The objective of this paper is to discuss a method to perform automatic and ongoing testing to determine a well's liquid inflow. The paper will further demonstrate how to automate wells using progressing cavity pumps by automatically identifying changes of well liquid inflow in real time and applying these changes to inflow performance relationship calculations, liquid level calculations, and pump performance analysis.
To correctly determine pump efficiency, pump slippage and cavity fillage must first be understood. By comparing the surface liquid production rate at two different speeds with the manufacturers’ theoretical pump displacement, an accurate pump slippage value can be determined. To determine the inflow value, the well has to be pumped down to the pump intake level (pump off condition). At this condition, the maximum flow that can be obtained from the well will match the inflow from the reservoir to the wellbore. Therefore, the measurement of the outflow will equate the inflow at that moment. Maintaining liquid production equal to or slightly less than the wells current inflow ensures that the well is constantly optimized. Matching pump speed to well production capacity will achieve a safe minimum bottomhole pressure. Performing the slippage and inflow test at regularly scheduled intervals will ensure that when a wells liquid production surges, or declines, the PCP system matches the adjusted production capacity.
Previously, when PCP automation systems used pump efficiency information to monitor a well, slippage and cavity fillage was not taken into consideration. Pump liquid production could vary drastically in these systems. Because efficiency values varied over pumping speeds, it was difficult for one to determine true well inflow and match capacity.
Real world data, gathered from a pilot project conducted with Pioneer Natural Resources, will be used to demonstrate the determination of well liquid inflow. Real-time data points gathered using SCADA system telemetry, such as measured bottomhole pressure, actual liquid production at surface, pump cavity fillage and slippage, will be trended together over time. The paper will also include operator observations and acoustical fluid level determination data.