Emerging Technologies For SAGD Drilling And Production

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Abstract SAGD, as originally conceived, consists of two parallel horizontal wells, one drilled directly above the other. Steam is injected into the upper well, forming a steam chamber. The heavy oil or bitumen is heated, reducing its viscosity, then drains by gravity, along with the condensed steam, to the lower well. Several other variants exist, including vertical injectors, and single well SAGD. Conventional, aggressive, heavy oil production methods have been labeled "poor reservoir management." In general, 80% of the reservoir energy is expended to produce 20% of the oil in the reservoir. "80/20 Rule"(1). SAGD stands out as an enticing and economically viable development method for operators holding heavy oil and tar sand properties worldwide, even in the current climate of lower heavy oil prices. Recoveries of 55 to 80% OOIP are possible, compared with 5 to 15% for conventional recovery methods, and 18 to 30% for enhanced thermal recovery methods. SAGD production rates of 200 to 1,400 bbl/day have been recorded compared with 0 to 100 bbl/day for non-thermal recovery in the same fields. Both factors combine to achieve production cost reductions of 30% or more. Drilling and completion costs generally run around 20% of the total cost of the project. "SAGD is very, very profitable when applied in the right reservoir." The challenge for SAGD technology lies in finding the right reservoir. This challenge holds true whether SAGD technology is applied to undeveloped areas of the reservoir, or when SAGD is used to clean out oil left behind by less efficient recovery processes. SAGD History 1978 - Imperial Oil drilled the first Hz SAGD well in Canada at Cold Lake. 1987 - AOSTRA lead the way in proving out the concept of twin well SAGD by drilling three 50 m SAGD pairs from a horizontal mine tunnel at the UTF site near Fort McMurray. 1993 - Surface drilled SAGD well pairs. Two well pairs were drilled for Shell Canada at Peace River, and one for Amoco at Wolf Lake. 1995 - First commercial scale SAGD project. CS, now Pan Canadian Resources, drilled and completed three well pairs at Senlac, Saskatchewan. 1998 - Sperry Sun Drilling Services has successfully drilled 44 SAGD well pairs worldwide to date. Technological Advances With conventional SAGD, large quantities of steam are required for production. By injecting approximately 1% of a noncondensable gas, along with the steam, steam requirements are drastically reduced.Laboratory experiments indicate a reduction in steam requirements on the order of 25% (2). An industry funded research project is currently underway involving eight companies and GravDrain Inc. Drilling and Production Issues With cold production of heavy oil, 1,000 m horizontal sections are common and multilateral wells with up to 8,000 m of horizontal section exist. However, with SAGD, horizontal lengths of more than 500 m have proven difficult to manage for two reasons. If product lifting cannot keep up with production, SAGD efficiencies are drastically reduced because hot water, being less viscous than oil, is produced preferentially. Second, establishing a uniform steam chamber in pairs longer than 500 m has proven difficult.