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Abstract
The Upper Devonian Grosmont Formation, located in the West Athabasca Oil Sands Deposit, contains an estimated 406 billion barrels of bitumen. The reservoir is a heavily karsted and fractured, bitumen-saturated carbonate. Initial thermal horizontal well development is currently underway in this resource. These horizontal wells have similar logistics, well construction and materials challenges to those in the McMurray Formation.

Laricina has been actively developing the Grosmont Formation. Production from the pilot began in 2011 and many lessons have been learned. The next phase of development is a 10,700 bbl/day commercial project scheduled for first steam
in 2014. The Grosmont, despite many drilling challenges such as severe lost circulation, also provides many opportunities not typically achievable in clastic oil sands developments. Carbonate rock is typically a good candidate for open-hole
completions due to its geomechanical properties. This paper will discuss the geomechanical investigation evaluating borehole stability during drilling and completion, steam injection and production operations.

Introduction
In many carbonate reservoirs throughout the world, open-hole or barefoot completions are commonplace. Carbonates typically have rock properties that prevent the hole from collapsing during production operations, however the in situ stress
state ultimately dictates whether or not open-hole completions will be successful. Combined with good drilling and production practices, the success of open-hole completions in horizontal wells depends on a moderate rock strength to stress ratio, linear elastic behavior, and consistent reservoir quality.

In general, open-hole horizontal completions are implemented only in very competent, hard formations, such as dolomites, hard limestones, hard sandstones, and siltsones that pose little risk for wellbore collapse and/or fines production.

The advantages of barefoot completions are cited as:
· Lower completion cost
· Simple and fast implementation
· Potentially decreased formation damage
· Increased productivity/injectivity per unit length due to full wellbore access to reservoir fluids

The risks and disadvantages of open-hole completions may include:
· Potential for wellbore collapse
· Potential for fines production
· Increased installation risks due to higher friction factors compared to a cased hole during completions and work overs

At present, the mechanisms around wellbore stability during drilling and during production operations are well understood, and several tools and techniques readily available to analyze this situation are discussed here. The evaluation of the stability of an open-hole completion during thermal cycles requires the use of a coupled geomechanics-thermal reservoir simulator and requires detailed numerical modeling. This work is currently underway but is not included within the scope of this paper.