Location
New York, New York
Date
15 Apr 2004, 1:00pm - 2:45pm
Abstract
The process for oil drilling through superficial deposits often results in ground movements. However, because of the rapid sequence of the operations, these movements are hardly noticed or monitored. Oil drilling is generally carried out over drilling slabs or platforms. Such a slab was constructed on a land location close to the Imo River in Niger delta of Nigeria. During the process of drilling over the slab, large depressions around the cellar pits were noticed. This development demanded the lowering of the rig and an investigation into the causes of the movements was initiated. The investigation confirmed the existence underneath the slab of sandy clay overlying badly sorted sandy gravel occasionally interbedded with thin argillaceous seams. The ground water table was high. The mean percentages of sand and gravel in the deposit were 20 and 80 percent respectively. This poor combination of sand and gravel gave rise to instability within the deposit. The drilling process, which had considerable disturbing effects on granular deposits, caused the sand to migrate to fill the interstices formed by the gravel particles with consequent creation of subsurface voids, which were the main contributors to the subsidence.
Department(s)
Civil, Architectural and Environmental Engineering
Meeting Name
5th Conference of the International Conference on Case Histories in Geotechnical Engineering
Publisher
University of Missouri--Rolla
Document Version
Final Version
Rights
© 2004 University of Missouri--Rolla, All rights reserved.
Creative Commons Licensing
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.
Document Type
Article - Conference proceedings
File Type
text
Language
English
Recommended Citation
George, E. A. J.; Thomas, L.; and Oko, C., "Ground Subsidence Induced by Oil Drilling Process" (2004). International Conference on Case Histories in Geotechnical Engineering. 6.
https://scholarsmine.mst.edu/icchge/5icchge/session07/6
Ground Subsidence Induced by Oil Drilling Process
New York, New York
The process for oil drilling through superficial deposits often results in ground movements. However, because of the rapid sequence of the operations, these movements are hardly noticed or monitored. Oil drilling is generally carried out over drilling slabs or platforms. Such a slab was constructed on a land location close to the Imo River in Niger delta of Nigeria. During the process of drilling over the slab, large depressions around the cellar pits were noticed. This development demanded the lowering of the rig and an investigation into the causes of the movements was initiated. The investigation confirmed the existence underneath the slab of sandy clay overlying badly sorted sandy gravel occasionally interbedded with thin argillaceous seams. The ground water table was high. The mean percentages of sand and gravel in the deposit were 20 and 80 percent respectively. This poor combination of sand and gravel gave rise to instability within the deposit. The drilling process, which had considerable disturbing effects on granular deposits, caused the sand to migrate to fill the interstices formed by the gravel particles with consequent creation of subsurface voids, which were the main contributors to the subsidence.
