This paper will present a record North Sea electric line milling operation carried out during March 2010, the success of which enabled access to the reservoir section, with subsequent interventions leading to a significant uplift in production.
The Operator was experiencing high water cut in one of its wells; previous interventions in other wells connected to the same reservoir indicated a high probability of scale. The plan was to log, isolate the watered out zone and then re-perforate in order to increase oil production rate. Electric line Tractor Milling equipment was mobilised as contingency, should well access be an issue, which happened to be the case.
In order to keep the bit clear during milling, cuttings were flowed back to surface. Progress was made until the surface choke packed off and flow was no longer achievable, the toolstring had to be retrieved whilst choke and lines were cleared. The scale sheath was eventually broached and the decision made to continue in hole in order to drift, as well as providing the capability of dealing with any further scale that may be present; the Tractor Miller was started once more with a minimum of resistance encountered. Target depth was attained, all Tools were then retrieved to surface with no issues.
The overall objective was achieved, resulting in a significant increase in production. One hundred and twenty one (121 metres, 390 feet) of calcium carbonate scale was removed during the operation, validating the use of light well intervention techniques when removing scale.
This paper will discuss the technical aspects of e-line milling and challenges overcome during this particular operation.