Smart Wireless network automates flow monitoring

Emerson has revealed how its Smart Wireless network, using open WirelessHart products, is automating flow monitoring to increase production on the Statoilhydro Gullfaks offshore platforms.

Statoilhydro was occasionally losing flow from the producing wells at its Gullfaks A, B and C platforms, caused by a loss of wellhead pressure.

Early detection of the loss of flow is important as this enables operators to flow the well through the test separator and re-establish flow by reducing pressure.

Bringing flow back quickly improves throughput and increases production over time.

The loss of flow was difficult to detect due to there being no existing flow-metering devices installed within the well pipes.

Installing such devices for this application was not practical as this would require a complete shutdown of production, which would be expensive in terms of lost throughput.

A non-intrusive solution was required, but the introduction of new sensors brings with it the problem of connecting them back to the control room.

The wellhead was already a crowded area and for safety reasons it must be kept as clear as possible.

Therefore, the introduction of additional equipment, such as new cabling, cable trays and junction boxes, was not possible.

In the past, Statoilhydro detected loss of flow by sending an operator to the wellhead where they placed their hand on the pipe to feel whether there was a difference between the pipe temperature and the ambient temperature.

Typically, well fluid is 60C so the pipe feels warm, but should flow be interrupted it slowly drops back to the ambient temperature.

Temperature readings were taken only at the start and the end of a shift, so a loss of flow could easily go undetected for long periods and production would be lost.

Needing to automate the monitoring so as to provide real-time data, while also reducing personnel presence in hazardous areas, Statoilhydro initially implemented a pilot installation on the Gullfaks A, B and C platforms.

Emerson Rosemount 648 wireless temperature transmitters were installed to indirectly indicate flow on lines at each of 40 wells.

The wireless devices are used to transmit data from clamp-on temperature sensors mounted on the surface of the flow pipes.

Anders Royroy, project manager, research-and-development projects at Statoilhydro Norway, said: 'Installing additional wired measurement points at the wellhead would mean long cable trays and a lot of wiring.

'Wireless offers an inherent reduction in cabling infrastructure, complexity and weight, resulting in lower installation costs.

'Because there is daily radio communication within the well area it is essential that the wireless field network can co-exist without any reduction in performance.

'We have found that Emerson's Smart Wireless mitigates the impact of interference and the data reliability is 100 per cent.

In contrast with the once-a-shift manual recordings, Emerson's wireless devices now transmit readings every 30s back to the Smart Wireless Gateway.

The gateway is hardwired straight into the existing control system, providing operators with the real-time information they need to react quickly to any change in flow.

Tormod Jenssen, staff engineer, plant integrity at Gullfaks field, said: 'Emerson wireless transmitters have enabled the quick and reliable detection of lost flow, and the immediate action to re-establish flow has increased production significantly.

Statoilhydro has now implemented additional Smart Wireless devices on Platforms A, B and C, bringing the total to 90 wireless transmitters covering all production flow lines at Gullfaks.

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