Determining Potential Scenarios for the Occurrence, Development, and Containment of Accidents and Incidents at Offshore Oil and Gas Facilities

At the current stage of development, hydrocarbon production on the continental shelf is a priority task for the development of the oil and gas complex of the Russian Federation. In the development of offshore oil and gas fields, a risk-oriented approach plays a special role, aimed at a comprehensive analysis of scenarios for the development of accidents and incidents at oil and gas production facilities, their prevention, and liquidation. Any scenario begins with an initiating event (leaks of varying intensity/equipment failure, etc.), which can occur with a certain frequency.

Analysis of accidents and incidents that occurred at hazardous production facilities (HPFs) of the offshore oil and gas complex allows us to note some common patterns of their occurrence and development.

The causes of accidents on oil and gas production platforms are:

• uncontrolled blowout of oil and/or gas from wells;
• violation of the integrity of load-bearing (or supporting) structures, as well as equipment failures (or malfunctions);
• personnel errors;
• external impacts of a man-made nature (collision with sea vessels, helicopter crash, sabotage);
• uncalculated natural impacts.

During the operation of offshore stationary platforms, the following emergency situations may occur [2]:

• fires and explosions resulting from leaks;
• well blowouts;
• vessel collision with the platform;
• fire in engine rooms;
• fire in the living quarters;
• falling loads during cargo operations;
• helicopter crash;
  

Analysis of possible causes of accidents and incidents allowed for the identification of the following possible scenarios for the development of emergency situations on offshore stationary and jack-up platforms:

1. Release from equipment without ignition

Typical scenario S1:

Release from a well (equipment) of oil (associated gas) → oil entering the premises of an offshore stationary or jack-up complex (gas contamination of premises) and/or oil entering the sea, environmental pollution.

2. Fire - uncontrolled combustion causing material damage, harm to human life and health, interests of society and the state, the size of the zone of which is limited by the area of the spill.

Typical scenario S2, leading to a pool fire:

Depressurization of equipment with flammable liquids (FL), combustible liquids (CL) → entry of the liquid phase into the environment → formation of a spill → presence of an ignition source → pool fire, impact of thermal radiation on people, neighboring buildings and structures.

3. Explosion - rapid chemical transformation of a medium, accompanied by the release of energy and the formation of compressed gases.

Typical scenario S3, leading to a vapor phase explosion during the release of combustible substances:

Depressurization of equipment with FL, combustible gases (CG) → (formation of a spill → evaporation from the spill surface) formation of a fuel-air mixture (FAM) cloud → appearance of an ignition source → FAM explosion, impact of a shock wave on people, neighboring buildings and structures.

4. Jet fire – formation of a burning jet under conditions of instantaneous ignition of a leak of compressed combustible gases, vapor, and liquid phase of FL.

Typical scenario S4, leading to jet fire:

Partial depressurization of equipment with CG → product outflow from an opening under pressure → instantaneous ignition → jet fire, impact of thermal radiation on people, neighboring buildings and structures.

5. Flash fire - combustion of a cloud of pre-mixed gas-vapor-air mixture without the occurrence of pressure waves dangerous to people and surrounding objects.

Typical scenario S5, leading to a flash fire

Depressurization of equipment with FL, CG → formation of a spill → evaporation from the spill surface (formation of a FAM cloud) → appearance of an ignition source → flash fire, impact of thermal radiation on people, neighboring buildings and structures.

6. Platform destruction.

Typical scenario S6:

Collision with a vessel (earthquake, unfavorable meteorological factors, etc.) → destruction of structures/platform capsizing, possible formation of fires, oil spill → personnel injury, oil pollution of the marine environment.

7. Well blowout – formation of a burning fountain under conditions of instantaneous ignition of a leak of compressed combustible gases, vapor, and liquid phase of FL.

Typical scenario S7, leading to a well blowout:

Depressurization of well shut-off equipment or cratering → outflow of reservoir product from the well opening under pressure → ignition of the emergency blowout by static electricity discharges → oil and gas blowout fire, impact of thermal radiation on people, neighboring buildings and structures.

8. Helicopter crash.

Typical scenario S8:

Helicopter crash during takeoff (landing) on the helideck of PZhM-1 → destruction of structures/equipment, possible formation of fires in case of kerosene ignition → personnel injury.