Well Test Analysis
Horner plot, Bourdet derivative, permeability & skin from pressure buildup data — free, browser-based.
Buildup Test Parameters
Using pre-loaded 20-point buildup data with typical radial flow signature.
Permeability k
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Skin Factor S
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Extrapolated P*
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Horner Slope m
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Radius of Investigation
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P @ 1hr (P1hr)
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Horner Plot (Semilog)
Bourdet Derivative (Log-Log)
Pressure vs Time
How this was calculated
Horner plot: Pws vs log[(tp + dt)/dt]. The straight-line portion corresponds to infinite-acting radial flow (IARF).
Permeability: k = 162.6 * q * B * mu / (m * h), where m is the Horner slope (psi/log cycle).
Skin: S = 1.1513 * [(P1hr - Pwf) / m - log(k / (phi * mu * ct * rw^2)) + 3.2275]
Bourdet derivative: d(Pws) / d(ln(dt)), computed using centered differences on log-spaced data.
Limitations: Assumes single-phase slightly compressible fluid, homogeneous reservoir, single rate before shut-in, infinite-acting (no boundary effects in data window).
Need multi-rate analysis, deconvolution, numerical well testing, or interference test interpretation? Our team specializes in advanced reservoir characterization.
Book a free strategy call →Understanding Well Test Analysis
Well test analysis is the primary method for determining reservoir properties from transient pressure data. A pressure buildup test involves producing a well at a known rate, shutting it in, and recording the pressure recovery over time. The shape of the pressure response contains information about permeability, skin (near-wellbore damage or stimulation), reservoir boundaries, and average reservoir pressure.
The Horner plot, introduced in 1951, plots shut-in pressure against the Horner time ratio (tp+dt)/dt on a semilog scale. During infinite-acting radial flow, the data falls on a straight line whose slope yields permeability. The Bourdet pressure derivative, introduced in 1983, revolutionized well test interpretation by making flow regimes visually identifiable on a log-log plot: a flat derivative indicates radial flow, a half-slope indicates linear flow (fracture), and upward trends suggest boundaries.
Commercial well test software provides type-curve matching, numerical models, and deconvolution. This free tool covers the fundamental Horner analysis suitable for screening and educational use. For complex reservoir characterization, contact Groundwork Analytics.
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