Commercial Deployment of Low-Dosage Hydrate Inhibitors in a Southern North Sea 69 km Wet-Gas Subsea Pipeline

Argo, Carl B.; Blain, R.A.; Osborne, C.G.; Priestley, I.D.

doi:10.2118/63017-pa

Cited by 13 publications

(6 citation statements)

References 5 publications

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“…It is believed that kinetic inhibitors do not prevent but delay hydrate formation (Sloan, 1995;Fu et al, 2002). A typical concentration of around 1 mass% is sufficient to control the hydrate formation process until the gas or oil is transported to the destination or the processing facility where it is outside the thermodynamic conditions of hydrate formation (Notz et al, 1996;Mitchell and Talley, 1999;Argo et al, 2000;Fu et al, 2001).…”

Section: Introductionmentioning

confidence: 99%

Characterization of inhibition mechanisms of kinetic hydrate inhibitors using ultrasonic test technique

Yang

Tohidi

2011

Chemical Engineering Science

122

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Section: Introductionmentioning

confidence: 99%

Characterization of inhibition mechanisms of kinetic hydrate inhibitors using ultrasonic test technique

Yang

Tohidi

2011

Chemical Engineering Science

122

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“…Shell is not aware of reliable theories that predict to what extent a shorter residence time balances a higher subcooling 3 . Normally it is not immediately apparent which time-subcooling history represents a worst case.…”

Section: Specification Of the Required Khi Hold-time To Be Met In Labmentioning

confidence: 99%

Laboratory Validation Of Kinetic Hydrate Inhibitors For Use In Sour Gas Fields

Klomp

Mehta

2007

All Days

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractA kinetic hydrate inhibitor (KHI) can only delay hydrate formation for a limited period of time (the hold time). Larger thermodynamic driving forces for hydrate formation result in shorter hold times. When using a KHI, an element of water must be produced out of a production system before the hold time elapses. The thermodynamic driving force for hydrate formation that a water molecule is exposed to whilst traveling through a production system is time-dependent and often complex. Detailed transient thermo-hydraulic simulations must be carried out to evaluate the worst-case "timesubcooling" history that a water molecule can experience during steady state flow and various transient operations. This time-subcooling history is taken as the basis for the experimental conditions of hydrate formation under which a KHI has to be tested in the lab. It also determines the required hold time. In addition to the time/driving force history, the hold time strongly depends on the composition of the condensate and gas and therefore the composition of the test fluids must closely match the composition of the pipeline fluids. The presence of other oil-field chemicals, in particular corrosion inhibitors that are used in sour gas/condensate systems, can significantly reduce the hold time and these chemicals must therefore be present during the testing. To further complicate matters, the observed hold times usually show large variations and depend on the type of test equipment used. Many kinetic inhibitors tend to precipitate or even form sticky clumps after injection in a warm water/condensate mixture. This behavior is affected by several factors, amongst which the pH of the water. This paper presents the procedures that Shell compiled to validate kinetic inhibitors for use in sour gas/condensate fields as well as some important (and sometimes surprising) observations made during this exercise.

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“…To have sufficient inhibition for some cases, particularly for those with high water cut, high concentrations (up to 60 mass%, hence a large volume) of MeOH and MEG may be required, which can lead to significant increase in capital expenditure and operational expenditure, and can also cause a severe impact on the environment (Brustad et al 2005;Cowie et al 2005). LDHIs are the other group of chemical additives that are usually divided into kinetic hydrate inhibitors (KHIs) and antiagglomerants (Lederhos et al 1996;Notz et al 1996;Mitchell and Talley 1999;Argo et al 2000;Fu et al 2002). It is generally believed that KHIs delay hydrate nucleation and inhibit hydrate growth within a certain degree of subcooling, while AAs allow hydrate formation but keep the oil transportable by preventing agglomeration of hydrate crystals.…”

Section: Introductionmentioning

confidence: 99%

A Novel Technique for Monitoring Hydrate Safety Margin

Yang

Chapoy

Mazloum

et al. 2012

SPE Production &Amp; Operations

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A novel technique has been developed for optimizing hydrateinhibitor dose rates by monitoring the actual hydrate safety margin. The technique is based on measuring acoustic velocity and electrical conductivity in an aqueous sample taken from the pipeline/separator. The developed system then determines salt and organic inhibitor concentration (e.g., methanol, monoethylene glycol, and kinetic hydrate inhibitors). In the case of thermodynamic inhibitors, the information is then fed to a thermodynamic model determining the hydrate stability zone (HSZ). Superimposing the pipeline operating conditions (e.g., pressure and temperature profile), the developed system can determine the hydrate safety margin.The system can provide warning if the operating conditions are inside the HSZ or if too much inhibitor is being injected.The technique can be used in optimizing inhibitor-injection rates, reducing the impact on the environment and operational costs. It can also improve production-system reliability by constant monitoring the hydrate safety margin and protecting the system against pump malfunction and/or changes in process variables (e.g., water cut).This technique has been developed through a joint-industry project, and its performance has been intensively evaluated using synthetic samples and real produced-water samples by the authors and the project sponsors in field trials. The results demonstrate that this system can be used for different inhibitor systems, including methanol (MeOH)/NaCl, monoethylene glycol (MEG)/NaCl, and kinetic-hydrate-inhibitor/salt systems, with good accuracy.The developed system can have a major impact on reducing the inhibitor-injection rates and environmental impact and improving the reliability of production systems against risks associated with hydrate formation. The developed system can be laboratory-based, a mobile unit, or online, with near-real-time samples taken from live pipelines/separators.

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Commercial Deployment of Low-Dosage Hydrate Inhibitors in a Southern North Sea 69 km Wet-Gas Subsea Pipeline

Cited by 13 publications

References 5 publications

Characterization of inhibition mechanisms of kinetic hydrate inhibitors using ultrasonic test technique

Characterization of inhibition mechanisms of kinetic hydrate inhibitors using ultrasonic test technique

Laboratory Validation Of Kinetic Hydrate Inhibitors For Use In Sour Gas Fields

A Novel Technique for Monitoring Hydrate Safety Margin

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