When an operator in Indonesia was preparing to perforate an offshore well, a drift run indicated an obstruction in the top of the existing producing zone, around 8,786 ft (2,678m).

The largest tool that could pass through had an Outer Diameter (OD) of 3.37". As the planned perforating gun’s possible swelling OD was up to 3.45", the operator needed to increase the minimum Inner Diameter (ID) to at least 3.5" to complete the perforation operation safely.

Unfortunately the operator was uncertain as to what was the cause of the restriction or the extent. Welltec® was called upon to provide a solution for removing the unknown obstruction to achieve the minimum ID required for the planned additional perforations and production.

The Well Tractor®, Well Stroker® and Well Miller® were mobilized to the wellsite with a variety of bit types and sizes to address contingencies.
The obstruction was first thought to be slightly damaged casing and the first run was made with an NPR bit to remove metal. The toolstring milled from 8,752 ft to 9,312 (2,667m to 2,838m) ft and was pulled back to surface.

Recovered debris indicated scale build-up rather than a damaged casing. The toolstring was then reconfigured for a more efficient operation, ending up with a 3.7" tapered scale removal bit and standoff.

Several runs were then made to accomplish the scale clean-out. The first with the proper bit and configuration cleaned out scale from 8,752 ft to 8,793 ft (2,668m to 2,680m). Then a second run continued the clean out from 8,787 ft to 9,312 ft (2,678m to 2,838m) then continued to run in hole by gravity to 10,100 ft (3,078m).

A final confirmation run was made with a 3.7" scale removal bit, running in hole by gravity, easily passing the problematic area and confirming that the scale obstruction had been successfully removed and access to the perforation intervals had been accomplished. The perforation operation was then begun.

The operator gained faster access to increased production; going from 1.5 MMscf/D to 12 MMscf/D, and saved the time and cost of mobilizing a CT unit, estimated at two weeks to arrive. The operator’s objective to ensure accessibility for the perforating guns was achieved in eight runs and a total operation time of ~ 96 hours.

This operation demonstrates Welltec’s responsiveness and capabilities to deliver a solution when faced with an unknown well environment.