costs and identification of areas with better fracture-matrix permeability by very selectively choosing drill sites.

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994