Modeling of an underbalanced-drilling operation using supercritical Carbon Dioxide

Document Type

Article

Publication Date

1-1-2009

Abstract

A mechanistic model of an underbalanced-drilling (UBD) operation using carbon dioxide (C02) is developed in this study. The use of carbon dioxide in UBD operations eliminates some of the operational difficulties inherent with gaseous drilling fluids, such as generating enough torque to run a downhole motor. The unique properties of C02, both inside the drillpipe and in the annulus, are shown in terms of optimizing the drilling operation by achieving a low bottomhole pressure range. Typically, C0 2 becomes supercritical inside the drillpipe at this high density; thus, it can generate enough torque to run a downhole motor. As the fluid exits the drill bit, it evaporates to a gas, hence achieving the required low density for UBD. The latest C02 equation of state (EOS) to calculate the required thermodynamic fluid properties is used. In addition, a heat-transfer model that takes into account varying properties of both pressure and temperature has been developed. A marching algorithm procedure is developed to calculate the circulating fluid pressure and temperature, taking into account the varying parameters. Both single-phase C02 and a mixture of C02 and water have been studied to show the effect of produced water on corrosion rates. The model also is capable of handling different drillpipe and annular geometries. Copyright © 2009 Society of Petroleum Engineers.

Publication Source (Journal or Book title)

SPE Drilling and Completion

First Page

599

Last Page

610

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