How to ensure HSE compliance during oilfield decommissioning?

At-a-Glance: To ensure HSE compliance in oilfield decommissioning, build a barrier-based plan that aligns regulatory requirements, engineered controls, and field execution, then verify with rigorous monitoring and documented close-out. Focus KPIs on zero harm, zero spills, and verified site restoration, supported by auditable evidence.

I. Objective & KPIs

I.1 Objective: Decommission wells, facilities, and pipelines safely and responsibly—eliminating hydrocarbon risk, managing hazardous materials, and restoring the site—while meeting all regulatory, environmental, and social obligations.

• I.2 Primary KPIs (monitor daily unless noted):
  • • HSE: TRIR (target “0”; “as low as reasonably practicable”), LTIF “0”; high-potential incident count = 0
  • • Process safety: Loss of containment events = 0; Permit-to-Work (PTW) conformance = 98% (estimated); LOTO compliance = 99% (estimated)
  • • Environmental: Hydrocarbon spills = 0; flared gas = planned baseline; waste recycling rate = 80% (estimated); NORM releases = 0; noise exceedances = 0
  • • Integrity: Verified barriers per well = 2 independent, tested; gas-free certifications 100% before hot work/confined space entry
  • • Uptime/Execution: SIMOPS conflicts resolved within 24 hours; audit action closure > 95% within target dates
  • • Documentation: Regulatory submissions 100% on-time; as-left verification packages 100% accepted

II. Critical Parameters & Target Ranges

II.1 Key formulas used in HSE compliance

• • Risk rating: \( R = L \times C \), where L = likelihood (1–5), C = consequence (1–5). Maintain \( R \leq R_{\text{ALARP}} \) with documented controls.
• • FMEA risk priority number: \( \text{RPN} = S \times O \times D \) (Severity, Occurrence, Detectability; each 1–10). Focus mitigations on high RPN items.
• • Noise dose: \( D(\%) = 100 \times \sum \left( \frac{C_i}{T_i} \right) \), where \( C_i \) = exposure time at level i, \( T_i \) = allowable time at that level.
• • Sling tension per leg (symmetrical 2-leg): \( T = \frac{W}{2\cos\theta} \), where W = load weight, \( \theta \) = sling angle from horizontal.
• • Gas dispersion screening (Gaussian centerline, steady state): \( C(x) = \frac{Q}{\pi u \sigma_y \sigma_z} \) for preliminary checks; use detailed modeling where required.

III. Step-by-Step Procedure / Workflow

1. III.1 Pre-Project Compliance Setup
   • 1.1 Regulatory mapping and gap analysis; define decommissioning consent/permit register and submission calendar.
   • 1.2 HSE case and Decommissioning HSE Plan (bridged with contractor HSE-MS); Bowtie/HAZID/ENVID completed and actions closed.
   • 1.3 Stakeholder engagement plan (communities, fisheries, shipping, landowners); grievance mechanism active.
   • 1.4 Baseline surveys: environmental (benthic/soil, water, noise), cultural heritage, UXO, NORM, asbestos/PCB/mercury.
   • 1.5 Emergency Response Plan (ERP): OSCP, medevac, SAR, spill tiers, mass casualty; drills before mobilization.
   • 1.6 SIMOPS matrix; bridging documents for PTW/LOTO, isolations, simultaneous marine/plant works.
2. III.2 Well Plug & Abandonment (P&A)
   • 2.1 Verify well status and barriers; run CBL/USIT as needed; identify annular pressure anomalies.
   • 2.2 Set mechanical/cement plugs across cap rock and at surface; test per standard (pressure test + inflow test).
   • 2.3 Remove downhole equipment; cut and pull casing/tubing as required; install permanent surface marker per permit.
   • 2.4 Document as-left barrier schematics and test charts; third-party verification if mandated.
3. III.3 Hydrocarbon Removal, De-Energizing, and Cleaning
   • 3.1 Isolate, depressurize, drain, purge, and gas-free process equipment and pipelines; verify LEL = target.
   • 3.2 Confined space entry program; ventilation and rescue plan; continuous gas monitoring.
   • 3.3 Chemical cleaning/pigging; segregate slops; manage NORM scale; certify tanks/vessels gas-free for hot work.
   • 3.4 Electrical and mechanical LOTO with positive isolation; zero-energy verification and try-out tests.
4. III.4 Cutting, Lifting, and Removal
   • 4.1 Engineering lift plans (CoG survey, rigging design, crane charts); toolbox talks before lifts; exclusion zones.
   • 4.2 Select cutting method per HSE constraints: cold-cut, abrasive water jet, diamond wire; explosives only under strict controls.
   • 4.3 Dropped-object prevention: secondary retention, tool lanyards, barricading; ROV/diver interface controls offshore.
   • 4.4 Structural integrity checks before sectioning; weather window enforcement for marine lifts.
5. III.5 Subsea Pipelines, Cables, and Umbilicals
   • 5.1 Prove line empty and clean; isolate and cut with verified abandonment ends; grout bags or rock placement as permitted.
   • 5.2 Burial or removal per consent; post-installation survey for span/debris; protect receptors (fisheries, navigation).
6. III.6 Waste and Materials Management
   • 6.1 Waste Management Plan: classification, segregation, labeling; cradle-to-grave manifesting.
   • 6.2 NORM, asbestos, mercury, PCBs handled by licensed contractors; radiation controls and dose tracking.
   • 6.3 Recycling and circular options prioritized; document recovery rates and destinations.
7. III.7 Site Clearance and Restoration
   • 7.1 Debris clearance surveys (ROV/side-scan offshore; magnetometer/visual onshore); remove snags.
   • 7.2 Soil and water verification sampling against baseline/criteria; erosion control and re-vegetation onshore.
   • 7.3 Navigation/marking updates; fishing community notification; remove temporary aids to navigation when cleared.
8. III.8 Documentation & Close-Out
   • 8.1 Compile as-left dossiers: barrier certificates, test records, waste manifests, survey reports, photos/videos, GIS layers.
   • 8.2 Submit regulatory close-out and lessons learned; set post-decommissioning monitoring plan and schedule.

IV. Risk & Mitigation (HSE, Reliability, Redundancy)

• IV.1 Top hazards and controls
  • • Hydrocarbon release: double isolation, verified zero-energy, purge/inert, continuous gas detection, hot work controls.
  • • Well control during P&A: maintain two tested barriers; real-time pressure monitoring; contingency fluid and BOP readiness.
  • • NORM/chemical exposure: surveys, containment, dedicated PPE/respiratory protection, controlled zones, licensed disposal.
  • • Dropped objects/heavy lifts: engineered lifts, certified rigging, taglines, exclusion zones, weather limits, lift supervisor authority.
  • • DP loss of position: redundancy per class, ASOG/WSOG limits, drift-off alarms, standby tugs as required.
  • • Diving operations: diving project plan, umbilical management, bailout, DCI readiness, ROV-first philosophy where possible.
  • • Confined space/oxygen deficiency: permit system, standby rescue, continuous monitoring, inerting controls.
  • • Explosives (if used): licensed blasters, safety radii, marine fauna monitoring, misfire procedures, exclusion zones.
  • • Environmental impacts: silt curtains (onshore/coastal), spill kits/booms, noise controls, fauna observers, waste containment.
  • • SIMOPS conflicts: SIMOPS matrix, daily coordination meetings, zone ownership, radio discipline, pause authority.
• IV.2 Emergency preparedness
  • • Scenario-based drills: spill, fire, medevac, well control, lost-time injury; after-action reviews within 24 hours.
  • • Onsite medical and first response capability with evacuation plan; ensure landing zones or vessel transfer procedures.
  • • Tiered spill response resources and contracts verified pre-mob; waste reception sites pre-approved.
• IV.3 Reliability and redundancy
  • • Critical equipment spares (cutting, lifting, gas detection, comms) = 1×; pre-mob FAT/SAT; proof-load where applicable.
  • • Communications redundancy (VHF/UHF, satellite, data); power redundancy for monitoring and alarms.
  • • Weather/sea-state forecasting with conservative triggers; no-go matrices enforced.

V. Optimization Levers (Compliance-by-Design)

• V.1 Digital/PTW excellence: Electronic PTW with geofenced hazards, LOTO verification via QR/NFC, automated gas monitor feeds; leading indicator dashboards.
• V.2 Exposure reduction: Remote tooling (ROVs, robotic cutters, drone inspections), modular lifts, pre-cut onshore where feasible; minimize diver hours.
• V.3 Data-driven planning: HAZID action tracking, bowtie barrier health metrics, predictive maintenance on critical assets (cranes, DP thrusters).
• V.4 Waste/logistics streamlining: Just-in-time waste pickups, on-site decontamination, standardized segregation; prequalify recyclers with audits.
• V.5 Contracting strategy: HSE-weighted evaluation; incentive schemes tied to leading indicators (audit closure, hazard reporting quality) and zero harm outcomes.
• V.6 ALARP demonstrations: Cost-benefit and risk reduction evidence packages for each major hazard; document why residual risk is ALARP.

VI. Verification & Monitoring Plan

• VI.1 Shift/Daily
  • • Pre-job safety meetings with JSA; verify barrier status and SIMOPS interface.
  • • PTW/LOTO audits (spot checks = 2 per shift); gas monitoring logs; dropped-object inspections.
  • • Environmental checks: spill kit readiness, containment integrity, noise/air monitoring where applicable.
  • • Waste tracking: weighbridge entries, manifests, photos; NORM readings logged.
• VI.2 Weekly
  • • HSE audits against plan; action register with due dates; verify close-out = 90% on time.
  • • Barrier verification review (well P&A tests, gas-free certificates); SIMOPS review/update.
  • • Stakeholder updates; community liaison notes; grievance log reviewed.
• VI.3 Monthly/Milestone
  • • Management site visit; KPI review (TRIR, spills, leading indicators like hazard observations per 10,000 hours).
  • • Emergency drill; scenario rotation; improvement actions implemented.
  • • Regulatory reporting; emissions/waste summaries; third-party verification where required.
• VI.4 Close-Out & Post-Decommissioning
  • • As-left surveys and acceptance criteria met; issue close-out report with evidence bundle.
  • • Post-decommissioning monitoring: seabed/soil, navigation hazards, integrity of any left-in-place infrastructure; schedule per consent for 1–5 years (estimated).
  • • Lessons learned captured into corporate standards; update checklists/templates.

Assumptions

• • Targets marked “estimated” reflect typical industry practice; align with local regulations and project-specific consents.
• • Scope covers both offshore and onshore decommissioning with SIMOPS potential.