Design of a Cyclonic-Jetting and Slurry-Transport System for Separators
Oil and gas wells often produce sand or solids with the well fluids. Despite exclusionary well designs, these solids can cause equipment failure, completion problems, or changes in production. This paper offers a way to remove solids in separators.
Sand and solids are removed from production separators either off line (shut down for physical removal) or on line by use of jetting systems. Traditional jetting designs use spray nozzles to fluidize and push the sand toward a covered outlet to evacuate the solids from the vessel. Cyclonic-jetting technology combines the fluidi- zation and evacuation functions into a single, compact device. On the basis of a hydrocyclonic platform, this technology converts jet- ting spray water into shielded vortex flow that fluidizes sand in a circular zone without disturbing the oil/water interface.
Total solids removal is primarily a function of set height, spray flow, and spacing. A single unit was optimized at a set height of 10 cm (4 in.) with spray pressure of 0.7 barg (11 psig) to provide an area of influence of 1.1 m² (12.0 ft²) with 28 cm (11 in.) of sand- bed depth. Placing two units in parallel with overlap of their af- fected zones reduces the “egg-carton” effect associated with this technology; however, optimum operation, in terms of total sand re- moved, occurs when the units do not overlap. Slurry at up to 60 wt% solids is transported from the jetting system to the handling equipment. The boundary design conditions for slurry transport are erosion velocity (upper limit) and particle-transport velocity (lower limit). By use of published models, the piping design for a four- unit cluster of cyclonic-jetting devices was validated at 5.0-cm (2- in.) nominal size. Integration and operation of a jetting system with transport, dewatering, and disposal stages of facilities sand man- agement are presented as guidelines for system design.