Vis enkel innførsel

dc.contributor.authorHolt, Rune Martin
dc.contributor.authorLarsen, Idar
dc.contributor.authorFjær, Erling
dc.contributor.authorStenebråten, Jørn
dc.identifier.citationJournal of Petroleum Science and Engineering. 2019, 187 .en_US
dc.description.abstractBorehole collapse during drilling operations in shale formations is a well-known and costly problem within the petroleum industry. Recently it has become evident that shales may also form sealing barriers around the casing, reducing the need for cement jobs on new wells, and reducing costs for plugging and abandonment of old wells. The forming of such barriers involves large deformations of shale through creep and plastic processes. Hence, it is important to be able to characterize to what extent shales may fail in a brittle or ductile manner, in both cases causing possible hole instabilities during drilling, and in the case of ductile shales, enabling permanent sealing barriers. Triaxial failure tests, creep tests and tests tailored to follow the failure envelope under simulated borehole conditions have been performed with two soft shales. One shale fails in a more brittle manner than the other and fails to form a sealing barrier in the laboratory. The more ductile shale has been proved to form barriers both in the laboratory and in the field. By comparing their behavior, it is seen that the ductile shale exhibits normally consolidated behaviour, while the more brittle shale is overconsolidated. This points to the stress history and possibly cementation as keys in determining the failure mode. In addition, porosity, clay content, ultrasonic velocities, unconfined strength and friction angle may be used as indicators of brittle or ductile post-failure behaviour. Ultrasonic velocity and in particular attenuation measurements are shown to be sensitive to the failure initiation process, although stress sensitivity is much lower in the ductile than in the brittle case. The experiments provide values for anisotropic velocities as well as P-wave impedances that are necessary for open as well as cased hole log interpretation, in particular for barrier verification and possibly for monitoring of barrier formationen_US
dc.rightsNavngivelse 4.0 Internasjonal*
dc.titleComparing mechanical and ultrasonic behaviour of a brittle and a ductile shale: Relevance to prediction of borehole stability and verification of shale barriersen_US
dc.typePeer revieweden_US
dc.typeJournal articleen_US
dc.source.journalJournal of Petroleum Science and Engineeringen_US
dc.relation.projectNorges forskningsråd: 280650en_US
dc.relation.projectNorges forskningsråd: 255365en_US
dc.relation.projectNorges forskningsråd: 244420en_US
dc.description.localcodeThis is an open access article distributed under the terms of the Creative Commons CC-BY license, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.en_US

Tilhørende fil(er)


Denne innførselen finnes i følgende samling(er)

Vis enkel innførsel

Navngivelse 4.0 Internasjonal
Med mindre annet er angitt, så er denne innførselen lisensiert som Navngivelse 4.0 Internasjonal