Hydraulic Workover Unit (HWU) Application in Down-hole Milling Operations in Niger Delta

Abstract

The major challenge with down hole milling operations using HWU is employing a suitable fluid circulating system, which is very critical for effective well bore cleaning and transporting of cuttings from the well bore to the surface. A bell nipple with sufficient side outlet diameter to ensure efficient fluid circulating system was designed and installed above the top of the BOP stack. During the HWU rig up, the height of the unit was kept as low as possible to ensure unit stability during operation, without further increasing the height of the unit and reducing its stability. Furthermore, HWU being directly rigged up on top of BOP stack, did not require the bell nipple to be a load bearing spool to support the weight of the unit and the work string when fully rigged up and operational. This paper reviews the application of Hydraulic Work over Unit in down hole milling operation in Niger Delta highlighting the steps taken to ensure good circulating system without compromising the unit stability, and eliminating additional cost of load bearing bell nipple/spool.

Key words: HWU; Milling; Cement retainers; Cement plug; Workover; Bell Nipple; Wellbore clean-up