Gas/liquid ratios (GLRs) typically increase later in the life of a sucker rod-pumped well, and unconventional reservoirs may have high GLRs from the beginning of production. How to handle that gas production is important for sucker rod pumps, as the efficiency is reduced when gas enters the pump. A project was undertaken to quantify several methods used to handle gas production with sucker rod pumps and the effectiveness of each.
This project focused on three areas of design or operation intended to improve gas handling:
Gas separator design: The sizing of downhole gas separators was reviewed, and steps were taken to match the pumping system with the proper separator. In cases where the separator was not pulled, the pump displacement was adjusted to ensure it was within the capacity of the existing separator. Where there was an opportunity to replace the separator, the design was modified to ensure the separator capacity matched the expected well production.
Variable speed drives: Horizontal wells do not provide consistent inflow, but rather exhibit slugging behavior as portions of the lateral load up with liquid or gas. This makes pump-off control difficult with conventional rod pump controllers, which stop the pump completely when there is a lack of fluid at the pump. The performance of variable speed drives was studied to determine if continuous operation while adjusting the speed to accommodate slugging would improve production.
Backpressure valves: Backpressure has been used as a method to improve the performance of wells with gas interference, but the benefits have been questionable compared to the negative impacts on equipment loading. Wells with elevated tubing backpressure were identified, the backpressure was reduced to line pressure, and the impact on performance was monitored.