CO2 miscible gas flooding is a popular method of improved oil recovery. It is widely used in the Permian Basin. Asphaltene deposition in many of these systems is a costly operational problem associated with the utilization of this method of recovery. A CO2 flood in West Texas was experiencing major problems with asphaltene deposition related ESP failures and tubing plugging.

Operational procedures, field experience and a successful chemical program have greatly reduced the cost of these problems over the last 3 years. A new inhibitor for continuous capillary injection was recently developed and performed well on live oil lab tests. To evaluate the field performance of this new asphaltene inhibitor, a wellhead side stream filter loop was constructed to monitor asphaltene precipitation/deposition. The objective was to measure and compare the time needed to plug a given size filter with untreated and chemical treated produced fluids. Pressure data at the filter loop and wellhead was also recorded to monitor the effectiveness of the treatments.

The field trial results proved the use of a filter-plugging side stream was an effective way of assessing asphaltene inhibitor performance. Based on the filter plugging and wellhead pressure data, it was concluded that asphaltene precipitation/deposition occurred if the produced fluid was not chemically treated. The standard field product used successfully in the past was able to reduce asphaltene deposition and doubled the filter plugging time. The new asphaltene inhibitor was shown to be more effective for stabilizing the asphaltenes in the CO2 flooded produced fluids. The new inhibitor extended the time needed to plug a filter by more than four times as compared to untreated fluids.

Case history information, laboratory tests results, side stream configuration, field test procedure and field test results are presented.

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