01
Field data
Measurements and operational records originating from the actual well, reservoir, facility or field.
Examples
- —Pressure measurements
- —Production rates
- —Injection rates
- —Wellhead conditions
- —PVT and laboratory measurements
← PEI Methods
PEI Evidence & Sources
Engineering decisions require a defensible evidence base.
Evidence provides the basis on which engineering analysis is performed and technical conclusions are formed. PEI is designed to keep important information identifiable, traceable and distinguishable from assumptions and interpretation.
Evidence discipline
Know what the information actually represents.
Engineering information can originate from measurements, technical references, calculations, assumptions or professional interpretation. These categories should not be treated as interchangeable.
A measured pressure, a published correlation, a calculated permeability and an assumed reservoir boundary have different origins and limitations. Their status should remain visible throughout the engineering record.
Information status
01Observed / measured
02Sourced / referenced
03Processed / derived
04Calculated
05Assumed
06Interpreted
Evidence classes
Different evidence serves different engineering roles.
Keeping evidence categories distinct helps prevent an assumption, calculation or interpretation from being mistaken for an observation.
02
Well & formation data
Information acquired during drilling, logging, formation evaluation, completion and well testing.
Examples
- —Wireline logs
- —LWD / MWD data
- —Core measurements
- —Formation tests
- —Well-test results
03
Technical references
Authoritative technical sources used to establish engineering principles, methods, correlations and recognised practices.
Examples
- —Technical literature
- —Industry publications
- —Engineering standards
- —Technical manuals
- —Recognised correlations
04
Engineering calculations
Results generated by applying defined engineering methods and equations to identified inputs.
Examples
- —Calculated reservoir properties
- —Pressure analysis
- —Productivity calculations
- —Material balance
- —Performance forecasts
05
Assumptions
Values, conditions or interpretations introduced where available evidence is incomplete or a method requires defined assumptions.
Examples
- —Estimated parameters
- —Boundary assumptions
- —Fluid assumptions
- —Model assumptions
- —Data substitutions
06
Engineering interpretation
Technical conclusions developed by interpreting evidence and analytical results within the context of the engineering problem.
Examples
- —Problem diagnosis
- —Mechanism interpretation
- —Risk assessment
- —Engineering options
- —Professional judgement
Evidence workflow
Establish the basis before relying on the information.
Available information is not automatically suitable evidence. Its origin, quality, context and limitations need to be understood before it is relied upon for an engineering purpose.
Identify
Determine what information is available and what evidence is needed for the engineering question.
Establish provenance
Record where the information originated and, where relevant, when it was acquired, generated or published.
Assess quality
Consider completeness, consistency, measurement quality, relevance and potential sources of error.
Classify
Distinguish observations, references, derived information, calculations, assumptions and interpretations.
Assess applicability
Determine whether the evidence is appropriate for the engineering question and conditions being considered.
Record limitations
Make material gaps, contradictions and limitations visible rather than hiding them inside a conclusion.
Source assessment
A credible source must still be appropriate for the question.
Technical authority is important, but a source may still be unsuitable if its conditions, assumptions or context do not match the engineering problem being considered.
Authority
Is the source technically credible and appropriate for the subject being investigated?
Relevance
Does the information actually address the engineering question being considered?
Applicability
Do the source conditions, assumptions and context apply to the problem at hand?
Provenance
Can the origin, acquisition or publication basis of the information be established?
Quality
Is the information sufficiently complete, consistent and reliable for its intended use?
Permitted use
Can the material be used within applicable licensing, copyright, contractual and confidentiality requirements?
Traceability
Important information should have a traceable basis.
A technical record should make it possible to understand where important information originated and how it was transformed or used during the analysis.
This makes it easier to revisit an input, challenge an assumption, reproduce an analysis or update an engineering conclusion when new information becomes available.
Traceability record
01Source or origin
02Acquisition or publication date
03Units and measurement basis
04Data quality and completeness
05Processing or transformation
06Assumptions introduced
07Calculation or analytical result
08Engineering interpretation
Conflicting evidence
Contradictions should remain visible.
Field measurements, technical studies and analytical results do not always agree. Differences may indicate data-quality problems, changing field conditions, inappropriate assumptions or an incomplete understanding of the system.
Material contradictions should therefore be documented and investigated rather than silently removed from the technical record.
Questions to consider
- —Do the measurements agree?
- —Are the datasets comparable?
- —Could operating conditions have changed?
- —Are the assumptions still valid?
- —Does another interpretation explain the evidence?
- —Is additional information required?
Evidence discipline
Transparency is part of engineering quality.
The purpose of evidence discipline is not to eliminate uncertainty. It is to ensure that the basis, limitations and status of important technical information remain visible.
- ✓Do not present an assumption as measured field data.
- ✓Do not present a calculated result as an observed field fact.
- ✓Do not remove contradictory evidence without documenting why.
- ✓Preserve the provenance of material technical inputs.
- ✓Use sources appropriate to the engineering question.
- ✓Expose important data gaps and limitations.
- ✓Keep material evidence distinguishable from engineering interpretation.