Location

New York, New York

Session Start Date

4-13-2004

Session End Date

4-17-2004

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

Appears In

International Conference on Case Histories in Geotechnical Engineering

Meeting Name

Fifth Conference

Publisher

University of Missouri--Rolla

Publication Date

4-13-2004

Document Version

Final Version

Rights

© 2004 University of Missouri--Rolla, All rights reserved.

Document Type

Article - Conference proceedings

File Type

text

Language

English

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Apr 13th, 12:00 AM Apr 17th, 12:00 AM

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.