The last separation step for emulsified water is now possible without consumables and without the need for specialised personnel. Reliably polishing wastewater to below discharge limits now comes as a robust, skid mounted solution.
TwinZapp technology consists of a two-step process:
- The emulsions are destabilised through an oxidisation process.
- The resulting neutrally buoyant particles are separated with a back-washable deep filtration system.[Page Break]
Emulsions in produced formation water are a given as corrosion inhibitors and other chemicals are injected. On drilling rigs, high amounts of slop water are generated while cleaning pits and decks. The emulsions are often too strong to simply let gravity and time do its job.
Space and time are exactly two major constraints in an offshore environment. Another constraint is manpower.
Twin Filter and Brilliant Water Solutions have developed a DNV and ATEX Zone II certified skid which operates independent of ongoing processes. No re-engineering is required. The skid is simply a last step add-on before water is discharged and treats the water continuously at a typical rate of 30 bbl per hour.
The emulsified water is first subjected to a mild, well controlled, electrical oxidation process. Release of reactive oxygen, hydroxyl and other radicals destabilise the present surface active components. The resulting free oil along with the neutrally buoyant particles (and associated oil) as well as a sizeable fraction of the dissolved aromatics is then removed by a fully re-generable filter at the final polishing stage.[Page Break]
Current technology mostly comes with drawbacks that in an offshore environment have serious consequences.
New separation equipment is installed onto older platforms as the discharge limits become more stringent.
An increasing water cut in production or a change in the chemical mix often results in a cycle of readjusting separation processes or an acceptance that volumes are sent to shore at high logistics and treatment cost. Hydro cyclones are limited to larger particle sizes, absorption media foul up and create logistics and waste problems of their own.
On a drilling rig there is mostly no standard separation equipment to deal with emulsified water since this is only required at particular stages: after an oil based mud placement or when a well is cleaned up or lifted. A solution needs to be mobile and at best require no additional personnel. The TwinZapp technology is supplied fully automatic in very compact skidmounted packages and can be installed in existing separation packages.[Page Break]
The technology was developed and tested offshore through 2011. Tests with two major operators on several platforms with emulsified produced water provided consistent results. The free oil content was typically reduced from 2,000 - 500ppm to well below 15ppm. The process parameters proved easy to control and correspond to changes in input and output.
Onshore tests on slop water achieved reductions from 1,000ppm to 2ppm in a single pass.
Update, June 2012: Two major operators have committed to commercial development and two units are under construction.
Paul Schouten is with Brilliant Water Solutions BV, The Hague The Netherlands. www.brilliantwater.org
Eric Wals is with Oilfield Division, Twin Filter BV, Zaandam, The Netherlands. www.twinfilter.com