Variation of velocity with effective stress in chalk – null result from North Sea well data

Lubanzadio, M.; Goulty, N.R.; Swarbrick, R.E.

Abstract

Wireline log data and pore pressure measurements from eight wells have been analysed to investigate how velocity in the Chalk of the Central Graben, North Sea depends on porosity and vertical effective stress. The main conclusion is that velocity shows no detectable dependence on vertical effective stress when porosity and vertical effective stress are treated as independent variables. This result contrasts with the behaviour of shales, which exhibit a reduction in velocity on unloading. The significance is that velocity in the Chalk cannot be used to detect the presence of any overpressure caused by unloading. It is suggested that the absence of an observable velocity reduction in unloaded Chalk is due to cementation.

Citation

Lubanzadio, M., Goulty, N., & Swarbrick, R. (2002). Variation of velocity with effective stress in chalk – null result from North Sea well data. Marine and Petroleum Geology, 19(8), 921-927. https://doi.org/10.1016/s0264-8172%2802%2900135-6

• Journal Article Type: Article
• Publication Date: Sep 1, 2002
• Deposit Date: Jun 7, 2010
• Journal: Marine and Petroleum Geology
• Print ISSN: 0264-8172
• Electronic ISSN: 1873-4073
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 19
• Issue: 8
• Pages: 921-927
• DOI: https://doi.org/10.1016/s0264-8172%2802%2900135-6
• Keywords: Over pressure, Velocity, Chalk.
• Public URL: https://durham-repository.worktribe.com/output/1576416