Injection rate control valves such as IRCDs or SkoFlos are required when point to point injection is not feasible due to the number of injection locations is too many to have single pumping, for example.
Many operators have little confidence in these valves. Many IRCV installations have failed and some have been made to work only after significant effort. While it can be difficult to definitively determine the particular reasons for their failure in many cases, it is not hard to picture why so many systems fail; there are multiple number of things that can go wrong with these systems.
Some issues with these valves include the following:
- Oversized valves - Chemical injection systems are difficult to size because of several uncertainties including well flowrate, the chemical to be used (and resulting physical properties) and the concentration of chemical required. If conservative estimates are used for all of these parameters, the injection system may be dramatically oversized, at least for some individual wells.
Oversized valves may still function effectively given adequate turndown, but the turndown of individual IRCVs may be significantly lower than expected. Turndown is decreased if there is significant frictional pressure drop in the injection system.
- Oversized Recycle Valves - The IRCV suction pressure control is important in the functioning of the valve. When this is achieved via a back pressure regulator, the valve is usually sized for 100% of the pump flow as a safeguarding feature and to facilitate startup. The resulting valve may be too large to effectively control pressure during normal operation.
- Proportional offset - As the system pressure drop increases, the IRCV has less impact on the flowrate. The proportional offset always exists, however, for a correctl sized valve operating at its sweet spot in a system with low to moderate pressured drop, the proportional offset appears to be
- Heat buildup - Too much recycle can build up heat in the system and gunk out intermediates (like in the case of LDHI).
- Port plugging with dirty chemical or injection system debris. Inadequate QC measures or bad chemical injection system design.
- Inadequate operator training.
- Inadequate understanding of pump dynamics.
More information can be found in SPE110205 - Successful Application of Chemical Injection Rate Control Valves.