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Abstract Shell Canada estimates that a thin-walled, slimhole design for liner equipment can save up to $3-4 million (U.S.) per well in deep re-entry applications by allowing existing wells to ix. deepened (or sidetracked) rather than drilling new wells from surface. The design makes it possible to reenter existing wells, successfully isolate depleted zones, and deepen the well into virgin-pressured reservoirs, The design includes thin-walled, close-tolerance liner hangers, liner top packers, tie-back seal assemblies, and liner setting sleeves that provide reasonable burst and collapse resistance while maintaining an inside diameter to facilitate drilling deep, deviated 4-3/4' hole with a tapered2-7/8' × 3-1/2' drill string, The authors will explain the design and the rationale behind it, and illustrate its value, using case studies from Shell Canada's Waterton field as examples. In this field, gas-producing wells originally drilled in the 1950s, '60s and '70s to depths of up to 14,760 ft (4500 m) were completed with perforations in 7' casing and open hole, These wells are now being reentered in an attempt to tap new reserves. The reentries encounter particular y challenging sour-gas/low-temperature/diverse formation pressure conditions. The objective of the reentry program is to seal off the depleted bottom zones of the wells and tap into the same fault-repeated formations at virgin pressure, at a deeper level. Introduction Like other operating companies, Shell Canada is faced with the challenge of continually lowering its finding andproducing costs. One way of meeting [his challenge is through reentry and deepening projects, which use existing well structure to tap new zones. Reentering and deepening an existing well rather than drilling a new one eliminates a major new capital investment, resulting in drilling and construction costs potentially less than half of what they would be for a new well. Further benefits accrue if the project can be carried out using slimbole techniques, Both of these factors influenced Shell Canada's decision to undertake a reentry and deepening project in 1995 in its Waterton field in western Canada. Waterton Field Background and Project Objective Waterton field production capability has recently declined to the point where produced volumes are unable to fully utilize the Waterton Plant, particularly as a result of the near depletion of the prolific Sheet if Rundle-Wabamun'A' pool. New reserves and additional deliverability are of utmost importance in keeping the plant at capacity in order to maximize revenue and maintain low unit operating cost. The purpose of the reentry and deepening initiative was to determine whether commercially viable pools of hydrocarbons exist at the south end of the Waterton complex, beneath the Devonian Wabamun formation. |
