A Mature Southern North Sea Asset Considers Conversion to Wet Gas Operation Which Requires the Development of Compatible and Novel Chemistries for Flow-Assurance and Asset Integrity

Abstract

As assets in the Southern North Sea continue to mature the tie in of new (high pressure) wells becomes more challenging. Additionally, the operators may consider centralizing their processing, increasing the complexity of the system. The wet gas then has to be transported over longer distances. Moreover, a greater emphasiss than before on the environment has created a drive to reduce production chemical usage. These factors combined have set new and challenging requirements for the chemicals that are to be applied to protect the existing facilities against hydrate formation and corrosion. Conventional offthe-shelf technologies were not able to meet the tough challenges, and required the development of a novel, and fit for purpose kinetic hydrate inhibitor (KHI) and corrosion inhibitor (CI). The minimum performance requirements for the KHI included protection against hydrate formation at conditions of 8 degrees Celcius subcooling and 200 hours of hold time. Besides the high level of subcooling and extended hold time, several secondary chemical properties were essential for successful application of the developed product. These included: solubility of the KHI and CI at elevated temperature and high salt concentrations (independent of each other and together), the chemicals are to be formulation in methanol and functionally compatible, have a minimum impact on oil in water and water in condensate separation, have low reservoir impact with produced water reinjection (PWRI), be HSSE acceptable (CEFAS sub-warning free) and comply with certified chemical cleanliness standards (SAE Class 6) to enable trouble-free umbilical application. All of these requirements were able to be met for the developed product packages. This paper describes the qualification process, lessons learned and the first successful field application of the newly developed chemistries into a recently developed reservoir block in the southern North Sea.

Combined Approach to Evaluate Hydrate Slurry Transport Properties through Wetting and Flow Experiments

“…One of the main cost savings when using LDHIs is the avoidance of CAPEX-intensive methanol or glycol regeneration facilities. 19 In addition, THIs often need to be used at 20–50 vol % relative to the water phase, 20 which is an order of magnitude higher than the volumes required with LDHIs.…”

Kinetic Hydrate Inhibitor Studies for Gas Hydrate Systems: A Review of Experimental Equipment and Test Methods

“…Second, the actual performance of KHIs on THF and cyclopentane hydrates can be different or even opposite to that on gas hydrate systems likely due to different KHI working mechanisms , or removal , of KHIs for future field applications, and (e) compatibility studies of KHIs with other types of production chemicals, in particular, corrosion inhibitors. , The current survey maintains its focus on the tools and methods of experimental KHI investigation and experimental and computational evidence for the proposed inhibition mechanisms in the literature.…”