What Is FEED?
Front End Engineering Design — universally abbreviated to FEED — is the engineering phase that bridges conceptual design and detailed engineering. It is where an idea becomes a project: defined well enough to estimate costs reliably, schedule realistically, and identify the major technical risks before significant capital is committed.
In the upstream oil and gas project lifecycle, FEED typically sits between a Pre-FEED (or Conceptual Study) and Full Field Development. It is the last engineering phase before a Final Investment Decision (FID).
The Project Lifecycle Context
Understanding FEED requires understanding where it sits in the broader sequence:
Conceptual Study / Pre-FEED Screening-level engineering. The goal is to evaluate technical feasibility and produce a rough order of magnitude (ROM) cost estimate — typically accurate to ±40%. Multiple concepts may be compared at this stage.
FEED Defined scope engineering. The goal is to produce a complete engineering package that supports procurement, contracting, and a bankable cost estimate — typically ±15 to ±20% (Class 3 AACE). Only one selected concept is taken through FEED.
Detailed Engineering (EPC/EPCM) Full engineering to construction. The goal is to produce every drawing, document, and specification needed to build, procure, and commission the facility.
FEED is the critical decision gate. It is expensive enough to require real investment, but cheap enough — relative to full development — that the cost of a bad FEED is recoverable. The same cannot be said of cost overruns discovered in detailed design or, worse, during construction.
What a FEED Package Contains
A complete FEED package typically includes:
Process Documentation
- Process Design Basis (PDB)
- Block Flow Diagrams (BFDs)
- Process Flow Diagrams (PFDs) with mass and energy balances
- Piping and Instrumentation Diagrams (P&IDs) — developed, not necessarily IFC
- Utility Flow Diagrams (UFDs)
- Equipment List with preliminary datasheets
- Chemical consumption summary
Engineering Studies
- Process simulation model (steady-state, and dynamic where required)
- Equipment sizing calculations
- Flare and relief load study
- Safety concept (process safety philosophy)
- HAZID study report
Layout and Civil
- Plot plan and equipment arrangement drawings
- Civil and structural design basis
- Tie-in list (brownfield projects)
Cost and Schedule
- Capital Cost Estimate (±20%)
- Project Execution Strategy
- Master Schedule (pre-FEED to first production)
- Long Lead Items register
Why FEED Quality Matters
The accuracy of a FEED study determines the quality of the investment decision. A poorly scoped FEED — one that misses process complexity, underestimates equipment counts, or overlooks tie-ins — produces a cost estimate that will not survive contact with the real world. The consequences appear months later, during detailed engineering, as scope growth and budget overruns.
The most common causes of poor FEED quality are:
Scope definition failure. The process design basis is not agreed with the client before engineering begins, leading to repeated redesign as requirements change.
Junior delivery. FEED is frequently staffed with mid-level or junior engineers supervised at a distance. This saves money in the short term and creates problems in the long term. A FEED process package written by someone who has never commissioned a separator will contain assumptions that an experienced engineer would never make.
Optimism in estimate. ROM cost estimates are sometimes produced to satisfy commercial requirements rather than to accurately reflect scope. A low estimate that enables project sanction is not a good estimate — it is a liability.
Inadequate simulation. An Aspen HYSYS model that has not been validated against vendor data or operating cases is not a reliable basis for equipment sizing.
When Do You Need a FEED?
A FEED study is appropriate when:
- The project is large enough to justify the investment in definition (typically above $10M capital cost)
- The client intends to seek competitive tenders for EPC or EPCM execution
- A financial institution or partner requires a defined scope and estimate as a condition of funding
- The project has significant technical complexity that cannot be adequately characterised at conceptual level
For smaller projects — modular early production facilities, package equipment, retrofit modifications — a Pre-FEED or Conceptual Study may be sufficient to proceed directly to procurement.
FEED for Fast-Track Projects
A common misconception is that fast-track projects cannot afford a proper FEED. The opposite is usually true: a fast-track project that skips FEED trades a short-term schedule gain for long-term execution risk. The engineering definition that FEED provides is exactly what enables fast contracting, parallel working, and early long-lead equipment procurement.
For fast-track EPFs and MOPU topsides, FEEC has executed FEED studies in four to eight weeks — compressed, but complete. The key is parallel working between disciplines and experienced engineers who do not need to learn on the job.
Conclusion
FEED is the engineering foundation on which a project is built. Its quality determines the accuracy of the investment decision, the competitiveness of EPC tenders, and the smoothness of detailed design execution. Invest in a FEED study that is thorough, properly resourced, and delivered by engineers with the experience to know what they do not know — and what questions to ask before committing capital.