Computational Fluid Dynamic Modeling For Hazardous Gas Dispersion Analysis In Deepwater, Brazil

Abstract

The production of hazardous gases such as CO2 and H2S impose high risks to offshore operations, with lethal impacts on personnel, along with special equipment required and environmental challenges. Hydrocarbon productions require that part of this gas could disperse on the atmosphere, so a comprehensive risk analysis is necessary to evaluate the gas disposal event. Computational Fluid Dynamic (CFD) can be used to effective study how the wind and environment can interfere with the gas dissipation in the air. In this work, a specific analysis was necessary to produce a gas well with up to 80% CO2 fluid composition. A CFD Gas Dispersion Analysis evaluated the turbulent airflow over and offshore drilling vessel perimeter to map the flammability levels and hazardous gases concentration zones, depending on winds speeds, wind directions, and well gas flowrates. Parallel processing was applied in order to reduce the computing time for simulation of 52 cases on gas release on burner booms and relief lines, and 56 cases for leak analysis on the process plant. The results permitted defining using 3D maps the concentration levels of hazardous gases on the rig expected on each scenario condition, as well as the coverage area outside the vessel affected by the gas release.

Downwind dispersion of CO2 from a major subsea blowout in shallow offshore waters

“…For example, the physical controls, basic physics, and simple mathematical models of subsea well blowouts and pipeline leaks were developed and tested experimentally several decades ago 32–34 . Jumping ahead to more recent times with powerful computers and software available, computational fluid dynamic (CFD) models have been demonstrated capable of simulating the dynamics of gas flow and dispersion at the meter scale and smaller representing a high level of detail for an offshore platform or ship 35–39 . As for the differences between light and dense gases with differing solubility in seawater, even the coupled subsea‐atmosphere systems during blowout scenarios of natural gas and CO 2 have been simulated using CFD and other approaches 40 …”

Consequence assessment considerations for toxic natural gas dispersion modeling

“…Computational Fluid Dynamics based codes and simulation software can model the complex thermodynamic processes during expansion and diffusion of H 2 S rich natural gas. CFD can be used to effective study how the wind and environment can interfere with the gas dissipation in the air (Franklin et al, 2020). Further research is recommended to evaluate the CFD software options and determine appropriate solver and turbulence model for modeling H 2 S rich natural gas.…”