The present-day stress regime of the southwestern part of the Aquitaine basin, France, as indicated by oil well data

Bell, J. S.; Caillet, G.; Marrec, Alain Le

doi:10.1016/0191-8141(92)90033-s

Cited by 11 publications

(2 citation statements)

References 30 publications

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“…We can assume that σ 1 could be a little more vertical at Lacq under the influence of a more extensive regime since the gas field stands in the southern part of the Aquitain Basin. Analyses of well ovalization in the Aquitain Basin favour a stress regime with σ v > σ H ∼σ h (where σ v is due to the overburden load at a specific depth, σ H and σ h are, respectively, the maximum and the minimum horizontal stresses) (Bell et al 1992). However Segall et al (1994) compare the Coulomb failure stress with earthquake locations for different regional environments, and show that the best fit occurs at Lacq when σ 3 (minimal stress) is vertical.…”

Section: Characteristics Of the Lacq Gas Field And Previous Studiesmentioning

confidence: 99%

Analysis of the induced seismicity of the Lacq gas field (Southwestern France) and model of deformation

Bardainne¹,

Dubos-Sallée

Sénéchal³

et al. 2008

Geophysical Journal International

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S U M M A R YThe goal of this paper is to propose a model of deformation pattern for the Lacq gas field (southwest of France), considering the temporal and spatial evolution of the observed induced seismicity. This model of deformation has been determined from an updating of the earthquake locations and considering theoretical and analogue models usually accepted for hydrocarbon field deformation. The Lacq seismicity is clearly not linked to the natural seismicity of the Pyrenean range recorded 30 km farther to the south since the first event was felt in 1969, after the beginning of the hydrocarbon recovery. From 1974 to 1997, more than 2000 local events (M L < 4.2) have been recorded by two permanent local seismic networks. Unlike previously published results focusing on limited time lapse studies, our analysis relies on the data from 1974 to 1997. Greater accuracy of the absolute locations have been obtained using a well adapted algorithm of 3-D location, after improvement of the 3-D P-wave velocity model and determination of specific station corrections for different clusters of events. This updated catalogue of seismicity has been interpreted taking into account the structural context of the gas field. The Lacq gas field is an anticlinal reservoir where 3-D seismic and borehole data reveal a pattern of high density of fracturing, mainly oriented WNW-ESE. Seismicity map and vertical cross-sections show that majority of the seismic events (70 per cent) occurred above the gas reservoir. Correlation is also observed between the orientation of the pre-existent faults and the location of the seismic activity. Strong and organized seismicity occurred where fault orientation is consistent with the poroelastic stress perturbation due to the gas recovery. On the contrary, the seismicity is quiescient where isobaths of the reservoir roof are closed to be perpendicular to the faults. These quiescient areas as well as the central seismic part are characterized by a surface subsidence determined by repeated levelling profiles. Moreover, the temporal evolution of the distribution of the seismicity clearly exhibits a spatial migration from the centre to the boundaries of the reservoir. We conclude that the entire field is strained but this deformation is seismically expressed only where faults are parallel to the isobaths of the reservoir roof and where these faults plunge towards outside the field according to one of the two theoretical deformation models considered in our study. Then we propose a temporal scenario of deformation along the principal axis of seismic deformation.

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Section: Characteristics Of the Lacq Gas Field And Previous Studiesmentioning

confidence: 99%

Analysis of the induced seismicity of the Lacq gas field (Southwestern France) and model of deformation

Bardainne¹,

Dubos-Sallée

Sénéchal³

et al. 2008

Geophysical Journal International

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“…The Lacq hydrocarbon field was formed at the Tertiary period when the maximum horizontal stress was oriented in the direction of N30øE consistent with the direction of the Pyrenean thrust fault (Grasso and Wittlinger, 1990). Moreover at local scale, the main crack directions as measured from core drilling are N30øE and N120øE in the gas reservoir (Feigner and Grasso, 1990) and a present-day NE-SW stress direction is also established from oil well data (Bell et al, 1992).…”

Section: Discussion A) Polarizations Of Split Shear Wave and State Ofmentioning

confidence: 99%

Anisotropy at the Lacq hydrocarbon field (France) from shear‐wave splitting

Herquel

Wittlinger

1994

Geophysical Research Letters

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Three‐component seismograms from local earthquakes located beneath the reservoir of the Lacq hydrocarbon field have been analysed for shear‐wave splitting. Shear‐waves recorded at the station USI located on top of the hydrocarbon reservoir show a clear splitting in an average polarization direction N30°–40°E which is different from the present‐day local and regional stress direction. This direction seems approximately parallel to the Tertiary period stress field in this area which corresponds to the measured main crack directions in the gas reservoir. At station LDB, located outside of the anticlinal structure, no splitting was detected but due to a poor signal‐to‐noise ratio, only nine events were available and anisotropy could be absent or obscured. For a 250 m thick oil or gas field the velocity anisotropy is estimated at about 6–10%, which is in the same range as values obtained from VSPs in other hydrocarbon fields. Monitoring induced‐seismicity by three component stations could be a useful tool to characterize hydrocarbon fields in term of the rock's average properties in a large volume.

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Exploration for and Production of Oil and Gas in France: A Review of the Habitat, Present Activity, and Expected Developments

Mascle¹,

Bertrand²,

Lamiraux³

1994

Hydrocarbon and Petroleum Geology of France

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The present-day stress regime of the southwestern part of the Aquitaine basin, France, as indicated by oil well data

Cited by 11 publications

References 30 publications

Analysis of the induced seismicity of the Lacq gas field (Southwestern France) and model of deformation

Analysis of the induced seismicity of the Lacq gas field (Southwestern France) and model of deformation

Anisotropy at the Lacq hydrocarbon field (France) from shear‐wave splitting

Exploration for and Production of Oil and Gas in France: A Review of the Habitat, Present Activity, and Expected Developments

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