Some Like It Hot

There is a lot of buzz about the Marten Hills Clearwater Heavy Oil play. And for good reasons. The play is extensive and has intriguing cost structure and reservoir attributes (5-25 m net pay, 20% to 30% effective porosity, 50% oil saturation, 5 to 500 milli-darcy permeability, and <300 cp. oil viscosity) low FD&C costs (in the order of $C10/bbl). this play is competitive with any other play in the Western Canada Sedimentary basin. Even more so when compared to the high cost structure of the East Shale Basin Duvernay and other tight oil plays.

One amazing aspect of this play is its location. This play lies along the southwestern fringe of the Athabasca Oil Sands area in which the same formations need to apply the much costlier Steam Assisited Gravity Drainage (SAGD) process to achieve commercial production. The otherwise puzzling producibility of this heavy oil can be understood in the context of Darcy's Law:

where Q = Flow Rate, k = Permeability, A = Cross Sectional Area, mu = Viscosity and dp/dx expresses the pressure drop from the formation to the wellbore. Given the reservoir characteristics, viscosity is the most important factor in heavy oil plays, followed by the pressure drop. The lower the viscosity, the better the production. The higher the reservoir pressure the better the production. And the more prone the formation is to produce oil the less prone it is to produce water due to relative permeability effects. Hence, higher formation temperatures contribute to lower Water Cut.

Crude oil viscosity varies logarithmically with formation temperature as illustrated by the graph below:

Being able to map out formation temperature is obviously a significant tool for these plays. But the oil viscosity also varies geographically and stratigraphically. So you need a method to map out the variation in viscosity by temperature and formation. Enlighten has been working on a process on how to do exactly that.

And we are making the results available through the newly launched Upper Mannville Heavy Oil, Geothermics and Hydrodynamics study.