ABSTRACT: Reservoir Characterization for Chevron's HASDrive Field Trial, Athabasca Oil Sands Area, Northeastern Alberta, Canada

Richard G. Chalcraft, Chris W. Grant

Chevron is currently field testing an in-situ thermal recovery process termed Heated Annulus SteamDrive (HASDrive) on the Lower Cretaceous Athabasca tar sand deposit at the Alberta Oil Sands Technology Research Authority (AOSTRA) Underground Test Facility (UTF) site. The HASDrive process applies heat through a subsurface horizontal pipe to the base of the bitumen-rich reservoir sands of the McMurray Formation. A vertical steam-injection well aids in mobilization of the heavy crude and sweeps hydrocarbons toward a horizontal subsurface producing well.

To evaluate the HASDrive technology, a geologic model was developed to predict the distribution and geometry of reservoir sands and intervening shales. Core studies indicated deposition took place in an estuarine environment, with sands representing tidal channel deposits and shales relating to tidal flat sedimentation.

A thorough program of conventional and special core analysis was done on samples from five wells. Special core analysis consisted of miscibly cleaning samples prior to determination of brine permeability. Vertical and horizontal permeability were determined for massive to cross-bedded sandstone as well as four types of shale-bearing sandstone. Of these four, thin shale beds and shale breccia were more effective in reducing permeability and may form barriers to fluid flow. Thin discontinuous shale laminae or shaly wisps merely impede flow.

Interactive workstation programs used core and log data petrophysical parameters as input to build a simulator grid of 2600 blocks in 10 layers to represent a field trial area of approximately 2000 m². Potential barriers capable of preventing or reducing the flow rate were identified, incorporated into the model, and treated as dimensionless shales (i.e., shaly beds with negligible thickness). The simulator model was then used to the match history of field trial fluid production.

AAPG Search and Discovery Article #91003©1990 AAPG Annual Convention, San Francisco, California, June 3-6, 1990