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.

An automated wireline milling solution targeted for removal of wellbore obstructions of a varying type, from scale to metal, with built-in capabilities of autonomous cruise navigation between consecutive obstacles, is presented. This paper highlights design features that made a step change in the efficiency and usability of milling services. Control challenges are still common in downhole milling technology. Changes in milling target composition, cuttings accumulation around the target, drag forces from production flow, and other variations can reduce system efficiency and result in lost time or failed interventions. In the case of wireline milling technology, inclusion of intelligent on-board electronics in the downhole equipment presents an opportunity to actively control the milling process to optimize rate of penetration and implement additional protections to reduce operational risk. We describe a robotic toolstring that automatically and independently controls a wireline tractor using real-time feedback from a milling cartridge and other on-board sensors. Embedded control algorithms implement intuitive workflows derived from the combined experience of multiple experts in well intervention. With this automated wireline milling system, the user can initiate the milling process by defining certain milling parameters and then can monitor progress in real time while the downhole robotic tool regulates weight on bit and the milling motor. This new automated downhole control system significantly improves torque-on-bit and weight-on-bit controls yielding superior performance, such as rate of penetration and usability. Dynamic load conditions are handled in a high-speed distributed control loop downhole to get most of bit torque capacity across the entire speed range defined by the motor power curve. Tractor push force is adjusted quasi-instantaneously with changes in cutting conditions. Control responsiveness along with software solutions for tracking of motor stall preconditions and a torque limiter greatly reduce the occurrence of motor stalls arising due to the bit wedging in highly reactive targets. With stall avoidance and an automatic backing-off feature to reengage the bit in case of a sporadic torque spike, direct involvement of an operator is significantly minimized compared to the previous tool generation. Head-voltage stabilization is another factor positively impacting the overall power stability and performance of electromechanical tools downhole. Safety features are also in place to prevent cable twisting and protect assets from overcurrent and overtemperature conditions. The progressive design of the automated milling tool boosts operational efficiency and autonomy, minimizes human mistakes, and reduces risk of getting stuck during the service. Case histories demonstrate the first field jobs and system integration tests performed with this new tool.