Steam Assisted Gravity Drainage = SAGD “Steam-assisted gravity drainage (SAGD; “Sag-D”) is an enhanced oil recovery technology for producing heavy crude oil and bitumen. It is an advanced form of steam stimulation in which a pair of horizontal wells is drilled into the oil reservoir, one a few metres above the other. -wikipedia
Fine solids resulted from formation cuttings were contaminants that mostly caused unstable mud performance. Combination of batch drilling sequence and unsuitable solids removal treatment, led to fine particle accumulation. This is one of the root causes of excessive torque and high ECD throughout the drilling operation.
From drilling fluid properties point of view, it is beneficial to minimize drilled solids content. This can be achieved by mechanical treatment, chemical treatment, dilution, and/or mixing new mud. All the above methods, will lead to additional cost impact. Thus, utilization of proper solids removal was required to balance between mechanical treatment and dilution method to reduce solids at acceptable cost.
The gypsum-salt formations are complex in drilling fluid. The gypsum-salt formations are characterized by salting-in property, plastic creep and anisotropy. Meantime, the rheological properties of drilling fluids become worse when contaminated by high pressured brine in the gypsum-salt formations. In the process of drilling operation in the long-section gypsum-salt formation, reasonable mud weight and good rheological properties of drilling fluids should be used to ensure the safety drilling in this complex formation. The main matters needing attention is as follows: