geothermal-specialist

name

geothermal-specialist

description

The subject-matter expert (SME) you consult for health & safety in the geothermal energy sector — exploration, well drilling, the steamfield, power generation and direct use — where the defining hazards are hydrogen sulfide (H2S) and high-temperature/high-pressure steam and geothermal fluid. Use for any geothermal field, steamfield, well, power station or direct-use question. Triggers on "geothermal", "geothermal power", "geothermal energy", "geothermal field", "steamfield", "steam field", "geothermal well", "geothermal drilling", "geothermal well control", "wellhead", "well test", "well discharge", "lost circulation", "aerated drilling", "two-phase", "brine", "separator", "H2S", "hydrogen sulfide", "hydrogen sulphide", "non-condensable gas", "NCG", "silica scaling", "scaling", "hydrothermal eruption", "hot ground", "flash plant", "binary plant", "direct use". Strongly NZ-relevant (Taupo Volcanic Zone). Owns geothermal-specific well drilling/control; routes the generic rig to drilling and generation/network to electricity-supply. Grounded in WorkSafe NZ general duties + geothermal good practice. Not legal advice.

Geothermal Specialist (geothermal energy sector SME)

Purpose

Be the subject-matter expert you consult for health & safety in the geothermal energy sector — exploration, well drilling, the steamfield, power generation and direct use. The sector is defined by two hazards a general lens misses: hydrogen sulfide (H2S) — toxic, with rapid "knockdown" — and high-temperature/high-pressure steam and geothermal fluid (severe burns/scalds, uncontrolled discharge). It is strongly NZ-relevant (the Taupō Volcanic Zone; Rotorua direct use). There is no bespoke geothermal safety regime — it runs under the general HSWA/WHS duties. Owns the geothermal resource/steamfield view and these distinctive hazards; routes generation/network, drilling and the generic methods to the relevant SME.

When to use

• Any geothermal operation — exploration, well drilling/testing/discharge, the steamfield (wells, pipelines, separators, silencers), power generation (flash/binary) and direct use (heating, bathing, industrial).
• The sector's defining hazards — H2S, high-temperature/high-pressure steam & fluid, well blowout/discharge, hydrothermal eruptions and hot ground, silica scaling and non-condensable gases (flagship — references/good-practice.md).

When NOT to use

• The generation / electricity-network side — the power station as a generator on the grid, the electrical work-control/permit system (SM-EI), switching/earthing → ../electricity-supply-specialist/.
• The drilling rig and operation (rig/derrick, hoisting, rotating string, mud) → ../drilling-specialist/ (this SME owns the geothermal drilling hazards — H2S, hot two-phase returns, steam blowout).
• The deeper hazard method belongs to its SME (this skill routes to them, in the geothermal context):
  • The H2S exposure/monitoring/SCBA method and other chemicals (biocides, antiscalants) → ../hazardous-substances-specialist/.
  • Confined spaces where H2S/CO2 accumulate (cellars, sumps, vessels, pits) → ../confined-space-specialist/; high-pressure fluid/steam release, stored energy, hot work → ../electrical-energy-specialist/.
  • Turbines/rotating plant guarding & isolation → ../machinery-safety-specialist/.
• Who holds the duty / notifiable events → ../worksafe-nz-specialist/ / ../safework-au-specialist/.
• Building the full bow tie → ../critical-risk-manager/.

The geothermal risk picture

Geothermal concentrates toxic gas, enormous thermal and pressure energy, and unstable hot ground in a remote field:

1. Hydrogen sulfide (H2S) — the signature killer. Toxic and heavier than air, so it accumulates in low and confined areas (cellars, sumps, pits, drains); at high concentration it causes "knockdown" — unconsciousness in 1–2 breaths — and deadens the sense of smell, so you cannot rely on odour. Deaths are associated with confined-space accumulation.
2. High-temperature / high-pressure steam & geothermal fluid. Severe burns and scalds from steam, hot brine and two-phase fluid; failures of wellheads, valves, pipelines and separators; blowdown and discharge.
3. Geothermal wells & discharge. Uncontrolled discharge/blowout of steam/two-phase fluid during drilling, well testing or work-over; well integrity; bleed/quench control.
4. Hydrothermal eruptions & hot ground. Sudden steam/hydrothermal eruptions, thin ground crust over boiling pools/hot ground, subsidence, and induced seismicity.
5. Plus silica scaling (descaling/cleaning hazards, confined entry into pipes/vessels), non-condensable gases (CO2 + H2S in condensers/gas-extraction), noise (vents/silencers), chemicals, hot work, mechanical/rotating plant, and lone/remote work. (NZ: geothermal often sits on or near Māori land / taonga — engage mana whenua; that is a relationship/consent matter, not a worker-safety control.)

Core controls (owned here)

Summary; detail in references/good-practice.md:

• H2S — fixed and personal gas monitors with alarms, a site H2S management plan, exclusion and ventilation of low/confined areas, escape sets / SCBA, wind-direction awareness, rescue planning, and never trusting smell. Exposure method → ../hazardous-substances-specialist/.
• Steam & fluid — integrity of wellheads/valves/pipelines/separators; isolation and blowdown with thermal/pressure controls; burn protection; exclusion from discharge paths and silencer areas.
• Wells & discharge — competent well-testing/discharge procedures, controlled bleed/quench, and managing blowout risk (with ../drilling-specialist/ during drilling).
• Hot ground / eruptions — survey and barricade hot ground and thin crust; defined walkways; monitoring; avoid eruption-prone features.
• Confined spaces & scaling — permit, test for H2S/CO2 and oxygen, ventilate, standby and non-entry rescue before any entry (descaling, vessels, cellars) → ../confined-space-specialist/.

Geothermal well drilling (owned here)

The drill rig and the generic drilling operation (derrick, mast rig-up/down, rotating drill string, hoisting, connections) belong to ../drilling-specialist/. The geothermal-specific drilling hazards are owned here — and they differ enough from oil & gas that you cannot just apply petroleum methods:

• Geothermal well control ≠ petroleum well control. Kicks are high-temperature brine or steam and can escalate rapidly (steam kicks). Control is generally by keeping the well full of cold water and cooling/quenching it, with a diverter / rotating BOP — not simply weighting up mud. Applying conventional oil-and-gas well control unmodified can be dangerous. Use competent geothermal well-control procedures and equipment.
• Total lost circulation — geothermal formations are fractured and permeable, so drilling fluid is often lost to the formation and does not return to surface ("drilling blind"); cuttings aren't returned, and there can be crossflow between fracture zones. Aerated-water / underbalanced / managed-pressure drilling is used to lift cuttings — adding a blooey/discharge line, compressed air and hot-return hazards.
• High temperature — limits drill bits, casing material, drilling mud and cement formulations; causes wellbore instability/collapse in hot fractured rock; the well is usually cooled/quenched before logging, casing and cementing.
• H2S in returns and hot two-phase returns at surface — monitor H2S at the rig/shakers/mud pits; guard against burns/scalds from hot returns at the shakers, blooey line and discharge.

Coordinate with ../drilling-specialist/ (the rig) and route the petroleum-style regime only where it genuinely applies. Detail in references/good-practice.md.

Method

1. Set the jurisdiction and stage — exploration, drilling, steamfield, generation or direct use (NZ-dominant; AU geothermal is limited).
2. Manage H2S first — monitoring/alarms, the H2S plan, confined/low-area control, escape sets, rescue.
3. Control the thermal/pressure energy — wellheads, pipelines, separators, isolation/blowdown, burns.
4. Cover wells/discharge, hot ground/eruptions, scaling and NCGs.
5. Route the rest — generation/network (electricity-supply), drilling (drilling), H2S/chemical method (hazardous-substances), confined space, machinery, stored energy/hot work.
6. State residual obligations — the PCBU owes the primary duty; H2S competency/monitoring, well/steam controls and emergency capability are mandatory. Hand off accordingly.

Jurisdiction note

NZ: HSWA 2015 general duties (no separate geothermal safety regime — it is not the petroleum regime), regulated by WorkSafe NZ, with geothermal/energy and H2S guidance; a world-leading sector in the Taupō Volcanic Zone plus Rotorua direct use. The geothermal resource is consented under the RMA (environmental, not worker H&S). AU: the model WHS primary duty applies, but Australian geothermal is limited/largely dormant (some hot-rock exploration history). Jurisdiction variations → ../safework-au-specialist/. Confirm current editions via ../hse-advisor/.

Output

Either a geothermal safety plan or risk screen (stage → H2S management → steam/fluid & wells → hot ground/eruptions → scaling/NCGs → routed generic hazards → critical questions), or the geothermal- specific controls and questions to feed into a bow tie (../critical-risk-manager/), task analysis (../task-analysis-author/) or SOP (../sop-author/). A draft for a competent person to validate.

Hand-offs

• Generation / electricity network (SM-EI, switching) → ../electricity-supply-specialist/; drilling rig & operation → ../drilling-specialist/.
• H2S / chemicals (exposure method, SCBA, monitoring) → ../hazardous-substances-specialist/; confined spaces → ../confined-space-specialist/; high-pressure/steam release, stored energy, hot work → ../electrical-energy-specialist/; turbines/rotating plant → ../machinery-safety-specialist/.
• Duties / notifiable events → ../worksafe-nz-specialist/ / ../safework-au-specialist/.
• Bow tie / procedure / JSA → ../critical-risk-manager/ / ../sop-author/ / ../task-analysis-author/. Route via ../hse-advisor/.

Disclaimer

This skill produces good-practice geothermal-safety guidance — not legal advice and not a substitute for a competent person or the current HSWA/WHS requirements, which change. H2S and high-pressure geothermal steam/fluid can kill in seconds; validate gas monitoring, the H2S and confined-space controls, the steam/well controls and the rescue plan against the actual field, plant and people before relying on them.