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.