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161.
This paper provides an example of an integrated multi-scale study of a carbonate reservoir. The Danian Lower R2 carbonate reservoir is located in the South of the Aquitaine Basin (France) and represents a potential underground gas storage site for Gaz de France. The Danian Lower R2 reservoir was deposited as a prograding carbonate platform bordered by a reef barrier. The effects of sedimentary and diagenetic events on the reservoir properties, particularly dolomitization, were evaluated. In this study, the reservoir quality has been assessed by seismic analyses at the basin scale, by log-analysis at the reservoir scale, by petrographic methods and by petrophysical tools at the pore-core scale.Two dolomitization stages, separated by a compaction event with associated fracturing and stylolites, have been identified. These diagenetic events have significantly improved the Lower R2 carbonate reservoir properties. It is demonstrated that the reservoir quality is mainly controlled by the pore-geometry, which is determined by various diagenetic processes. The permeability values of the reservoir range over 4 orders of magnitude, from 0.1 to 5600 mD and the porosity values range between 2 and 42%. Reservoir unit 4 (a karstic dolomite) shows the best reservoir properties with average porosity values ranging between 11.1% and 19.3% and an average permeability ranging between 379 and 766 mD. Reservoir unit 2 (a fine-grained limestone) shows the worst reservoir properties. The cementation factors range from 1.68 to 2.48. The dolomitic crystal carbonate texture (mainly units 3 and 4) shows the highest value of the cementation factor (1.98–2.48) and formation factor (9.54–36.97), which is due to its high degree of cementation. The saturation exponents vary between 1.2 and 3.4. Using these experimental electrical parameters and the resistivity laterolog tool we predicted the water saturation in the various reservoir units. The permeability was predicted by combining the formation factor with the micro-geometric characteristic length. The best fit is obtained with the Katz and Thompson's model and for a constant of 1/171. 相似文献
162.
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164.
Roger Hekinian Peter Stoffers Dietrich Akermand Nicolas Binard Jean Francheteau Colin Devey Dieter Garbe-Schönberg 《Marine Geophysical Researches》1995,17(4):375-397
The Easter microplate-Crough Seamount region located between 25° S–116° W and 25° S–122° W consists of a chain of seamounts forming isolated volcanoes and elongated (100–200 km in length) en echelon volcanic ridges oriented obliquely NE (N 065°), to the present day general spreading direction (N 100°) of the Pacific-Nazca plates. The extension of this seamount chain into the southwestern edge of the Easter microplate near 26°30 S–115° W was surveyed and sampled. The southern boundary including the Orongo fracture zone and other shallow ridges (< 2000 m high) bounding the Southwest Rift of the microplate consists of fault scarps where pillow lava, dolerite, and metabasalts are exposed. The degree of rock alternation inferred from palagonitization of glassy margins suggests that the volcanic ridges are as old as the shallow ridges bounding the Southwest Rift of the microplate. The volcanics found on the various structures west of the microplate consist of depleted (K/Ti < 0.1), transitional (K/Ti = 0.11–0.25) and enriched (K/Ti > 0.25) MORBs which are similar in composition to other more recent basalts from the Southwest and East Rifts spreading axes of the Easter microplate. Incompatible element ratios normalized to chondrite values [(Ce/Yb)N = 1–2.5}, {(La/Sm)N = 0.4–1.2} and {(Zr/Y)N = 0.7–2.5} of the basalts are also similar to present day volcanism found in the Easter microplate. The volcanics from the Easter microplate-Crough region are unrelated to other known South Pacific intraplate magmatism (i.e. Society, Pitcairn, and Salas y Gomez Islands). Instead their range in incompatible element ratios is comparable to the submarine basalts from the recently investigated Ahu and Umu volcanic field (Easter hotspot) (Scientific Party SO80, 1993) and centered at about 80 km west of Easter Island. The oblique ridges and their associated seamounts are likely to represent ancient leaky transform faults created during the initial stage of the Easter microplate formation ( 5 Ma). It appears that volcanic activity on seamounts overlying the oblique volcanic ridges has continued during their westward drift from the microplate as shown by the presence of relatively fresh lava observed on one of these structures, namely the first Oblique Volcanic Ridge near 25° S–118° W at about 160 km west of the Easter microplate West Rift. Based on a reconstruction of the Easter microplate, it is suggested that the Crough seamount (< 800 m depth) was formed by earlier (7–10 Ma) hotspot magmatic activity which also created Easter Island. 相似文献
165.
In order to construct monthly fields of sea surface fugacity of carbon dioxide (fCO2) on a large scale in the Indian Ocean, we use a one-dimensional model which takes into account the main physical and biogeochemical processes controlling fCO2 variations in the ocean. Physical and biogeochemical processes are constrained by the monthly variations of sea surface temperature, salinity, chlorophyll concentration, wind speed and mixed-layer depth. The model is applied to four locations in the Indian Ocean and it well predicts observed temporal variations in fCO2 at these locations. Regarding to monthly fCO2 observations, the model also well simulates the fCO2 distribution and its temporal variations along a track located between 20 ° and 50 °S with a maximal error of + 10 μatm. The model is also used to predict fCO2 for 2 ° × 2 ° grids over the entire Indian Ocean and simulates seasonal cycles that are consistent with observations. The monthly fCO2 fields derived from the model are used to estimate a global air-sea CO2 flux over the Indian Ocean basin. We estimate a net sink of 0.5 Gt/yr C for the Indian Ocean (20 °N-50 °S), with the main sink located between 20 ° and 50 °S. 相似文献
166.
Based on a new quantitative analysis of sidescan sonar data combined with coring, we propose a revised model for the origin
for Mediterranean Ridge mud volcanism. Image analysis techniques are used to produce a synthetic and objective map of recent
mud flows covering a 640 × 700 km2 area, which represents more than half of the entire Mediterranean Ridge mud belt. We identify 215 mud flows, extruded during
the last 37,000–60,000 years. This time period corresponds to the limit of penetration of the sonar, that we evaluate through
geoacoustic modeling of the backscattered signal returned by the mud breccia-hemipelagites contact, and calibrate by coring.
We show that during this period, at least 96% of the mud volume has been extruded at the Mediterranean Ridge-Hellenic backstop
contact, the remaining being scattered over the prism. We suggest that the source is a Messinian (5–6 Ma) mud reservoir that
remained close to the backstop contact, at variance with the classical transport-through-the-wedge model. A revised mud budget
indicates that steady-state input is not needed. We propose that the source layer was deposited in deep and narrow pre-Messinian
basins, sealed by Messinian evaporites, and finally inverted in post-Messinian times. Onset of motion of the Anatolia-Aegea
microplate in the Pliocene resulted in change from slow to fast convergence, triggering shear partitioning at the edges of
the backstop and basin inversion. Mud volcanism initiation is probably coeval with the latest events of this kinematic re-organization,
i.e. opening of the Corinth Gulf and activation of the Kephalonia fault around 1–2 Ma. 相似文献
167.
Neogene exhumation and relief evolution in the eastern Betics (SE Spain): Insights from the Sierra de Gador
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Marianne Janowski Nicolas Loget Cécile Gautheron Jocelyn Barbarand Nicolas Bellahsen Jean Van Den Driessche Julien Babault Bertrand Meyer 《地学学报》2017,29(2):91-97
The Betics are a key area to study an orogenic landscape disrupted by late‐orogenic extension. New low‐temperature thermochronology (LTT) data (AHe and AFT) coupled with geomorphic constraints in the Sierra de Gador (Alpujarride complex) are used to reconstruct the cooling history and evolution of relief during the Neogene. We document three stages: (1) a fast cooling event between 23 and 16 Ma associated with the well‐known extensive tectonic exhumation of the Alpujarride unit, (2) a period of slow cooling between 16 and 7.2 Ma related to a planation event and (3) a post‐7.2 Ma surface uplift associated with the inversion of the Alboran domain undetected by LTT. The planation event followed by this late uplift can explain the occurrence of inherited low‐relief surfaces overlain by Tortonian–Messinian platform deposits at the top of the range. Finally, we propose that the Sierra de Gador is a more transient landscape than the nearby Sierra Nevada. 相似文献
168.
The Oman‐Emirates is the largest and best‐exposed ophiolite; consequently, it has attracted significant interest among scientists, together with serious conflicts. Most geologists regard this ophiolite as having formed in an intra‐oceanic subduction zone before being accreted to the Arabian continent. Here, we propose an alternative scenario, supported by detailed field observations and integrated geophysics. The smaller Emirates part of the ophiolite was forced into a nearby continent, in the pre‐collision stage of Tethyan closure. The contraction led to the exhumation of the mantle floor of segmented basins accreted in a rifted system similar to the present‐day Gulf of California. The implied high temperature–high pressure metamorphism and the range of geochemical signatures were introduced during the process of rifting, whereas the larger Oman ophiolite was emplaced by obduction onto and along the subducting continental shore. This Ridge–Trench–Transform system might call for a new process to obduct over continents in particular Tethyan ophiolites. 相似文献
169.
Quantin et al. [Quantin, C., Allemand, P., Mangold, N., Delacourt, C., 2004a. Icarus 172, 555-572] tabulated crater count data for 56 landslides along the walls of Valles Marineris. Under the assumption of a constant cratering rate after about 3 Gyr ago, as used in the 1999-2005 iterations of the crater chronology isochron system of Hartmann, and in the Hartmann and Neukum system, these data indicate a regularly increasing rate of landslides, which would be difficult to explain. We suggest that these data may support a decline in inner Solar System cratering rates by about a factor of 3 since 3 Gyr ago, not unlike predictions based on asteroid belt collision models. Such a decline is also supported by our review of data on lunar impact melts and glass spherules in a companion paper [Hartmann, W.K., Quantin, C., Mangold, N., 2007. Icarus 186, 11-23]. Such models produce not only a more uniform rate of landslides over the last 3 Gyr, but also a more uniform rate of resurfacing processes which also had an apparent increase under the assumption of a constant cratering rate. 相似文献
170.
Nicolas Saspiturry Ccile Allanic Philippe Razin Benoit Issautier Thierry Baudin Eric Lasseur Olivier Serrano Sophie Leleu 《地学学报》2020,32(4):253-260
The Early Cretaceous hyperextended Mauléon rift is localized in the north‐western Pyrenean orogen. We infer the Tertiary evolution of the Mauléon basin through the restoration of a 153‐km‐long crustal‐scale balanced cross‐section of the Pyrenean belt, which documents at least 67 km (31%) of orogenic shortening in the Western Pyrenees. Initial shortening, accommodated through inversion of inherited crustal structures, led to formation of a pop‐up structure, in which the opposite edges underwent similar shortening with different tectonic reactivation styles, localized versus. distributed. Underthrusting of the Iberian margin accommodated further convergence, forming the Axial Zone antiformal stack of crustal nappes within a lithospheric pop‐up. Thin‐skinned and thick‐skinned structures propagated outward from the heart of this pop‐up, a block of strong mantle acting as a buttress inhibiting complete inversion of the Mauléon rift basin. 相似文献