ABSTRACT:

When revitalizing mature oil or gas fields, the ability to maximize productivity while minimizing operating costs is critical. Achieving these goals becomes more challenging where sand control is required. This is especially true for complex reservoir lithology, which leads to a variety of fracture and pore pressure gradients and premature water breakthrough. In addition, reduced deliverability, resulting from pressure depletion presents, additional complications related to achieving acceptable project economics. The Barbara field, located in the central Adriatic Sea, is an example of this type of reservoir. For this project, a dedicated work team was assigned to identify and implement the solutions to improve field performance through continuous operations optimization. The Barbara field consists of stacked pay sections that have been depleted since the early 1980's. To achieve favorable economics, techniques had to be used that would both maximize the deliverability of each well and minimize operational costs. This paper reviews the Barbara field workover program. The evolution of techniques, equipment, and products leading to enhanced productivity while substantially reducing costs is described. The fluid systems and operation procedures designed to optimize frac-pack geometry are discussed. In addition, the one-trip multi-zone gravel pack assemblies are described that allow multiple zones to be individually frac packed in a single run, thus providing significant rig-time reductions without sacrificing completion efficiency. Finally, the complex nature of this reservoir dictates a need for a variety of completion techniques. This means that frac-packing was not necessarily an option for all zones. For the intervals where fracturing was not employed, productivity still needed to be maximized. To accomplish this goal, perforation tunnel clean up procedures have been optimized

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