Abstract
"Pump Stroke Optimization" or PSO was invented to address problems encountered when rod pumping in rapidly changing flow regimes observed with oil production from horizontal wellbores. Current RPC ("Rod Pump Controller") technology was developed for vertical wells. The application of RPCs to horizontal wells often results in frequent full spectrum speed changes and excessive low pump fillage events, both which are undesirable.
The common method operators employ to mitigate this problem is to manually reduce the maximum working speed setpoint to a value slightly above that required to handle all the daily production. This intervention must be done routinely, and is counterproductive should the well see increased deliverability due to events such as downtime or offset fracs. Pump Stroke Optimization (PSO) replaces human intervention by regularly adjusting the maximum working speed based on analysis of several hours of observed pumping speeds and low pump fillage events.
Some RPC's allow for the downstroke to operate at a slower speed than the upstroke. For RPC's with this feature, the PSO device decreases the downstroke pumping speed preferentially, leaving the upstroke pumping speed unchanged until an operator set differential is reached. This practice results in less pump slippage, as well as additional time for evolving gas to exit the rod pump's gas anchor. This results in less strokes per day for the same production, which results in less downhole wear and less power consumption.
Field trials began in two Eagle Ford wells in March of 2015, with initial very successful results presented at an industry workshop in September 2015. An expanded twenty well Eagle Ford pilot test was begun December 3 of 2015. Rather than handpicking wells that were similar to the initial two well pilot, a wide range of production rates were chosen. After 45 days of operation, the following indicators were reviewed by the operator to determine overall success or failure:
Algorithm Convergence (Indicating successful PSO device supplied pumping speeds)
Greater average pump fillage (earlier load transfer better for downhole equipment)
Less Strokes per day without production loss (provided by greater fillage and less slippage)
Higher Bottom Minimum Stress in final rod taper (indicating less buckling tendency)
Less electrical power consumption
The data was obtained using standard industry SCADA and data analysis software, as well as manually reading power meters. In summary, the operator deemed ten wells highly successful, five marginally successful, and five were not successful. The reasons contributing to success and failure will be expounded upon to obtain higher success rates in future applications.
