The Ocean Riser In-balanced Intervention System (ORIBIS) allows the Bottom Hole Pressure (BHP) to be controlled independent of flow rate through the well bore. The 7 3/8 inch High Pressure (HP) riser will carry a Subsea BOP and a LRP (Low Riser Disconne ct Package). On top of the HP riser will be the working BOP with choke/kill lines, placed underneath the rig floor in the moon-pool area. A low pressure slip-joint will connect the riser to the drilling flowline. The high pressure riser will have a specia lly designed instrumented riser section with an outlet, that can be placed anywhere in the riser between the rig and the sea floor. The particular designed riser section will be connected to a subsea pump that will be able to pump the fluid/solids returns from the well up to a choke manifold on the vessel. The pump will be controlled by a system that will regulate the liquid level inside the riser section, which again will regulate the hydrostatic pressures acting in the well. This system allows through t ubing rotary drilling (TTRD) and well intervention to take place using jointed drill pipe. TTRD has never been carried out from a floater. The system allows for increased flexibility. Sand control operations can be performed in-balance or under balance c onditions. Sand washing can be performed more effectively using a rotating drill string. Long perforation guns can be run and pulled out in under-balanced conditions. Drilling and completion of drainholes in severely depleted reservoirs having a pore pres sure much lower than the normal seawater gradient can take place using a drilling fluid with specific density larger than 1.0, i.e., no need for gas-lift, foam, etc. These operations can be performed without the need to kill or flood the reservoir. This K MB project will investigate the potential benefit of performing well operations with less overpressure, and develop the technology needed for this purpose with main focus on the modelling and labtesting of the PMS.
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