Geothermal repurposing of depleted oil and gas wells in Italy

The decarbonisation of the energy sector is probably one of the main worldwide challenges of the future. Global changes urge a radical transformation and improvement of the energy-producing systems to meet the decarbonisation targets and a reduction of greenhouse gas emissions. The hydrocarbon industry also contributes to this transition path. In a mature stage of oil and gas fields, the production of hydrocarbons is associated with formation waters. The volume of produced water increases with the maturity of the assets and the geothermal repurposing of depleted oil and gas wells could be an alternative to the mining closure. In the described transition scenario, the geothermal energy seems very promising because of its wide range of applications depending on the temperature of extracted fluids. This flexibility enables us to propose projects inspired by a circular economic vision considering the integration in the territory and social acceptance issues. In Italy, since 1985, 7246 wells have been drilled for hydrocarbon, of which 898 are located onshore with a productive or potentially productive operational status. This paper presents a preliminary investigation of oil and gas fields located onshore in Italian territory based on the available information on temperature distribution at different depths. Then, taking into account the local energy demand, existing infrastructure, and land use of the territory, a conversion strategy for the producing wells is proposed for three case studies

Stratigraphical and sedimentological relationships of the Bolognano Formation (Oligocene–Miocene, Majella Mountain, Central Apennines, Italy) revealed by geological mapping and 3D visualizations

The characterization and comprehension of buried reservoirs receive remarkable benefits from detailed studies of outcropping analogues which help to define the architecture of the buried sedimentary units and their petrophysical features. In particular, modern 3D techniques of geological data analysis can better constrain the geological mapping process and reveal the geometry of the sedimentary units with complex lateral and vertical relationships. By means of the 3D Move software, we define the sedimentological and stratigraphical relationships between lithostratigraphic units of the Bolognano Formation, outcropping in the northernmost sector of the Majella Mountain (Central Apennines, Italy). The study area belongs to the Apulian carbonate platform and the Majella Mountain represents the northward outcropping portion of its margin. The sedimentary succession of the Majella Mountain consists of Upper Jurassic to upper Miocene limestone and dolostone deposits. In the investigated area, outcropping deposits mainly belong to the Oligo-Miocene Bolognano Formation characterized by five lithofacies associations and representing a carbonate ramp developed in a warm subtropical depositional environment within the oliaophotic to aphotic zone. The Bolognano Fm. represents, due to its specific hydraulic properties (e.g. porosity and permeability), an outcropping analogue of worldwide common reservoirs (i.e. porous calcarenite deposits of a carbonate ramp formed by benthic foraminifers such as lepidocyclinids, nummulitids, red algae, corals). In the study area, several geological units of the Bolognano Fm. are characterized by abundant hydrocarbon (bitumen) occurrences infilled within the high-porosity of the cross-bedded calcarenites ascribed to the Chattian and Burdigalian interval. The geological field mapping of the area and the visualization of the geological data in a 3D environment show that the unit formed by mid-ramp calcarenites (Lepidocyclina calcarenites 2 unit, Chattian-Burdigalian) increases in thickness towards the NE (basinward) direction as a consequence of sediment shedding from inner ramp. Our study illustrates how the geological mapping and the visualization and analysis of geological data in a 3D environment of the northernmost sector of the Majella Mountain confirms depositional models of the Bolognano Formation and represents a valid tool for the characterization of the lateral stratigraphic relationships within this formation, and hence of its potential hydrocarbon occurrences

The tectonic puzzle of the Messina area (Southern Italy): Insights from new seismic reflection data

The Messina Strait, that separates peninsular Italy from Sicily, is one of the most seismically active areas of the Mediterranean. The structure and seismotectonic setting of the region are poorly understood, although the area is highly populated and important infrastructures are planned there. New seismic reflection data have identified a number of faults, as well as a crustal scale NE-trending anticline few km north of the strait. These features are interpreted as due to active right-lateral transpression along the north-eastern Sicilian offshore, coexisting with extensional and right-lateral transtensional tectonics in the southern Messina Strait. This complex tectonic network appears to be controlled by independent and overlapping tectonic settings, due to the presence of a diffuse transfer zone between the SE-ward retreating Calabria subduction zone relative to slab advance in the western Sicilian side

On the geodynamics of the northern Adriatic plate

The northern Adriatic plate underwent Permian-Mesozoic rifting and was later shortened by three orogenic belts (i.e., Apennines, Alps and Dinarides) developed along three independent subduction zones. The inherited Mesozoic horst and graben grain determined structural undulations of the three thrust belts. Salients developed in grabens or more shaly basins, whereas recesses formed regularly around horsts. A new interpretation of seismic reflection profiles, subsidence rates from stratigraphic analysis, and GPS data prove that the three orogens surrounding the northern Adriatic plate are still active. The NE-ward migration of the Apennines subduction hinge determines the present-day faster subsidence rate in the western side of the northern Adriatic (> 1 mm/year). This is recorded also by the SW-ward dip of the foreland regional monocline, and the SW-ward increase of the depth of the Tyrrhenian sedimentary layer, as well as the increase in thickness of the Pliocene and Pleistocene sediments. These data indicate the dominant influence of the Apennines subduction, which controls the asymmetric subsidence in the northern Adriatic realm. The Dinarides front has been tilted by the Apennines subduction hinge, as shown by the eroded Dalmatian anticlines subsiding in the eastern Adriatic Sea. GPS data suggest that southward tilting of the western and central Southern Alps, whereas the eastern Southern Alps are uplifting. The obtained strain rates are on average within 20 nstrain/year. The horizontal shortening obtained from GPS velocities at the front of the three belts surrounding the northern Adriatic plate are about 2-3 mm/year (Northern Apennines), 1-2 mm/year (Southern Alps), and < 1 mm/year (Dinarides). The shortening directions tend to be perpendicular to the thrust belt fronts. The areas where the strain rate sharply decreases along a tectonic feature (e.g., the Ferrara salient, the Venetian foothills front) are proposed to be occupied by locked structures where stress is accumulating in the brittle layer and thus seismically prone. Finally, we speculate that, since the effects of three independent subduction zones coexist and overlap in the same area, plate boundaries are passive features

RETRACE-3D PROJECT, a multidisciplinary approach for the construction of a 3D crustal model: first results and seismotectonic implications

The RETRACE-3D (centRal italy EarThquakes integRAted Crustal modEl) Project has been launched with the ambitious goal to build, as first result, a new, robust, 3D geological model of broad consensus of the area struck by the 2016-2018 Central Italy seismic sequencePublishedBologna3T. Sorgente sismica4T. Sismicità dell'Itali

Data integration and conceptual modelling of the Larderello geothermal area, Italy

n/

La zona d'interferenza tra le strutture dell'Appennino centrale e meridionale : assetto tettonico ed evoluzione del sistema di sovrascorrimenti

Dottorato di ricerca in scienze della terra. 8. ciclo. Docente guida M. Parotto. Coordinatore G. ValentiniConsiglio Nazionale delle Ricerche - Biblioteca Centrale - P.le Aldo Moro, 7, Rome; Biblioteca Nazionale Centrale - P.za Cavalleggeri, 1, Florence / CNR - Consiglio Nazionale delle RichercheSIGLEITItal

Geothermal potential assessment for oil&gas fields in Italy

The decarbonisation of the energy sector is probably one of the main worldwide challenges of the future. The main contributors to the EU's greenhouse gas emissions today are heating and cooling systems. According to the literature, heating and cooling needs in buildings and industry account for about 50% of the EU’s energy consumption and only about 20% generated from renewable energy. In this scenario, oil&gas fields can be repurposed to produce geothermal energy, a secure, clean and renewable resource. The great amount of water stored in hydrocarbon reservoirs represents, now, a waste heat that can be used, thanks to the flexibility and wide availability of geothermal energy applications. The possibility of a crossover from oil & gas to geothermal energy production represents a chance to increase the share of renewable energy production and to reuse existing infrastructures but also to reconcile the social fabric with an industrial sector considered harmful to the environment. The most promising oil&gas fields for geothermal repurposing in Italy have been selected starting from the available information on fields and wells provided by the Italian Ministry of Economic Development, integrated with data retrievable in the scientific literature, and combined with the estimated temperatures at depth from the Italian National Geothermal Database. With this simplified approach, 42 fields have been identified at depths deeper than 2000-3000 m and with temperatures higher than 60-70 °C. However, harnessing the waste heat also of fluids at lower temperatures could have potential use for a variety of local direct geothermal applications. To produce a vision of the geothermal energy that could be recovered by repurposing the hydrocarbons fields on the Italian territory, this work has assessed the geothermal potential stored in five representative depleted oil & gas fields, which have been chosen among the selected most promising fields for geothermal repurposing. The volume method has been applied to these five representative fields to assess their geothermal potential. Then the technical potential has been estimated, assuming a value for the recovery factor, the efficiency and the life span of geothermal plants. This passage from geothermal potential to technical power is crucial to quantify the effective impact generated by the repurposing of Italian oil&gas fields into geothermal ones. The results are encouraging, although the applied method is preliminary and it has provided only a rough evaluation, which uses the data derived from exploration and production of hydrocarbons reservoirs, whose volumes may not coincide with the geothermal reservoirs. Those volumes may be greater and only an ad hoc analysis of the data collected by the owner companies of the existing fields and wells may produce a more precise evaluation

Hydrocarbon wells potentially suitable for geothermal repurposing in Italy. A first assessment

Global changes urge a radical transformation and improvement of the energy production systems to meet the very ambitious and challenging decarbonisation targets of the European economy by 2050. In this context, the possible repurposing of depleted hydrocarbon wells for geothermal heat production represents a promising contribution, with an approach inspired by the circular economy, to the decarbonisation of energy production systems. The mature stage of oil and gas wells is often characterized by the production of hydrocarbons and associated formation waters, which must be treated continuously being often reinjected into the reservoir. Usually, the volume of produced water increases with the maturity of the fields until the production of hydrocarbons becomes uneconomic and the wells are cemented and closed. However, according to their depth and the local geothermal gradient, these oil and gas wells could have bottom-hole temperatures high enough to sustain the geothermal exploitation of the reservoirs fluids. Therefore, when the hydrocarbon wells are going to be depleted and where a geothermal potential exists, the conversion into geothermal wells could be a reasonable alternative to the mining closure, which will compromise the possibility to repurpose the existing wells for geothermal applications. Many existing Italian oil and gas (O&G) wells are approaching the end of their economic lifespan. This irreversible process necessarily requires an in-depth and systematic assessment of their conversion potential for heat production. To identify the most promising hydrocarbon wells suitable for geothermal repurposing we have combined information on onshore wells and fields made available by the Italian National Mining Office for Hydrocarbons and Georesources, which have been integrated with data retrieved in the scientific literature, with the estimated temperatures at depth derived from the Italian National Geothermal Database. According to the latest available data, there are 892 active wells in Italy located onshore in the existing mining licenses with different operational status (i.e., productive wells, potentially productive wells, reinjection, monitoring or other purposes), With this simplified approach, we have selected wells, associated with 42 hydrocarbons fields with depths deeper than 2000-3000 m and with temperatures higher than 60-70 °C, which have the potential to be repurposed for geothermal application. For five of these oil & gas fields, the geothermal potential has been evaluated, by applying the volume method. An estimation of the geothermal energy that could be recovered by repurposing the exiting hydrocarbons fields has been obtained. Finally, we discuss how the use of a screening matrix, based on a review of the approach already proposed by Soldo and Alimonti (2015), can allow an analysis of the existing wells to define the more appropriate technology for their geothermal repurposing

The Ombrina-Rospo Plateau (Apulian Platform): Evolution of a Carbonate Platform and its Margins during the Jurassic and Cretaceous

In this paper we analyze the Jurassic and Cretaceous evolution of the buried northwards stretch of the Apulia Platform (Southern Italy) (Ombrina-Rospo Plateau - ORP), and adjacent Adriatic Basin. Exploration wells indicate that inner platform carbonate facies across the ORP in the Jurassic and Lower Cretaceous are capped, along a subaerial exposure surface, by Oligocene/Miocene carbonates. A NW-trending intra-platform basin ("Casalbordino Corridor") was infilled with shallow- to deeper-water sediments in the late Early to Late Cretaceous interval, while platform margins were experiencing tectonic reactivation. The ORP-to-basin transitional belt formed a corner, defining a NW and a NE margin. The NW margin was essentially stationary. A syn- and early post-rift platform-toe bypass wedge formed when late Hettangian-Sinemurian extension produced the platform/basin relief. Export of platform material, coupled with a halt of faulting, made the platform/slope profile continuous in the late Early or early Middle Jurassic (possibly across an ooidal rim). Late Jurassic Ellipsactinia/coral reefs passed downdip into bioclastics. The Maiolica Fm. displays two cycles (M1, M2), where M2 onlaps the slope built by M1. In the Aptian, with lithospheric arching, a high angle fault rejuvenated the margin. Off this margin, a narrow basin, locked between the ORP and a pelagic carbonate platform, was largely infilled with turbidites sourced by the ORP, but the high hampered the dispersal of the sand fraction. The NE margin displays prograding ooidal to bioclastic clinoforms (Middle and Upper Jurassic) downlapping onto the rift basin. In the Lower Cretaceous, the platform recovered after a slow-down of carbonate productivity (M1/2 boundary). The Marne a Fucoidi Fm. thickens at the toe of, and seals, a fault backstepping the margin. Further backstepping occurred similar to 5 km platformwards along a (Cenomanian?) normal fault, producing room for a rudist factory. A retreating rocky shoreline sourced breccias, while downdip the shallow water facies graded into the Scaglia Fm. basin along a ramp-like profile with low angle clinoforms, merging with turbidites. (C) 2012 Elsevier Ltd. All rights reserved