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70th EAGE Conference and Exhibition incorporating SPE EUROPEC 2008
- Conference date: 09 Jun 2008 - 12 Jun 2008
- Location: Rome, Italy
- ISBN: 978-90-73781-53-5
- Published: 09 June 2008
1 - 20 of 556 results
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Thermochronological Evolution of the Northern Apennines
Authors M. L. Balestrieri and M. ZattinIn this work we show the results obtained with the apatite fission-track and (U-Th)/He methods applied on the Oligo-Miocene foredeep successions of the Northern Apennines. Results show that samples coming from west of the present drainage have been clearly totally reset for both thermochronological systems. Time of cooling below ca. 100°C is between about 10 and 3 Ma, with a slight decrease eastward. This decrease is more marked for cooling below 70°C, which vary from about 9 Ma to as young as 1 Ma. East of the drainage divide, fission-track and He systems are either partially reset or unreset. Here the amount of cover removed above the analyzed apatites was not sufficient to completely anneal fission tracks or to cause a total loss of He. Burial depths estimated from the data allow reconstructing the shape of the Ligurian Unit as a lid overriding the foredeep rocks until nearly the Adriatic Sea.
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Relation between Diagenetic Evolution and Tectonic Regimes in Thrust-fold Belt – The Calcari Grigi Group, Jurassic, Asiago Plateau, Northern Italy
Authors A. Ceriani, R. Di Cuia, A. Scifoni and A. RivaDolomitization and dolomite cements precipitation in Jurassic platform carbonates has been studied from outcrop samples of the Calcari Grigi Group (eastern Southern Alps, northern Italy). In the studied area various types of dolomites can be described at all scales of observation. On outcrops, primary dolomite can be recognised only in some stratigraphic intervals. By contrast, pervasive replacive dolomites are widespread throughout the area, mostly confined in the central and lower part of the sequence. The collected data demonstrate that the massive dolomite replacement was followed by a multiphase precipitation of dolomite and late calcite cements. The replacement occurred during burial, into a passive margin regime, due to compaction driven flow of formational fluids. Conversely, fluid inclusions data crossed with thermal history prove that dolomite and calcite cements precipitated when the study area was involved in collisional tectonics. Fluid inclusions data display a decreasing salinity trend from sea water to freshwater fluids. This observed dilution of fluids can be related to the infiltration of meteoric waters from the emerging Alpine chain. These data proof useful to interpret the diagenetic evolution of the unit as related to the evolution of the hydrogeological system in relation with the tectonic regime of the area.
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Thermo-kinematic Modelling and Organic Matter Maturity Analysis of the Alpine Rifting in the Southern Alps, N. Italy
Authors D. Scrocca, E. Carminati, D. Cavazza and C. DoglioniIn this paper we demonstrated how thermo-kinematic models and organic matter maturity data can be integrated to unravel the evolution of continental rifts. In particular we apply this model to an E-W 400 km long transect that cuts across the whole Southern Alps in northern Italy (Fig. 1). This profile, published by Fantoni and Scotti (2003), provides a valuable picture of the Mesozoic passive continental margin of the Adriatic plate at the end of Lower Cretaceous time (Aptian pp.). It is largely based, in its western and central part (about 250 km extending from the Biellese area to the Trento Plateau), on the palinspastic reconstruction proposed by Bertotti et al.(1993). Further east, this profile has been extended by Fantoni and Scotti (2003) to include the Belluno Basin and the Julian Plateau (Sarti et al., 1993).
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Thermal Modelling of the Extensional Mesozoic Succession of the Southern Alps and Implications for Oil Exploration in the Po Plain Foredeep
Authors P. Scotti and R. FantoriIn order to reconstruct the thermal history, organic matter maturity data were obtained from samples collected from sedimentary units outcropping in the Southern Alps. Resulting heat flow values are quite high and relatively uniform in the whole of the Southern Alps during Norian-Liassic; it progressively decreased after the Bathonian to reach values similar to the present ones at the end of the Cretaceous. This reconstruction is consistent with the known tectonic evolution of the Mesozoic extension in the Southern Alps, characterised by a rifting stage up to the Lias followed by a drifting stage from the Middle Jurassic. This kind of thermal regime evolution has strong implications for hydrocarbon exploration in the Po Plain.
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Thermal Conductivity of Sedimentary Rocks and Appropriate Corrections for In-situ Conditions
Authors V. Pasquale, G. Gola, P. Chiozzi, A. Frixa and E. VitaglianoWe attempt to remedy the existing deficiency of thermal conductivity data of sedimentary rocks by making a series of measurements in laboratory on several bottom core samples, collected from petroleum explorative wells and representative of the main sedimentary rocks recognized in the western Po Basin, Northern Italy. The in-situ bulk thermal conductivity is then estimated using calibrated formulas taking into account the mineralogical composition, the porosity and the effect of temperature.
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Automated Thermotectonostratigraphic Reconstruction of Sedimentary Basins in Frontier Areas
Authors L. H. Rupke, Y. Y. Podladchikov and D. W. SchmidWe demonstrate that automated reconstruction of the thermal, tectonic, and stratigraphic evolution of sedimentary basins is possible and fast. We achieve this by coupling a numerical forward model with an optimization module. The numerical model allows for self consistent implementation of virtually unlimited physical processes. The optimization module modifies the parameters of the forward model iteratively until a best fit satisfying the constraints is found. The package is tested with the benchmark case study of the Viking Graben, North Sea. The petroleum system of the Viking Graben is well studied and allows for detailed comparison of the model results. In particular, we show that the predicted hydrocarbon maturity corresponds well to actual production fields. The possibility to implement additional physics is exploited in the presented case with mantle phase transitions activated. These density changes are known to occur in the mantle but are not implemented in other models. In essence the effect of phase transitions is to amplify the effect of thinning and perturbing the thermal field, leading to smaller (depth dependent) stretching factors compared to cases with phase transitions deactivated. This leads to smaller heat input and consequently a relatively cooler evolution of sedimentary basins.
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Diagenetic Evolution and Distribution of Dolomite Bodies in a Partially Dolomitised Sequence - The Calcari Grigi Group
Authors R. Di Cuia, A. Scifoni, A. Riva, A. Moretti and A. CerianiA multidisciplinary study conducted over the carbonate platform deposits of the liassic Calcari Grigi Group (Southern Alps), highlighted how the use of a 3D field analogues can contribute to better define the distribution of dolomitic bodies related to fault networks, to characterise the petrophysical properties of the dolomitic sequence and to unravel a complex diagenetic history. Pervasive unimodal and patchy polymodal dolomites characterize a thick portion of the Group, and are topped by a smoothly curved - not stratigraphic front. This latter tend to uprise near to the major faults and fracture swarms, with massive–chaotic dolomite. Associated to these zones there is the development of stacked high-porosity and permeability bedding-parallel bodies that show excellent petrophysical properties. Thin section, Cathodoluminescence, isotopic and fluid inclusions analyses were used to constrain the paragenetic evolution of the sequence. The result is a complex paragenetic evolution, in which good porosity developed but in later stages porosity was reduced by the deposition of calcite and dolomite cements. Fluid inclusions results relate the evolution to a complex interplay between fluid evolution, tectonics, burial and hydrological processes, while isotopic analysis suggests a Miocene age as a timing for the late diagenetic stages.
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Insights on the Evolution of Oligocene-miocene Carbonate Buildups from 3D Seismic Data, East Java Basin, Indonesia (Best of AAPG)
Authors A. S. Ruf, T. Simo, T. M. Hughes and K. SteffenThe High Density MC3D seismic survey, acquired by PGS in 2003 over the North Madura platform, is an excellent data set for quantitative interpretation of carbonate mound evolution. Detailed imaging of the growth histories of Oligocene-Miocene carbonate buildups provides insight into geometric parameters characteristic of platform initiation, development, and demise. Mound initiation occurs with development of small (<100m to 500m diameter), closely spaced, domal buildups, which become the nuclei for the formation of intermediate mounds (2km to 3km diameter). Nucleation mounds build concentrically to form intermediate mounds, which selectively coalesce into amalgamated platforms (>5km diameter), become isolated platforms of varying size (<5km diameter), or die off altogether. The high quality seismic data enables visualization and quantitative analysis of geometry, orientation, and spatial distribution of nucleation and intermediate mounds, generating models of preferential morphology for development of isolated vs. amalgamated platforms. Flattened discontinuity time-slices from the 3D data provide clear images of mound size, distribution, and morphology at discrete growth steps, which record a complex history of initiation, aggradation, coalescence or isolation, progradation, potential exposure, and demise.
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Three-dimensional Seismic- and Sequence-stratigraphic Framework of a Lower Cretaceous, Aptian, Supergiant Carbonate Field in Onshore Abu Dhabi (Best of Shu'aiba)
Authors L. A. Yose, C. J. Strohmenger, A. S. Ruf, I. Al-Hosani, A. M. Gombos, G. Bloch, S. Al-Maskary and Y. S. Al-MehairiA three-dimensional (3-D) dataset over a carbonate field in onshore Abu Dhabi was evaluated to develop integrated sequence-stratigraphic and reservoir models for the Lower Cretaceous (Aptian) Shu’aiba Formation. The study area is positioned over the Shu’aiba platform-to-basin transition and provides a type area for linking the stratigraphic framework across the shelf, slope and basin environments (Yose et al., 2006). The more than 50 kilometer long shelf-to-basin transect records a diverse range of depositional facies and stratal geometries that have a large impact on reservoir quality and connectivity across the study area. The Aptian reservoir interval (Shu’aiba Formation) records a second-order supersequence that is divided into five (5) depositional sequences. Rudists, carbon and strontium isotopes and nanno-fossils provide internally consistent age constraints on Upper versus Lower Aptian sequences. The age dating also allows for tying sequences to the higher resolution Aptian (AP) chronostratigraphic zonation in Hardenbol (1998). Sequence 1 (Lower Aptian; possible AP-1 and AP-2 age) and Sequence 2 (Lower Aptian; dated as AP-3, lower part) were deposited during the transgressive phase of the supersequence. These sequences are retrogradational, record the initial formation of a low-relief ramp, and are dominated by algal-microbial facies. Ramp interior and margin facies of the transgressive phase are characterized by high porosity and low permeability due to mud-dominated textures and development of microporosity. Sequence 3 (Lower Aptian; dated as AP-3, upper part) was deposited during the highstand phase of the supersequence, is mainly aggradational, and records the proliferation or rudists across the platform top. Grain-dominated platform interior and margin facies of Sequence 3 are the highest quality reservoir facies within the Shu’aiba reservoir. Sequence 4 (Upper Aptian; dated as AP-4) and Sequence 5 (Upper Aptian; dated as AP-5), were deposited during the late highstand phase of the supersequence. These sequences are progradational and record the progressive downstepping (forced regression) of the platform margin onto a low-angle (1-2 degree) slope. Clinoforms of the late highstand phase are characterized by alternations of high (grainy) and low (muddy) reservoir quality developed in response to relative sea level changes. Sequence 6 (probable AP 6 time; Upper Aptian to Albian?) was deposited during the second-order lowstand, records the influx of fine-grained siliciclastics, and forms the base of the next overlying supersequence. Results from the study have led to an improved understanding of platform evolution and reservoir architecture. A new platform margin was recognized to the south, indicating the development of an intra-platform seaway. With margins now recognized to the north and south, it is possible that the Shu’aiba evolved into a series of isolated platforms during the transgressive to highstand phases in the Early Aptian. Some of these isolated platforms are interpreted to have coalesced via progradation as second-order sea level began to fall in the Late Aptian. The platform interior and margin facies show a marked asymmetry from north to south that are interpreted to be related to ocean currents or prevailing winds. These results provide new insights on reservoir quality and connectivity. In the platform interior area of Sequence 3, 3-D seismic data reveal a complex mosaic of tidal channels, high-energy rudist shoals, and inter-shoal ponds that impact reservoir sweep and conformance. At the basin margin, the seismic data provide high definition images of platform margin clinoforms that impact reservoir architecture and well-pair connectivity.
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Definition and Distribution of the Bab Sequence – The Last Upper Aptian Shu’aiba Sequence in the Bab Basin (Best of Shu'aiba)
The Shu’aiba Formation consists of six depositional sequences. The first five sequences make up a 2nd order supersequence, while the sixth sequence is the lowstand sequence of the next supersequence. The sequence is deposited within the Bab basin as a set of prograding clinoforms. This sequence is here called the Bab Sequence and is equivalent to the “ap6”, “sequence 6”, and the “Upper Shu’aiba sequence 3” of other authors. The sequence boundary at the base of the Bab sequence coincides with the supersequence boundary and is characterized by a major exposure across the Shu’aiba platforms and down-stepped deposition. The onset of clay deposition marks the beginning of the Bab Sequence. Internally the Bab Sequence consists of nine clinoforms (high-frequency sequences) that prograded into the Bab Basin in a series of clinoforms over more than 30km. The most striking observation is the extremely regular and seaward progression of the clinoforms, sub-linear along the southern margin and concentric around the eastern isolated platforms, resulting in a series of almost perfectly parallel clinoforms. The prograding clinoforms can be grouped into three sets. The 4 clinoforms in the first set are relatively wide, with mounded topsets at the margin. They reach a thickness of 120 meters. The top surface of these first clinoforms lies 30 to 40 meters below the top of the previous shelf break (sequence ap5). The 3 clinoforms of the second set are relatively narrow, reach 115 m in thickness and have a slightly steeper slope than the first set of clinoforms. The last two clinoforms (third set) are broader and thinner (75 meters in thickness) and have a very low angle slope. The almost perfect parallel geometry of clinoforms is likely the result of the regular distribution of clay and carbonate mud along the margins by long-shore currents. The lithologic content of the clinoforms varies within the three sets. The topsets of the first set of clinoforms tops are rudist-bearing wackestone – rudstone, the foresets are composed of burrowed argillaceous wackestone, and the bottomset of calcareous shale. In the topsets of the second set of clinoforms the rudist facies is missing and replaced by marl-limestone alternations with occasional skeletal packstone layers. The third set is dominated by clay and marl-limestone alternations. The rudist-bearing topsets form the main reservoirs in the Bab sequence, whereas the clay-rich intervals may provide seals for a stratigraphic play.
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Regional Depositional History and Stratigraphy of the Shu’aiba Formation in the Middle East (Best of Shu'aiba)
Authors H. Droste and B. J. PiersonThe carbonates of the Aptian Shu'aiba Formation form major oil reservoirs in the Middle East. The formation shows a complex internal stratigraphic architecture and significant lateral variations in reservoir character. During a 3-day workshop held in Oman, which was attended by Shu’aiba experts all over the world, a common understanding of the stratigraphic framework was reached, which led to a consistent regional model at the scale of the southern Arabian Plate. The Shu'aiba Formation represents a depositional cycle within a Cretaceous epeiric carbonate platform system. It is built by three composite sequence sets, each with different facies associations and internal stacking patterns and, consequently, also different reservoir architecture. The lowermost unit is early Aptian in age and includes the Hawar Member of the underlying Kharaib Formation and the basal Shu'aiba Formation. It forms a Transgressive Sequence Set with laterally extensive shallow-marine to intertidal sediments followed by shallow-marine algal limestones that transgressed over exposed limestones of the Kharaib Formation. The development of algal-mound complexes led to a differentiation on the platform. Between these mounds fine-grained, in places organic-rich, deeper-water deposits represent the maximum flooding interval. The second unit is early to late Aptian in age, and consists of a Highstand Sequence Set (HST) with progradational geometries. The "carbonate factory" was then dominated by rudist-biostrome complexes, which colonized the mounds. Intermound depressions were progressively filled leading to the formation of a large platform that surrounded an intra-platform basin. The third unit is formed by a Lowstand Sequence Set (LST) deposited in the late Aptian during and following a regional drop in sea level. The drop caused subaerial exposure of the HST platform and the influx of fine-grained clastics. The LST contains off-lapping wedges of argillaceous carbonates and carbonate-rich claystones along the margins of the intra-platform basin. Clays deposited during the following transgression provide a regional seal to the Shu'aiba reservoirs. The advantage of this sequence stratigraphic framework is that it can be used as a template which: 1) Explains the regional variation in reservoir/flow properties. 2) Allows grouping of fields according to stratigraphic setting for comparison / analogues in reservoir studies.
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Pore Geometry as an Indicator of Depositional Texture and Velocity Variations in Chalks
Authors M. R. Saberi, T. A. Johansen and R. AgersborgThe complex pore geometry in carbonates makes their velocity behavior difficult to predict. Integration of geology information can help to make a predictive pattern for pore geometry and as a result for velocity. In this paper, based on available diagenetic models for chalks, an integrated modeling strategy is developed for velocity variation in a mineralogically uniform chalk. It can be shown that different depositional texture in chalks can be expressed by different depositional pore aspect ratio. This depositional aspect ratio transforms to other aspect ratio by post-depositional processes. This transformation of pore aspect ratio in chalks can be predicted from geology information and mostly from foraminifer’s contents and sorting information of the sediment. Mechanical compaction and cementation although both decrease porosity with depth but may increase the velocity by different rates, since one makes more compliant pore throats while another one close cracks and makes stiffer pore bodies, respectively. These show the relevance of pore geometry consideration in velocity interpretation, since some variations in velocity data may results from pore geometry (depositional texture) and its transformation (post-depositional process) through different diagenetic environments rather than mineralogy, fluid or porosity.
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Fluid-escape Features Due to Silica Diagenesis in the Faeroe-Shetland Basin
Authors N. R. Goulty and R. J. DaviesConversion of opal-A to opal-CT in biosiliceous sediment during burial expels water expulsion by porosity reduction and dehydration. This release of water occurs over large tracts of sedimentary basins within discrete diagenetic reaction zones at burial depths in the range 200-800 m. Seismic data from the Faeroe-Shetland Basin provide evidence for a variety of fluid conduits which terminate upwards in roughly circular erosional depressions at an Early Pliocene unconformity, interpreted as the contemporaneous seabed. These features are indicative of water expulsion and focused fluid flow emanating from the opal-A to opal-CT reaction zone. The sediment immediately below the reaction zone contains, on average, ~30% opal-CT by weight. The estimated volumetric rate of water expulsion per unit surface area during the Quaternary has averaged ~6 m3 My-1 per square meter, which is greater than the vertical flux of water at the same depth from compaction of the deeper basin fill, and amounts to a volumetric rate of ~120 km3 My-1 across the whole basin. In late Miocene times, the calculated rate of water expulsion was around six times greater, which explains why the fluid-escape features terminate at the Early Pliocene unconformity.
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Shale Dependent Sediment Compaction - Is There a Global Porosity Relationship? Scanning of Parameters in Wells
Authors A. E. Lothe, Ø. Sylta, E. Fjær and H. M. HelsetA silisiclastic porosity compaction relationship has been derived for sedimentary basins, where shale volume contents (Vshale) from well logs are used as input. The relationship has been derived from simplified assumptions about stress-paths and rock compressibilities, in combinations with a published relation between mean grain size an sea-floor porosity and a relation between mean grain size content and clay content. The porosity-depth relationship has been tested on well data. Two input parameters may be optimized and result in a narrow range of low misfit values between observed and measured porosities.
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Subsurface Geometries in Central Sicily FTB as a Premise for Hydrocarbon Exploration
Authors R. Catalano, V. Gatti, G. Avellone, L. Basilone, A. Frixa, R. Ruspi and A. SulliThe study concerns a sector of the Maghrebian Sicilian Fold and Thrust Belt (FTB), located in central Sicily between the southern edge of the Madonie Mts. and the Caltanissetta trough. Interpretation of recently acquired seismic profiles, constrained by joint detailed stratigraphy and field investigation, revealed the structure of the study area as formed by a thick pile of deep water carbonate (Imerese and Sicanian) thrusts lying on carbonate platform imbricates. In the forward migration of the FTB, two main tectonic events were envisaged; shallow and deep seated thrusts occurred during the Miocene-early Pleistocene time interval that deformed the former sedimentary cover of the continental margin. The kinematic model and the occurrence, at depth, of carbonate platform rock bodies indicate the study area as a potential frontier for hydrocarbon opportunities.
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Overview of the Italy's Petroleum Systems and Related Oil and Gas Occurences
Authors F. Bertello, R. Fantoni and R. FranciosiItaly bears a big variety of petroleum systems. The hydrocarbon occurences can be classified as associated with three main tectono-stratigraphic systems: 1) biogenic gas in the terrigenous Plio-Quaternary foredeep wedges, 2) thermogenic gas in the thrusted terrigenous Tertiary foredeep wedges, and 3) oil and thermogenic gas in the carbonate Mesozoic substratum. The potential of the hydrocarbon reserves makes the country the most important hydrocarbon province of the southern Europe.
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Nuclear Magnetic Resonance and Data Integration in Murzuq Basin, Libya - Case Study
Authors J. Dessay, J. M. Gonzalez Muñoz, M. Sweed and A. BoitelRepsol Exploration Murzuq S.A. (REMSA) utilizes Nuclear Magnetic Resonance (NMR) data through two different procedures: - Qualitative interpretation tool: NMR porosity-permeability information is integrated and combined with the petrophysical formation evaluation, logging formation pressure data, core(s) evaluation (when available) and used to decide a possible well production test. - Part of Quality assessment: as part of the geological data management workflow, the NMR data is combined with the rest of wireline logging data, core informations and drilling & gas data for an integrated quality control.
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The Main Tectono-sedimentary Domains of the Pyrenees
Authors J. J. Biteau, J. Canerot, P. Mallard and G. NesenThis presentation covers extensively the whole area located between the Charentes, in France, to the North, and the Ebro Basin, in Spain, to the South. It aims to describe the main components of the very contrasted Petroleum systems (P.S.) that have been evidenced in this area, where there has been more than 60 years of hydrocarbon exploration and production
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Hydrocarbon Bitumen in Deepwater Gulf of Mexico - An Integrated Petroleum Systems and Engineering Perspective
Authors J. Huang, G. Han, K. Grush, N. McCormack and G. SulistyoHydrocarbon bitumen, here defined as a highly viscous hydrocarbon accumulation, has been encountered during the exploration and development of several deepwater discoveries in the Gulf of Mexico (GOM). These bitumen occurrences pose significant challenges to deepwater GOM drilling operations. Several field development projects experienced substantial increase in drilling costs associated with such bitumen encounters. Our study was aimed at a holistic understanding of subsurface bitumen behavior through a broad integration of both geoscience and engineering approaches. Petroleum systems analysis indicated that bitumen encountered in the greater Pony area is low-maturity kerogen derived from a mobilized source rock of Jurassic age. This bitumen was most-likely mobilized in early Miocene, prior to peak oil and gas generation. A series of rock mechanics tests revealed that bitumen mechanical and flow properties are primarily controlled by temperature and conditions of confining stress. The highly viscous nature of subsurface bitumen at source level forces the bitumen migration and emplacement process to utilize sediment interfaces such as fractures, faults, and salt welds, rather than Darcy flow through porous media. These multidisciplinary findings provide important constraints to bitumen emplacement timing, spatial distribution and geometry which, in turn, have direct implications for mitigation strategies in drilling operations.
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Tectonic Heat Flow Models - Workflow and Cases
Authors H. J. M. Verweij, J. D. Van Wees, D. Bonte, P. David and R. Abdul-FattahTo obtain a pragmatic workflow solution for tectonic heat flow prediction, we have developed in the recent years a multi-1D probabilistic tectonic heat flow model, which is capable of calculating tectonic heat flows, incorporating a variety of tectonic scenarios (including rifting, underplating, mantle upwelling). The model has been applied for a range of basin settings. For (frontier) deep water basins in the Caribbean and Mediterranean regions, we show that basin maturation is significantly higher and occuring much earlier when adopting tectonic heat flow instead of a constant heat flow. For mature basins such as in the Netherlands, we show that tectonic heat flow scenarios considerably aid in identifying and understanding of unexplored play systems, by putting temporal and spatial constraints on paleo heat flow. In particular modelling results indicate that the interplay of rifting, underplating and foreland formation and inversion, has resulted in much stronger temporal and spatial tectonic heat flow variations than hithertoo assumed.
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