Paulo Legoinha

The Paleogene and Neogene of Western Iberia (Portugal): A Cenozoic Record in the European Atlantic Domain

The Portuguese mainland, located in western Iberia, represents a key area for understanding the evolution of the European Atlantic margin during the Cenozoic and the establishment of relations with the Mediterranean, in particular through the transition area between those two oceans which is well documented in the Algarve region.

Stochastic Simulation of the Morphology of Fluvial Sand Channel Reservoirs

This paper presents an innovative methodology designed to simulate 3D stochastic images of the morphology of fluvial sand channel reservoirs. This methodology is successfully tested for a hypothetical channel sand reservoir where some of the conditioning data were derived from a Middle Eastern reservoir of this type. Results are discussed with particular regard to the images of local orientations and analysis of the local and global uncertainties of the model.

Combined Use of Object-Based Models, Multipoint Statistics and Direct Sequential Simulation for Generation of the Morphology, Porosity and Permeability of Turbidite Channel Systems

This work presents a new methodology for simulating the morphology and petrophysical properties of hydrocarbon reservoirs in turbidite channel systems. The simulation of the morphology uses an object-based algorithm that imposes multipoint statistics of azimuth angle classes and cdfs of width and thickness as measured from training images of channels. A facies is then assigned to each block of the reservoir grid according to a conceptual model of facies both laterally and vertically within the channels. Following this, as each facies has a specific cdf for both porosity and permeability, simulated images of these petrophysical properties are generated using direct sequential simulation (DSS) with local histograms. For illustrative purposes, a case study of a reservoir in the Lower Congo Basin is presented.

Refinement of the Biostratigraphy and Biochronology of the Belverde Borehole (Setúbal Peninsula, Portugal) Using Calcareous Nannofossil Data

In this paper, we present a combined study of planktonic foraminifera and calcareous nannofossils that refines the previously established stratigraphic framework of the Belverde Borehole (Portugal). For the first time, some of the classic Miocene lithostratigraphic units of the Lower Tagus Basin are correlated with calcareous nannoplankton standard biozones: the top of unit IVa—NN3; units IVb, Va1, Va2, Va3, Vb, and Vc—NN4; unit VIa—NN5; unit VIb—NN6; units VIc and VIIa, b—NN7 or later.

Improved Realism of Channel Morphology in Object Modelling with Analogue Data Constraints

Preserving realism of geological structures is a challenge for the reservoir engineer when history matching. Object based models offer the chance of enforcing realism but are hard to constrain to observed data. In this paper we present a novel approach for generating channels that is easier to match to observed data than the standard object-based approach. Our new technique uses Object Modelling as the first step, mimicking the geometry of fluvial sand channels. Object Modelling enables us to constrain channel geometry with analogue information of channel local orientation and dimension. However, the morphology of the output models is smoothed and the transition channel/no-channel zones are associated with uncertainty as they are not constrained by a variogram or multi-point statistics. The second step, Probability Field Simulation, adds realism in a final output model imposing a variogram to the transition zones. Probability Field Simulation preserves the channel geometry of the object models and shows a significant CPU advantage compared with currently available approaches. The new method was applied to a synthetic problem in which 3 different channel scenarios were considered: low density, high density, and high density with thin channels. The results show that the proposed method can handle this range of channel densities, and we can therefore assume that the approach could be implemented for different channel density data. A further important finding was that there is no significant difference between the CPU time for each case. In summary, our new technique is able to constrain object models to a variety of observed data types such as channels size, density and orientation, while showing significant CPU saving and preserving the geological realism of the matched model.

Discussion of “The bioeroded megasurface of Oura (Algarve, south Portugal): implications for the Neogene stratigraphy and tectonic evolution of southwest Iberia” by Cachão et al. ( Facies 55(2): 213–225, DOI 10.1007/s10347-008-0172-2)

With reference to the above cited paper, we were surprised to see that the authors present four isotopic ages obtained in diVerent localities from that of the Wgured section (Oura Neogene section, Fig. 2) and use them to support very speculative (and most likely erroneous) conclusions. None of the four numerical dates presented were obtained from the Oura section. Instead, they derive from diVerent outcrops and diVerent sections, with no direct correlations. In addition, no reference to isotopic dates from the Oura section published in Pais et al. (2000) was made despite the paper was cited by Cachao et al. (2009). Also, some paleontological and biostratigraphic data (Antunes et al. 1981) concerning the Oura section are not discussed. The Oura Neogene section coordinates (Google) are 37°05 02 /8°13 50 . In fact, the numerical dates of 8.15 Ma (§0.29) and 7.15 Ma (§0.27) presented in the lower part of bed 3 (Fig. 2; Cachao et al. 2009) were obtained by Boski et al. (1995) in glauconitic sediments from the Gale/Castelo region, at a location with coordinates 37°04 25 /8°17 50 (Fig. 1). We obtained another date of 10.1 Ma (§0.25 Ma), in the same Gale/Castelo region, from a locality with coordinates 37°04 51 /8°18 58 , which is not referred to by Cachao et al. The isotopic age 3.0 (+2.5/i1.0) Ma presented from the upper part (bed 8) of the Wgured succession (Oura Neogene section, Fig. 2) was obtained by us in a diVerent section named “Olhos de Agua”, with coordinates 37°05 27 / 8°10 40 , in a mollusc-rich bed, intercalated with whitish, and thin Xuvial sandstones (Fig. 2; Legoinha (2001), p. 178, Wg. 64). Although the description presented by Cachao et al. for bed 8 (Oura Neogene section, Fig. 2) may correspond with that of the original level dated in the Olhos de Agua section, it does not bear much similarity to the observed lithology of bed 8, in the Oura section, which is a conglomerate containing quartz and highly abraded oyster clasts. We also studied and logged the “Oura Neogene Section”, but under the name Auramar (“Corte de Auramar”) (Antunes et al. 1981; Pais 1982; Legoinha 2001). A correspondence between our description and measured section (see Legoinha 2001, p. 177, Wg. 63) and the graphic columnar section of Cachao et al. (2009) can easily be established. Notice that in bed 3 (where they place the age from Boski et al. 1995) we have obtained an isotopic age of 9.5 (+1.0/i0.5) Ma (which was also referred to in Pais et al. 2000, in the table of isotopic age data). Furthermore, we have obtained an isotopic age of 8.3 (+2.2/i3.3) Ma, for bed 6 of Cachao et al. (2009), which they do not make reference to. Notice again that in bed 12 of our section (coarse conglomerate with large oysters), which corresponds to bed 8 of Cachao et al. (2009), they erroneously put the age that we obtained in the Olhos de Agua section. On the other hand, in the “Oura Neogene section”, we have not obtained any numerical dates for the Lagos Biocalcarenite (Lagos Portimao Formation). However, Cachao et al. indicate 11.3 Ma (+0.9/i1.3), which was obtained by us at an outcrop (some 7 km westward) at Gale Beach. We should note that in the Olhos de Agua section, which is nearer to the Oura section (some 3 km eastward), we obtained an isotopic age of 14.4 Ma (+0.5/i0.6) for the top of the Lagos Biocalcarenite (Lagos Portimao Formation) J. Pais (&) · P. Legoinha CICEGe, Faculdade de Ciencias e Tecnologia, Universidade Nova de Lisboa, 2829-516 Caparica, Lisbon, Portugal e-mail: jjp@fct.unl.pt