Many wells have a hydraulic control line running down along the casing or tubing for various reasons, it be controlling a valve or sleeve or other equipment.
Sometimes these control lines develop a leak and can no longer be used, sometimes they are just not needed anymore.
These control lines can run hundreds and often thousands of meters down the well.
A faulty control line can be a source of an undesired leak. In an abandonment phase the control line can be a source or a conduit for pressure migration.
A leaking control line is mostly useless and can be a source of leak and pollution. More problematic is that a control line at some stage will be a possible leak path for pressure moving from one depth to another. It can also be a breach of well control barrier in a well.
Pulling the line up is normally not possible, repairing it is very difficult, so the best option is to seal it up to prevent any migration of fluids and undesirable pressure build up.
To seal a deep mostly very small line is difficult, you would need a very low viscosity fluid to be able to pump it into for example a 4000 m long ¼” control line with an ID of maybe 4-5 mm.
The line will also run across low temperature sections at and around the seabed on offshore wells making most fluids very viscous and not feasible to pump.
The Wellcem resin has extremely low viscosity and even at low temperatures can the resin be pumped through a small control line and thousands of meters down in a well.
It is normally a one-man job easily done in a few hours with very little equipment and chemicals. The chemicals are normally mixed on site and only a few liters are normally needed. The surface lines are flushed clean after the resin has been pumped to ensure no resin is left at surface.
The carefully controlled curing time allows for secure placement and the control line can normally be tested the next day to ensure it holds and the line is secured.
The testing is normally done by the same engineer with the same equipment that has been used for pumping the resin into the line. The pressures test is recorded and submitted to the operator together with a full end of job report.
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The primary objective is to ensure that no leaks to surface exist and that no formation fluid migration occurs even many years after the well has been abandoned.