David Iacopini

Inversion structures in a foreland domain: Seismic examples from the Italian Adriatic Sea

AbstractPositive structural inversion within foreland domains ahead of thrust belts can create structures with significant hydrocarbon potential in mature and underexplored areas. Within this context, the Adriatic region represents a well-established hydrocarbon province constituting a foreland domain bounded by the Apennines, Southern Alps, and Dinaric fold-and-thrust belts. Newly reprocessed regional 2D seismic data and a renewed exploration interest in the area motivate a reappraisal of the regional structure and stratigraphy of the deformed Central Adriatic region of Italy (i.e., the Mid-Adriatic Ridge). Here, we developed and discussed examples of inversion structures that have different structural styles. The structural interpretations displayed on time-to-depth converted profiles had been validated by 2D structural-kinematic balancing and forward modeling. Our aim was to better define the geometry, style, and timing of the analyzed inversion-related folds. Positive inversion structures appeared loc...

Biases in three-dimensional vorticity analysis using porphyroclast system: limits and application to natural examples

Abstract A description of the systematic errors associated with the measurement of the vorticity number from poryhroclasts in natural systems is presented and discussed. We show that strong biases and systematic errors could derive both from some erroneous physical (i.e. no slip across clast/matrix boundary, homogeneity within the matrix) as well as geometrical assumptions (i.e. the radius ratio and angular measurements carried out in two dimensions on outcrop surfaces and thin section). By comparing natural datasets of porphyroclast shape preferred orientation (SPO) with different theoretical curves plots, we suggest that at least one of the Jeffery physical assumptions can be tested when applying vorticity techniques. The comparison of different possible sources of systematic errors indicates that, for medium-to-low vorticity numbers (Wm<0.8), vorticity data are strongly biased and that a minimum systematic error of 0.2 should be taken into account. Finally, we use data from natural shear zones from the Southern Variscan Belt in Sardinia to test and discuss the starting assumptions of the Jeffery model.

The use of geologic expression workflows for basin scale reconnaissance: A case study from the Exmouth Subbasin, North Carnarvon Basin, northwestern Australia

AbstractThe focus of this study is to demonstrate how seismic attributes can be used in the interpretation workflow to rapidly obtain a high-resolution view of the geology that is imaged within a seismic data set. To demonstrate the efficacy of seismic attribute analysis to basin scale reconnaissance, we apply a workflow to seismic data sets from the Exmouth Subbasin, northwestern Australia, with the aim of determining the geologic expression of the subsurface. Of specific interest are Barrow Group Jurassic and Cretaceous fluvial and marine sediments, that were faulted during the Jurassic-Cretaceous rifting associated with the breakup of East Gondwana. Regional-scale interpretations are made to develop a tectonostratigraphic context to the investigation. Target-level analyses, focused on features of exploration interest identified using regional reconnaissance, are made to calibrate attribute response and demonstrate the effectiveness of seismic attributes for rapid evaluation of prospectivity in the init...

Occurrence and development of folding related to normal faulting within a mechanically heterogeneous sedimentary sequence: a case study from Inner Moray Firth, UK

Abstract Folds associated with normal faults are potential hydrocarbon traps and may impact the connectivity of faulted reservoirs. Well-calibrated seismic reflection data that image a normal fault system from the Inner Moray Firth basin, offshore Scotland, show that folding was preferentially localized within the mechanically incompetent Lower–Middle Jurassic pre-rift interval, comprising interbedded shales and sandstones, and within Upper Jurassic syn-rift shales. Upward propagation of fault tips was initially inhibited by these weak lithologies, generating fault propagation folds with amplitudes of c. 50 m. Folds were also generated, or amplified, by translation of the hanging wall over curved, convex-upward fault planes. These fault bends resulted from vertical fault segmentation and linkage within mechanically incompetent layers. The relative contributions of fault propagation and fault-bend folding to the final fold amplitude may vary significantly along the strike of a single fault array. In areas where opposite-dipping, conjugate normal faults intersect, the displacement maxima are skewed upwards towards the base of the syn-rift sequence (i.e. the free surface at the time of fault initiation) and significant fault propagation folding did not occur. These observations can be explained by high compressive stresses generated in the vicinity of conjugate fault intersections, which result in asymmetric displacement distributions, skewed towards the upper tip, with high throw gradients enhancing upward fault propagation. Our observations suggest that mechanical interaction between faults, in addition to mechanical stratigraphy, is a key influence on the occurrence of normal fault-related folding, and controls kinematic parameters such as fault propagation/slip ratios and displacement rates.

Evolução complexa de um meio-gráben: seção rifte da Bacia de Campos baseada em análise sismoestratigráfica

The rift section in the Campos Basin, comprises the basal and median portions of the Lagoa Feia Group, and includes the main source rocks in the basin, as well as carbonate reservoir rocks. Interpretation and systematic mapping of 2D seismic lines across two main half-grabens, integrated with lithological well-log data, allowed the construction of a chronostratigraphic chart and an evolutionary model for the initial phase of this basin. Ten seismic stratigraphic units, with corresponding bounding surfaces, and three seismic facies were defined, representing the main lithological groups in the rift section: border fault deposits, fine grain-dominated re-sedimented deposits and coarse grain-dominated re-sedimented deposits. The Campos Basin stratigraphy was subdivided in tectonic systems tracts, which reflect its tectonostratigraphic evolution. The rift initiation systems tract presents a well distributed tectonic. The high tectonic activity systems tract is marked by the significant fault movement. Finally, the low tectonic activity systems tract is characterized by processes of fault restriction. Analysis of each evolutionary step led to a tectonostratigraphic model. Initially, the rift sediments were deposited in synformal depression with no border fault. With continuation of the rifting process, deformation was concentrated along main faults, which led to the development of two half-grabens structure with defined border faults and increasing tectonics. This phase was followed by a stage of incipient fault movement until the cessation of rifting. Basin filling was thus complex and interdependent in the different troughs during the development of the Campos Basin.

Reconhecimento e análise das fácies sísmicas nas sucessões rift das bacias de Campos e Santos

Apresentando reservatorios em aguas profundas, o pre-sal das bacias de Campos e Santos e um cenario com depositos heterogeneos e complexos, e assim traz novos desafios para a interpretacao sismica. O presente trabalho tem como objetivo a caracterizacao sismica do intervalo rifte (de idade Hauteriviano Superior ao Barremiano, imediatamente abaixo dos reservatorios pre- -sal) nas bacias de Campos e Santos com a utilizacao de dados de sismica 2D e dois perfis de pocos. Foram analisadas as texturas sismicas e com a integracao dos dados litologicos se definiu tres sismofacies correspondentes: Sismofacies 1 (deposito de falha de borda) – apresenta comportamento semelhante em ambas as bacias e com ocorrencia encaixada na falha de borda em uma zona ampla e bem definida; Sismofacies 2 (deposito de sedimentos finos) – amplamente identificada nas bacias de Campos e Santos e que grada lateralmente para a sismofacies 3; Sismofacies 3 (deposito de grainstones e rudstones ) – em ambas as bacias tem ocorrencia restrita e de ocorrencia erratica, tanto em zonas altas da margem flexural, quanto nas zonas profundas proximas do depocentro dos meio-grabens analisados.

Seismostratigraphy of the Ceará Plateau: Clues to Decipher the Cenozoic Evolution of Brazilian Equatorial Margin

The Ceara Plateau offshore Fortaleza holds some particular characteristics when compared to the other seamounts of the Brazilian Equatorial Margin (BEM). Not only it is the largest and the closest to the continent, it is also located at the boundary between the continental and the oceanic crusts, while all the others seamounts along the BEM are located on oceanic crust. Seismic imaging of the Ceara Plateau shows a “disorganized” interior, probably of volcanic origin, overlain by a series of horizontal seismic reflectors that can be interpreted as pelagic/hemipelagic sediments. As large uncertainties exist about the age of the initial formation of this seamount, three scenarios must be considered. If the age of the volcanic edifice is Coniacian (1), then the overlying pelagic/hemipelagic sedimentary succession can include an almost continuous record of the last ~90 Ma at the Equatorial Atlantic Ocean. In the case that the volcanic edifice is Eocene in age (2), the sedimentary sequence would still encompass the upper Paleogene and all the Neogene. There is also the possibility that the volcanic edifice was built during multiple magmatic events (3). In this case, it is likely that the sediments are interfingered with volcanic rocks at the edge of the structure. Although the age estimation (between Coniacian and Eocene) has an uncertainty of more than 40 Myr, the current interpretation is that it developed initially as a volcanic edifice, formed by a series of magmatic events that occurred between the Santonian and the Eocene. Since then, the topography has been leveled by pelagic/hemipelagic sedimentation. Whichever was the initial age, a continuous and constant sequence of sediments deposited onto the Ceara Plateau, at the same latitude, and thus under the same oceanographic conditions, for the last several tens of million years. This represents a unique opportunity to record a long-term history of the Atlantic Equatorial Margin.

Limits and biases on the three-dimensional vorticity analysis using porphyroblast system: a discussion and application to natural example

The Subandean Basins of South America extending from Trinidad to Tierra del Fuego have been the object of intensive exploratory activities (Fig. 1). The largest amount of hydrocarbons discovered during the last 30 years in these basins was found in complex structural terrains. A total of 59 Billion Barrels of Oil Equivalent (BBOE) have been discovered in areas affected by compressional tectonics. Of these basins, the largest discoveries are in the Furrial Trend of Venezuela (24 BBOE), followed by the Chaco area in Bolivia and Argentina (13 BBOE), the Llanos Foothills of Colombia (4.4 BBOE), and the Madre de Dios Basin of Peru (4.2 BBOE).