Project Engineering – Basic/Conceptual, FEED, Detailed and Engineering
What is Project Engineering?
Project Engineering is the discipline that integrates technical expertise with project management to transform a project from an initial idea into an operating facility. It provides the framework that connects early conceptual studies with construction and commissioning, ensuring that design intent is maintained throughout the project lifecycle.
In large oil and gas greenfield developments, project engineering is the backbone of execution. It coordinates multidisciplinary teams i.e., process, mechanical, piping, electrical, instrumentation, and civil/structural; while balancing safety, quality, cost, and schedule. This integration ensures that the facility not only meets technical and regulatory standards but also remains constructible, operable, and maintainable.
Project engineering is typically divided into three progressive phases:
- Basic Engineering/Conceptual Design: Establishes the technical and economic foundation of the project.
- Front-End Engineering Design (FEED): Refines the scope and provides the definition needed for EPC tendering.
- Detailed Engineering: Produces the construction-ready documents and packages used for procurement, fabrication, installation, and commissioning.
Each phase builds on the previous one, progressively reducing uncertainty and adding detail, until the project is fully defined and ready for implementation.
1. Basic Engineering (or Conceptual / Pre-FEED Phase)
This is the initial definition stage of a project, right after feasibility studies. The purpose is to establish a technical and economic framework for the project.
Typical Activities
- Define the project scope and overall configuration (e.g., refinery capacity, type of gas processing, number of trains).
- Identify major process units and high-level block flow diagrams (BFDs).
- Perform preliminary material & energy balances.
- Select technology licensors (for example, amine sweetening, LNG liquefaction, catalytic reforming).
- Develop high-level plot plan options and site layout.
- Preliminary equipment sizing for major items (compressors, reactors, exchangers).
- Early cost estimate (± 30–40% accuracy).
- Establish project execution strategy (EPC vs EPCm, modularization, etc.).
Deliverables
- Block Flow Diagrams (BFDs).
- Early Process Flow Diagrams (PFDs).
- Preliminary Heat & Material Balance.
- Initial equipment list (major tagged items only).
- Conceptual plot plans.
- Technology selection report.
- CAPEX & OPEX rough estimate.
2. FEED (Front-End Engineering Design)
This is the bridge between Basic Engineering and EPC. The objective is to freeze the technical scope, reduce risks, and provide enough definition for tendering EPC contracts.
Typical Activities
- Develop detailed Process Flow Diagrams (PFDs) and Piping & Instrumentation Diagrams (P&IDs).
- Perform detailed material & energy balances.
- Define utility and offsite systems (water, steam, power, flare, etc.).
- Prepare equipment datasheets for all major items.
- Carry out HAZID / HAZOP / SIL assessment for safety review.
- Develop plot plan and general arrangement drawings.
- Prepare preliminary piping MTO (material take-off).
- Electrical single-line diagrams and load lists.
- Instrumentation I/O lists, control philosophy.
- Conduct constructability reviews.
- Provide cost estimate with better accuracy (± 15–20%).
- Prepare Invitation to Bid (ITB) packages for EPC.
Deliverables
- Process Flow Diagrams (final).
- P&IDs (final for EPC issue).
- Heat & Material Balance (final).
- Equipment datasheets and specifications.
- Plot plans, preliminary 3D model.
- Project execution schedule (Level 2/3).
- EPC Tender Package (technical scope, specs, drawings).
- Updated CAPEX estimate.
3. Detailed Engineering (Execution Phase, EPC Stage)
This is where every nut and bolt is defined. The objective is to produce construction-ready drawings and vendor-validated designs.
Typical Activities
- Develop shop drawings and construction details.
- 3D modeling (full detail, clash-free).
- Issue piping isometrics with BOM.
- Vendor design and integration (compressors, turbines, vessels).
- Detailed structural drawings (foundations, pipe racks, buildings).
- Detailed electrical & instrumentation layouts, wiring diagrams, loop diagrams.
- HVAC, fire protection, drainage system design.
- Procurement of all equipment and bulk materials.
- Construction work packs, method statements.
- Commissioning and pre-startup plans.
Deliverables
- “Issued for Construction (IFC)” drawings.
- Piping isometrics and stress analysis reports.
- Civil and structural foundation drawings.
- Cable schedules, loop diagrams, instrument hook-ups.
- Equipment GA drawings and vendor docs.
- Final Material Take-Off (MTO).
- Construction work packages.
- As-built drawings after completion.
Key Differences Between the Phases
| Aspect | Basic Engineering | FEED (Front-End) | Detailed Engineering |
|---|---|---|---|
| Purpose | Establish concept, technology, and feasibility | Freeze scope, reduce risk, prepare EPC tender | Fully define design for construction |
| Design Maturity | 10–20% defined | 30–40% defined | 100% defined |
| Deliverables | BFDs, early PFDs, equipment list, concept layouts | Final PFDs, P&IDs, datasheets, specs, ITB | IFC drawings, vendor docs, 3D model, MTO |
| Cost Estimate Accuracy | ±30–40% | ±15–20% | ±5–10% |
| Stakeholder Decisions | Technology selection, project viability | Scope freeze, EPC bidding | Construction, procurement, commissioning |
| Who Uses Output | Owners / management (for investment decision) | EPC bidders, licensors, regulators | Construction contractors, fabricators, site teams |
Project Engineering Deliverables by Discipline
In large EPC projects, each engineering discipline contributes a defined set of deliverables that collectively form the project’s technical baseline. Mechanical engineers issue datasheets, equipment specifications, and vendor integration documents. Civil and structural teams provide foundation drawings, building layouts, and structural steel detailing. Piping engineers develop isometrics, stress analysis reports, and material take-off lists. Electrical engineers prepare single-line diagrams, cable schedules, and load lists, while instrumentation engineers issue I/O lists, hook-up drawings, and control philosophy documents. Together, these discipline-specific deliverables ensure consistency, accuracy, and seamless handover to procurement and construction teams.
The following table summarizes the typical deliverables produced by each discipline in an oil and gas EPC project, serving as the backbone of engineering execution.
| Discipline | Key Deliverables |
|---|---|
| Process Engineering | • Process Flow Diagrams (PFDs) • Piping & Instrumentation Diagrams (P&IDs) • Heat & Material Balance (H&MB) • Process Datasheets (all equipment & instruments) • Process Control Philosophy • Safeguarding Memoranda / Cause & Effect Diagrams • Relief Valve Sizing & Relief Load Summaries • Process Simulations & Design Basis Documents • Process Design Calculations & Reports • Process Operating Manuals |
| Mechanical Engineering | • Equipment Datasheets (static & rotating) • Mechanical Specifications & Standards • General Arrangement (GA) Drawings • Fabrication Drawings (vessels, tanks, exchangers) • Rotating Equipment Layouts & Foundation Loads • Technical Bid Evaluations (TBE) • Vendor Data Review & Integration • Mechanical Design Calculations • Equipment Lists (all tagged items) • Maintenance & Spare Parts Lists |
| Piping Engineering | • Piping Material Specifications (PMS) • Line Designation Tables (LDT) • Plot Plans & Piping Layouts • 3D Model & Clash Reports • Piping Isometrics with Bill of Materials (BOM) • Pipe Stress Analysis Reports • Material Take-Off (MTO) for all bulk items • Specialty Item Datasheets (valves, strainers, etc.) • Tie-In Lists • Welding & Insulation Specifications |
| Civil & Structural Engineering | • Foundation Design Drawings (equipment & structures) • Structural Steel Design & Fabrication Drawings • Building Layouts & Structural GAs • Pipe Rack & Equipment Support Details • Roads, Paving, and Yard Drainage Layouts • Underground Utilities (sewer, water, firewater) • Earthwork & Grading Plans • Concrete Reinforcement Details • Geotechnical Investigation Reports • Structural Material Take-Off (MTO) |
| Electrical Engineering | • Single-Line Diagrams (SLDs) • Electrical Load Lists & Equipment Schedules • Cable Routing Layouts & Cable Schedules • Lighting Layouts & Small Power Layouts • Earthing & Lightning Protection Layouts • Motor Control Center (MCC) Specifications • Substation Layouts & Equipment GA • Power Distribution & Protection Schemes • Electrical System Studies (short circuit, load flow, arc flash) • Electrical MTO |
| Instrumentation & Controls | • Instrument Index & I/O Lists • Instrument Datasheets (all instruments & analyzers) • Control System Architecture Diagrams • Loop Diagrams & Wiring Schematics • Hook-Up Drawings • Cause & Effect Diagrams • Logic Diagrams & Control Narratives • Cable Block Diagrams • DCS/PLC/ESD/FGS System Specifications • Instrument Material Take-Off (MTO) |
| Safety & Loss Prevention | • Hazard Identification (HAZID) Reports • Hazard & Operability (HAZOP) Studies • Safety Integrity Level (SIL) Reports • Quantitative Risk Assessment (QRA) • Fire & Gas Detection Layouts • Escape & Evacuation Route Drawings • Firewater Hydraulic Calculations • Fire Protection System Design • Safety Equipment Layouts • Safety Case / Compliance Reports |
Download our comprehensive Engineering Deliverables Sequence sheet to understand the critical path and dependencies for process, piping, electrical, and instrumentation documents. Follow downloads page.
Project Engineering Challenges and Solutions
Project engineering in large oil and gas EPC projects involves navigating a variety of technical and management hurdles. Below are some of the most common challenges and the strategies typically used to overcome them.
1. Delays in Vendor Data
Late submission of vendor drawings and datasheets can stall progress across multiple disciplines. For example, piping layouts may be frozen late if compressor or pump GA drawings are delayed, which in turn affects foundation loads and electrical load lists. Such delays often create a ripple effect, forcing rework and rescheduling of downstream activities.
Solution: Strong vendor management, proactive follow-up, and integrating vendor data into the engineering document control system (EDMS) ensure timely availability. Maintaining a vendor data schedule and linking it to engineering deliverables helps track dependencies effectively.
2. Design Changes During Execution
Unexpected changes—arising from client requirements, regulatory reviews, or site conditions—often disrupt the project baseline. If not managed properly, even small changes can escalate into cost overruns, scope growth, and schedule delays.
Solution: Implementing a robust Management of Change (MOC) procedure, along with impact assessments on cost, schedule, and quality, allows informed decision-making. Early engagement with clients and regulators helps reduce late-stage surprises.
3. Scope Creep and Requirement Growth
Additional requirements introduced after FEED can significantly increase engineering hours, material take-offs, and procurement budgets. Scope creep is particularly common in greenfield projects where operating philosophies evolve over time.
Solution: Project engineers mitigate this risk by maintaining a well-defined scope baseline, documenting all changes, and ensuring that only approved changes are incorporated. Regular alignment meetings with the client are essential to control scope.
4. Multidiscipline Coordination Issues
Inconsistent inputs between process, piping, civil, electrical, and instrumentation teams can lead to clashes, duplication of work, or design conflicts. For example, uncoordinated pipe rack loads may not match civil foundation capacity, or electrical cable routing may conflict with piping.
Solution: Regular interdisciplinary reviews—such as 30%, 60%, and 90% model reviews—help identify issues early. Assigning interface owners and maintaining updated interface registers ensure seamless coordination between disciplines.
5. Maintaining Quality and Consistency in Deliverables
Large EPC projects often generate thousands of documents, drawings, and calculations. Without structured control, outdated or inconsistent documents may reach procurement or construction, causing errors in the field.
Solution: Use of Engineering Document Management Systems (EDMS), along with strict document control workflows, ensures that only the latest approved versions are issued. A clear RACI (Responsible, Accountable, Consulted, Informed) matrix helps define ownership of deliverables.
6. Risk Anticipation and Mitigation
Many engineering problems—such as soil settlement issues, utility undersizing, or vendor insolvency—can be predicted early if risks are systematically tracked. However, some projects only react to problems after they surface.
Solution: Maintaining a project risk register, conducting regular reviews, and assigning ownership for mitigation actions enable proactive management. Early identification and communication of risks give teams the chance to implement corrective measures before they escalate.
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