For nearly a century oil producers have come to rely on reciprocating rod lift to keep marginal wells producing for as long as is economically possible. However, the constant up-and-down movement of a sucker rod creates the possibility of erosion wear on the rod or tubing, which if left unchecked requires a costly intervention to make repairs.

To extend the working life of a sucker rod, the industry has come to rely on the use of rod rotators – ratchet-type mechanical devices that incrementally rotate the rod with each stroke. This rotation distributes the frictional wear caused by the interference between the rod and the tubing to become more evenly distributed around the entire circumference rather than isolating this wear to just one spot.

Rod rotators have been used in the industry since the 1950s; however, methods of accurately monitoring their function have been lacking. An inefficient rod rotator puts the integrity of the entire rod-pumping system at risk. Without going to the well site and visually verifying the operation of the rod rotator, there has not been a way for operators to know if the rotator has slowed down or stopped working altogether.

Weatherford developed an intelligent rod rotator to significantly reduce the time to identify a failed rod rotator, thus extending the life of the rod and avoiding an unplanned shutdown of the well. The idea for this technology was inspired from a conversation with a client in California, who had some 6,000 rod-pumped wells concentrated in a 26-sq-km (10-sq-mile) area. About half of the wells included a rod rotator, but the operator did not have a reliable or efficient means of knowing whether they were working.

A rod-rotator issue was typically discovered when field personnel visited a well site about once every three to four weeks. With no monitoring system in place, it was difficult to tell if the rotator stopped functioning three weeks prior to their visit or just a few minutes before the crew pulled up.

The operator’s original plan was to hire dedicated personnel tasked with driving from one side of the field to the other, stopping at each well, and visually inspecting the working condition of each rotator. This process would take two full days just to identify those wells with rod-rotator problems and then place them into the maintenance schedule. It could take several days or weeks to get a crew out to repair the rod rotator, during which time the rod would remain stationary and could increase risk of failure caused by sustained rod/tubing contact in the same spot.

Given the many other work requirements in the field on a daily basis, the operator quickly decided that this was not the best use of its manpower.

A revolution in rotation

An ideal solution needed to be affordable and integrate seamlessly with the rod-pump controller system already in place. The intelligent rod rotator was designed to meet these requirements by incorporating several new sensing technologies that take the guesswork out of rotator failures.

The first of these technologies is the intelligent rod rotator itself, which incorporates an internal rotation sensor and a built-in anti-rotation mount. The sensor detects each rotation of the rod and sends a signal to the WellPilot rod-pump controller, which controls the pumping system with high accuracy and includes a large number of input/output ports that provide a framework for incorporating future devices such as the controller.

The controller was connected to many of these wells with all the accompanying cables already installed. The company devised an application that senses each rotation of the rod based on the signal coming from the sensor into one of the controller’s ports to indicate the total number of rotations per day. With those data, the controller can calculate when the rotator has stopped working.

This software application, which also is built into Weatherford’s Life of Well Information Software (LOWIS) – a web-based well management and production optimization platform – collects the rotation data being sensed by the controller once per day. As part of Weatherford’s Field Office software suite, LOWIS software also provides real-time monitoring and alarm capabilities. When the software reads the rotation values from the controller while the well is running and determines that the rod has stopped rotating, an alarm is generated locally at the well site and in the software application that indicates a rod-rotator failure and prompts the operator to deploy a team to the well and make necessary repairs.

The signal generated from the intelligent rod rotator can be detected by any real-time software package monitoring the well. The information obtained by the tool is not dependent solely on the company’s software, so a client can use an existing software monitoring system to track rod-rotator data as well.

This flexibility in field deployment prompted the second sensing technology upgrade – a modification kit that can be installed on wells with a competitor’s rod rotator already in place. This upgrade kit comprises a rotation sensor, sensing magnet and strap, mounting kit, load cell, and ancillary cables. It enables operators to take advantage of the monitoring power of the company’s system without having to completely discard the rod rotator that they already have in place.

The third technological advancement is how signals are transmitted. The company devised a special cable and connector that enables the load sensor signal and rod-rotator data to transmit to the rod-pump controller on the same cable. Both parameters can be measured without deploying additional cables in the field, which can provide further safety and economic benefits.

Meeting business objectives

The solution had to help the operator achieve two objectives: First, it had to reduce the time to identify a failed rod rotator. Second, it had to provide increased well surveillance capabilities remotely, which would increase well surveillance capabilities while reducing the likelihood of lost production.

The first field trials for the client were conducted in summer 2012, and all criteria were met, including the capability to count the number of strokes per day, detect when a rod rotator had failed, and significantly reduce the time to detect a failure. The system consistently and accurately notified the operator within 24 hours of a failure.

The intelligent rod rotator enables a client to manage wells by exception and to prioritize their maintenance activities such that they can address rotator problems based on well productivity. Higher producing wells with rod-rotator problems move to the front of the maintenance schedule, which can increase the effectiveness of maintenance efforts and flows straight to the client’s bottom line.

Future advances

While the rod-rotator system is still in the final stages of commercialization, its field trial successes already have prompted some upgrades. The company is in the process of building prototypes of other rod-rotator systems of different sizes based on load requirements and well depth. And while the first generation uses a wire to transmit the signal from the rod rotator to the WellPilot system, the company is working on an option to transmit the signal wirelessly. This version is expected to be available in 2Q 2013.

A software application is in development that can further reduce the notification time for rod-rotator failure from once per day to once per hour. Additional upgrades include an intelligent tubing rotator – a sensor based on the same general design as the rod-rotator system that is affixed below the wellhead to monitor tubing rotation below ground.