Schlumberger

Technical Paper: Asphaltene Alley: Improving ESP Run Life In A Co2 Flood

Society: Other
Paper Number: 20020215
Presentation Date: 2007
 

Abstract

Between 1995 and 1997 Oxy's South Wasson Clearfork Unit electrical submersible pump installations had experienced severe asphaltene plugging and some significant gas cycling from CO2 flooding. An area of the field became known as 'Asphaltene Alley' due to the high amounts of asphaltene plugging. With an aggressive program of chemical treating and paraffin cutting, the ESP failure frequency moved from 1 to .5 during this period. In 1997, due to the industries economics, the CO2 flooding was reduced from 25 mmcf to 5 mmcf for the 98 producers in this field.

As economics improved Oxy planned to resume CO2 flooding in the second quarter of 2001. Oxy also planned to infill drill in an area of this CO2 flood that had already accumulated unrelieved CO2 build up. Oxy anticipated continued severe asphaltene plugging and gas cycling in this area. Oxy teamed up with strategic partners to proactively improve run times to be closer to the company average of .19.

The method selected was to run large volume compression pump designs internally coated with Teflon. The large volume vane openings were to help pass larger asphaltene solids and larger volume gas slugs. The Teflon would provide a 'slicker', lower friction coefficient, to avoid accumulating asphaltenes and to provide some additional throughput efficiency. The efficiency difference was measured by testing bare stages then retesting the same stages coated with Teflon.

Oxy has run 20 subs with this method. The earliest unit was run 12/15/00. The infill drilling, unrelieved CO2 pressure, and asphaltene production were realized in 2001, however the new CO2 flood has been postponed. No units have failed due to asphaltenes or gas cycling yet. There were two failures not related to asphaltenes or gas cycling that gave favorable indication of the effectiveness of the coating.

Further results will be presented as this project continues.

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