What are the key steps in wireline logging operations?

At-a-Glance

Wireline logging operations follow a disciplined sequence: plan, rig up, run, log/QC, and rig down—while controlling depth, speed, tension, and well pressure. The core objective is high-quality, depth-accurate logs with zero HSE incidents and minimal NPT.

I. Objective & KPIs

I.1 Objective definition

• Acquire petrophysical-quality logs (open hole or cased hole) safely and efficiently, correctly depth-matched, with verifiable data quality (repeatability, SNR, tool integrity).
• Minimize operational risk (stuck tool, well control, radiation) and non-productive time.

I.2 Key KPIs

• Data quality: GR repeatability = ±2 API; density correction |??| = 0.15 g/cc; neutron repeatability = 2–3 porosity units; sonic slowness repeat = 2–3 µs/ft; image coverage = 90% of borehole; resistivity repeat = 5–10%.
• Depth accuracy: depth match to reference = ±0.5 m; pass-to-pass shift = ±0.3 m; TVD error = ±0.1% of depth.
• Operational efficiency: logging speed per tool target met; uptime = 98%; NPT = 2 hours per job.
• HSE: TRIR = 0; well integrity—no influx/losses; radiation control—0 anomalies.
• Conveyance control: head tension within 10–60% of cable MBL; tension SF = 1.5 to weak point; no slack events.
• Emissions/OPEX: minimized rig time; optimized rig-up/rig-down hours.

II. Critical Parameters & Target Ranges

Assumptions (estimated): vertical/deviated open hole, WBM 9.5–12.5 ppg; cable 7/32–9/32 in; downhole T = 150 °C; max pressure 10,000–15,000 psi.

II.1 Key equations and practical use

• Sampling vs speed: ensure spatial sampling = 20–30% of tool vertical resolution

  $v_{max} \approx f_s \times \Delta z_{sample}$, with $\Delta z_{sample} \le 0.3 \times L_{res}$

• Buoyancy-corrected apparent weight:

  $W_{app} = g(\rho_t - \rho_m)V = W_{air}\left(1 - \dfrac{\rho_m}{\rho_t}\right)$

• Elastic stretch (depth correction):

  $\Delta L_e = \dfrac{F\,L}{A\,E}$; Thermal: $\Delta L_T = \alpha\,L\,\Delta T$

• Capstan/sheave friction (tension across sheave):

  $T_{load} = T_{hold}\,e^{\mu \theta}$

III. Step-by-Step Procedure / Workflow

III.1 Pre-Job Planning & Engineering

1. Define objectives (1.1): formation evaluation needs, zones of interest, cased/open hole program (e.g., triple/quad combo, image, sonic, NMR, formation tester, CCL, GR baseline).
2. Review well data (1.2): trajectory, MD/TVD, casing/tubing, shoe depths, restrictions, mud system/properties, expected P/T, losses/influx history, deviation/doglegs, max tool OD allowances, SIMOPS.
3. HAZID/permits (1.3): pressure control plan, radiation handling, lockout/tagout, simultaneous operations coordination, lifting plan, contingency/fishing plan.
4. Toolstring design (1.4): mechanical order (head tension, GR/CCL, caliper, density/neutron pads, sonic, resistivity, image/NMR/FT, sinker bars as needed); centralizers/eccentering; roller bowsprings for rugose holes.
5. Conveyance selection (1.5): electric line size (7/32–9/32 in); consider tractors for high deviation/horizontal; memory backup for critical tools if telemetry-limited.
6. Engineering calculations (1.6): expected head tension vs depth (drag/buoyancy), weak point selection, speed plan per tool, sampling checks, cable stretch and depth corrections, PCE stack-up length and ratings.
7. QA/QC & calibrations (1.7): pre-job functional checks; source inventory and leak tests; density block and neutron standards; sonic bar; resistivity loop; GR API reference; telemetry bandwidth verification.
8. Log plan & checklist (1.8): pass order (typically primary data on up-logs), repeat sections, station stops (NMR/formation tests), depth reference, correlation points, acceptance criteria.

III.2 Rig-Up & Surface Testing

1. Position and secure unit (2.1): winch and mast orientation; sheave aligned with well centerline; certify slings/anchors; barriers in place.
2. Pressure Control Equipment (PCE) (2.2): assemble lubricator, BOPs, quick-test sub, grease head/packer, valves; pressure test to 1.1–1.5 × MAWP and hold; function test rams/valves; confirm bleed/flow paths.
3. Electrical safety & grounding (2.3): ground mats/bonds, UPS online, E-stop checks; verify line insulation and continuity.
4. Tool makeup & zeroing (2.4): install weak point, rope socket; verify head tension transducer; confirm tool dimensions for lubricator; quick wet-connect test if applicable.
5. Calibration & function test (2.5): run surface calibrations; verify telemetry; record baseline GR/CCL; log short surface pipe for CCL/GR correlation if needed.
6. Depth reference (2.6): set zero at RT or wellhead reference; document KB/RKB; enable real-time stretch correction.

III.3 Run-In-Hole (RIH) & Conditioning

1. Pressure transition (3.1): equalize lubricator; open well in control; set grease pressure margin (live well); monitor leak-off.
2. RIH control (3.2): maintain positive head tension; avoid slack; monitor line speed, tension, voltage/current; slow across ledges/MD doglegs; use centralizers/rollers if required.
3. Bottom reach confirmation (3.3): tag bottom gently; confirm depth with drilling tally correlation if available.

III.4 Logging & Real-Time QC

1. Primary pass (4.1): acquire on up-log for pad-contact tools (density/neutron, images, sonic); maintain target speed; stabilize tension.
2. Repeat sections (4.2): 30–100 m repeats over critical zones; verify overlay within KPI tolerances; adjust speed/contact if needed.
3. Station work (4.3): NMR sequences; formation tester pretests/drawdowns/build-ups; pressure gradient; sample QC; monitor tool seal integrity and drawdown limits.
4. Additional passes (4.4): targeted intervals (e.g., imaging at slower speed); acquire down-logs if required (e.g., resistivity stabilizations) while minding tension.
5. Depth controls (4.5): correlate to casing shoe/liners with CCL; use GR markers; apply stretch corrections; annotate any depth shifts.
6. On-the-fly QC (4.6): watch SNR, count rates, pad standoff (density correction), caliper vs bit size, sonic semblance, image coverage, resistivity focusing; adapt speed accordingly.

III.5 Pull-Out-of-Hole (POOH) & Rig-Down

1. POOH control (5.1): steady tension; avoid sticking across tight zones; stop for sweeps if trending risk; maintain pressure control sequence.
2. Secure tools (5.2): close well; bleed lubricator; lay down tools; post-job calibrations for drift; radiation survey and storage.
3. Preliminary products (5.3): deliver field QC plots, depth shift report, LAS/DLIS with metadata; document deviations and lessons learned.

IV. Risks & Mitigations (HSE, Reliability, Redundancy)

• Well control/pressure exposure (4.1): live-well PCE, pressure tests, grease margin +500–1,000 psi, valve lineup checks; crew drills; remote bleed lines; pressure monitoring with alarms.
• Stuck tool/differential sticking (4.2): minimize overbalance; pre-job hole conditioning; centralizers/rollers; maintain tension; avoid stationary holds in permeable zones; set weak point correctly; include jars and contingency fishing tools.
• Conveyance failure (cable/weak point) (4.3): tension windows and SF; avoid sharp sheave angles; monitor capstan effect; regularly check head tension vs computed profile.
• Radioactive source risk (4.4): inventory, transport/handling protocols, source lock checks, exclusion zones, recovery plan.
• Electrical hazards (4.5): grounding, insulation tests, E-stop functionality, lockout/tagout; avoid wet connections energized.
• Data loss/poor quality (4.6): repeat sections; memory backup where critical; speed reduction to raise SNR; mid-job recalibration if drift detected.
• SIMOPS conflicts (4.7): interface management plan; crane lifts sequencing; radio comms protocol; barrier management.

V. Optimization Levers

• Adaptive speed control (5.1): tie speed to real-time SNR, density correction, image coverage, sonic quality; slow down in rugose or high-noise zones; speed up in competent formations.
• Depth management (5.2): continuous stretch correction using tension/temperature; apply capstan correction at sheave; frequent GR/CCL correlations; minimize depth uncertainty.
• Borehole conditioning (5.3): pre-log wiper trips, short circulation, viscosity tweaks; reduce rugosity and differential sticking risk.
• Conveyance enhancements (5.4): deploy tractors in high deviation; add sinker bars for drag stability; roller bowsprings for pad contact; use eccentralizers for images.
• Telemetry utilization (5.5): optimize frame rates vs speed; buffer management; record full waveform data only where needed to reduce time without sacrificing quality.
• Maintenance strategy (5.6): condition-based checks on winch motors, sheave bearings, tension cells; spare tool modules on-site; hot-swap capability to cut NPT.
• Program sequencing (5.7): log highest-value data first if borehole stability risk; defer optional passes; batch station work to minimize stop–start cycles.

VI. Verification & Monitoring Plan

VI.1 What to measure

• Tension/speed/voltage/current: trend and alarm limits; detect slack or overpull precursors.
• Depth correlations: GR markers, CCL events, shoe/tie-back; document shifts; stretch-adjusted depth.
• Data quality metrics:
  • GR: API repeatability and noise level.
  • Density: correction magnitude, pad standoff indicator, caliper vs bit size, PEF stability.
  • Neutron: porosity repeatability and mud effect indicators.
  • Sonic: semblance/coherence, monopole/dipole QC flags, Stoneley noise.
  • Resistivity: focusing quality, borehole correction flags, repeat overlap.
  • Imaging: coverage %, button gains balance, stick–slip artifacts.
  • NMR: CPMG echo stability, T2 distribution consistency, SNR thresholds.
  • Formation tester: pretest drawdown curves, supercharge effects, seal indicators, pressure repeatability, sample contamination.
• PCE integrity: pressure charts, grease differential, leak checks, valve position log.
• HSE compliance: radiation survey logs, PTW adherence, SIMOPS checklist completion.

VI.2 How often

• Continuous: tension/speed/depth; data QC flags; PCE pressures.
• Per section/pass: repeat overlays vs KPI thresholds; depth match check and adjust.
• Per tool change/start/finish: calibration verification; zero/baseline checks.
• Post-job: final depth shift report; calibration drift comparison; lessons learned.

VI.3 Acceptance criteria

• All KPIs within limits (Section I.2); any deviations documented with rationale and impact assessment.
• Depth reconciliation within ±0.5 m to reference; station data match model expectations.
• HSE: zero incidents; PCE test certificates complete; radiation accounting reconciled.