Denmark’s Welltec parlayed its Well Tractor technology into added value by introducing the Well Miller, a milling technique that allows operators to drill with electric wireline by using metal machining technology tied to the Well Tractor. The same system also allows drilling on wireline.

The key component of the Well Miller is a milling bit. Using the Well Tractor, the company can

The Well Miller combined with the Well Tractor can mill out obstructions in the well bore at low cost. (Image courtesy of Welltec)
mill through the hardest materials by controlling the advance of the bit. According to the company, the system allows an operating company to “carry out keyhole surgery in their completions at the end of electric wireline.” Keyhole surgery refers to the precision of the placement and the cut.

One example of the operation allows configuration of the Well Miller to drill a hole in flapper or ball valves, either with a minimum of rig time or with a rigless operation. A rigless operation represents a sharp decline in cost from conventional rig intervention, not only in the cost of the rig but through a 50% saving in people, operations time and time needed to work the tool.

Among operations to date, operators have used the Well Miller to drill out flow paths through isolation valves of various alloys and create pressure relief, even in Iconel materials.

An operator used the system to removed barium sulphate scale bridges in a dry gas well.
Next of the to-do list to increase the flexibility of the system, the company plans to make a smaller, more versatile version of the Well Miller. It also is adding a vacuum behind the milling bit to retrieve debris and cuttings from the well bore.

The first field operation for the tool involved using wireline milling to drill out a stuck isolation valve that blocked the borehole on oil producing well with an 86º deviation on a North Sea platform. Total operation time was 11.5 hours, but the actual milling operation took only 7 minutes. The best alternative, a coiled tubing operation, would have taken 3 or 4 days.

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