Abstract
An openhole multistage completion required selective fracture stimulation, flow control, and sand control in each zone. An openhole multistage completion was designed by combining a production sleeve integrated with sand screens and inflow control devices and a fracture sleeve with high open flow port. The system was designed to use a ball drop to isolate the bottom intervals while fracturing upper intervals. After fracture stimulation, the fracture seat/ball needed to be milled. The production sleeve were designed to be shifted to the open position and the fracturing sleeve to the closed position through mechanical shifting tool to put the well on production. The fracturing sleeve and the production sleeve were located close to each other and a successful shifting operation needed an appropriate shifting tool, with a real-time downhole telemetry system that met the temperature limitations while providing accurate depth control, differential pressure readings, and axial force (tension and compression) measurements.
Hydraulic-pressure-activated shifting tools were used to manipulate the sleeves. A coiled tubing (CT) rugged downhole tool with real-time telemetry was used to run the shifting tools. Yard tests were conducted to identify the optimum rates and pressures to actuate the hydraulically activated shifting tools and study their behavior. The expansion of the fracturing sleeve shifting tool keys initiated at 1.6 bbl/min (400 psi) and the keys were fully expanded at 1.8 bbl/min (600 psi), whereas the expansion of production sleeve shifting tool keys initiated at 0.3 bbl/min (700 psi), and the keys were fully expanded at 0.4 bbl/min (900 psi). During the design and planning of the shifting operation, simulations were conducted, and surface and downhole tools were selected carefully to ensure the CT could provide enough downhole upward force (5,000 to 6,000 lbf) to close the fracture ports and 2,000 to 4,000 lbf to open production sleeves.
Following the fracturing operation, the first CT run aimed to mill fracture seats/balls to clear the path for the subsequent shifting operation. In the second CT run, all the fracturing sleeves were shifted to the closed position while production sleeves were shifted to the open position. The CT rugged downhole tool proved critical for depth correlation and accurate placement of the shifting tools. The real-time downhole acquisition of differential pressure across the toolstring also allowed operating the shifting tools under optimum conditions, while downhole force readings of tension and compression confirmed the shifting of completion accessories.
Two fracturing sleeves were shifted to the closed position at 2.4 bbl/min and 700-psi downhole differential pressure, with the downhole weights of 700 lb and 1,000 lbf. Three production sleeves were shifted to open position at 0.6 bbl/min and 1,200-psi downhole differential pressure, and the maximum surface and downhole weights recorded were 73,000 lb and 19,200 lb, respectively. That operation led to sand-free production and confirmed the success of the first multistage completion enabling fracturing operation and controlling sand production in Saudi Arabia.
This study describes the use of real-time downhole measurements and their significance when surface parameters do not give clear indication of shifting. It also features the first-time use of two hydraulically activated shifting tools operated during the shifting operation in Saudi Arabia's first multistage completion enabling fracturing operation and controlling flow/sand production.
