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Papers by Paola Ronchi

66th EAGE Conference & Exhibition, 2004

P246 REGIONAL DISTRIBUTION OF THE EOCENE CARBONATE RESERVOIRS OF THE METLAOUI GROUP (C137 & N... more P246 REGIONAL DISTRIBUTION OF THE EOCENE CARBONATE RESERVOIRS OF THE METLAOUI GROUP (C137 & NC41 OFFSHORE LIBYA) Objective and method The objective of the poster is to illustrate the main parameters which control both the regional and local distribution of Eocene carbonate reservoirs located in offshore Libya. These reservoirs include the nummulite limestone of the El Gueria Formation and the dolomite of the Chouabine Formation. The method has resulted in a geological model constrained by the integration of merged 3D seismic well and core data from C137 and NC41 areas respectively operated by Total and ENI. Regional framework The regional

P023 EL GUERIA FORMATION IN LIBYA OFFSHORE FACIES AND RESERVOIR COMPARISON BETWEEN C137 AND NC41 ... more P023 EL GUERIA FORMATION IN LIBYA OFFSHORE FACIES AND RESERVOIR COMPARISON BETWEEN C137 AND NC41 WELLS 1 P.RONCHI 1 B. CALINE 2 P.MASSE 2 AND S. CANTALOUBE 2 1 ENI Exploration and Production Division Via Emilia 1 20097 San Donato Milanese (MI) Italy 2 TotalFinaElf Geoscience Technologies avenue Larribau 64018 Pau Cedex France Introduction The main reservoir of the carbonate series in offshore Libya is represented by the nummulite facies of the El Gueria Formation of Eocene age (late Ypresian to early Lutetian). Thanks to the exchange of geological data between TFE and ENI regarding some of Bouri field wells

All Days

During the Early Cretaceous South-Atlantic opening, in large lacustrine basins a series of shallo... more During the Early Cretaceous South-Atlantic opening, in large lacustrine basins a series of shallow water carbonate platforms grew along lake margins and paleo-highs. These carbonates are giant reservoirs in the Brasil offshore, while in Angola are productive in Cabinda (Lower Congo Basin) and are being explored in the Kwanza Basin with minor success. These carbonates have peculiar facies associations represented mainly by microbialites and coquinas, and are affected by dolomitization which modified the original pore system in different ways. In presence of deep-seated extensional faults, bounding the paleo-highs, the hydrothermal dolomitization affected the reservoir carbonate improving its quality; in fact the hydrothermal dolomite produced the so-called zebra dolomite which is characterized by high porosity and permeability. On the other hand, when there is a limited influx of hydrothermal fluid, some dolomitization is observed, but it did not produce the zebra facies and the poro...

Bollettino Della Societa Geologica Italiana, 2003

In this work petrographic and geochemical analyses allowed us to construct a genetic model of the... more In this work petrographic and geochemical analyses allowed us to construct a genetic model of the pervasive dolomitization in the reference section of the Castel Manfrino Dolostones which includes the dolomitized Calcare Massiccio platform and the basinal Corniola sediments (Liassic). Cathodoluminescence and SEM analysis indicates a multiphase dolomitization: an initial calcite replacement (Dolomite 1) followed by recrystallization (Dolomite 2) and cementation events (Dolomite 3), and precipitation of saddle dolomite (Dolomite 4). Carbon and oxygen isotopic data suggest that dolostones underwent several recrystallization and stabilization events under increasing temperatures, in the presence of sea-water derived fluids. Fluid inclusion analyses established that Dolomite 3 took place at temperatures of around 70 degrees C, and Dolomite 4 precipitated at temperatures up to 132 degrees C. The fluid inclusions show salinity values for Dolomite 4 (average 16% NaCl equivalent) higher than Dolomite 3 (average 12%) suggesting a change in fluid geochemistry through time. The burial history, reconstructed from regional data and the succession outcropping in the Montagna dei Fiori area, enables us to match the diagenetic phases with the geological evolution of the area. The shallow burial phase of dolomitization (Dolomite 1) could have occurred during burial from the Upper Jurassic to the Middle Cretaceous. The second dolomitization phase (Dolomite 3), took place starting from the Middle Miocene, when the Lower Jurassic series reached temperatures of about 70 degrees C. After this period the area was subject to the Apennine thrusting, and hydrothermal fluids (with temperatures of 110-130 degrees C) arriving from deep seated faults are believed to have been the dolomitizing fluids for the last event (Dolomite 4).

The dolomitization in a carbonate platform can occur at different times and in different diagenet... more The dolomitization in a carbonate platform can occur at different times and in different diagenetic environments from synsedimentary to deep burial settings. A well constrained diagenetic interpretation allows assumptions to be made about the distribution of the dolomitized bodies. This is particularly important in the oil industry because the dolomitised bodies frequently have the best petrophysical properties. The results of diagenetic analyses do not always point to a unequivocal conceptual model. In this situation a numerical modelling exercise may help to select the model that best honours the mass balance, kinetic and thermodynamic constrains. Moreover, the effects of the diagenetic processes on reservoir properties may be estimated. The subject of this study is an application of the software ‘Toughreact’ in which three different dolomitization models have been tested, in order to strengthen the conceptual interpretation and to evaluate the main constraints on the dolomitizati...

In the Jurassic–lower Cretaceous sequence of central Apennines and their foreland (onshore and of... more In the Jurassic–lower Cretaceous sequence of central Apennines and their foreland (onshore and offshore Marche–Abruzzi regions), the dolomitization processes enhanced the petrophysical properties of the carbonate platform and slope series. The area experienced a first phase of passive-margin regime, from the Lower Jurassic to the Miocene: the Liassic carbonate platform underwent extensional tectonics that established the southern Apulian–Apennines persisting platforms and the northern Umbria-Marche basin; within the basin, differential subsidence rates created faulted horsts characterized by condensed series. From upper Miocene, the area entered the collision-margin phase when its eastern part was involved in the Apennines orogeny. The aim of this study was to analyze the dolomitization process in relation with the fluid-flow changes caused by the evolution of the geological framework. Dolomitized bodies are mainly located at the Jurassic–Early Cretaceous platform edges and in the p...

Geological Society London Special Publications

64th EAGE Conference & Exhibition, 2002

Tectonophysics, 2017

Billi et al. (2017) proposed a new interpretation for the origin and internal structure of thermo... more Billi et al. (2017) proposed a new interpretation for the origin and internal structure of thermogene travertine deposits. On the basis of evidence from two quarries located in southern Tuscany (Italy), they interpreted some travertine beds as calcite veins and argued that undulating travertine beds formed by syn-diagenetic (i.e. non-tectonic) folding that was caused by laterally-confined volume expansion caused by incremental veining. They assumed that such a process causes changes to the rock properties, including porosity reduction, rock strengthening, and age rejuvenation. The interpretations by Billi et al. (2017) challenge and question the current understanding and interpretation of thermogene travertine deposits. This understanding, based on numerous studies since the 1980s, is that these deposits form from thermal water flowing downslope, and precipitating calcium carbonate. Here, we explain how the comparison with active depositional systems is essential for the understanding the origin of structures in older, inactive travertine deposits, such as those studied by Billi et al. (2017). We further argue that the three-dimensional setting of travertine deposits should be taken into account in order to discuss the possible development of secondary structures. Indeed travertine deposition on slopes typically leads to the formation of terraced morphologies with pools bordered by rounded rims and separated from each other by steep walls. The resulting three-dimensional structures can be misinterpreted as asymmetric folds in two-dimensional views (i.e., in saw-cut walls of quarry). In this paper we debate the interpretations offered by Billi et al. (2017) and their criteria to recognise syn-diagenetic, non-tectonic folds in travertine deposits, and explain why many of their ideas are questionable.

Journal of Petroleum Geology, 2015

ABSTRACT

International Journal of Earth Sciences, 2011

Calcite veins and related sulphate-sulphide mineralisation are common in the Buda Hills. Also, ab... more Calcite veins and related sulphate-sulphide mineralisation are common in the Buda Hills. Also, abundant hypogenic caves are found along fractures filled with these minerals pointing to the fact that young caveforming fluids migrated along the same fractures as the older mineralising fluids did. The studied vein-filling paragenesis consists of calcite, barite, fluorite and sulphides. The strike of fractures is consistent-NNW-SSEconcluding a latest Early Miocene maximum age for the formation of fracture-filling minerals. Calcite crystals contain coeval primary, hydrocarbon-bearing-and aqueous inclusions indicating that also hydrocarbons have migrated together with the mineralising fluids. Hydrocarbon inclusions are described here for the first time from the Buda Hills. Mixed inclusions, i.e., petroleum with 'water-tail', were also detected, indicating that transcrystalline water migration took place. The coexistence of aqueous and petroleum inclusions permitted to establish the entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (\1.7 NaCl eq. wt%) implies that hydrocarbon-bearing fluids were diluted by regional karst water. FT-IR investigations revealed that CO 2 and CH 4 are associated with hydrocarbons. Groundwater also contains small amounts of HC and related gases on the basin side even today. Based on the location of the paleo-and recent hydrocarbon indications, identical migration pathways were reconstructed for both systems. Hydrocarbon-bearing fluids are supposed to have migrated north-westward from the basin east to the Buda Hills from the Miocene on. Keywords Calcite Á Petroleum inclusion Á Hydrocarbon migration Á Miocene Á Buda Thermal Karst Á Pannonian Basin Introduction: previous research on hydrothermal events and related karst processes of the Buda Hills The Buda Hills is famous for its extensive hypogenic cave system (sensu Klimchouk 2007; Goldscheider et al. 2010) and abundant actual thermal springs. There are also abundant mineralised veins recognised in this area. Caves often occur along these mineralised fractures. These phenomena suggest that thermal water contribution must have been significant both to the paleofluid and to the recent

Sedimentology, 2011

... FLAVIO JADOUL , ANDREA CERIANIà, ANDREA DI GIULIOà, PAOLO SCOTTI*, ANDREA ORTENZI* and ELISAB... more ... FLAVIO JADOUL , ANDREA CERIANIà, ANDREA DI GIULIOà, PAOLO SCOTTI*, ANDREA ORTENZI* and ELISABETTA PREVIDE MASSARA§ *Eni E&amp;amp;amp;amp;P Division, Via Emilia 1, 20097 San Donato Milanese, Italy (E-mail: paola.ronchi@eni.com ... Associate Editor Dave Cantrell ...