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.

Completion components integral to well design are selected for their required functionality. These components range from simple profiles used for securing retrievable plugs, to valves of varying complexity and design used during the completion or production phases. Often, remedial work is required to remove these components if they are no longer working or needed when they are a hinderance to well access or its productivity. This paper presents two case histories of completion component milling operations that were efficiently carried out by applying recent developments in combined tractor and mechanical application technologies. Electrohydraulic tractors were developed in the mid-1990s initially as means to convey electric line tools in highly deviated sections of wells. Applications were soon developed to include rotational capability run in conjunction with the tractor, enabling milling of well debris or completion components. For this, the tractor is used not only for payload conveyance, but also to provide weight on bit (WOB) during a milling operation. Recent technology developments are providing an increased level of control, enabling more complex component milling to be carried out efficiently and with greater degree of confidence. Such components, including flapper valves and nipple profiles, are made from a variety of steel alloys, shapes and dimensions. Efficient milling of these requires an optimal bit design, coupled with optimised milling parameters, for example, WOB, torque and RPM. The challenges of milling with limited available power are discussed, new milling solutions are disclosed, and the importance of real time feedback of milling parameters to ensure success are illustrated. This paper discusses new electronic and hydraulic developments applied to the tractor-milling platform. Case histories will demonstrate the hi-fidelity measurement, independent control and optimisation of all relevant milling parameters adjusted on the fly, delivering performance across all stages of the milling operation. They will show the high level of instrumentation now available which ensures the milling operation is conducted within prescribed and tested limits and allow performance parameters, designed and demonstrated in the lab, to be replicated one-to-one in the downhole environment. Improvements also include specific bit designs that have been developed though a rigorous testing program to minimise tool jamming and the metal debris created during the milling process, which could inadvertently cause other issues in the well. The technology enables switching between the tractors driven and rolling rotational anchor functionality whilst providing continual rotation and back-reaming capability to minimise the possibility of a stuck tool scenario. The case histories show that these developments have delivered unprecedented success in challenging cased hole milling operations.

Until recently, electric line tractor driving speeds have been lying significantly below their true potential, because of elements related to design, working principles and system dynamics. Several case histories from recent electric line tractor conveyance operations illustrate the number of operational benefits that have resulted from an engineering re-design, through applying the latest electronic and hydraulic technologies to electric tractor conveyance. Electrohydraulic tractors were developed in the mid 1990s as an alternative means to convey electric line deployed tools along the highly deviated or horizontal sections of wells. The application of this tractor technology has grown considerably over the years, having been applied to convey an increasing range of technology payloads (for example, logging tools, ballistic devices and powered mechanical applications) to an expanding stock of deviated wells with increasing length and tortuosity. The performance and capability of electric line tractor tools has always been a trade-off between numerous limiting factors including the electric line cable (strength, weight, length, voltage and current rating), the surface power supply, the tractor components (downhole motor power and drive train efficiency), and the completion size into which it is deployed. This has until now necessitated tractor pre-set requirements to successfully perform a job, resulting in limitations on performance criteria such as tractor pull force and speed. This paper discusses recent improvements to the tractor platform achieved through redesign and by applying new electronic and hydraulic developments which enable in-well, on-the-fly optimisation of the tractor components and parameters. The field operations demonstrate the transformation in tractor conveyance speeds achieved, in the order of three and a half times that previously delivered, representing a new standard in electric line tractor conveyance efficiency. These speeds, coupled with increased payload conveyance capability and the improved mission certainty which can be achieved, are even more relevant in wells of significant measured depth, lateral length and challenging well profiles and trajectory complexity. The technology presented will also allow well completion engineers to plan complex well intervention jobs in demanding wells with more confidence now that it is available to increase operational success.