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Pereira R.,Partex Oil and Gas | Pereira R.,University of Lisbon | Azeredo A.C.,University of Lisbon | Feist M.,Montpellier University
Journal of Micropalaeontology | Year: 2010

The re-evaluation of the charophyte content of 'Purbeckian' sediments from several sections around Lisbon (Olelas and Brouco) and Sintra-Cascais (Murches, Atrozela and Malveira-Guincho) revealed new palaeofloral associations from the Late Tithonian of the South Lusitanian Basin (Portugal). These sections contain Globator rectispirale, G. aff. nurrensis, Nodosoclavator bradleyi, Clavator reidi, Clypeator cf. discordis, Porochara maxima, and newly described occurrences of P. jaccardi, Mesochara harrisi and nodosoclavatoroide utricles. These revised data reinforce the evidence for assigning most of the studied deposits to a Late Tithonian age, instead of the formerly accepted wider interval Tithonian to Early Berriasian ('Purbeckian'). Population analysis and statistics were applied in order to better assess population variation of the different species. The results of this study are relevant as they contribute to improve the biostratigraphical definition of the 'Purbeckian' formations of Portugal and allow more accurate palaeobiogeographical interpretations within the central Tethyan domain, by comparison of the identified charophyte assemblages with documented Jurassic-Cretaceous transition charophytes from other regions. J. Micropalaeontol. © 2010 The Micropalaeontological Society.


Azevedo L.,University of Lisbon | Azevedo L.,University of Aveiro | Nunes R.,University of Lisbon | Correia P.,University of Lisbon | And 3 more authors.
Geophysics | Year: 2013

Due to the nature of seismic inversion problems, there are multiple possible solutions that can equally fit the observed seismic data while diverging from the real subsurface model. Consequently, it is important to assess how inverse-impedance models are converging toward the real subsurface model. For this purpose, we evaluated a new methodology to combine the multidimensional scaling (MDS) technique with an iterative geostatistical elastic seismic inversion algorithm. The geostatistical inversion algorithm inverted partial angle stacks directly for acoustic and elastic impedance (AI and EI) models. It was based on a genetic algorithm in which the model perturbation at each iteration was performed recurring to stochastic sequential simulation. To assess the reliability and convergence of the inverted models at each step, the simulated models can be projected in a metric space computed by MDS. This projection allowed distinguishing similar from variable models and assessing the convergence of inverted models toward the real impedance ones. The geostatistical inversion results of a synthetic data set, in which the real AI and EI models are known, were plotted in this metric space along with the known impedance models. We applied the same principle to a real data set using a crossvalidation technique. These examples revealed that the MDS is a valuable tool to evaluate the convergence of the inverse methodology and the impedance model variability among each iteration of the inversion process. Particularly for the geostatistical inversion algorithm we evaluated, it retrieves reliable impedance models while still producing a set of simulated models with considerable variability. © 2013 Society of Exploration Geophysicists.


Caeiro M.H.,Partex Oil and Gas | Soares A.,University of Lisbon | Demyanov V.,Heriot - Watt University
Society of Petroleum Engineers - Abu Dhabi International Petroleum Exhibition and Conference, ADIPEC 2015 | Year: 2015

Reservoir modeling involves the characterization of the internal gridded petrophysical properties distribution and the simulation of fluid production. However, a common problem associated with reservoir modeling is the highly non-linear relationship between the distribution of the petrophysical parameters (frequently with a non-stationary character) and the fluid production. To tackle this problem, this paper presents a new methodology for integrated reservoir modeling by addressing a multiscale optimization approach applied for non-stationary geostatistical history matching of complex connectivity hydrocarbon reservoirs. The methodology comprises a two staged procedure for multiscale optimization, which includes a global optimization stage followed by a local refining stage. The former consists of optimizing the geological spatial anisotropy trend by coupling the stochastic optimization over the anisotropy multiparameter space with an image generation algorithm - direct sequential simulation with local anisotropy correction. The latter aims at refining the small scale heterogeneity by performing the local optimization based on a regional image perturbation method. The local refining optimization is achieved by taking into account the best individual well production matches. A complex deltaic reservoir case study is presented to illustrate the applicability of the proposed methodology. An ensemble of multiple optimized history matched models is obtained respecting both the production data and the geological settings. The results show that the deltaic complex channelized pattern is well reproduced and also that the multiscale optimization improves the match between the simulated fluid profiles and the observed production data. As such, optimization is performed at multiple scales: the anisotropy trend model accounts for larger scale variability of the structures, while consecutive local refining improves convergence to dynamic response around individual wells. The contribution of this work to petroleum technology is the implementation of a novel methodology for the reproduction of the fluids production profiles through the perturbation of the subsurface petro-physical models while honoring complex geological constrains. Copyright 2015, Society of Petroleum Engineers.


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.


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.


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.


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.


Dias A.,Partex Oil and Gas | Alves F.,Partex Oil and Gas
Society of Petroleum Engineers - SPE Reservoir Characterisation and Simulation Conference and Exhibition 2011, RCSC 2011 | Year: 2011

A reliable fluid characterization achieved through the use of an Equation of State (EOS) is vital to reproduce the phase behaviour of a reservoir fluid and consequently, to improve understanding of the reservoirs EOR potential. In this case, an EOS model was developed aimed at accurately reproducing the phase behaviour of two reservoir oils in the same field that contain, besides H 2S, substantial amounts of organic sulphur components. The tuning of the EOS for both oils was more difficult to achieve than in cases without such level of sulphur components. The tuning of the Peng-Robinson EOS was achieved with 9 pseudo-components for both oils, following the selection of the lumping scheme considered adequate for reservoir simulation studies. Organic sulphur components are concentrated in the higher range of molecular weights and, consequently, were incorporated into the heavy fraction. The tuned EOS was then used on a 1 D reservoir simulation compositional model to match the available slim tube experiments, to verify the validity of the EOS tuning. Using the compositional simulation of slim tube displacements, minimum miscibility pressure (MMP) was estimated for both oils and different injection gases. Although a 9 component scheme is adequate for reservoir performance purposes, engineering of surface facilities requires more detail. Therefore, a delumping methodology was developed to allow engineers to estimate detailed fluid composition from the lumped components obtained from reservoir simulation studies. One of the objectives of this study is to obtain a table of variation of the detailed components distributions that can be used for delumping purposes at different stages of the gas injection project. Copyright 2011, Society of Petroleum Engineers.


Ines N.,Partex Oil and Gas | Bizarro P.,Partex Oil and Gas | Ribeiro T.,Partex Oil and Gas
Society of Petroleum Engineers - SPE Reservoir Characterisation and Simulation Conference and Exhibition, RCSC 2015 | Year: 2015

Carbonate reservoir characterization is often a complex task, due to the interplay between primary processes (e.g. depositional environments, facies changes) and secondary processes (e.g. burial, diagenesis, faulting and fracturing, cementation). In order to properly characterize and model such a reservoir, it is paramount to unravel the order by which such processes have affected the rock, leading to the present day petrophysical properties. In the presented case study (onshore dolomitized carbonate reservoir in Central Asia), a multi-step approach was taken for its characterization and modelling. The characterization phase was focused in understanding the key processes and controls on porosity and permeability. From the core and log data, a detailed sedimentologic and diagenetic study was performed, to identify the depositional environments and facies, as well as the pore system geometry, and its impact on fluid flow. Furthermore, several trends on reservoir quality were identified, related to faults, and associated with depositional cyclicity. From the above work, a reservoir model was built, to support field development planning and associated uncertainties. A structural and stratigraphic framework was built, and Flow Unit Types (FUT) were defined using seismic, cores, thin sections, logs and mercury injection capillary pressure data (MICP). Property modelling was carried out for porosity and permeability, honouring FUT, depositional and diagenetic trends. In particular, two trends were modelled: a fault-related trend, to introduce the impact of diagenetic leaching related to faults (observed in core data); and a cyclicity related trend, to introduce the impact of preferential fluid flow pathways that occur at or near cycle tops. The uncertainty in the reservoir property models was evaluated with different FUT, driven by depositional and diagenetic concepts. The results indicate that a significant improvement in reservoir understanding can be achieved with the use of an integrated study and model workflow, focusing on the key control factors that affect the pore system and the distribution of permeability. In this way it was possible to recognize spatial trends and capture the relationship between petrophysical properties, pore architecture and sweep efficiency. Copyright 2015, Society of Petroleum Engineers.


De Sousa A.,Partex Oil and Gas | Bizarro P.,Partex Oil and Gas | Ribeiro M.T.,Partex Oil and Gas
7th EAGE Saint Petersburg International Conference and Exhibition: Understanding the Harmony of the Earth's Resources Through Integration of Geosciences | Year: 2016

One of the largest challenges in reservoir modelling is to obtain representative Reservoir Rock Types for permeability and saturation modelling. The present case study provides an example from a complex siliciclastic reservoir, where an integrated Fishbone workflow was applied. Rock typing concepts can be used to establish the relationship between petrophysical data from standard well logs and core data, through the utilization of Hydraulic Flow Units and Neural Networks. Flow Zone Indicator, Rock Quality Index and Hydraulic Flow Units were calculated using mathematical equations through a dedicated software. The application of Principal Components Analysis allowed the identification of the logs to be used in Neural Networks, thus enabling the propagation of the cored-based reservoir properties into the non-cored wells. Finally, a set of logs consisting of porosity, permeability and reservoir rock types were used in the reservoir modelling.

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