Petroleum Productivity Index From Buildup Calculator
Extract Horner-fit intercept and matched prior-flow PI from actual selected buildup trace, natural-log Horner input explicit; not supplied-reservoir-pressure simplePI or full transient interpretation. Caller independently verifies units, applicability and matching conditions; no operational recipe, safety certification, causal efficacy or legal/resource classification is inferred.
Description
A selected buildup pressure branch can be fitted against natural-log Horner coordinates to estimate a pressure intercept.
A selected buildup pressure branch can be fitted against natural-log Horner coordinates to estimate a pressure intercept.1
This tool uses that intercept with prior flowing pressure and rate to calculate an apparent productivity index.
When to use Petroleum Productivity Index From Buildup 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 Productivity Index From Buildup 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 observedNaturalLogHornerRatios, observedBuildupPressuresPa, observedPriorFlowingPressurePa, observedPriorFlowRateM3Day, following the field table and calculation rules below, then run the tool.
- Read fittedBuildupPressureInterceptPa, buildupInferredPiM3DayPa. 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 |
|---|---|---|---|
| observedNaturalLogHornerRatios | Observed natural log horner ratios | list of number | Required |
| observedBuildupPressuresPa | Observed buildup pressures pa; pressure or stress in pascals, with the sign convention described above. | list of number | Required |
| observedPriorFlowingPressurePa | Observed prior flowing pressure pa; pressure or stress in pascals, with the sign convention described above. | number | Required |
| observedPriorFlowRateM3Day | Observed prior flow rate m3 day; volume rate in cubic metres per day. | number | Required |
Require nonnegative natural-log Horner ratios, positive aligned buildup pressures, and nonnegative prior flowing pressure and rate. Fit a free-intercept line with at least two pairs and nonzero predictor variance. Require intercept minus prior flowing pressure strictly positive, then divide prior rate in m³/day by that drawdown in Pa. Inputs are already logarithms; no further log is applied.
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.
PI=qPrior/(fittedInterceptPa−priorFlowingPressurePa) Read these symbols with the field meanings and branch or reference rules above.
| Output field | Meaning | Value type |
|---|---|---|
| fittedBuildupPressureInterceptPa | Fitted buildup pressure intercept pa; pressure or stress in pascals, with the sign convention described above. | number |
| buildupInferredPiM3DayPa | Buildup inferred pi m3 day pa; pressure or stress in pascals, with the sign convention described above. | number |
{
"input": {
"observedNaturalLogHornerRatios": [
0,
1,
2
],
"observedBuildupPressuresPa": [
10,
9,
8
],
"observedPriorFlowingPressurePa": 5,
"observedPriorFlowRateM3Day": 20
},
"output": {
"fittedBuildupPressureInterceptPa": 10,
"buildupInferredPiM3DayPa": 4
}
}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 Horner Plot Slope Calculator: A Horner buildup plot uses the logarithm of prior-flow-plus-shut-in time divided by shut-in time. This tool fits observed buildup pressure against base-ten Horner coordinates and preserves the signed fitted slope. For a complementary step, 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.
References
Similar or alternative tools
- Petroleum Horner Plot Slope Calculator
A Horner buildup plot uses the logarithm of prior-flow-plus-shut-in time divided by shut-in time. This tool fits observed buildup pressure against base-ten Horner coordinates and preserves the signed fitted slope.
- 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.