Capillary Pressure Calculator
Calculate capillary pressure using the Leverett J-function. Determine free water level and transition zone height from rock and fluid properties.
Input Parameters
Pc = J(Sw) × σ cosθ / sqrt(k/φ) | h = 144 × Pc / Δρ
Capillary Pressure
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psi
Height Above FWL
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ft
sqrt(k/φ)
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microns
Δρ
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lb/ft³
Pc in kPa
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Height in meters
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How this was calculated
Leverett J-function: J(Sw) = Pc / (σ cosθ) × sqrt(k/φ), which normalizes capillary pressure data across different rock types.
Capillary Pressure: Pc = J(Sw) × σ cosθ / sqrt(k/φ). Units: σ in dyne/cm, k in mD, φ fraction. Result in psi after unit conversion.
Height Above FWL: h = 144 × Pc / Δρ, where Δρ is density difference in lb/ft3.
Rock Quality Factor: sqrt(k/φ) in microns indicates reservoir quality. Higher values = better quality rock.
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Open Tool →Need help with SCAL analysis, transition zone modeling, or reservoir characterization?
Book a free strategy call →Understanding Capillary Pressure and the J-Function
Capillary pressure is the pressure difference across a curved interface between two immiscible fluids (oil-water or gas-water) in a porous medium. It controls fluid distribution in the reservoir, particularly in the transition zone between the oil column and the free water level (FWL). Understanding capillary pressure is essential for determining initial water saturation, estimating reserves, and designing completion strategies.
The Leverett J-function normalizes capillary pressure data by accounting for differences in rock quality (permeability and porosity), interfacial tension, and wettability (contact angle). This allows capillary pressure data from core plugs to be scaled to reservoir conditions. The transition zone height depends on the density contrast between phases: small density differences (as in gas-oil systems) produce tall transition zones, while large density contrasts yield thin ones. This calculator implements the J-function approach. All calculations run in your browser. Built by Groundwork Analytics.