INVESTIGATING AND MODELING FLUID AND RESERVOIR ROCK HETEROGENEITIES OF AN OIL SANDS RESERVOIR, A CASE STUDY FROM WESTERN CANADIAN SEDIMENTARY BASIN

Oil Sands of Northern Alberta is the largest unconventional resources in North America, but it is usually highly heterogeneous reservoir, making it very challenging to produce from. The McMurry formation of lower Cretaceous age in Western Canadian Sedimentary Basin is characterized by highly heterogeneous strata that have been attributed to fluvial, estuarine and/or deltaic depositional settings. It is mainly composed of siliciclastics; interbedded Sandstone, Siltstone units, breccia at channel lag and shale-mud lamination/layering to form Inclined Heterolithic Stratification. Understanding the reservoir heterogeneities (from both rock and fluid point of view) is paramount for a successful development and production strategy.

We have tried to take a multi-disciplinary geology and engineering approach in order to integrate seismic, well log, core and organic geochemistry data to be able to create realistic, geologically sound, high resolution 3D reservoir model reflecting depositional, sedimentological and geochemical interpretations for the middle McMurry formation of Long Lake project located in Canada’s Athabasca oil sands deposits. Such a model improves reservoir simulation results and helps to develop better production designs with higher recovery factors form the oil sands.

A point bar model that evolved through lateral channel migration is created from seismic time slices to build reservoir architecture. Facies model is obtained by use of core log data and sedimentary structures (physical and biogenic) present. A fluid model to address bitumen heterogeneity and define compartmentalization of reservoir elements is created through molecular geochemistry analysis of core extracted bitumen and viscosity measurements. It helps to understand reservoir continuity and is important to the efficient placement of injector and producer well pairs during thermal process production design. Permeably and porosity values calculated and populated from grain size distribution, core and log data. Geo-model is created in Petrel software, up-scaled and imported for thermal simulation of a SAGD process in CMG simulator. Different well geo-tailoring patterns were simulated to determine optimized production configuration with the fluid and reservoir rock heterogeneities considered into the model.