Water injection is a common way to extend reservoir life through intelligent well management. In order to raise the reservoir pressure and improve the production rate, sea water or produced water is injected into the well. The injected water quantities are monitored by flow meters and transmitted to the process control system.
The sea water injection takes place in two steps. Firstly the booster pumps suck the water out of the reservoir's water tank to create a slight admission pressure of approximately 200 psi. The injection pumps need this pressure in order to work cavitation free. Secondly the injection happens via thick walled steel pipes, where pressures of about 4500 psi can be reached during the process.
Measuring such injection rates accurately can be challenging: The high pressure, high velocity water typically causes severe abrasion on traditional inline flow meter technologies.
One European producer found this out the hard way on a North Sea platform. Erosion and deposits caused the precision of the employed differential pressure flow meters in the water injection lines to decrease continuously.
A non-invasive flow measurement with the FLUXUS clamp-on ultrasonic flow meter was the ideal solution. The installation of the meters takes place without interrupting the production and without cutting into the pipe. The transducers are simply clamped onto the pipe and do not cause any pressure loss. Since they do not come in contact with the medium, they are not subject to wear. Nevertheless, as of its sophisticated ultrasonic transducers and superior signal processing capabilities, the measurement system is highly accurate and reliable.
These advantages make the system a perfect solution - not only for retrofit installations. The benefits are also important when considering new installations, taking the system’s comparably low weight and non-existent pressure loss into account.
The company reports that its FLUXUS flow meters require little or no maintenance yet and are completely immune from performance fall-off caused by the high velocities and pressures found in water injection.