Petroleum Drawdown Pressure Analysis Calculator
Audit actual pressure drawdown versus natural-log elapsed time against independently established slope reference, not permeability inversion or model-selected regime; signed fit evidence retained. Caller independently verifies units, applicability and matching conditions; no operational recipe, safety certification, causal efficacy or legal/resource classification is inferred.
Description
Drawdown analysis can summarize a selected pressure branch by fitting pressure change against natural log of elapsed time.
Drawdown analysis can summarize a selected pressure branch by fitting pressure change against natural log of elapsed time.1
This tool retains the signed slope and its difference from an independently supplied reference rather than selecting a radial regime.
When to use Petroleum Drawdown Pressure Analysis 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 Drawdown Pressure Analysis 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 observedDrawdownTimesSeconds, observedDrawdownPressurePa, callerRadialAnalysisLogSlopeReferencePa, following the field table and calculation rules below, then run the tool.
- Read fittedDrawdownNaturalLogSlopePa, fittedDrawdownInterceptPa, signedSlopeMinusReferencePa. 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 |
|---|---|---|---|
| observedDrawdownTimesSeconds | Observed drawdown times seconds | list of number | Required |
| observedDrawdownPressurePa | Observed drawdown pressure pa; pressure or stress in pascals, with the sign convention described above. | list of number | Required |
| callerRadialAnalysisLogSlopeReferencePa | Caller radial analysis log slope reference pa; pressure or stress in pascals, with the sign convention described above. | number | Required |
Require positive times, nonnegative aligned drawdowns, and a nonnegative natural-log slope reference. Fit drawdown versus ln(time) with a free intercept using at least two pairs with nonzero transformed-time variance. Return slope, intercept, and slope minus reference; a negative fitted slope remains visible.
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.
drawdown≈intercept+m×ln(time); signedDifference=m−reference Read these symbols with the field meanings and branch or reference rules above.
| Output field | Meaning | Value type |
|---|---|---|
| fittedDrawdownNaturalLogSlopePa | Fitted drawdown natural log slope pa; pressure or stress in pascals, with the sign convention described above. | number |
| fittedDrawdownInterceptPa | Fitted drawdown intercept pa; pressure or stress in pascals, with the sign convention described above. | number |
| signedSlopeMinusReferencePa | Signed slope minus reference pa; pressure or stress in pascals, with the sign convention described above. | number |
{
"input": {
"observedDrawdownTimesSeconds": [
1,
2.718281828459045,
7.3890560989306495
],
"observedDrawdownPressurePa": [
1,
3,
5
],
"callerRadialAnalysisLogSlopeReferencePa": 2
},
"output": {
"fittedDrawdownNaturalLogSlopePa": 2,
"fittedDrawdownInterceptPa": 1,
"signedSlopeMinusReferencePa": 0
}
}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 Well Test Permeability Calculator: A constant-rate radial pressure test can relate pressure slope against natural log of elapsed time to permeability. This tool fits independently selected radial observations and applies the SI pressure-slope relation using supplied fluid and well properties. For a complementary step, use Petroleum Pressure Derivative Calculator: Bourdet pressure derivatives summarize pressure change against natural log of elapsed time using neighboring intervals. This tool evaluates the three-point weighted derivative on unequal sample times and returns only interior observations.
References
Similar or alternative tools
- Petroleum Well Test Permeability Calculator
A constant-rate radial pressure test can relate pressure slope against natural log of elapsed time to permeability. This tool fits independently selected radial observations and applies the SI pressure-slope relation using supplied fluid and well properties.
- Petroleum Pressure Derivative Calculator
Bourdet pressure derivatives summarize pressure change against natural log of elapsed time using neighboring intervals. This tool evaluates the three-point weighted derivative on unequal sample times and returns only interior observations.