A major issue for deepwater high rate wells is delivering completion reliability and performance that ensures well life sand control and operational simplicity. Multi-path screen systems are designed to ensure placement of the annular gravel pack in frac pack applications by transporting proppant slurry past annular bridges or by filling voids within the pack and in open hole by bypassing areas of formation collapse. The next generation of multi-path screen technology has been optimized to reduce rig time, eliminate excessive fluid velocity and provide enhanced proppant placement by incorporating a spiral design. This paper reviews the design improvements, testing and development process for technology advancement, as well as the field installation process and results of delivering void free annular gravel placement in high rate wells.
The first field installations of the next generation multi-path screen were in the deepwater subsea development, Simian/Sienna, offshore Egypt. The application of this technology was driven by the need to have placement of an effective sand control completion in the presence of highly reactive shales. Analysis showed that the most productive completion method was an open-hole completion. This completion type was challenging given that water based fluids were to be used for drilling and completing with exposed reactive shales. The operational risks were centered around completing the wells from a floating rig while experiencing hole instability during completion equipment placement and while placing the annular gravel pack.
To ensure well life sand control, the latest state of the art multi-path screen system was chosen because of its ease of assembly, ability to transport proppant slurry past annular blockages, and the minimization of multi-path tube slurry exit velocity. For proppant transport, the latest non-ionic viscoelastic surfactant (VES) was selected for its shale stabilizing properties, excellent sand suspension and transport properties, and high return permeability characteristics.
The Simian / Sienna fields situated in the Nile Delta region off the coast of Egypt are located in the West Delta Deep Marine Concession (WDDM) in water depths ranging from 600 to 1,000 meters Figure 1. It is operated by the Burullus Gas Company, a sister company of the Rashid Petroleum Company (Rashpetco) on behalf of the Egyptian Government Petroleum Corporation (EGPC), BG and Petronas. Development of the Simian/ Siena Fields consists of 8 sub sea wells with expected gas production of each well in excess of 100 MSCFD. The wells were predrilled and cased with 9 5/8″ casing down to the production zone and then suspended Figure 2. They are scheduled for batch completion with a semi-submersible rig which includes re-entering the predrilled wells, drill through the production zone and install a sand control completion to a depth of 2000 to 2200 meters TVDSS. Due to various up hole conditions the finial casing string was set above a 10 to 15 meter layer of extremely reactive shales. This is in addition to the reactive shale interbedding with the sand section. This meant if the wells were to be completed as open hole gravel packs the 100 meter unconsolidated formation sand would need to be controlled with the reactive shale section exposed. Trying to case off the shale section by conventional means would result in reduced screen ID and additional cost. For those reasons and other operational factors casing and fraccing the formation was not considered to be the most advantageous for the sand control completion program. Given the high permeability of the formation sand, high predicted production velocity and the low rock strength of the formation open hole gravel packing was selected for the optimum sand control completion method. An open hole completion of the formation would reduce the production velocity into the well bore by increasing the exposed formation area as compared to a perforated casing. Completing the wells open hole would also maximize the screen ID that could effectively be used.