A major issue for the deepwater high-rate gas completions in the Simian/Sienna field off the coast of Egypt was the placement of an effective sand-control completion in the presence of highly reactive shales. Analysis showed the most productive completion method to be an openhole completion. However, this presented a challenge, as the shale encountered during the drilling phase was very reactive and could destabilize during completion equipment placement or during pumping operations such as gravel packing.
One of the most concerning obstacles of open hole gravel packing is exposed reactive shales that can destabilize. If the shale section of the wellbore swells or flakes off, they can prevent running of the gravel-pack assembly to bottom, plug screens and/or collapse into the wellbore to prevent complete gravel placement. Isolating the shale section behind casing will solve the problem; however, this process most often means having to reduce the screen size to be used, which may impede production.
A completion design using two newly developed technologies and other carefully selected proven techniques was applied to minimize the risks of shale instability. A new design of an alternate path screen system was chosen because of its ease of assembly, ability to transport gravel-pack slurry past annular blockages such as collapsed shales and its minimization of slurry exit velocity from the alternate path tubes while packing. Another new technology that was selected for application was the use of a non-ionic visco-elastic surfactant to transport the gravel-pack sand downhole. This fluid was chosen for its shale stability properties, excellent sand suspension properties and the high-return permeability characteristics of the fluid. Application of these technologies and observing other best practices mitigated the risks associated with gravel packing in an open hole in the presence of reactive shales.