Going deep to fix borehole problems

A simple assembly of concentric parts can be lowered down a borehole to locate the exact positions of restrictions and problems – all in one go

Oil and gas industry engineer Matthew Nangle devised the assembly, which he calls the Mechanical Multi Drift.
“Scaling of oil and gas wells is a common problem in exploration and production, and occurs where produced water/emulsified oil and heavier fractions solidify and become adhered to the walls of a borehole, creating bore restrictions,” states Nangle’s patent. “This is a particular problem in borehole lining/tubing, in completions where scaling reduces the available bore diameter, restricting the passage of well tools and production fluid flow. To overcome this problem, it is necessary to run a milling tool down the hole to remove the scale. However, this operation cannot be performed effectively and efficiently until the location of the restriction, and the extent of the restriction, has been determined.”
Nangle’s solution is such that, when it is lowered down the hole and it encounters the first restriction, the outer part lodges there, but the inner parts can continue to be lowered. The reduction in weight can be detected at the lowering winch, so it is known at once exactly where this is and the approximate reduction in diameter – which may be caused by scale or by a landing nipple above a sub surface safety valve. Nangle’s device allows the rest of the multi drift to continue downwards. He envisages his appliance having four concentric parts, which would allow the lowest part to get past up to three obstructions as it descends. The idea also works in an inclined directionally drilled well, where obstructions are even more difficult to get past with conventional devices than in vertical boreholes.

Tom Shelley

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