SWD Well Injection
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SWD Well Injection Pressure Calculator

Surface & BHP per Frac Gradient + Hall Plot for UIC Class II Wells

Estimate SWD well injection pressure at surface and at the perforations. Checks against the EPA/state frac-gradient limit, computes hydrostatic + tubing friction, and back-calculates injectivity (bbl/day/psi) via the Hall plot method for steady-state radial flow.

Well Geometry

ft
in
2-7/8" L80 ≈ 2.441; 3-1/2" L80 ≈ 2.992
ft
psig
Static BHP at start of injection
ft
mD
ft
40-ac spacing → r_e ≈ 660 ft
ft
8-1/2" hole = 0.354 ft

Fluid & Reservoir

BWPD
—
cP
Brine 0.5 – 1.5 cP
—
Positive = damaged; negative = stimulated
psi/ft
0.60 – 0.80 typical sandstone/shale
—
EPA UIC max = 0.90 × frac pressure

Surface Equipment

in
0.0018" commercial steel
psi
Pump discharge to wellhead
psig
Monitored per UIC mechanical integrity

📚 Learn the Theory

Frac gradient, hydrostatic + friction stack, Hall plot transmissivity, UIC Class II rules, induced seismicity overview.

Read Engineering Guide →

Key Equations

Frac pressure limit:

Pfrac = depth · Gfrac | PBHP,max = SF · Pfrac

Hydrostatic:

Phydro = depth · 0.433 · SGw

Surface injection pressure:

Psurf = PBHP − Phydro + ΔPfriction + ΔPsurface

Steady-state radial inflow (BHP at perfs):

PBHP = Pe + (141.2 · q · μ · B / k·h) · (ln(re/rw) + s)

Injectivity index:

II = q / (PBHP − Pe) [BWPD/psi]

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⚠️

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Removes free water upstream of SWD.
🔧

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Gathering line to SWD pad.