Robert Brelsford
Downstream Technology Editor
Chevron Nigeria Ltd. (CNL) has let a contract to Frames Group BV, Alphen aan den Rijn, the Netherlands, to provide a natural gas dehydration unit for the 165-MMcfd Okan offshore gas gathering and compression platform (GGCP), which CNL 40% operates in Nigeria's western Niger Delta region on behalf of partner Nigerian National Petroleum Corp. (NNPC) 60% under their Escravos gas project joint venture (OGJ, Apr. 20, 1998, p. 78).
Frames' scope of work will include design and construction of the glycol-based gas dehydration unit, which will be installed as part of an expansion of the GGCP's existing dehydration system, the service provider said.
Expanded gas dehydration capacity at the platform comes as part of CNL's Okan GGCP debottlenecking program to increase production from Okan field, Frames said.
A value of the contract package was not disclosed.
This latest contract follows CNL's April 2016 award to a consortium of NNCP subsidiary National Engineering & Technical Co. (Netco) and PAI Engineering Ltd. to deliver detailed engineering design (DED) services for the Okan GGCP debottlenecking project, which is intended to boost handling of additional nonassociated gas (NAG) supply from new NAG wells CNL plans to drill as well as surplus NAG from the new Okan pig-receiver platform (PRP), according to a June 2016 Netco publication.
Designed to sustain Nigeria's domestic gas supply, the Okan GGCP debottlenecking project will include:
• Mitigating declining associated gas (AG) rates.
• Debottlenecking to increase NAG handling capacity to 200 MMcfd.
• Increasing capacity of the glycol regeneration system to 320 MMcfd from its current 200 MMcfd capacity.
• Diverting excess NAG gas from Sonam NWP field to Okan GGCP.
Okan GGCP debottlenecking project
Located off Nigeria in about 25 ft of water within OML-96, Okan field's GGCP currently dehydrates both AG from the Okan production platform and NAG from two NAG wells, OK-33 and OK-72.
Composed of three existing 55-MMcfd compressors, the Okan GGCP compresses and dehydrates AG in a nameplate 32-MMcfd triethylene glycol (TEG) gas contactor-currently operating at 57 MMcfd capacity-and routes it through a 20-in. pipeline to Escravos Gas Plant (EGP) Train 1's slug catcher. NAG used for gas lifting is routed through the lift-gas separator and TEG lift-gas contactor into Okan's gas-lift network.
With the most recent reservoir-deliverability forecast predicting a decline in rich gas supply to EGP Train 1, however, there is need to increase Okan GGCP's NAG-handling capacity to make up for the declining AG rate, Netco said.
According to current project plans, Okan GGCP's existing 200-MMcfd glycol regeneration system will be replaced with a 320-MMscfd capacity regeneration system to allow for increased NAG-handling capacity.
Alongside NAG supplies arriving from new wells in Okan field, additional NAG will be routed to Okan GGCP via a 16-in. pipeline from the new Okan PRP, which receives excess NAG from Sonam NWP field.
Based on Netco's June 2016 contract description, Netco and PAI Engineering's scope of work on the Okan GGCP debottlenecking project will include delivery of DED for the following components:
• Modifications to existing interconnecting piping and instrument between the NAG separator, GGCP Stage 3 scrubber, and TEG gas contactor to increase NAG flow rate to 200 MMcfd from 128 MMcfd.
• Debottlenecking of Stage 3 scrubber to enable a 300-MMcfd handling capacity.
• Replacement of existing glycol regeneration package with a 320-MMcfd capacity system.
• Modification of existing flare system to accommodate new operating conditions.
• Updating of existing utility adequacy report to ensure it entails checks on power, vents, instrument air, chemical, fire water, and open and closed-drains systems.
• Installation of new pig receiver and associated piping, including riser.
• Extension of deck to accommodate new pig receiver.
• Installation of a flow meter downstream of pig receiver.
• Detailed review of constructability issues related to replacement of glycol regeneration package, interconnecting piping, pig receiver, new flow meter, and other equipment.
For the Okan PRP portion of the project, the service companies will cover DED on the following installations:
• A two-phase separator.
• A pig launcher and associated piping for the proposed 16-in. Okan PRP-Okan GGCP pipeline.
• An ultrasonic flow meter on pipeline.
• Interconnecting piping valves.
• Pipeline tie-in, including riser and validation of tie-in point on Okan PRP design as well as condensate tie-in on the Okan PRP-Okan NWP field line.
Nigeria-based CAKASA Engineering Services Ltd. previously completed front-end engineering design for the Okan GGCP debottlenecking project in 2015, according to the service provider's web site.
A timeline for full startup of the completed debottlenecking project has yet to be disclosed.
