Why is acid gas topical?
The term acid gas implies the presence of CO2 and/or H2S where there is no more than 2% hydrocarbon. H2S is a concern because it is toxic and, in critical quantities, lethal. CO2 is a concern because it is a greenhouse gas and, as such, has centre stage as a global environmental issue. These concerns have spurred industry interest in understanding acid gas and have led to a variety of acid gas projects including disposal, sequestration, cycling and enhanced oil recovery in order to handle and process these fluids.
How widespread are acid gas operations?
There are currently over 50 acid-gas injection projects in Alberta (Pembina, Hansman Lake, Mirage, and Zama) and North East British Columbia, making Canada the location of the largest activities in acid gas operations worldwide. In Alberta, the Energy Resources Conservation Board (ERCB) has implemented regulatory requirements to ensure standards are met to maintain public safety in areas of acid gas operation.
What makes modelling acid gas so different?
Acid gas behaviour is not intuitive because of its particular fluid behaviour which involves flashing between phases with significant changes in fluid density and viscosity. These fluid property changes can significantly impact the flow regimes in the operation of wellbores and pipelines and in reservoir management. Because of its complex behaviour, when modelling acid gas it is necessary to account for phase and property changes which affect the pressure and temperature profiles in the whole system. Modelling allows for better development planning of the facilities required to process acid gas and understanding of the associated operational challenges.
What are Neotec's solutions for modelling acid gas?
Neotec's program PIPEFLO can be used to examine all aspects of pipeline hydraulics including:
- Phase behaviour
- Flow pattern determination
- Hydrate prediction
- Elevation effects
- Liquid holdup
The figure below shows a pressure versus temperature plot with the phase envelope along with the pressure profile of the high H2S acid gas as it goes from the central facility, through the pipeline and down the wellbore.
The following can be noted in the figure:
- Fluid is in the liquid phase as it goes from the plant to the wellhead choke. The loss in pressure and temperature are evident once it reaches the choke at the wellhead
- The fluid flashes across the choke
- There is an increase in temperature with a slight increase in pressure up to the phase equilibrium line where the fluid enters the dense phase and the pressure losses become hydrostatically dominated
PIPEFLO offers superior solutions in modelling the relation of acid gas fluid behaviour to hydraulic behaviour in pipelines along with many other complex flows in all sorts of systems.