There are various issues that can develop during the lifetime of the well that can negatively affect operations and decrease production rates. These issues can include failures of various downhole assemblies, scale & wax build-up, increasing water cut, decreases in injection pressure or well plugging due to sand.
With 70% of all oil and gas fields world-wide producing solids, wellbores being blocked by a sand plug is a common issue. Sand plugs form because there is not sufficient energy (thereby flow rate) to transport the sand up the well to surface. The sand falls back into the well flow, accumulating in the wellbore, and eventually brings production to a halt. Intervention operations are required in order to remove the sand plug, making sand clean-up the most common coiled tubing (CT) operation.
The process of cleaning sand or solids out of a wellbore requires pumping fluids down into the well, to mix with the solids, followed by circulating the solids to the surface. The solids, entrained in wash fluid during the CT operation, need to be removed prior to the fluids reaching the production system or waste well, depending on the rig up. Alternatively, the wash fluid could be reused in a loop back to the high pressure (HP) pump, however the recirculating fluid still needs to have the solids removed prior to entering the HP pump.
A solids removal system, DualFlow, developed by FourPhase has been successfully used together with CT to remove solids from the flowback fluids in order to increase efficiency of well clean-ups. The DualFlow system allows for solids to be removed in any rig up with no manual handling, positively affecting operational safety.With a separation efficiency of up to 99.8%, DualFlow is the most effective tool for solids removal in sand clean-up intervention operations. Besides sand, DualFlow can effectively remove different types of solids, including fines, chalk, scale, proppants and cement.
In a recent operation in the North Sea, the FourPhase DualFlow system was used during a clean-up operation where frac proppants were separated from the wellbore fluid. Well performance data indicated a downhole plug between the downhole gauge and the shallowest fractured zone. Repeated well start-up attempts moved the plug further up the well. A large amount of solids, and fracturing proppant returns, were expected in returning fluids that could possibly block the logging tools. In addition, the choke manifold and piping would be exposed to excessive amounts of solids during clean-up circulations that could result in erosion damage and eventual component failure.
The solution was to perform a wellbore cleanout using CT accompanied by a DualFlow solids removal system. DualFlow, with it’s excellent solids removal capacity and separation abilities, removed 8,800kg of solids throughout the operation. At a maximum flow rate the DualFlow was removing an average of 700 kg/hour of fracture proppants. All separated solids are continuously weighed by the onboard logging unit. With no recorded downtime or HSE incidents, the high separation rate and solids handling capability, DualFlow contributed to the increased efficiency of the well clean-up operation.
The DualFlow solids removal system has proven to be a safe and cost effective solution for flowback and coiled tubing well intervention operations. With its compact footprint of 2m x 2m and 3m height, including the possibility for installation on top of the choke, the DualFlow is made for a safe and easy installation.