The contract for Salt Separation Services is worth approximately £1.1 million. The F15-A5 well of Total E&P Nederland, produces gas from Volpriehausen sandstone. The peak initial gas production of F15-A5 is 350 kNm3/d. Performance of the well has been reduced by salt deposition. Salt accumulates in the well riser and limits the gas flow. Seawater is to be treated and injected to the well riser to dissolve the salt. Seawater contains suspended solids, bacteria, dissolved salts and dissolved oxygen, all of which can have an adverse effect on the injection system as well as on the well. Therefore their quantity in the injection water is to be reduced to an acceptable level to prevent any corrosion and plugging. Due to the fact that the platform is unmanned, the use of chemicals has been limited as far as possible. As the platform may be permanently unmanned in the future, the unit has been designed to operate automatically. The solution includes: • Over sized pre-filtration to improve filtration efficiency and reduce the frequency of disposable filter changes. • Two pass RO system with only one high pressure pump to reduce package footprint and weight, whilst also simplifying the process and controls. • Recycling of second pass RO concentrate back into first pass RO feed to dilute the influent seawater and increase the net overall recovery. • Reduced first pass RO recovery to remove the requirement for antiscalant dosing. • RO arrays designed at low flux rates to reduce potential fouling. • No CIP system – thereby reducing package footprint, weight, complexity and cost. Due to the relatively low number of RO membrane elements (3 × 8 inch and 3 × 4 inch) a cost-benefit exercise identified that RO membrane replacement instead of RO membrane cleaning would be the most cost-effective solution. Production of the containerised water purification system, deaerator column and storage tank has now started and is expected to be completed and delivered later this year.
