Significant Surge and Swab Offshore Brazil Induced by Rig Heave During Drill Pipe Connections
- John-Morten Godhavn (Equinor) | Banzi Olorunju (Equinor) | Dmitri Gorski (Heavelock Solutions) | Martin Kvernland (Heavelock Solutions) | Mateus Sant'Ana (Heavelock Solutions) | Ole Morten Aamo (Norwegian University of Science and Technology NTNU) | Sigbjørn Sangesland (Norwegian University of Science and Technology NTNU)
- Document ID
- Society of Petroleum Engineers
- SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition, 29-30 October, Denver, Colorado, USA
- Publication Date
- Document Type
- Conference Paper
- 2020. SPE/IADC Managed Pressure Drilling and Underbalanced Operations Conference and Exhibition
- 1.12 Drilling Measurement, Data Acquisition and Automation, 1.7 Pressure Management, 3 Production and Well Operations, 1.6 Drilling Operations, 1.11 Drilling Fluids and Materials, 1.10 Drilling Equipment, 1.12.1 Measurement While Drilling, 3 Production and Well Operations, 4.5 Offshore Facilities and Subsea Systems, 1.1 Well Planning, 1.10 Drilling Equipment, 1.12.6 Drilling Data Management and Standards, 4.5 Offshore Facilities and Subsea Systems, 1.7.2 Managed Pressure Drilling
- Deepwater Applications, Rig heave, Case Histories/Lessons Learned, Surge and swab
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- 29 since 2007
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This paper describes measured and simulated downhole pressure variations ("surge and swab") during drill pipe connections when drilling an ultra-deepwater well offshore Brazil on the Carcará field. Floating rig motion caused by waves and swell ("rig heave") induces surge and swab when the drill string is suspended in slips to make up or break a drill pipe connection and topside heave compensation is temporarily deactivated. This is a known issue in regions with harsh weather such as the North Sea, where pressure oscillations of up to 20 bar have been reported during connections. Recorded downhole drilling data from the Carcará field reveals significant pressure oscillations downhole (in the same order of magnitude as in the North Sea) each time the drill string was suspended in slips to make a connection in the sub-salt 8 ½" section of the well. Mud losses were experienced around the same well depth and they might have been caused by surge and swab.
Measured surge and swab pressure variations have been reproduced in an advanced proprietary surge and swab simulator that considers rig heave, drill pipe elasticity, well friction, non-Newtonian drilling mud, well trajectory and geometry. Moreover, findings in this paper suggest that surge and swab was in fact significantly higher than recorded by the MWD (Measurement While Drilling) tool. The true magnitude of surge and swab is not captured in the recorded MWD data due to low sampling frequency of the downhole pressure recording (one measurement every six seconds, a standard downhole pressure sampling rate used on many operations today).
This work shows that surge and swab during drill pipe connections on floaters may challenge the available pressure window for some wells even in regions with calm weather such as Brazil. Managed Pressure Drilling (MPD) is a technique that improves control of the downhole pressure. It is, however, not possible to compensate fast downhole pressure transients, such as heave-induced surge and swab, using MPD choke topside. This is due to the long distance between the choke and the bit, which translates into a time delay in the same order of magnitude as typical wave and heave periods. A downhole choke combined with continuous circulation is one of potential solutions.
Surge and swab during drill pipe connections can result in a loss or an influx and should be considered in the well planning phase when mud weight, section lengths, etc. are selected.
|File Size||4 MB||Number of Pages||11|
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