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Environmental regulations require the addition of expensive sulphur recovery units to prevent the emission of H2S. This can still result in large amounts of CO2 being released to the atmosphere. Acid gas injection into existing reservoirs can provide a more feasible solution, sometimes with added benefits.
In the first example, our client needed to process additional third party gas. Epic investigated the feasibility of injecting the acid gas into an abandoned portion of a producing reservoir. Of critical importance to the study was the breakthrough time of the acid gas after onset of injection. During the analysis an extremely high degree of gravity override was identified. Combined with low solubility at high temperatures, the acid gas would immediately segregate to the top of the pinnacle structures into which the gas was being injected. Critical simulation issues included proper grid resolution of the pinnacle structures. Initial estimates using coarse grids set the breakthrough time at 1.5 years. Further grid refinement of the reservoirs "pinnacle" structures resulted in a breakthrough time of 7 years.
In the second example, our client could not develop a new discovery without a plan for the acid gas (mainly CO2). Our modeling showed that injection of the acid gas into an existing gas reservoir which was experiencing water influx would result in significantly more gas recovery (an 'enhanced gas recovery' effect - EGR) while providing storage for the acid gas at a lower cost.
See Epic Written Papers on Acid Gas Injection
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