Jeff Saponja, Oilify
Trey Kubacak, Ovintiv
Dr. Anand Nagoo, Nagoo & Associates
Rod pumping horizontal wells is more complicated and challenging than for vertical wells. For system reliability reasons, it is common for horizontal wells to have a rod pump placed in the vertical section above the wellbore’s curve, which limits drawdown. This means the pump is placed a vertical distance above the producing zone and a pressure gradient of fluid between the pump and the producing zone exists. This pressure gradient can add 200- 500 psi of back pressure to the producing zone, limiting drawdown.
Drawdown is also limited by multiphase flows emanating from the horizontal wellbore that are inconsistent and sluggy. Flow regimes and inconsistent flow slugging tendencies are different in the horizontal, curve and vertical sections of the wellbore and these sections can compound each other for a bad unmanageable slugging condition at the pump’s location. Such inconsistent flows make efficient downhole pump gas separation very challenging. Consequently, a troublesome fluid level in annulus above the pump often remains. This fluid level can add an additional 200-500 psi of back pressure to the producing zone, further limiting drawdown.
To resolve these drawdown limitations and to therefore maximize drawdown, the pump would need to be lowered down into the curve section of a horizontal well. This presents several reliability risks, including:
• reduced run life with increased wear on the pump, rods and tubing,
• increased costs for surface pumping equipment and rod string due to increase loadings,
• reduced downhole gas separation efficiency at high wellbore inclinations, and
• reduce rod pump performance with valves not opening and closing efficiently at high inclinations.
Engineering a rod pumping system to operate at high inclinations reliably around the wellbore’s curve was undertaken. Field implemented has demonstrated a high success rate for dramatically increasing production and achieving good slugging conditions, while not realizing an increase in failure frequency. Results will be reviewed and shared.