Well Miller® removes carbonate scale and regains access to tubing in a Middle East horizontal well

    Oil producer
    8560 ft


A horizontal oil producer in the Middle East had significant scale accumulation throughout the tubing. The carbonate scale deposition restricted production, and the operator needed it cleaned out to regain full access to the tubing. At the time, neither a workover rig nor a coiled tubing (CT) unit was readily available in the target time frame. Additionally, costs were a major concern to the operator; a viable, cost-effective method was needed. With these constraints, the operator decided to initiate an e-line scale clean-out intervention.

Welltec® was contacted and planned a three-stage milling operation with different milling bit sizes. The operation would be run utilizing a combined Well Tractor® and Well Miller. After pre-job safety checks and accommodations were made, the tools and crew were mobilized to the jobsite.


The tools were mobilized and rig-up completed. All milling was performed with the well in “controlled production” mode, which enabled the flow of the well to carry out milled scales and cuttings. During all runs, the Well Tractor conveyed the toolstring and applied weight-on-bit and also counter torque generated by the Well Miller.

Three different bit sizes­—2.35”, 2.29”, and 2.2”—were used to clean the 2.875” tubing, which included several restriction points of varying sizes. The first milling phase required the 2.35” milling bit. During the first milling phase, Welltec milled to the first restriction of 2.34” at 6927 ft, covering a distance 934 ft. Then, the 2.29” bit was swapped in and milling commenced at the next restriction at 7750 ft, from the travel joint to three feet above the nipple at 7980 ft, covering 230 ft.

The final phase, with the 2.2” bit, required milling through the nipple to the wireline entry guide (WEG) at 8560 ft. Initially, milling reached 8415 ft, but personnel noted a drop in tension. The likely reason for this is that the inner diameter of the tubing deviated and narrowed to 2.2” at this point, leaving little headroom for the tools. The toolstring was then shortened and milling resumed. Depth correlations confirmed that the Well Miller milled through the WEG.

The Power Suction Tool® removed residual cuttings left after milling operations. The Well Miller with a wire brush was also run to clean around the nipple profiles. The working schedule for this job mandated that work could only be completed during daylight hours, increasing the number of runs required; the entire operation required ten runs


Welltec’s e-line scale clean-out job successfully removed scale deposits from the initial tag at 842 ft to the WEG at 8560 ft. The operation enabled the client to regain full access to the tubing and resulted in an increase in production.

Welltec worked with the operator’s detailed safety guidelines to successfully clean out the carbonate scale in this horizontal well safely and efficiently.

With no available workover rig or CT unit, Welltec’s e-line solution helped the client avoid deferred production in this well. Additionally, running the operation on e-line resulted in significant cost and time savings over heavier alternatives.

Tools Applied

  • Well Miller® for Scale Removal

    The Well Miller for Scale Removal transforms the power of the Well Miller into a clean-out application for those scale deposits which can’t be removed effectively with standard clean-out tools.

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  • Well Cleaner® Power Suction Tool

    Our clean-out solutions ensure access into new wells and optimized production from old wells: removing sand and debris; cleaning SSSV seats; clearing obstructions; eliminating scale deposits; accessing isolation valves.

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  • Well Tractor®

    The Well Tractor was regarded as a revolution in the industry when it was introduced in the 1990’s. It enables operators to extend the reach of traditional e-line deployment into highly deviated and horizontal wells.

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  • Welltec Release Device®

    Welltec Release Device (WRD®) is a simple tool which adds versatility and risk reduction to the operation. It provides predetermined locations in the toolstring where it can be parted, should it become stuck.

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