A new approach to interpret high CO2 gas well test
Abstract
Although flow testing a CO2 well should be similar to testing a natural gas well, differences in the thermodynamic properties of CO2 affect the analysis of the well test considerably. In particular, the non-Darcy skin effect is more pronounced and the wellbore and surface flow can involve dramatic phase changes, such as the formation of ice. Also, since CO2 is more compressible than a typical natural gas, the accurate measurement of the flow rate becomes more challenging. It is also apparent that the use of pseudo pressure, as opposed to simpler methods of dealing with the pressure dependency of key properties, is essential to the successful analysis of the pressure response to the CO2 production.
Some gas discoveries in Tri Ton horst (South of Song Hong basin show the average content of CO2 is around 32% - 37%. During build up period in DST test, decreasing pressure phenomenon occurred which makes it impossible to analyse the reservoir properties.
This research concentrates on the effect of CO2 during DST test, evaluates the current methods and suggests a new approach to collect more data about the reservoir properties which will facilitate the establishment and improvement of field development plans.
References
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