Reservoir Darcy Radial Flow Calculator

Q: What causes positive wellbore skin factor?

Common causes include drilling mud filtrate invasion and clay swelling, inadequate or plugged perforation tunnels, scale or paraffin deposition, high-velocity non-Darcy turbulence (pseudo-skin), and partial well penetration.

Q: What is Flow Efficiency (FE)?

Flow Efficiency is the ratio of actual well productivity to ideal productivity without skin damage: FE = (Drawdown - ΔP_skin) / Drawdown. A damaged well with FE = 0.50 is producing only half of its undamaged potential.

Q: How does pseudosteady state differ from steady state flow?

Steady state assumes constant boundary pressure (e.g. active water aquifer support). Pseudosteady state (PSS) assumes a closed, bounded reservoir where pressure drops at an identical constant rate throughout the drainage area (dp/dt = const).

Petroleum production & reservoir engineering: Compute radial Darcy inflow rates, near-wellbore skin pressure loss (ΔP_skin), productivity index (J), and flow efficiency.

Reservoir & Fluid Properties

Permeability k (md): Formation effective permeability

Net Pay Thickness h (ft): Producing interval thickness

Reservoir Pressure P_e (psi): Drainage boundary pressure

Flowing BHP P_wf (psi): Bottomhole flowing pressure

Oil Viscosity μ (cP): In-situ live oil viscosity

Formation Volume Factor B_o: bbl / STB

Skin Factor s: Damaged >0, Stimulated/Frac <0

Drainage / Well Radius r_e / r_w (ft):

r_e (ft) / r_w (ft)

Inflow Performance & Skin Loss

Actual Flow Rate (q)

Skin Pressure Drop (ΔP_skin)

Flow Efficiency (FE)

FE = q_actual / q_ideal

Productivity Index (J)

STB/day/psi

Reservoir Drawdown (ΔP)

P_e - P_wf

Flow Capacity (k · h)

Permeability-thickness product

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Frequently Asked Questions

What causes positive wellbore skin factor?

Common causes include drilling mud filtrate invasion and clay swelling, inadequate or plugged perforation tunnels, scale or paraffin deposition, high-velocity non-Darcy turbulence (pseudo-skin), and partial well penetration.

What is Flow Efficiency (FE)?

Flow Efficiency is the ratio of actual well productivity to ideal productivity without skin damage: FE = (Drawdown - ΔP_skin) / Drawdown. A damaged well with FE = 0.50 is producing only half of its undamaged potential.

How does pseudosteady state differ from steady state flow?

Steady state assumes constant boundary pressure (e.g. active water aquifer support). Pseudosteady state (PSS) assumes a closed, bounded reservoir where pressure drops at an identical constant rate throughout the drainage area (dp/dt = const).