Prediction of Asphaltenes Behaviors in Reservoir during CO2 Injection

Asphaltenes study for its precipitation has been a regular study for a field which has its Enhanced Oil Recovery (EOR) by Water Alternating Gas (WAG) technique. This technique uses CO2 gas injected into the reservoir alternately with injection water. This technique will results in better field ultimate recovery. Unfortunately, besides increasing the recovery factor of the hydrocarbon, the presence of CO2 cause a slight change in the oil composition, this change destabilizes the asphaltenes in the crude oil. As the asphaltenes is no longer stable in the crude oil, it will precipitate. This Asphaltenes precipitation creates major problems to the production performance of particular reservoir. Problems encountered as the results of asphaltenes precipitation are it can plug the wells and causes separation difficulties at the separation facilities. For a long time in the industry, remedial approach for this problem has been practiced by the operator instead of preventive approach from the beginning of well life.
Asphaltenes Onset Pressure (AOP) is the very important in understanding the asphaltenes behavior in the reservoir [2]. AOP are mostly conducted using a mixture of reservoir fluid and the injection gas. However this approach only shows the static behavior of asphaltenes in reservoir. AOP will be measured using Solid Detection System, (SDS) using Near InfraRed (NIR) technique. Besides of experimental study, AOP can be predicted by mathematical modeling. This numerical method of finding AOP has been incorporated in the simulation software. In addition some simulation software can calculate the possible amount of asphaltenes precipitate. In some case of the cases shows that results from the static analysis of asphaltenes behavior is inconsistent with the real field fact, there is occurrence of asphaltenes precipitation at the region where no precipitation estimated using static asphaltenes behavior of asphaltenes precipitation envelope.
For better understanding of asphaltenes precipitation, dynamic behavior of the asphaltenes in the reservoir needs to be understood for a realistic risk evaluation. This research is to investigate the behavior of asphaltenes in the reservoir by developing the Asphaltenes Precipitation Envelope (APE), calculate the amount asphaltenes precipitate and also determine the AOP of the crude oil.