Wireline Tractor System with User Programmable Behaviors for Semi-Autonomous Restriction Navigation

A semi-autonomous wireline tractor solution for casedhole applications enabling navigation through complex restrictions with minimal operator interaction in absence of digital telemetry is presented. The robotic conveyance technology provides a foundation for applications where programming of tractoring behaviors is available to field personnel as a part of the job design. Digital telemetry may not be available for wireline tractor tools. A conveyance system with programmable behaviors allows downhole navigation when conventional telemetry is nonexistent or has prohibitively low bandwidth or a protocol conflict, which is relevant in configurations with third-party tools. The presented control technology utilizes downhole on-board measurements with tracking and decoding of head voltage waveforms where electrical power is supplied by the surface system. Voltage is set by an operator to fall into one of several predefined bands representing specific tool commands that trigger a set of robotic sequences. The logging cable can be freed to carry a high-frequency communication signal to payload tools while powering both the tractor and its payload. Although the tractor does not have feedback through its telemetry data, tractor operational condition can be derived from the variations of electrical current measured at surface. A head voltage stabilization system along with a load calibration method compensates voltage fluctuations due to load changes and losses in the logging cable. An advanced signal-processing algorithm implemented in downhole embedded software quantizes denoised voltage and reliably maps it to operational bands, effectively eliminating transient processes resulting from high-power jobs. The voltage estimation technique supports a finite set of commands to be interpreted by the downhole tools and to activate control logic implemented as scripted state machines with a core based on the deterministic finite automaton concept. Behaviors scripted and parametrized by an operator in custom metalanguage use a dictionary of actions and conditions provided by the embedded software that runs the tools. Controllers may be designed and put into action by nonprogrammers to solve restriction navigation needs for a known well completion. The availability of design and simulation software aids job planning. Multiple tractor configurations with individually controlled arms were successfully tested at locations in the USA and Eurasia, with and without third-party tools with their own telemetry. Reliable restriction navigation using preprogrammed behaviors controlled by voltage levels has been demonstrated. The design opens development opportunities for other semi-autonomous downhole applications. Run-time pattern recognition of electrical current in the software enables further automation of the surface power system to drive the downhole navigation, detect and respond to anomalies, and reliably manipulate voltage transitions. The presented technology removes the compatibility barrier between different telemetry systems and elevates flexibility of systems lacking telemetry while preserving their usability and robustness.