STRATIGRAPHY AND DIAGENESIS OF THE THAMAMA-B RESERVOIR ZONE AND ITS SURROUNDING DENSE ZONES IN ABU DHABI OILFIELDS AND EQUIVALENT OMAN OUTCROPS

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Agent and Broker Intermediaries in Insurance Markets - An Empirical Analysis of Market Outcomes

Insurance markets are characterized by profound market imperfections. Insurance intermediaries reduce transaction costs and information asymmetries. From transaction cost economics, agency theory, and law and economics literature the hypothesis is derived that insurance brokers may provide more high-quality information and advisory services which are better suited for the needs of the consumers than insurance agents. Empirical tests for German insurance intermediaries confirm this thesis. But there are also findings that structural factors like firm size, employment structure and degree of specialization may outweigh the incentives set by different legal settings

Late Cenozoic Dolomites of the Bahamas: Metastable Analogues for the Genesis of Ancient Platform Dolomites

The petrographic and geochemical characteristics of a more than 80 m thick sequence of shallow‐burial Late Cenozoic dolomites from Little Bahamas Bank (LBB), northern Bahamas, indicate that these dolomites are seawater‐derived and partially metastable. Dolomites range in composition between calcian and stoichiometric (Ca .60 Mg .40 CO 3 –Ca .51 Mg .49 CO 3 ). Strontium content and oxygen isotopes covary with the major element composition. It is suggested that part of the 2‰ spread in oxygen isotopic composition is a result of natural and laboratory isotope fractionation. After correction for these effects oxygen isotopes are in equilibrium with seawater at 20–22°C. Iron and manganese content of the dolomites is essentially precursor‐controlled. The geometry of one of the dolomite bodies suggests that dolomitization occurred in the seawater phreatic zone. Seawater circulation through LBB was probably driven by an overlying freshwater/mixing zone system during (partial?) platform exposure. Maturation of the metastable dolomites from LBB during future diagenesis may cause evolution of petrographic and geochemical signatures to those typical of many ancient dolomite sequences. Hence, Late Cenozoic dolomites of the Bahamas can be used as analogues for the genesis of many ancient platform dolomites. Their diagenetic potential permits the prediction of secondary diagenesis and the understanding of its impact seen in older platform dolomites

A Regional Analysis of Clumped Isotope Geochemistry to Define the Timing of Creation of Micro-Porosity in a Lower Cretaceous Giant Reservoir

Abstract Clumped isotope geochemistry of calcite minerals measures temperature independently of the isotopic composition of the precipitating water, allowing in combination with basin modeling to define the depth and timing of major diagenetic events. This technique has been applied to a regional selection of samples from the most prolific Thamama reservoir unit in Abu Dhabi in an attempt to further constrain the creation of the micro-porous system that volumetrically dominates the pore system of the reservoir. A total of 38 samples from 8 crest wells in 8 different fields from onshore Abu Dhabi were analyzed, indicating precipitating temperatures of 47°C to 110°C, and diagenetic water isotopic composition of 0.2‰ to 5.6‰ d18O. Carbon and Oxygen stable isotope values are in line with existing values for this reservoir (-9.17 to -5.27 d18O; 2.99 to 4.10 for d13C). From the same cores and at the same depth as the 38 samples, thin sections were created for a semi-quantitative petrographic analysis to provide further insight on ?47 temperature variations. Samples with a higher volume of intraclasts have lower temperature of precipitation while samples with higher volume of diagenetic cement show higher temperatures of precipitation. Cutoffs were applied to filter out these early and late diagenetic overprints. Using the existing basin model, ?47 temperatures translate into a depth for diagenesis of between 610 and 1370 m and an Upper Cretaceous age. Both the range of temperatures and depths reflect differential transformation of the individual structures during the late Cretaceous caused by the emplacement of the Semail Ophiolite. This is in agreement with a recently proposed regional burial diagenetic model (Vahrenkamp et al., 2014 ). The isotopic composition of the diagenetic fluids indicate the presence of heavy burial diagenetic brines on a regional scale. The results show that the effects of deep burial diagenesis are present throughout the Abu Dhabi region and that a strong regional burial flow system is controlling the evolution of the poro-perm system. An understanding of this large scale fluid-flow system is important in resolving issues related to the regional distribution of reservoir properties