Waterdrive recovery, also known as water drive or natural water drive, is a primary recovery mechanism in oil and gas reservoirs where the natural pressure from an underlying or adjacent aquifer (a water-bearing formation) helps push hydrocarbons (oil and gas) toward the production wells. This process relies on the energy provided by the water in the reservoir system, which displaces the oil or gas as it moves through the porous rock toward the wellbore. In a waterdrive system, the reservoir is in contact with an aquifer, which contains water under pressure. As oil or gas is extracted from the reservoir, the pressure drops, and the aquifer responds by pushing water into the reservoir. The encroaching water displaces the hydrocarbons, driving them toward the production wells. This maintains reservoir pressure longer than in reservoirs without waterdrive (solution gas drive or depletion drive reservoirs).
Waterdrive is one of the more efficient natural recovery mechanisms because it sustains reservoir pressure over time. Recovery factors typically range from 30% to 60% of the original oil in place, depending on factors like reservoir geology, fluid properties, and the strength of the aquifer. However, if the water encroaches too quickly or unevenly (through high-permeability zones), it can lead to "water coning" or "fingering," where water bypasses oil and reduces recovery efficiency.
Waterdrive Recovery Formula |
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| \( E_r \;=\; 54.898 \cdot \left( \dfrac{ n \cdot ( 1 - S_w ) }{ B_{oi} } \right)^{0.0422} \cdot \left( \dfrac{ \mu \cdot \eta_w }{ \eta_o } \right)^{0.0770} \cdot S_w^{-0.1903} \cdot \left( \dfrac{ p_i }{ p_d } \right)^{-0.2159} \) | ||
| Symbol | English | Metric |
| \( E_r \) = Fractional Recovery Efficency | \(dimensionless\) | - |
| \( n \) = Porosity | \(dimensionless\) | - |
| \( S_w \) = Water Saturation | \(dimensionless\) | - |
| \( B_{oi} \) = FVF at Initial Conditions of Reservoir | \(RB\;/\;STB\) | - |
| \( \mu \) (Greek symbol mu) = Permeability | \(D\) | - |
| \( \eta_w \) (Greek symbol eta) = Water Viscosity | \(cP\) | - |
| \( \eta_o \) (Greek symbol eta) = Oil Viscosity | \(cP\) | - |
| \( p_i \) = Initial Pressure (psi) | \(lbf\;/\;in^2\) | - |
| \( p_d \) = Pressure at Depletion (psi) | \(lbf\;/\;in^2\) | - |
Key Points Affecting Waterdrive Recovery
Aquifer Strength - A strong, active aquifer provides consistent pressure support, while a weak aquifer may not sustain production for long.
Reservoir Permeability - Higher permeability allows water to move more easily through the rock, aiding displacement.
Oil Viscosity - Lighter, less viscous oil is displaced more effectively than heavy, viscous oil.
Heterogeneity - Variations in rock properties can lead to uneven water movement, leaving oil trapped in less permeable zones.
