Development and Field Results of a Unique Drilling Fluid Designed for Heavy Oil Sands Drilling

Abstract Drilling Heavy Oil Sands are traditionally fraught with many technical challenges. Stability of the wellbore, accretion of the tar on drill string and solids control equipment, torque-drag considerations, extreme temperature conditions, as well as the handling of oily solids are just some of the challenges that need to be met. This paper describes the development and testing of a new drilling fluid designed to meet these challenges. The water-based fluid is based upon two guiding principles, the ability to incorporate the bitumen into the mud itself, and the capability of the system to later break the bitumen from the mud system. Incorporation of the bitumen into the mud is via a direct emulsification and results in zero accretion, virtually oil-free sand from the solids control equipment, fast drilling rates and good hole stability. The post drilling breaker allows for the oil/bitumen/tar to be skimmed from the surface of the drilling fluid allowing for conventional disposal of the liquid fraction. Data from a six well horizontal heavy oil program in Northeastern Alberta shows the robustness and effectiveness of the system. The new oil in water direct emulsion system drilled 1100 meter average horizontal wells 35% faster, when compared to conventional inhibition salt technology based drilling fluids. Highlights include sand from centrifuging operation containing < 0.5% oil, elimination of accretion and common foaming problems, fluid reuse from well-to-well, as well as simple land disposal of liquid mud wastes. Total well costs, drilling fluids costs and disposal costs were significantly less than those wells drilled with conventionally inhibited drilling fluid systems.