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Geomechanical behaviour of the overburden above compacting hydrocarbon reservoirs--what would we predict from coalmining experience?

Goulty, N.R.

Authors

N.R. Goulty



Abstract

Observations of subsidence due to longwall coalmining and a time-lapse seismic profile over a longwall working have several implications for the geomechanical behaviour of the overburden above compacting hydrocarbon reservoirs. Subsidence at the ground surface or seabed is expected to amount to ~90% of the vertical compaction of the reservoir. Stress arching is unlikely to occur to any great extent in the overburden above a compacting reservoir unless the overburden contains thick beds of massive, competent sedimentary rock. The sensitivity of seismic velocity to vertical extensional strains is likely to be high in time-lapse seismic surveys because subsidence causes an irreversible disruption of the rock fabric with the development of fresh cracks and microcracks. Other observations consistent with the inferred behaviour of the Coal Measures during mining subsidence are difficulties experienced with extended reach drilling at Valhall, and the large differences in sonic velocity between the highly overpressured and normally pressured intra-reservoir Jurassic shales of very similar bulk porosity on the Halten Terrace, offshore mid-Norway.

Citation

Goulty, N. (2008). Geomechanical behaviour of the overburden above compacting hydrocarbon reservoirs--what would we predict from coalmining experience?. First break, 26(10), 67-70

Journal Article Type Article
Publication Date Oct 1, 2008
Deposit Date Jun 3, 2010
Journal First Break
Print ISSN 0263-5046
Electronic ISSN 1365-2397
Publisher Blackwell
Peer Reviewed Peer Reviewed
Volume 26
Issue 10
Pages 67-70
Publisher URL http://fb.eage.org/content.php?id=28556