Abstract
Hydraulically actuated sucker rod pumps have been around since the 1940’s but have not received a widespread adoption or acceptance on the order of beam pumps, ESP’s or PCP’s. This is in no small part, due to a reputation of high maintenance costs and frequent failures. Innovations in hydraulically actuated sucker rod pumps, with a keen insight for the oilfield environment, have helped improve reliability and reduce maintenance costs. Among these improvements are the elimination of persistent external hydraulic leaks, a long-stroke capability, and a simplified control system. The instrumentation and control of the hydro-mechanical system is accomplished with an innovative method for determining both polished rod position and load based solely on the hydraulic fluid dynamics. This eliminates any sensors, or points of failure, at the wellhead. Vast improvements in control and data acquisition have greatly reduced the failure rates of hydraulic sucker rod pumping systems by automatically responding to adverse conditions. By allowing operators to remotely interact and troubleshoot the system, a finer grained level of optimization can be achieved by closely matching the wells inflow to the production rate. In some down-hole failure cases, such as a stuck pump, a unique advantage of a hydraulic system allows the operator to attempt unsticking the pump by overloading the polished rod. Although this procedure is not always successful, it does provide a last resort that may save the cost of pulling the well. This procedure is unique to a hydraulic system because there are no structural or reducer load limitations beyond that of the rod-string capacity. The long-stroke improves down-hole equipment runtimes by distributing the wear over a larger surface and by reducing the cyclic fatigue on the rod-string. While the hydraulically actuated sucker rod pump is not appropriate for every well, it does offer significant advantages in those wells where it is suitable. These advantages include long-stroke capability, remote optimization, and safe operation in terms of no external moving parts. The complete system is simple, cost effective, and portable, making it ideal for both permanent and trial installations.
