Many ancient carbonate build-ups are impacted by meteoric diagenetic processes including karstification. However, very little is known about the acoustic properties and seismic expression of karstified reservoirs. This paper investigates potential seismic expressions of karstified buildups by means of synthetic seismic modelling. The overall stratigraphic architecture and rock physical properties are derived from published examples of southeast Asian carbonate buildups. Various karst systems, corresponding to distinct stages of karstification of varying intensity, have been superimposed to the background facies-related acoustic model. Three-dimensional synthetic seismic cubes have been computed from the karst-bearing acoustic model and by testing various wavelet frequencies. The proposed approach allowed several types of palaeokarsts to be reproduced, from dendritic karst and flank margin caves to cave networks, in amplitude sections. However, geometrical seismic attributes, like coherency, cannot be accurately reproduced with modelling based on the available literature data. In addition, the exploration of this synthetic seismic shows that non-stratiform diagenetic bodies (i.e leached carbonate wedge in a mixing zone), appears as stratiform even in very high resolution seismic. Thus, their detection and characterisation require advanced techniques or prior knowledge such as borehole data.

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Hydrocarbon exploration along the Arabian Peninsula is almost celebrating a century of successes. Major structures were drilled and hundreds of billions of barrels consequently discovered and still producing at increasing rates. Remarkable multi-scale and multi-disciplinary dataset (e.g., 2D, 3D seismic data, core and well log data and imagery…) have been acquired in the past decades allowing geoscientists to better assess the diverse onshore and offshore Petroleum Systems’ potential. Many challenges linked to the exploration of new hydrocarbon resources in such Mature Basins are driving innovative ideas towards the identification, the assessment and the de-risking of new subtle Plays. "Integration" remains a key problematic that needs to be tackled in order to answer properly to how much resources are still left unexplored. Thus, multi-disciplinary expertise, multi-scale dataset combination should be supported by recent technological advances in data acquisition and processing (e.g., 3D Seismic inversion and characterization) as well as by integrated modelling approaches (e.g., 4D Forward Stratigraphic and Basin Modelling). This paper discusses the results of an innovative methodology developed to assess the exploration potential of the Lower Cretaceous along a wide sector of the mature Eastern Arabian Plate that extends over more than 35 000 km2 (Onshore and Offshore Kuwait). As major structural features have already been drilled, a focus is set on the detection of subtle stratigraphic trapping mechanisms using multi-disciplinary and multi-scale sedimentological, stratigraphic, petrophysical and geophysical techniques. Seismic stratigraphy study based on reflectors configuration and internal geometry analysis has enabled the delineation of geobodies, i.e. reservoir/seal pairs and proposed conceptual models associated to the presence of subtle traps. A regional DionisosFlow™ 4D forward stratigraphic model using process based deterministic approaches was built to enhance the understanding of the sedimentary facies lateral and vertical variation and stratigraphic architecture with time. The calibrated stratigraphic model resulted in the generation of 23 facies for 5 main stratigraphic units deposited in carbonate ramp settings (e.g., oolitic shoals, algal mounds), mixed carbonate and siliciclastic depositional environments, as well as fluvio-deltaic settings. Seismic inversion and characterization on wide 3D data allowed to pin-point subtle sedimentary features along the various depositional environments permitting a 3D prediction of lithology and porosity for the different formations, as well as a TOC estimation in parallel with an extensive geochemical study of pyrolysis data. The generation of integrated facies maps was used in a TemisFlow™ basin model that combined the results of the stratigraphic forward model and the seismic characterization in order to define facies variation in the 3D basin model and then simulate the impact of basinal evolution on hydrocarbon generation, migration and trapping. The Petroleum System Modelling also allowed a better understanding of (1) overpressures distribution, (2) complex migration pathways through the thick Gotnia evaporite and mudstone units as well as between Upper Jurassic and Lowermost Cretaceous source rocks (i.e., Najmah and Makhul Fms) and the major Lower Cretaceous reservoir units. This key modeling task permits a better localization of sectors with potential new "subtle" targets. This innovative and integrated workflow applied in mature sectors of the Arabian Plate sets new grounds for the generation of regional Play Fairway Maps, Common Risk Maps for the different Petroleum systems elements (reservoir, seal, trap and charge) as well as Composite Common Risk Maps. These tasks are aimed at assessing the overall risk associated to Plays and thus contribute to the identification of new exploration Lead Areas to be further de-risked in the near future.

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