«Onshore and offshore oil and gas well construction»

Eccentric bottom-hole milling machine

UDC: 621.193.16
DOI: 10.33285/0130-3872-2022-3(351)-15-17

Authors:

¹ SOCAR, Baku, Republic of Azerbaijan

Keywords: production string, casing wall thickness, restricted zones, emergency end, milling, downhole milling machine, eccentric downhole milling machine

Annotation:

The production string along its entire length consists of casing pipes of the same type-size with different wall thicknesses: larger in the upper part, relatively smaller in the lower part. The article discusses the inner diameter reductionwhen applying some methods of restoring the casing stringstightness. Emergency operations in wells, the operation of which was suspended by forced milling of emergency ends by milling cutters of a smaller diameter, often causes even greater deformation of the emergency ends, up to breaking. This leads to a complication in the well, ultimately prolonging the time spent on the workover. That’s why, the use of eccentric cutters when repairing emergency wells is very relevant. After passing through the narrowed zone of the operational production casing string, when milling by a relatively small diameter milling cutter during rotation, depending on the distance of eccentricity, the required size of the large diameter is covered. This allows milling the emergency end of the pipe over the entire cross section of the well. The article provides information about the design features of eccentric downhole milling cutters and their advantages in appropriate downhole conditions.

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