What are the safety protocols for well testing on FPSOs?

At-a-Glance: Safe well testing on FPSOs hinges on robust barriers, process containment, flare/radiation control, and iron integrity under marine motion. The protocols below integrate ESD/F&G, SIMOPS, and marine constraints into a single, auditable workflow.

I. Objective & Key KPIs

1.1 Objective: Execute well testing on FPSO topsides without loss of containment, ignition, or environmental harm while safeguarding personnel and maintaining marine stability.

• 1.2 Primary KPIs:
  • HSSE: TRIR = 0; LOPC events = 0; Unplanned ESDs = 1/test; H2S alarms = 0; Oil spill = 0 m³.
  • Integrity: Pressure test pass rate = 100%; SCE (Safety Critical Elements) uptime = 99.5%.
  • Uptime: Planned test window achieved = 95%; SIMOPS conflicts = 0.
  • Emissions/Flare: Peak flare radiation at deck = 4.7 kW/m²; Visible smoke duration = 15 min/event [estimated].
  • MOC/PTW Compliance: 100% adherence; Deviations closed within 24 hours.

II. Critical Parameters & Target Ranges

2.1 Assumptions [estimated]: HP separator MAWP 1,440 psig, flare rated 60 MMSCFD, burner boom clear of helideck = 45 m, H2S potential unknown (treat as sour until proven).

Relevant formulas:

• 2.2 Hydrotest pressure: For piping, test at P_test = 1.5 × MAWP (cold). For flowlines: P_test = 1.25 × MAOP [estimated].
• 2.3 Gas PSV sizing (idealized): For choked gas relief: \( W = C \, K_d \, A \, P_1 \sqrt{\dfrac{M}{Z T}} \, K_b K_c \), where W = mass flow, A = orifice area, P1 = upstream absolute pressure, T = absolute temperature, M = molecular weight, Z = compressibility, K’s = constants/corrections.
• 2.4 Flare thermal radiation: Keep surface exposure = 4.7 kW/m² (escape). Estimate at location r: \( q'' \approx F \, \chi \, \eta \, \dfrac{\dot{m} \, \text{LHV}}{4 \pi r^2} \), with view factor F, radiative fraction ?, efficiency ?.
• 2.5 Minimum flare purge (conceptual): \( Q_{purge} \propto D \sqrt{\dfrac{MW}{T}} \) to maintain velocity above air backflow; set per flare design and standards.

III. Step-by-Step Safety Protocols / Workflow

3.1 Planning & SIMOPS Control

• 3.1.1 Develop integrated Well Test Safety Case Addendum and SIMOPS matrix; bridge marine, production, and well testing procedures.
• 3.1.2 Conduct HAZID/HAZOP and risk workshops; close actions before mobilization. Validate cause & effect for PSD/ESD/F&G.
• 3.1.3 Lock down test envelope (max WHTP/WHTT, GOR, H2S/CO2) and flare capacity. Define test flow tiers (e.g., 25%/50%/75%/100%).
• 3.1.4 Establish SIMOPS constraints: no ramp-up during cargo offloading, bunkering, hot work, or helideck ops in adverse wind.
• 3.1.5 Emergency response plans: blowdown, H2S muster, medevac, engine room air shutdown strategy, and abandon ship routes.

3.2 Equipment Mobilization & Assurance

• 3.2.1 Verify certifications and FAT/SAT for test package: choke manifold, heat exchanger, HP/LP separators, sand trap, surge tank, metering, burner/flare, KO drum, pumps, NRVs, SDVs/ESDVs, subsea test tree (if applicable).
• 3.2.2 Pressure test all iron to documented limits; gauge calibration within 30 days [estimated]; NDE on critical spools; verify hammer unions/spec breaks.
• 3.2.3 Install double block and bleed (DBB) at tie-in; fit check valves upstream of separators; verify correct flow orientation.
• 3.2.4 Conduct full ESD/F&G functional tests: detector voting, blowdown valves, fusible loops, deluge/foam, flare pilots/ignitors, purge flow.
• 3.2.5 Lay out with positive drainage, dropped-object exclusion, whip checks, and restraint for hoses; maintain walkways and escape routes.

3.3 Pre-Startup Readiness (PSR)

• 3.3.1 Toolbox talk and permit to work (PTW); finalize JSA for each phase; confirm competent personnel and 24/7 supervision.
• 3.3.2 Verify two-barrier rule: SCSSV test, tree valves integrity; surface safety valve (SSV) and subsurface test tree function tested.
• 3.3.3 Confirm methanol/MEG injection availability; lines heat-traced/heated operational; hydrate curves reviewed.
• 3.3.4 H2S readiness: fixed and portable detectors, escape sets, muster plan, windsock/meteorology checks.
• 3.3.5 Marine checks: heading control to keep flare downwind of LQ/helideck; sea state and motion limits monitored.

3.4 Controlled Start-Up & Ramp

• 3.4.1 Line-up verification using signed checklists; purge/pressure test lines with inert gas where required.
• 3.4.2 Start with minimum choke; stabilize each tier. Record pressures, temperatures, rates, vibrations, and flare behavior before stepping up.
• 3.4.3 Maintain separator pressures below design; verify flare backpressure within limit; monitor KO drum level and seal integrity.
• 3.4.4 Enforce helideck and hot work restrictions during visible flame/smoke; post fire watch.
• 3.4.5 Validate burner tip performance; no liquid carryover (no flame lift-off or dark smoke). Adjust atomizing air/steam if installed.

3.5 Steady Operations

• 3.5.1 Routine checks hourly: F&G status, ESD availability, iron leak inspection, sand trap differential pressure, vibration/noise, flare radiation readings.
• 3.5.2 Maintain methanol dosage; insulate cold spots; drain/heat low points; keep OIW within permit for any produced water handling.
• 3.5.3 Manage SIMOPS: hold points before hose connection/disconnection; confirm plume trajectory before helideck ops resume.

3.6 Shutdown & Depressurization

• 3.6.1 Normal shutdown: reduce choke to zero, close SSV/SDVs, route residuals to KO drum, depressurize to flare, drain/purge with inert gas as required.
• 3.6.2 Emergency shutdown: auto-trips on high-high pressure/level, fire/gas, H2S, or manual ESD. Sequence tested and documented.
• 3.6.3 De-isolation via PTW after zero energy verification; confirm no hydrocarbon inventory and atmosphere gas-free before dismantling.

IV. Risk Register & Mitigations

• 4.1 Loss of Containment from Iron/Connections
  • Mitigation: Rated iron; hydrotest; torque control; restraint; motion monitoring; leak checks; DBB isolation; spare seals/unions.
• 4.2 Overpressure/Surge
  • Mitigation: PSVs to flare; high-integrity pressure protection (HIPPS) if required; automated choke control; ramp procedures; subsea test tree fast close.
• 4.3 Ignition/Fire at Burner/Flare
  • Mitigation: Pilot reliability, purge, wind/heading control, exclusion zones, radiation monitoring, firewater/foam standby, smoke minimization.
• 4.4 Gas Dispersion to LQ/Intakes
  • Mitigation: Maintain positive purge, close non-essential intakes on alarm, reorient vessel, enforce no hot work, F&G zoning.
• 4.5 H2S Exposure
  • Mitigation: Treat as sour until lab confirms; fixed/portable detectors; escape sets; muster drills; designated H2S safe areas; iron material compatibility.
• 4.6 Hydrates/Wax/Emulsion
  • Mitigation: Thermal management; chemical injection; controlled rate ramps; depressurize/warm strategy; sampling plan to avoid carryover.
• 4.7 SIMOPS Conflicts (Offloading/Helideck/Hot Work)
  • Mitigation: SIMOPS board; radio discipline; holds and permits; plume prediction; timed flow steps.
• 4.8 Marine Motion/Dropped Objects
  • Mitigation: Weather windows; taglines; lift plans; exclusion zones; secondary retention; shock supports on long spools.
• 4.9 Environmental Discharge/Sheen
  • Mitigation: Burner setup to prevent liquid carryover; KO drum level control; spill kits; scupper plugs; oily water management; sheen watch.
• 4.10 Human Factors/Fatigue
  • Mitigation: 12-hour shift max; competency checks; clear roles/responsibilities; alarms rationalized to avoid fatigue.

V. Optimization Levers (Safety-Focused)

• 5.1 Data & Analytics: Real-time dashboards for F&G status, flare rate/backpressure, radiation meters, and motion sensors; alarm flood suppression with priority logic.
• 5.2 Control Strategy: Cascade choke–separator pressure control; anti-surge logic; auto step-test sequences with abort on deviation.
• 5.3 Maintenance & SCE: Condition-based checks on ESD valves, pilots/ignitors, and KO drum level instruments; quick-connect spares; calibrated portable gas detectors rotation.
• 5.4 Debottlenecking for Safety: Temporary additional KO capacity, secondary flare/burner tip, or increased purge to stabilize combustion; temporary wind screens if permitted.
• 5.5 Barrier Health Monitoring: Online verification of SCSSV and SSTT status; valve position feedback; leak-off testing intervals during long tests.

VI. Verification & Monitoring Plan

• 6.1 Before Test (once):
  • Function test of all ESD levels; F&G detector bump tests; deluge/foam flow test; flare pilot/ignitor verification; hydrotest and leak test sign-offs.
  • Cause & effect simulation with full crew drill (fire/gas, H2S, abandon ship).
• 6.2 During Test (continuous/defined intervals):
  • Continuous: pressures, temperatures, choke position, separator levels, flare rate/backpressure, radiation, wind direction/speed, KO drum seal, methanol rate.
  • Hourly: iron leak walkdown, sand DP, vibration/noise, detector status, OIW if discharging water.
  • Per step change: verify stability criteria met for 15–30 minutes before increasing rate.
• 6.3 After Test (close-out):
  • Gas-free verification; de-isolation; waste handling and environmental reporting; flare/emissions accounting; lessons learned/MOC closure.
  • KPIs review: TRIR/LOPC, SCE impairments, unplanned ESDs, flare performance, SIMOPS deviations.

Alarm/Trip Examples (set per asset)

• 6.4 Trips: HH separator pressure, HH KO drum level, flame-out with gas flow, H2S trip, LEL trip, SDV/EIV fail-to-close, fusible plug melt.
• 6.5 Alarms: Pilot fail, rising flare backpressure, high burner differential, high vibration, low purge flow, approaching wind to LQ/helideck.