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.

The client had a leaking gas lift valve (GLV), which needed to be replaced to restore the integrity of the well. The side pocket mandrel (SPM), was located at a high angle part of the well, positioned on the low side and sand debris had accumulated in and around the GLV, impairing its retrieval. Tests carried out on surface to attempt to latch a GLV through the sand proved ineffective, even with jarring. To further optimise production, SPMs are being installed at increasing well depths, enabling deeper gas injection into the tubing. Placing SPMs into the high angle section of deviated wells inherently increases the risk of them retaining debris, as was the case in this well. A novel solution, to remove the accumulated sand debris from the SPM was proposed, utilising an orientation sub, run in conjunction with an electric line deployed tractor-suction tool configuration, incorporating a bespoke side facing inlet nozzle. Tests on the designed solution were conducted in the engineering facility, recreating the deviation, orientation and debris expected and evaluating the nozzle alignment and cleanout capability for the expected debris type. These tests proved to be highly successful, giving the customer the confidence to perform the job. The deviation also necessitated electric line tractor deployment of a modified retrieval device. Following a drift and plug setting run, the well tractor and suction tool assembly was deployed and two litres of sand was collected from within the SPM. The subsequent run to pull the faulty GLV was successful, as was the deployment of a replacement GLV. The operation proved this to be an excellent and highly effective example of a rapidly designed and tested, bespoke, electric line deployed SPM cleanout solution.