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Hydrate project taken into third phase
Researchers at Heriot-Watt University's Centre for Gas Hydrate Research have just kicked-off phase three of a joint industry project that aims to develop a Hydrate Monitoring and Early Warning System (HMES). The project secured support from five operating companies with help from the Industry Technology Facilitator (ITF).
Gas hydrates are ice-like crystalline molecular complexes that can form from mixtures of water and gas molecules under the high pressure, low temperature conditions that commonly occur in offshore pipelines. The formation of gas hydates can cause major flow assurance problems, and as the indsutry continues to mature, with more developments in deeper waters, longer subsea tiebacks and higher water cuts, formation of gas hydrates is likely to become more of a problem.
Prof Bahman Tohidi, Director of the Centre for Gas Hydrate Research said "A number of approaches are used to control the formation of gas hydrates, including pipeline heating, insulation and chemical inhibitors. Currently, hydrate inhibitors are injected at the upstream end of pipelines, but in general, no means have been avaliable along the pipeline or downstream to assess the degree of inhibition. Inhibitor dosages are based on the calculated or measured hydrate phase boundary, water cut, worst pressure and temperature conditions, and the amount of inhibitor lost to the non-aqueous phases. In many cases, high safety margins are used to account for uncertainties in these parameters and minimise the gas hydrate risks. However, despite all these efforts, hydrates do still form and can have considerable economic and safety impacts."
Earlier phases of the HMEWS project resulted in the development of a hydrate inhibition monitoring system called HydraCHEK which is being commercialised through Heriot-Watt University spin-out company, Hydrafact. To date the system has been purchased by two operating companies, with field trials being undertaken by a further two companies, and it is reported to have shown very promising results.
The HydraCHEK system uses electrical conductivity and acoustic velocity measurements, along with neural network based software to determine hydrate inhibitor concentration within the pipeline, calculate hydrate phase safety margins, and ultimately determine the risk of gas hydrate formation. This information can then be used to adjust the amount of hydrate inhibitor added to the pipeline.
Phase three of the project is aiming to develop the system further to make it more robust and also to develop a system for early detection of hydrate formation.
Prof. Tohidi explains "Electrical conductivity is an intrusive measurement - in other words, a sensor needs to be in the aqueous phase where it can easily become clogged. What we want to do now is replace the electrical conductivity measurements with a non-intrusive techinique. This should reduce the need for maintenance, make the system more reliable and therefore more attractive to the operator.
Previous phases of the project included some work on detecting the early signs of hydrate formation, which we now hope to progress this work towards a field trial. Detecting early signs of hydrate formation, will allow action to be taken before a blockage occurs. Additionally, it can provide a back-up to the HydraCHEK system, allow greater confidence in working close to the zone of hydrate formation, and thus minimising inhibitor dosing."
Phase three will also allow some promising techniques for hydrate early warning and monitoring that were identified in earlier phases to be explored further.
Keith Mackie, ITF's Technology Manager said "This technology could have a number of benefits and has good potential for further development - not only could it reduce the incidence of hydrate blockage, but more precise dosage of hydrate inhibitors will have cost and environmental benefits and the system could be used to automate the adjustment of inhibitor injection rates in response to the risk of hydrate formation. In addition, the technology could see application in carbon dioxide capture and storage, as well as gas storage, where hydrate formation can be an issues". Share this article: