New Torque Balancing Algorithm Improves Pulling Force and Speed With Wireline Electro-Mechanical Tractor

Abstract

The electro-mechanical eline tractor introduced in 2019 (Lee et al. 2019) has completed over 120 jobs. As discussed in the paper, one of the unique technology drivers was high tractoring speed to improve intervention efficiency. The tractor has several runs where the average rate exceeded 100 feet per minute and one job at 115 feet per minute over a 2900 ft lateral section. An additional attribute was the surface readout (SRO) telemetry and sensor data that proved invaluable in assessing tool performance, and specifically downhole tractor traction. Initial deployment of the electro-hydraulic eline tractor uses an active traction control system primarily based on wheel speed. During the evaluation of the SRO data, including wheel torque, wheel speed, downhole tension, relative bearing, inclination, and CCL, it was apparent that the variance in the wheel torques values was higher on longer lateral sections expected. This inconsistency in torque was unexpected and suggested possible wheel slippage. The CCL helped confirm that the tractor wasn't traveling the expected distance between casing joints and supported a wheel slippage scenario. Interestingly, monitoring the winch operation and reducing the hold back line tension, muted wheel slippage on several runs. Unfortunately, it was not a consistent control as it was both well trajectory and winch operator dependent. Even a qualified winch operator's attention to detail can wane on long lateral sections, which can cause wheel slip. Noting the ladder would be a challenging key performance measurement to accurately control an engineered solution was developed to improve tractor traction. Armed with a large sensor data suite from previous runs, engineers adopted a completely new active feedback traction control system. The new philosophy undertaken provides a weighting measure for wheel speed and torque, downhole tension, and the electrical power drawn by each tractor section. The DC motors used on the electro-mechanical tractor have individual programmable high-speed motor controllers allowing for a precise feedback loop called"GripPro." Test track results showed this new traction algorithm not only minimized wheel slippage but improved the power-sharing equalization, which allowed for continuous downhole tractor force to be increased by 25%. SRO field data highlighted a much smoother deployment with both speed and torque laying over on all wheels and no large power swings when the tractor encountered sections of increased downhole force due to a dog leg change. On the longer laterals, the symmetry of speed & torque allowed the tractor to travel without increased power demands and offered a satisfactory deployment even when the winch operator wasn't consistent while running in the lateral section.