Qwestrum Engineering360 · Petroleum & Energy · Reservoir Engineering
Enhanced Oil Recovery
EOR methods improve sweep and displacement efficiency after primary and secondary recovery decline, targeting residual oil.
Exam tip: keep SI units consistent end-to-end, write the governing relation symbolically before substituting, and sanity-check magnitude and sign.
Key formulas & points
Skim these first — then read the full notes below.
- Miscible gas CO₂ or nitrogen injection
- Steam flood for heavy oil viscosity reduction
- Chemical EOR alkaline-surfactant-polymer ASP
Topic details
Introduction
Beggs and Ahmed highlight selecting EOR by crude viscosity, reservoir temperature, and salinity constraints. In Indian B.Tech discussions, mobility ratio and IFT reduction are core conceptual checkpoints.
Key relations & formulas
Formulas (Indian textbook notation)
Formulas (Indian textbook notation)
Formulas (Indian textbook notation)
Notation and sign conventions
Relation 1 —
Formulas (Indian textbook notation)
Write this relation with symbols exactly as in Dake Reservoir Engineering — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 2 —
Formulas (Indian textbook notation)
Write this relation with symbols exactly as in Dake Reservoir Engineering — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Relation 3 —
Formulas (Indian textbook notation)
Write this relation with symbols exactly as in Dake Reservoir Engineering — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.
Concept in depth
Thermal methods lower heavy-oil viscosity, gas methods improve miscibility and swelling, and chemical methods control mobility or reduce interfacial tension. Economic screening is essential because chemical losses, gas sourcing, and steam generation costs can dominate project viability.
Assumptions and validity limits
State assumptions explicitly before using any relation for enhanced oil recovery — steady state, uniform properties, linear elastic material, ideal gas, incompressible flow, etc., as applicable.
Wrong assumptions invalidate the entire solution even when the formula is correct. In Reservoir Engineering viva and GATE descriptive questions, listing valid assumptions often earns separate marks.
Step-by-step problem approach
1. Read the question and list given data with SI units (common in Reservoir Engineering papers).
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to enhanced oil recovery.
4. Use equation 1:
5. Use equation 2:
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.
2. Draw a neat labelled diagram where applicable — examiners in Indian universities award diagram marks even when arithmetic slips.
3. Identify which relation from this topic applies to enhanced oil recovery.
4. Use equation 1:
.
5. Use equation 2:
.
6. Substitute values, compute, and verify units and sign (direction).
7. State conclusion in one line — e.g. safe/unsafe, stable/unstable, feasible/infeasible.
Applications & exam relevance
Enhanced Oil Recovery appears in field development plans. In Indian petroleum curricula this topic is tested because it connects theory to reservoir behaviour and recovery.
GATE and semester exams often combine enhanced oil recovery with earlier units — revise prerequisites before attempting mixed problems.
Industry interview panels sometimes ask: "Where did you use enhanced oil recovery?" — answer with a lab, mini-project, or plant visit example if possible.
Common mistakes in exams
Typical errors are assuming one EOR method fits all reservoirs, ignoring salinity/temperature limits for chemicals, and confusing sweep efficiency with microscopic displacement efficiency.
Quick revision checklist
Before attempting enhanced oil recovery problems, confirm you can:
1. Miscible gas CO₂ or nitrogen injection
2. Steam flood for heavy oil viscosity reduction
3. Chemical EOR alkaline-surfactant-polymer ASP
2. Steam flood for heavy oil viscosity reduction
3. Chemical EOR alkaline-surfactant-polymer ASP
Revise the solved examples in Dake Reservoir Engineering — Standard reference and one previous-year GATE or university paper for this unit.
Worked examples
Try the problem first — open the solution when you are ready to check.
Simple WOR Tracking
Problem
If daily water production is 480 bbl and oil production is 160 bbl, find WOR.
Solution
WOR = water/oil = 480/160 = 3.0. Rising WOR signals sweep breakthrough or maturity effects.
Conceptual check — Enhanced Oil Recovery
Problem
In a Reservoir Engineering semester or GATE paper you are asked: "State the main assumption, the governing relation, and one practical consequence of enhanced oil recovery." What should a complete answer include?
📖 Standard books (India)
Dake Reservoir Engineering — Standard reference
Read: Syllabus unit
Referenced in Indian B.Tech syllabus
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