Predicting the performance of in-situ recovery processes in the McMurray Formation is required to optimize development planning and resource management. These performance predictions are sensitive to many parameters; however, vertical permeability is perhaps the most critical geological parameter. There are many challenges associated with the estimation of vertical permeability:
it is difficult to collect representative core measurements,
the high viscosity of the bitumen makes it impossible to perform well testing,
statistical approaches and the notion of representative elementary volumes (REVs) are challenged by heterogeneities at all scales, and
the nature of the heterogeneities is variable within different depositional environments.
This paper summarizes these challenges, then presents a consistent numerical modeling framework based on core data, core photographs, conventional well logs, high resolution image logs and detailed geological interpretation. The framework includes: dividing the stratigraphic column into facies with similar spatial arrangement of sand/shale, constructing high resolution models of sand/shale, assigning porosity and permeability to sand/shale, calibrating the models to direct measurements, solving for effective horizontal and vertical permeability at the appropriate scale and transferring the results to geomodeling. This framework is described in detail and demonstrated with illustrative examples. Considerations for even better results are discussed.
The McMurray Formation contains a vast resource of heavy oil. The economic production of this heavy oil often makes use of thermal processes to reduce viscosity and horizontal wells that have a large contact area with the formation. Steam is often injected to introduce thermal energy. The rates of steam rise and water/oil drainage are predicted by flow simulation. A critical input parameter in that flow simulation is the vertical permeability. Accurate prediction of fluid flow would permit optimization of the recovery process and operating parameters; thus, accurate estimation of vertical permeability is of great interest in the McMurray formation.
The ability of the reservoir formation to transmit fluids (permeability) has a large affect on the reservoir response for given operating conditions. Permeability is a constant that relates the flow rate through a porous medium to an imposed pressure gradient. Small scale variations in the clastic deposits of the McMurray cause permeability to be variable and direction dependent. Permeability in the vertical direction is of primary concern because operators are concerned with (1) the rise of steam through the formation, (2) the possible escape of steam and thermal energy to overlying formations, and (3) the rates at which condensed water and oil will drain to horizontal production wells.
This paper is concerned with absolute vertical permeability. There are important confounding effects that are not considered such as changes to permeability because of multiple fluids present in the formation and changes to permeability because of time varying geomechanical effects. This paper is primarily concerned with the influence of small scale geological heterogeneities on the estimation of vertical permeability.
The challenges that make the reliable estimation of vertical permeability will be reviewed. Historical approaches to permeability estimation will be summarized.