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Study notes

Qwestrum Engineering360 · Petroleum & Energy · Production Engineering

Production Logging

Production logging identifies where fluid enters the wellbore and in what phase, enabling selective remedial actions.

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.

Spinner flow profile across perforations
Noise log detects channeling behind casing
Water shut-off candidate identification

Topic details

Introduction

Craft & Hawkins and Beggs describe PLT as a diagnostic tool for uneven inflow, channeling, and water-producing intervals. In Indian exam writing, explain what each sensor measures before interpreting result.

Key relations & formulas

Formulas (Indian textbook notation)

$phase holdup Y_{l} from spinner and density$

Formulas (Indian textbook notation)

$zonal contribution q_{i} fraction per perforation$

Formulas (Indian textbook notation)

$PLT temperature anomaly gas entry$

Notation and sign conventions

Relation 1 —

phase holdup Y_{l} from spinner and density

Formulas (Indian textbook notation)

$phase holdup Y_{l} from spinner and density$

Write this relation with symbols exactly as in Beggs Production Optimization — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 2 —

zonal contribution q_{i} fraction per perforation

Formulas (Indian textbook notation)

$zonal contribution q_{i} fraction per perforation$

Write this relation with symbols exactly as in Beggs Production Optimization — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Relation 3 —

PLT temperature anomaly gas entry

Formulas (Indian textbook notation)

$PLT temperature anomaly gas entry$

Write this relation with symbols exactly as in Beggs Production Optimization — Standard reference before substituting numbers. Examiners award partial marks for a correct setup even when arithmetic slips.

Concept in depth

Spinner tools estimate local velocity, density logs infer phase holdup, temperature profiles detect fluid entry anomalies, and noise logs indicate behind-casing movement. Integrating these signals with completion data allows zonal rate allocation and prioritization of shutoff or reperforation candidates.

Assumptions and validity limits

State assumptions explicitly before using any relation for production logging — 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 Production 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 Production 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 production logging.
4. Use equation 1:

phase holdup Y_{l} from spinner and density

.
5. Use equation 2:

zonal contribution q_{i} fraction per perforation

.
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

Production Logging appears in producing fields. In Indian petroleum curricula this topic is tested because it connects theory to well performance and artificial lift.

GATE and semester exams often combine production logging with earlier units — revise prerequisites before attempting mixed problems.

Industry interview panels sometimes ask: "Where did you use production logging?" — answer with a lab, mini-project, or plant visit example if possible.

Common mistakes in exams

Usual mistakes are interpreting spinner response without flow calibration, assuming all temperature anomalies are gas entry, and ignoring tool pass direction effects.

Quick revision checklist

Before attempting production logging problems, confirm you can:

1. Spinner flow profile across perforations
2. Noise log detects channeling behind casing
3. Water shut-off candidate identification

Revise the solved examples in Beggs Production Optimization — 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.

Zonal Contribution Fraction

Problem

If total well rate is 1200 bpd and zone A contributes 300 bpd, find zone A fraction.

Solution

q_i fraction = 300/1200 = 0.25, i.e., 25% contribution from zone A.

Conceptual check — Production Logging

Problem

In a Production Engineering semester or GATE paper you are asked: "State the main assumption, the governing relation, and one practical consequence of production logging." What should a complete answer include?

📖 Standard books (India)

Beggs Production Optimization — Standard reference
Read: Syllabus unit
Referenced in Indian B.Tech syllabus

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