Bubble Point Pressure

The bubble point pressure of a reservoir refers to the pressure at which the first bubble of gas comes out of solution in the reservoir fluid as the pressure decreases.  The bubble point pressure is a necessary property in reservoir engineering that influences how oil and gas are produced and managed from a reservoir.

Key Characteristics

• Reservoir Fluid  -  In many oil reservoirs, the fluid consists of a mixture of oil and dissolved gas under pressure.
• Bubble Point Pressure  -  As the pressure in the reservoir is reduced, usually due to production, the gas dissolved in the oil starts to come out of solution.  The bubble point pressure is the specific pressure at which this begins to happen.
• Above the Bubble Point  -  At pressures above the bubble point, the reservoir fluid exists as a single-phase liquid with all gas dissolved in the oil.
• Below the Bubble Point  -  Once the pressure drops below the bubble point, free gas begins to form in the reservoir, leading to a two-phase (gas and liquid) system.

Importance in Reservoir Management

• Production Strategy  -  Knowing the bubble point pressure is essential for designing production strategies.  Producing oil below the bubble point can lead to complications like gas production, reduced oil recovery, and changes in reservoir dynamics.
• Reservoir Performance  -  Understanding the bubble point helps predict how the reservoir will perform as the pressure decreases, which is critical for optimizing recovery and managing reservoir pressure.