Petroleum Horner Plot Slope Calculator
Fit actual pressure versus log10[(tp+Δt)/Δt] Horner history, explicit prior-flow/shut-in elapsed durations, negative buildup slope retained; not natural-log slope or pressure-star verification. Caller independently verifies units, applicability and matching conditions; no operational recipe, safety certification, causal efficacy or legal/resource classification is inferred.
Description
A Horner buildup plot uses the logarithm of prior-flow-plus-shut-in time divided by shut-in time.
A Horner buildup plot uses the logarithm of prior-flow-plus-shut-in time divided by shut-in time.1
This tool fits observed buildup pressure against base-ten Horner coordinates and preserves the signed fitted slope.
When to use Petroleum Horner Plot Slope Calculator
Use this tool when you need to calculate the stated measurement summary or conditional model from matched observations. Prepare completed matched measurements, SI or explicitly stated oilfield units, and independent evidence for the selected branch or calibration.
How to use Petroleum Horner Plot Slope Calculator and understand its results
- Prepare completed matched measurements, SI or explicitly stated oilfield units, and independent evidence for the selected branch or calibration.
- Enter observedPriorFlowDurationSeconds, observedShutInDurationsSeconds, observedBuildupPressurePa, following the field table and calculation rules below, then run the tool.
- Read fittedHornerLog10SlopePaPerDecade, fittedHornerPressureInterceptPa, hornerFitRSquared. For result objects, inspect the nested output fields below, including any missing evidence or selected indices.
- Correct any input issues and run again. Before using a successful result, review its units, signs, evidence coverage, and stated model or reference assumptions.
| Input field | Meaning | Value type | Requirement |
|---|---|---|---|
| observedPriorFlowDurationSeconds | Observed prior flow duration seconds | number | Required |
| observedShutInDurationsSeconds | Observed shut in durations seconds | list of number | Required |
| observedBuildupPressurePa | Observed buildup pressure pa; pressure or stress in pascals, with the sign convention described above. | list of number | Required |
Require positive prior-flow seconds, positive shut-in durations, and aligned positive pressures with at least two distinct transformed coordinates. Compute log10(1+priorFlow/shutIn) using log1p divided by ln(10), then fit a free-intercept line. Return slope in Pa per decade, intercept, and R²; no chronological sort is required by the fit helper.
The regression helper accepts 2–10000 aligned finite pairs with nonzero predictor variance. It fits ordinary least squares with a free intercept using shifted coordinates; samples need not be sorted unless this tool additionally requires it. R² is clamped to [0,1] and is one for constant responses. Transformed fits use the stated predictor/response basis. Only fields present in this tool’s output are returned; an internal R² calculation does not add an undocumented output. R² is a fit summary rather than a confidence interval.
x=log10(1+priorFlowSeconds/shutInSeconds); P≈intercept+slope×x Read these symbols with the field meanings and branch or reference rules above.
| Output field | Meaning | Value type |
|---|---|---|
| fittedHornerLog10SlopePaPerDecade | Fitted horner log10 slope pa per decade | number |
| fittedHornerPressureInterceptPa | Fitted horner pressure intercept pa; pressure or stress in pascals, with the sign convention described above. | number |
| hornerFitRSquared | Horner fit r squared | number |
{
"input": {
"observedPriorFlowDurationSeconds": 99,
"observedShutInDurationsSeconds": [
1,
11
],
"observedBuildupPressurePa": [
10,
20
]
},
"output": {
"fittedHornerLog10SlopePaPerDecade": -10,
"fittedHornerPressureInterceptPa": 30,
"hornerFitRSquared": 1
}
}Limitations and assumptions
Measurements, unit conventions, branch identity, and model applicability must be independently established. The result does not infer a complete reservoir or flow model, operational settings, or a reserve classification.
Missing required fields, unknown fields, wrong types, and violated calculation rules return input issues. Numeric values must be finite; nonfinite numeric outputs are rejected. Arrays must be dense, with no missing cells. Numeric lists allow at most 10000 entries, subject to smaller tool-specific bounds above.
Alternative or Complementary methods
For a related task, use Petroleum Buildup Pressure Horner Calculator: A fitted Horner pressure branch can be evaluated only within an independently established shut-in interval. This calculator uses supplied base-ten slope and intercept rather than extracting a fit from the query times. For a complementary step, use Petroleum Productivity Index From Buildup Calculator: A selected buildup pressure branch can be fitted against natural-log Horner coordinates to estimate a pressure intercept. This tool uses that intercept with prior flowing pressure and rate to calculate an apparent productivity index.
References
-
Petroleum Horner Plot Slope Calculator — tool.io
Similar or alternative tools
- Petroleum Buildup Pressure Horner Calculator
A fitted Horner pressure branch can be evaluated only within an independently established shut-in interval. This calculator uses supplied base-ten slope and intercept rather than extracting a fit from the query times.
- Petroleum Productivity Index From Buildup Calculator
A selected buildup pressure branch can be fitted against natural-log Horner coordinates to estimate a pressure intercept. This tool uses that intercept with prior flowing pressure and rate to calculate an apparent productivity index.