CrudeSep™
CETCO Offshore has been working on produced water applications for more than four years; typically providing Crudesorb™ as a polishing treatment downstream of malfunctioning existing equipment. During this time, CETCO has recognised the limitations that standard oilfield-produced water equipment has, for example, skim tanks, corrugated plate interceptor vessels, Wemco units, centrifuges and hydrocyclones are all susceptible to changes in operational parameters. Units are designed for a certain flow rate, pressure, solids loading and oil loading. At these predefined parameters, this equipment can adequately treat produced waters. Typically, however, these parameters do not remain constant. CETCO, in searching for a suitable mechanical pre-treatment to its CrudeSorb™ waterpolishing technology, soon realised that the key was a mechanical unit that can cope with changes in operational parameters, e.g. increases or decreases in flow rate and pressure when treating produced waters.
Consequently, CETCO Offshore has designed their CrudeSep™ unit for the high-efficiency removal of oil, gas and solids, for example, either upstream or downstream of a three-phase separator in order to ensure longevity of the CETCO CrudeSorb™ adsorption units on produced water applications. CrudeSep™ will also meet many produced-water discharge requirements as a standalone treatment package.
The principle of the CrudeSep™ is a vertical vessel operating at near-atmospheric pressure. Gravity oil separation is enhanced by induced gas flotation and swirling flow, where gas bubbles are injected midway up the vessel using eductors. Produced water is withdrawn from the CrudeSep™ in the lower half of the unit and used to drive the eductors, the gas being taken from the top of the vessel. Hence, there are no cumbersome moving parts with swirling flow achieved by a series of tangential feed nozzles at the wall.
Flotation is a liquid-liquid (or solids-liquid) process, applicable for separation of droplets that have a similar or lower density than the suspending fluid. Although oil droplets naturally float, aided flotation is defined as using external means to improve the recovery. Swirling flow ensures excellent mixing and flotation to the surface
CrudeSep™ operates efficiently as a de-gassing vessel. Produced waters enter through hydraulically balanced tangential nozzles just below the vessel’s liquid surface, entrained gases rapidly rise through the swirling fluid. Multiple inlet nozzles are designed to minimise the effects of surge on the vessel’s treatment capacity as the rotating fluid simply spins faster.
Heavy solids accumulate in the vessels lower head where removal from the CrudeSep™ is achieved with solids removal systems that create a slurry to displace the solids for subsequent treatment. Flow from the CrudeSep™-produced water or injector recirculation pumps is the motive force for solids removal. This operation does not affect the induced gas flotation, which occurs simultaneously.
Experience to Date
CETCO Offshore has an extended client and job reference list – regular customers include BP, Shell, Chevron-Texaco, Exxon Mobil, Agip, TotalFinaElf, Kerr McGee, Statoil, Abu Dhabi Marine Operating Company (ADMA-OPCO), Marathon Oil, Talisman Energy, Encana, Amerada Hess, Schlumberger and Halliburton. CETCO’s turnkey approach to treating wastewater fluids ensures conditions that are safe and results that are clear – environmentally compliant platforms with increased oil recovery and maximum productivity.
Category:
Environment
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