Which term defines the pressure difference between the average reservoir pressure and the flowing bottomhole pressure?

Which term defines the pressure difference between the average reservoir pressure and the flowing bottomhole pressure?

• A. Backpressure
• B. Overbalance
• C. Drawdown
• D. Underbalance

Answer: (C)

The term describes the pressure drop that drives production: the difference between the reservoir’s average pressure and the pressure at the bottom of the well while it’s flowing. This pressure drop, or drawdown, is what pushes fluids from the formation into the wellbore. If the reservoir pressure is higher than the flowing bottomhole pressure, fluids flow toward the well, and the magnitude of that difference is the drawdown. For example, with a reservoir pressure of 3500 psi and a flowing bottomhole pressure of 2000 psi, the drawdown is 1500 psi. The other terms relate to different situations. Backpressure refers to the pressure at the surface or the resistance the surface system must overcome, not the subsurface pressure difference. Overbalance and underbalance describe drilling conditions relative to formation pressure: overbalance means bottomhole pressure exceeds formation pressure to prevent influx, while underbalance means bottomhole pressure is lower to permit influx. These are not the general production-drawdown concept.

The term describes the pressure drop that drives production: the difference between the reservoir’s average pressure and the pressure at the bottom of the well while it’s flowing. This pressure drop, or drawdown, is what pushes fluids from the formation into the wellbore. If the reservoir pressure is higher than the flowing bottomhole pressure, fluids flow toward the well, and the magnitude of that difference is the drawdown. For example, with a reservoir pressure of 3500 psi and a flowing bottomhole pressure of 2000 psi, the drawdown is 1500 psi.

The other terms relate to different situations. Backpressure refers to the pressure at the surface or the resistance the surface system must overcome, not the subsurface pressure difference. Overbalance and underbalance describe drilling conditions relative to formation pressure: overbalance means bottomhole pressure exceeds formation pressure to prevent influx, while underbalance means bottomhole pressure is lower to permit influx. These are not the general production-drawdown concept.