CETCO Oilfield Services exceeded expectations during another successful clean up operation of oily water streams onboard the Stena Spey rig, as part of a series of well intervention and clean-up operations in Chevron’s Strathspey and Captain Fields.
The two part operation, which utilised CETCO’s CrudeSorb technology, exceeded client expectations with reduced operating time and lower discharge rates than the legal limits set by the BERR.
Chevron contracted CETCO to assist in the treatment of the oily water waste streams resulting from a series of well interventions carried out in the Strathspey and well clean up operations in the Captain Field.
CrudeSorb technology was used to treat the fluids prior to release overboard. CrudeSorb is a proprietary adsorption media based on resin, polymer and clay technology. It has been proven to be extremely efficient at removing oil, grease and soluble organics from water. The treatment on the Stena Spey was achieved through the use of two CETCO RFV4000’s, each consisting of two sock filter vessels and two adsorption media vessels which can run in series, parallel or though a single vessel.
When run in parallel each system is capable of processing up to 10,000 bbl of fluid per day. This dual configuration meant that the system operators could switch from one set to the other without having to interrupt the flow at any time, reducing rig time and cost.
CETCO successfully treated all contaminated fluids at a rate below approved discharge level of less than 40mg/l. Much of the influent was found to have oil-in-water content which was already less than the overboard discharge limit.
This provided the opportunity to improve efficiency by-passing the units when not required. Constant flow monitoring ensured that at no time was there any risk of fluid being discharged to the environment that exceeded the limits set by the BERR.
CETCO also treated fluids which had come directly from secondary operations within the well. These included all wash water, including that from the solids washing operations and all other water from equipment involved.
Perhaps the most interesting well in the combined Stena Spey contracts was the Strathspey M3 well, which is a water injector which was once an oil producer.
The M3 intervention was a good demonstration of the benefits CETCO’s CrudeSorb system can bring to a project. The well has a 900 foot sump and after 10 years as a producer and 3 years as an injector it was anticipated that some, or all, of this sump had been filled with debris of various origins.
The project covered extraction of the crude oil entrained within the fluids and solids build up contained in sump of well M3, prior to additional perforations being added to the well. The fluids from the M3 intervention were cleaned using a series of treatment equipment on board the drilling rig.
The fluids and associated solids were flowed back to the Stena Spey through the coil tubing and completion annulus. When on board the fluids were directed through Expro sandfilters and a hydroclyclone desander to remove solids. The fluids from the well were then directed through the two CETCO RFV4000s to remove any hydrocarbons prior to discharge over board. The wash water from the sand wash vessel was also treated by CETCO to remove hydrocarbons, prior to disposal.