Gel Pills for Downhole Pressure Control during Oil and Gas Well Drilling

Mahmoud Khalifeh, Larisa Penkala, Arild Saasen, Bodil Aase, Tor Henry Omland, Knut Taugbøl and Lorents Reinås
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Mahmoud Khalifeh: Department of Energy and Petroleum Engineering, University of Stavanger, NO-4036 Stavanger, Norway
Larisa Penkala: Department of Energy and Petroleum Engineering, University of Stavanger, NO-4036 Stavanger, Norway
Arild Saasen: Department of Energy and Petroleum Engineering, University of Stavanger, NO-4036 Stavanger, Norway
Bodil Aase: Equinor, NO-4035 Stavanger, Norway
Tor Henry Omland: Equinor, NO-4035 Stavanger, Norway
Knut Taugbøl: Equinor, NO-4035 Stavanger, Norway
Lorents Reinås: Department of Energy and Petroleum Engineering, University of Stavanger, NO-4036 Stavanger, Norway

Energies, 2020, vol. 13, issue 23, 1-16

Abstract: During drilling of petroleum or geothermal wells, unforeseen circumstances occasionally happen that require suspension of the operation. When the drilling fluid is left in a static condition, solid material like barite may settle out of the fluid. Consequently, the induced hydrostatic pressure that the fluid exerts onto the formation will be reduced, possibly leading to collapse of the borehole or influx of liquid or gas. A possible mitigation action is placement of a gel pill. This gel pill should preferably be able to let settled barite rest on top of it and still transmit the hydrostatic pressure to the well bottom. A bentonite-based gel pill is developed, preventing flow of higher density drilling fluid placed above it to bypass the gel pill. Its rheological behavior was characterized prior to functional testing. The designed gel pill develops sufficient gel structure to accommodate the settled barite. The performance of the gel was tested at vertical and 40° inclination from vertical. Both conventional settling and the Boycott effect were observed. The gel pill provided its intended functionality while barite was settling out of the drilling fluid on top of this gel pill. The barite was then resting on top of the gel pill. It is demonstrated that a purely viscous pill should not be used for separating a high density fluid from a lighter fluid underneath. However, a bentonite or laponite gel pill can be placed into a well for temporary prevention of such intermixing.

Keywords: gel formation; viscous pill; gel pill; bentonite (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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