UK flowmeter specialist Litre Meter has shipped a number of flowmeters to Petrobras for use in a chemical injection application for offshore production in Azerbaijan. The Buckingham-based company shipped three different sizes of VFF positive displacement flowmeters for chemical injection measurement at different flow rates.
The range of meters supplied demonstrates Litre Meter's expertise and versatility in chemical injection applications. Each meter was calibrated to work at different rates of flow in the chemical injection process.
The order consisted of three HF40 m, a V125 positive displacement (PD) flowmeter and a VFF8 PD flowmeter, all of which were supplied to measure the flow of triethylene glycol (TEG) - high purity ‘lean' TEG before coming into contact with hydrates and ‘rich' TEG, which has absorbed water later in the process.
The HF40 meters were pressure rated to ANSI1500 and constructed from 316L stainless steel. The meters were manufactured with 1.5 in. 1500 ring type joint (RTJ) wafer connections. As standard these meters have a flow range of 0.4 to 40 litres/minute, a viscosity range of 0.5 to 100 000 cSt or greater and a repeatability of +/- 0.25%.
TEG is used as a hydrate inhibitor. Gas hydrates can solidify as ice-like crystals which may block pipelines and valves, impeding the transfer of oil and gas. This can result in a shutdown and the risk of explosion or unintended release of hydrocarbons into the environment.
The chemical is placed into contact with natural gas and strips the water out of the gas. The used TEG is heated to a high temperature and put through a condensing system, which removes the water as waste and reclaims the TEG for continuous re-use within the system.
This process prevents hydrates forming in wells' sub-surface valves under high pressure and low temperatures during long shutdowns. The Litre Meter HF40 positive displacement flowmeters measure the flow of TEG to ensure the correct amount is injected to prevent hydrate formation.
The V125 and VFF8 meters were included to work with higher flow rates in the system. The V125 is designed to handle flow rates of 1.25 to 125 litres/minute. The VFF8 can measure liquids at flow rates of 5 to 800 litres/hour. Both meters have a repeatability of +/- 0.25% and are designed to operate at the range of temperatures created by the chemical injection process.
The flow capability of the meters has been improved by coating the pressure balance chamber and titanium rotor with physical vapour deposition (PVD) designed to lower the friction properties of the meter. The additional hardness provided by the PVD coating also improves wear resistance.
In addition, Litre Meter recommended filtration at 100 micron in order to keep particulates out of the flow chambers of the meters to maintain efficient operation and assure continual flow.
Litre Meter CEO Charles Wemyss said: "Subsea repairs and the associated loss of production are high cost, so protecting deepwater well bores from hydrate formation, plugging and organic fouling is a major flow assurance concern in offshore operations.
"Hydrate, scale and corrosion prevention strategies provide protection during normal operation, start-up and shutdown. Litre Meter's VFF flowmeter is ideally suited for use in the oil and gas industry and in particular for low flow / high pressure applications.
"Years of experience in chemical injection applications onshore and offshore have confirmed the instrument's capability to reliably measure fluids under extreme conditions of both temperature and pressure."
Adapted from a press release by David Bizley