72 research outputs found
The contribution of Anisotropy of Magnetic Susceptibility (AMS), Anisotropy of P-wave Velocity (APV) and Petrophysic analysis in the strain characterisation at Sheep Mountain Anticline (Wyoming, USA)
No full textRobion, P., Amrouch, K., Callot, J., Lacombe, O., Daniel, J., Bellahsen, N
From paleostresses to paleoburial in fold–thrust belts: Preliminary results from calcite twin analysis in the Outer Albanides
No full textAbstract not availableOlivier Lacombe, Julien Malandain, Nadège Vilasi, Khalid Amrouch, François Rour
Palaeostress magnitudes in the Khao Khwang fold-thrust belt, new insights into the tectonic evolution of the Indosinian orogeny in central Thailand
No full textAbstract not availableFrancesco Arboit, Khalid Amrouch, Christopher Morley, Alan S.Collins, Rosalind Kin
Fluid pressure evolution in overpressured limestone reservoir at basin-scale: example of the Bighorn Basin (Wyoming, USA) and lessons from comparison with other reservoirs
No full textNicolas Beaudoin, Olivier Lacombe, Nicolas Bellahsen, Khalid Amrouch, and Jean-Marc
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Mapping permeable subsurface fracture networks: A case study on the Cooper Basin, Australia
No full textThe spatial distribution of permeable fracture networks is constrained in the subsurface Cooper Basin (Australia) through the integration of most positive curvature (K₊) analysis of five three dimensional (3D) seismic surveys, wellbore fracture data, and geomechanical modelling. The K₊ provides the likely distribution of subsurface extensional fractures based on the stress redistribution along the outer arc of an anticline. These results are reprocessed into the semblance (similarity) attribute to improve the signal-noise ratio prior to being extracted along the gas-rich and low permeability Patchawarra Formation. The subsurface fracture distribution maps show the geometry and density of extensional fractures that have been shown to facilitate fluid migration in this province, particularly those striking SE-NW and E-W, as these are properly oriented to undergo tensile reactivation. The density of these permeable SE-NW and E-W striking fracture sets is predicted to significantly increase along E-W elongate anticlines and may contribute to improved hydrocarbon recovery in this low permeability stratigraphic interval. We show that wellbore fracture data (n=917) in the Patchawarra Formation presents a close relationship to K₊ results and can be used to generate high density structural data in this basin, with the methodology applicable to other subsurface and offshore provinces.David Kulikowski, Khalid Amrouch, Hugo B. Burgi
Geomechanical modelling of fault reactivation in the Cooper Basin, Australia
No full textThe Australian Cooper Basin is a structurally complex intra-cratonic basin with large unconventional hydrocarbon potential. Fracture stimulation treatments are used extensively in this basin to improve the economic feasibility; however, such treatments may induce fault activity and risk the integrity of hydrocarbon accumulations. Fault reactivation may not only encourage tertiary fluid migration but also decrease porosity through cataclasis and potentially compartmentalise the reservoir. Relatively new depth-converted three-dimensional seismic surveys covering the Dullingari and Swan Lake 3D seismic surveys were structurally interpreted and geomechanically modelled to constrain the slip tendency, dilation tendency and fracture stability of faults under the present-day stress. A field-scale pore pressure study found a maximum pressure gradient of 11.31 kPa/m within the Dullingari 3D seismic survey, and 11.14 kPa/m within the Swan Lake 3D seismic survey. The present-day stress tensor was taken from previously published work, and combined with local pore pressure gradients and depth-converted field-scale fault geometries, to conclude that SE-NW-striking strike-slip faults are optimally oriented to reactivate and dilate. High-angle faults striking approximately E-W appear most likely to dilate, and act as fluid conduits irrespective of being modelled under a strike-slip or compressional stress regime. Near-vertical SE-NW and NE-SW-striking faults were modelled to be preferentially oriented to slip and reactivate under a strike-slip stress regime. Considering that SE-NW-striking strike-slip faults have only recently been interpreted in the literature, it is possible that many reservoir simulations and development plans have overlooked or underestimated the effect that fault reactivation may have on reservoir properties. Future work investigating the likelihood that fracture stimulation treatments may be interacting, and reactivating, pre-existing faults and fractures would benefit field development programs utilising high-pressure hydraulic fracture stimulation treatments.D. Kulikowski, K. Amrouch and D. Cook
Calcite twining constraints on late Neogene stress patterns and deformation mechanisms in the active Zagros collision belt
No full textMechanically induced calcite twins in veins and host rocks of Late Cretaceous to Miocene age in Iran have been used to determine regional Arabia-Eurasia collisional stresses. A late folding stress regime with a compression oriented 025° (±15°) has been identified across the Zagros belt and the southern Iranian Plateau. This late Neogene stress pattern agrees with the current stress field determined from the focal mechanisms of basement earthquakes and suggests that the Hormuz salt décollement poorly decouples the basement and cover stress fields. Our data show that the collisional state of stress has been relatively constant since ca. 5 Ma. The magnitudes of the stresses obtained from the twinning analysis are unexpectedly low, and, to a first approximation, they are constant across the Zagros simply folded belt. This result supports an overall mechanism of buckling of the detached Zagros cover. Internal viscous-plastic processes help to relieve stress within this cover, thus lowering its seismogenic potential. Beyond these regional implications, this study underlines the potential of paleostress analyses in constraining both the tectonics and the mechanics of ancient and active foreland fold belts.O. Lacombe, K. Amrouch, F. Mouthereau, L. Disse
Determination of the tectonic evolution from fractures, faults, and calcite twins on the southwestern margin of the Indochina Block
No full textIn polyphase tectonic zones, integrating a study of fault and fracture with calcite twin analysis can determine the evolving paleostress magnitudes and principle stress directions that affected the area. This paper presents the results of the analyses of fractures, striated faults, and calcite twins collected within the Khao Khwang Fold-Thrust Belt in central Thailand (SE Asia). Here we attempt to reconstruct the orientation of the principal stresses that developed during the tectonic evolution of this highly deformed, polyphase orogen. Tectonic data were collected in the Permian carbonates of the Khao Khad Formation of the Saraburi Group, and five successive tectonic stages are determined that are interpreted to have developed before, during, and after, the Triassic Indosinian Orogeny. The first three stages predate the main deformation event: the first stage is interpreted as a pre-Indosinian N-S extensional stage, the second stage described a N-S strike-slip and compressional regime, largely perpendicular to the fold axes of the main structures, while the third stage is associated with an E-W compressional strike-slip phase. A further two stages took place after, or during, the main folding event and correspond to N-S compression and to an E-W composite strike-slip/contractional stage, the latter which is interpreted to represent Cenozoic deformation related to the India-Asia collision.Francesco Arboit, Khalid Amrouch, Alan S. Collins, Rosalind King, and Christopher Morle
Geomechanical modelling and consequences for fluid-flow in complex rifted settings: A case study in the Otway Basin, Australia
No full textPoster presented at the EGU General Assembly 2019Geomechanical modelling of dilation tendency has been completed on more than 900 faults from nine three dimensional seismic surveys within the Otway Basin, Australia. As the in-situ stress regime within the basin is currently debated, scenarios of normal, strike-slip and reverse regimes of in-situ stress have been modelled. Additionally, the stability of natural fractures from seven wellbore image logs has been modelled under the same scenarios, with the consequences for each explored. NW-SE striking faults that define the basin’s major structural fabric are at critical risk of dilation irrespective of the regime of in-situ stress, while similarly striking fractures require very low (<5MPa under a strike-slip scenario) increases in pore pressure in order to be reactivated. N-S striking and W-E striking faults show lower risks for reactivation although their propensity to dilate is still significant. Our results in part explain why fault seal within the Otway Basin has been historically so poor, and suggest that while natural fracture networks may be optimally oriented for reactivation in order to increase secondary permeability – promising for unconventional prospectively - there is a high associated risk with respect to up-dip contamination along regional faults. This case study also provides insight into possible fluid flow pathways within other more frontier passive margin settings.Hugo Burgin, Khalid Amrouch, David Kulikowski, Simon Holford, and Philippe Robio
An integrated approach to determining 4D stress development at Castle Cove
No full textModels for basin evolution and natural fracture development often contain many uncertainties. Multiscale approaches to structural analysis assist in reducing these by providing checkpoints for structural evolution to better constrain the development of paleostress phases through time. In this study, we integrate the analysis of calcite twins, magnetic fabrics, stylolites and natural fractures at Castle Cove in the eastern Otway Basin, producing a five-phase model for stress evolution consisting of: phase 1 ~NW–SE Mid-Cretaceous strike-slip or compression; phases 2 and 3 Late Cretaceous extension, coinciding with the development of ~NW–SE and ~NE–SW striking extensional fracture sets; phase 4 ~NE–SW strike-slip and compression, representing an enigmatic period of stress evolution with respect to the current understanding of the Otway Basin; and phase 5, present day ~NW–SE strike-slip stress. The results contribute to a 4D structural history construction for the eastern Otway Basin and suggest that the evolution of the region may require reassessing in order to determine the timing and nature of the detected ~NE–SW oriented compressional event. This study also demonstrates how the use of a calcite stress inversion technique can assist in providing mechanical checkpoints for the evolution of complex natural fracture networks, which can easily be expanded within the sub-surface.Hugo B. Burgin, Khalid Amrouch, Philippe Robion and David Kulikowsk
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