This paper describes a job on a well in the Valhall field to remove approximately 241 liters of settled barite in order to gain access to retrieve a bridge plug assembly that had been installed in the well for more than seven years. The traditional industry methods of cleaning out such debris are mechanical bailers run on slickline, or coiled tubing. The clean out was initially started as planned with conventional bailers run on slickline. After 19 runs and 88 liters of debris removed, mechanical slickline bailers made no further progress, as a result of increased debris compaction. The powered wellbore cleanout system was then run. This system had been extensively tested on a test rig before the job with samples simulating expected downhole debris conditions. This testing resulted in a number of toolstring configuration options dedicated to the downhole challenges expected in the well and the use of two technologies (debris collector and suction tool), to retain and transport the debris from the well.The powered wellbore cleanout system successfully removed all the remaining debris (152 liters). It was able to continue from where the mechanical slickline bailers stopped and removed the remaining debris three times faster than the mechanical slickline bailers. Each run with a powered wellbore cleanout system could collect, on average, approximately five times the volume of debris collected by conventional slickline bailers.

Barium Sulphate (BaSO4) scale is classified as a hard scale and removal is extremely resistant to both chemical and mechanical methods. Coiled-tubing deployed mechanical intervention is effective, but with inherent logistics, footprint and cost implications. Electric-line deployed wellbore cleanout systems have the advantage of being light and easily deployable. In wellbores with inside diameters (ID) of less than 3 in., removal and downhole collection of hard debris has proved to be a particular challenge. This paper describes a wellbore cleanout operation on powered electrical wireline in the North Sea. The main operational objective was to clear out the wellbore to the top of a suspected malfunctioning Sliding Side Door (SSD), with a drift ID of 2.797 in. Access was required to run a tubing punch to establish communication with the target reservoir and therefore restore well production. The debris severely plugging the wellbore was predominantly BaSO4 scale. Slickline broaching was initially attempted to remove the obstruction, but could not make sufficient progress. An electric-line deployed wellbore cleanout system, with bottomhole assembly (BHA) outside diameters (OD) of 2.625 in. and 2.75 in. and reservoir chamber OD of 2.5 in. was subsequently deployed, which was effective and consistently able to interact with, and remove to surface, the scale blockage. 168.6 litres of debris was collected by the electric line wellbore cleanout system. Contributing to the success of the operation was extensive pre-job testing and measurements executed in the laboratory. These simulated downhole completion geometry and expected debris condition and interaction. The pre-job test results fed in to the design of an optimum BHA and were a basis for decision-making during the operation. The resulting system design maximised solids recovery per run, which increased cleanout and collection efficiency. A surface wellsite washout system was used to clean out the collection chambers, which enabled the rapid turnaround of equipment in-between runs. Cleanout was executed through multiple runs, with the majority returning maximum fill to surface, which ultimately gained access to target depth as efficiently as possible. A multi-finger caliper log run confirmed the removal of the obstruction and a tubing puncher was run to perforate the inner tubing. Production was restored, with an average (over the first three months) oil production rate of 1,290 STB/D (205 Sm3/d), gas rate of 7.2 MMscfd/D (204,321 Sm3/d) and water cut of 69%. This is the first time that an electric-line deployed wellbore cleanout system with an OD as small as 2.625 in. has delivered high, successive, repeatability in cleaning out hard BaSO4 scale from a completion with an ID as small as 2.797 in.

Electric line deployed well intervention technologies are continuing to grow in use and relevance, this is due to the value provided by a highly efficient and effective means of intervention. It is light on equipment, personnel and logistics, is controlled and precise in its in-well execution, and is less obtrusive to the wellbore, the reservoir and the environment. These valuable characteristics are making electric line deployed solutions the preferred choice of customers for many interventions, whether that be for addressing new well completion, old well rejuvenation or repair, or eventual plug and abandon (P&A) operational scope. Preference is also increasing with those customers who are keen to push the boundaries of these technologies to leverage their beneficial impact across a broader range of intervention operations. Often, the tasks or workscope assigned to electric line deployed intervention technologies are reserved for what would be considered the lighter end of the spectrum, for example, low volume debris cleanout, small component milling and low force tool manipulation. However, as full system-based intervention technology platforms are developed, incorporating advanced interconnected technology components, the magnitude of what can be achieved has expanded electric line intervention solutions into the realms of work scope previously reserved for heavier methods, like coiled tubing or drill pipe based. That, coupled with the efficient and precise execution and inherently light footprint that electric line deployed intervention brings, is adding to the increased interest in expanding its use. Two recent electric line deployed wellbore cleanout operations carried out on the Norwegian Continental Shelf involving high volumes of debris demonstrate the advantages this advanced intervention technology platform has enabled, the scalability of its performance, and why it is challenging the traditional thinking and perception of what is possible on electric line. In the case operation 1, extensive volumes of produced sand had accumulated in a large mono-bore completion preventing the execution of a required P&A operation. In case operation 2, the well had significant Barium Sulphate (BaSO4) scale deposits over much of its length, which prevented well access for a required gas lift valve (GLV) change out. In both these cases, efficient and effective electric line deployed remediation was possible due to the increased performance, in-well task visibility and real-time task control provided by the advanced electric line intervention technology platform that was utilised. Attempting both these cases was strongly encouraged by the customer, leading a one team approach. For case operation 1, high speed tractor conveyance speeds of over 26 meters/minute were achieved on this multi-run operation. Instrumentation provided real-time indication of collection chambers being full, ensuring minimal time on depth during collection. Consistent high volume recovery rates of 100% were achieved on all but one of the collection runs, with a total of 1400 liters of sand debris being collected, clearing 280 meters of wellbore, at an average of 140 liters per 24 hours. For case operation 2, over 2000 meters of hard scale was milled, at a rate of penetration (ROP) of 44 meters/hour, on average, re-establishing access for required electric line intervention runs and the subsequent change out of the leaking GLV to restore the integrity of the well, enabling it to be put back on line and resume production. Record breaking achievements regarding the volume of debris removed and depth intervals cleaned via the intervention technology platform were made in both cases.