Pressure Loss / Friction Pressure Calculator

    Calculate pressure loss and friction pressure in pipes and drill strings using flow rate, pipe dimensions, and fluid properties based on the Darcy-Weisbach equation.

    Calculation Inputs

    Total pipe or drill string length

    Internal diameter of pipe

    Volumetric flow rate through pipe

    Mud weight or fluid density

    Darcy friction factor (typically 0.015 - 0.03 for drilling). Use Friction Factor Calculator for precise values.

    What Is Drilling Fluid Pressure Loss?

    Drilling fluid pressure loss is the frictional pressure drop that occurs as mud flows through the circulation system: surface equipment, drillpipe, drill collars, bit nozzles, and annulus. Understanding pressure losses is essential for sizing pumps, estimating ECD, and managing well control margins.

    Basic Concept (Darcy–Weisbach Form)

    A widely used form for frictional pressure loss in pipe flow is the Darcy–Weisbach-type relationship:

    ΔP = f × (L / D) × (ρ × V² / 2)

    Where:

    • ΔP = pressure loss
    • f = friction factor (depends on flow regime and rheology)
    • L = length of the section
    • D = hydraulic diameter
    • ρ = fluid density
    • V = average velocity

    In drilling, non-Newtonian mud models (e.g. Bingham Plastic or Power-Law) are often used when calculating f and effective viscosity terms.

    Components of System Pressure Loss

    • Surface equipment: standpipe, hoses, surface lines.
    • Drillstring: drillpipe, drill collars, tools.
    • Bit nozzles: high local pressure drop across jets.
    • Annulus: flow between drillstring and open hole or casing.

    The total circulating pressure is the sum of the pressure losses across all these sections plus hydrostatic pressure.

    Pressure Loss and ECD

    Annular pressure loss contributes directly to ECD at the depth of interest. Higher flow rates improve hole cleaning but also increase frictional losses and ECD. The pressure loss calculator helps balance these competing effects.

    Pressure Loss FAQ

    Why does pressure loss increase so quickly with flow rate?

    In turbulent or high-shear flow, frictional losses typically increase faster than linearly with velocity. Doubling flow rate can more than double pressure loss, depending on rheology and geometry.

    Does pipe roughness affect pressure loss?

    Yes. Internal roughness influences the friction factor, especially in turbulent flow. Worn or scaled pipe can have higher friction than new, smooth tubulars.

    Basic Formula:

    ΔP = f × (L/D) × (ρV²/25.8)

    Darcy-Weisbach equation for pipe flow

    ΔP: Pressure loss (psi)
    f: Darcy friction factor (dimensionless)
    L: Pipe length (ft)
    D: Pipe diameter (ft)
    ρ: Fluid density (ppg)
    V: Flow velocity (ft/sec)

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