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Pereira R.,Partex Oil and Gas | Pereira R.,University of Cardiff | Alves T.M.,University of Cardiff
Tectonophysics | Year: 2011

A dense grid of multichannel (2D) seismic profiles, tied to borehole, dredge and outcrop data are used to analyze the multiphased rifting, structural architecture and rift-locus migration across the southwest Iberian margin. In the study area, three distinct sectors show different structural evolutions from the Late Triassic to the Late Jurassic-earliest Cretaceous. The three structural sectors are distinguished by: 1) the presence of incipient tilt-blocks on the inner proximal margin, which denotes limited syn-rift subsidence; 2) developed tilt-blocks on the outer proximal margin; 3) evidence of significant fault-related subsidence on the outer proximal margin during the Middle Jurassic, followed by an Oxfordian-Tithonian/Berriasian(?) rift phase leading to seafloor spreading; and 4) marked crustal stretching on the distal margin, where highly-rotated tilt-blocks overlain by thick Late Triassic to Late Jurassic units are observed. This work demonstrates that significant subsidence occurred in Southwest Iberia several millions of years prior to the latest Jurassic-earliest Cretaceous extensional episode leading to continental breakup. The magnitude of early-subsidence episodes approaches that of the last subsidence pulse preceding continental breakup. Across the southwest Iberian margin the observed structural sectors differ from each other in terms of the age of rift climax of syn-rift strata. We interpret the multiple extensional pulses recorded in Southwest Iberia as resulting not only from continental rifting between Iberia and Newfoundland, but also between Nova Scotia and Morocco. Thus, it is considered that pre-breakup units in the deep-offshore basins of Iberia comprise multiple rift-related sequences whose distribution and relative thickness depends on local subsidence rates, on the diachronous northward-migration of rifting, and on the relative crustal stretching experienced by individual sub-basins. © 2011 Elsevier B.V. Source

Pereira R.,Partex Oil and Gas | Pereira R.,University of Cardiff | Alves T.M.,University of Cardiff | Cartwright J.,University of Cardiff
Journal of the Geological Society | Year: 2011

An extensive grid of 2D seismic reflection data imaging the non-volcanic continental margin of SW Iberia is used to investigate the post-rift compressional evolution in the transition zone between continental and oceanic crust. Tectonic compression affected the margin almost continuously since the latest Cretaceous, but was predominantly focused during the mid-Eocene and the late Oligocene-mid-Miocene. The detailed interpretation of post-rift structures and their adjacent strata shows that crustal shortening in the various sectors of the margin is neither synchronous nor similar in style. Main post-rift structures include: (1) thickskinned transpressional deformation on the distal margin; (2) localized basin shortening on the outer proximal margin; (3) limited reverse faulting and inversion on the inner proximal margin. The location and magnitude of crustal shortening are dependent on the inherited syn-rift geometry, the existence of evaporite (or clay-rich) detachments at depth, the rheological behaviour of previously extended continental crust and the position of the ocean-continent transition zone. The mechanisms of compression are mainly dominated by plate collision associated with the southeastern migration of the Iberian microplate during the Alpine orogeny and with recent westward convergence with the oceanic domain. Source

Pereira R.,Partex Oil and Gas | Pereira R.,University of Cardiff | Alves T.M.,University of Cardiff
Tectonics | Year: 2012

[1] Regional 2D multichannel seismic, borehole, dredge and outcrop data, together with burial models for strata in southwest Iberia, are used to investigate the tectono-stratigraphic signature of multiphased rifting on divergent margins. Our burial model reveals that Mesozoic extension occurred during three main phases, each comprising distinct subsidence pulses separated by short-lived periods of crustal uplift. The importance of the three phases varies across discrete sectors of the margin, each one revealing similar depositional architectures and associated tectonic systems tracts: 1) the Rift Initiation phase, characterized by incipient subsidence and overall aggradation/progradation over a basal unconformity, 2) the Rift Climax phase, which marks maxima of tectonic subsidence and is characterized by retrogradation-progradation, and 3) the Late Rift phase, recording the progradational infill of the basin and the effects of eustasy. The Rift Initiation systems tracts comprise Sinemurian and late Callovian-early Oxfordian strata. Marine units in the Pliensbachian and Late Oxfordian-Kimmeridgian represent the Rift Climax phase, a period marked by the development of Maximum Flooding Surfaces. Late Rift deposits were identified in the Rhaetian-Hettangian, Toarcian-Bathonian and Kimmeridgian-Berriasian. The results of this work are important to the economic exploration of deep-offshore rift basins, as they reveal that sequence stratigraphy can be used to predict sedimentary facies distribution in more distal segments of such basins. Significantly, this work recognizes that multiple tectonic-stratigraphic (rift) cycles can occur on deep-offshore rift basins, from the onset of rift-related extension until continental break-up, a character that contrast to what is known from deep-sea drilling data from the distal margin of Northwest Iberia. © 2012. American Geophysical Union. All Rights Reserved. Source

Pereira R.,Partex Oil and Gas | Pereira R.,University of Cardiff | Alves T.M.,University of Cardiff
Tectonophysics | Year: 2013

Using a dense grid of high-quality 2D seismic profiles, dredge and outcrop data, the offshore prolongation of a first-order transfer zone, the Messejana-Plasencia Fault Zone (MPFZ), is explained within the context of oblique rifting between Southwest Iberia, Newfoundland, and West Tethys. The offshore MPFZ is shown to comprise a 5-10. km wide region of deformation, oblique to the continental margin, reactivated in the Mesozoic as part of a wider transcurrent domain, the São Vicente sub-basin. Here, the geometry of faults and strata denotes the generation of a pull-apart basin during the Jurassic-Early Cretaceous. In contrast, its Late Cretaceous to Cenozoic evolution favours left-lateral transpression during the counter-clockwise rotation and eastward migration of Iberia towards its present position. Erosion was subsequently enhanced in the São Vicente sub-basin due to the reactivation of syn-rift structures. By documenting the evolution of the São Vicente sub-basin, and adjacent MPFZ, this work demonstrates: 1) the temporal and spatial scales in which first-order transfer zones accommodate crustal movements during continental rifting and subsequent inversion episodes; 2) the generation of an extensive region of strain accommodation in the vicinity of the MPFZ, an observation with profound implications to future palaeogeographic reconstructions of the North Atlantic Ocean; and 3) that the São Vicente Canyon, the physiographic expression of the MPFZ, incised the margin as early as the latest Cretaceous-Paleocene, synchronously with the onset of tectonic uplift in Southwest Iberia. In such a setting, the São Vicente sub-basin and MPFZ formed important by-pass corridors for sediment sourced from proximal areas of the margin. At present, the MPFZ comprises a complex releasing-restraining bend accommodating important vertical and horizontal movements in Southwest Iberia. Based on earthquake data from similar transfer zones, the MPFZ should be able to generate large-magnitude earthquakes and potentially destructive tsunamis. © 2013 Elsevier B.V. Source

Da Silva Caetano Caeiro M.H.,Partex Oil and Gas | Demyanov V.,Heriot - Watt University | Soares A.,University of Lisbon
14th European Conference on the Mathematics of Oil Recovery 2014, ECMOR 2014 | Year: 2014

History matching with a single objective function reflects only some global aggregated reservoir match quality and is not flexible enough to distinguish between local effects and provide a spread of diverse models for the forecast. On the contrary, multi-objective optimization (MOO) can distinguish between the contributions to the goodness to fit from some local parts of the model. History matching with MOO results in more diverse matched solutions and more robust prediction. Use of MOO in history matching also provides extra flexibility in matching local parts of the model especially in non-stationary cases. In this work we show how MOO improves the match quality of a non-stationary geostatistical model of a deltaic reservoir. Ensemble of multiple history match models achieved with MOO feature of better quality local matches.. Complex reservoirs descriptions with non-stationary characteristics are hard to match due to their high intrinsic heterogeneity and uncertainty associated with non-stationary description. Direct sequential simulation with local anisotropy correction (DSS-LA) provides a way to account for large scale trends, which are subject to uncertainty. The implementation of local anisotropy tackles the problem of non-stationary of the geostatistical model by imposing a trend in spatial correlation structure. The anisotropy change follows the trend in spatial correlation range and orientation across the reservoir model. While the uncertainty in the trend and spatial correlation is resolved through history matching using multiobjective optimisation. The proposed adaptive stochastic sampling framework integrates DSS-LA with the multi-objective history matching. Multiple optima matched models of porosity and permeability were obtained allowing the uncertainty assessment of the anisotropy model parameters. Source

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