Rolyn Oilfield Services Nigeria Limited (ROSNL) with its base of operations in Port Harcourt, Rivers State, Nigeria, is providing leading edge tank cleaning and related services to Nigerian oil companies. Rolyn Oilfield Services is a shareholder and the primary technical partner in ROSNL.

Case Study 1 – Forcados Terminal

Recently, a new tank cleaning technology was introduced in Nigeria and applied for the first time at SPDC’s Forcados terminal. Rolyn Oilfield Services Nigeria Limited (ROSNL), (http://www.rolynoilfield.net), successfully completed the cleaning of slop oil Tank 602.

The technology employs both a high-pressure jet mixing system coupled with phase separation equipment to remove virtually all solids from the oil and water recovered during the cleaning process. In the case of Tank 602, approximately 3,000 bbls of oil that would normally have been diverted to the slop pits with the solids were recovered and sent to one of the crude tanks via the dehydration line. During the recovery procedure, samples of the oil and water were taken and evaluated and consistently demonstrated that only a trace of solids remained in the liquid phase.

This jet mixing technology can have varying results depending on the type of tank and the nature of the oil and solids contained. With Tank 602, much of the solids were lifted during the mixing phase and extracted and separated through the centrifuge, generating approximately 2,000 bbls of oil. A second jet mixing was then done, liberating an additional 1,000 bbls of oil from the remaining solids resting on the floor of the tank. Unlike historic methods of removing sludge solids that contain up to 40% or 50% oil, the solids generated by the centrifuge unit typically contain 1-3% oil while the balance is recovered and returned to the customer. What remains at the end of the project are a small level of solids and water, which are then conventionally removed via suction prior to washing.

The technology also employs a proven proprietary biodegradable chemical that aids in the separation of oil, water and solids and is proven to significantly reduce the LEL levels inside the tank to create a safer working environment. This chemical was also used for flushing the 10-inch dehydration line to remove sand and solids that had built up during the past 8 years, since the slop oil tanks were first built and for the final wash prior to ultrasonic inspection.

SPDC was pleased to be able to provide ROSNL with their first venue to showcase their technology and we look forward to working with them more in the future and to developing new jobs for our young Nigerians.

Case Study 2 - SPDC Soku LGSP Terminal

Prior to commencing this project, confirmation of the estimated volume of tank bottom sludge contained in the subject tank was completed. The volume of solids contained in the bottom of the tank determined the chemical requirements for the project.

The fire hydrant spool pieces (10” and 8”) located at the eastern part of the bund wall were removed and reconnected after placing into position the various pumps to be used for this project.

A man-way cover was removed and a 6” companion flange was welded onto it. This modification had a gate valve and the jet/stinger assembly attached. Also a 2” flange hook-up was made to discharge the recovered condensate from T5501 to the closed drain drum. A strainer, with a ¼” mesh was positioned for the pump-down of condensate from T5501. It was designed to prevent sludge solids contained in the tank from being pumped into the underground closed-drain condensate drum tank. At various intervals of the pumping down of the residual condensate to the closed drain drum, the strainer had to be cleaned out. The particles observed included peeled off paint coating, foam and sand.

During a period of 4 working days a total of 7,243.30 bbls of condensate were recovered and returned to the terminal, equating to a minimum market value of more than $400,000.

A 3 ¾ “ cold cut was made through the man-way cover shown in the picture above, providing access into the tank for the jet stinger assembly used for circulation and agitation and for injecting the degassing and proprietary washing chemical.

Once the circulation was completed the pump was turned off for a period of 48 hr. to allow complete settling of the tank contents.

The wash water was drawn off from the tank, leaving a small deposit of solids in the center of the tank which were removed conventionally once the tank was open and accessible.