Marc Diraison

Late Ordovician tunnel valleys in southern Jordan

Abstract The Upper Ordovician glacial record of southern Jordan (Ammar Fm.) essentially consists of palaeovalley infills and of a subordinate time-transgressive fluvial to shallow-marine succession overstepping both the palaeovalleys and interfluvial areas. Valley size (depth, 60–160 m; width, 1–3 km), steep (20–50°) margins, internal organization and depositional facies point to an origin as tunnel valleys. The tunnel valleys are infilled by either fluvioglacial sandstones or fluviodeltaic coarsening-upward successions including fine-grained clayey sediments. Re-occupation of previous valleys is evident in places. At least three generations of tunnel valleys are inferred from cross-cutting relationships, although they most probably only reflect temporary standstills and minor re-advances related to the overall recession following the main glacial advance recorded in Saudi Arabia. Petrophysical measurements indicate that higher permeabilities are located in the glacially related strata (1.5–3 darcy in fluvioglacial infills), with a somewhat reduced porosity (22–28%) relative to the preglacial sandstones owing to a higher clay content, probably of diagenetic origin. Sandstone amalgamation, however, gives the fluvioglacial sandstones a high reservoir quality.

Fractured Crystalline Reservoir: a Field Analog Analysis on Tamariu’s Granite (Catalonian Coastal Ranges)

Tamariu’s granite has been studied with the aim to characterize the fracture network and the porosity through the analysis of cementation associated to paleo-fluids circulation. With the help of regional and outcrop studies (Le Garzic 2010, Place 2010), we could interest on the fracture network over 8 orders of magnitudes. We used 1D scan lines and 2D fracture mapping on outcrop pictures to precisely define the fracture network and the organization of the flow in this network. The data acquired on our maps show a power law distribution of the cumulative fractures numbers and faults lengths between the centimeter scale and the hundred kilometers scale. This homogenous length distribution over a large range of scales contrasts with the fracture orientation distribution that highly depends on the scale observation and on their location relative to the larger structures. The volume of paleo-fluids associated cementation has been quantified using calcimetry and mapping of different parts of the porous network: the veins, breccias cemented by carbonates, fractured granite and poorly fractured granite. The percentage of percolated rock volume reaches to 3% of the total granitic body, and the main part of them are localized in fractured corridors composed of mains veins and breccias.

How Use Electrical Image Log for Fractured Basement Reservoir Characterization. Example of the Kharir Field (Yemen)

No standard workflow, nor rules or common practices exist in the industry to describe reservoir properties of fractured basement. The purpose of this work, focused on a highly documented field case in Yemen (Kharir, block 10), is to develop a wide integrated analysis of structural data from well scale to reservoir scale to extract any possible driver which could be relevant for reservoir modeling. A new concept of interpretation based on field observations was developed for analyzing and upscalling wellbore electrical image log. This method aims to identify and characterize the first order structural domains: fault zones (thickness, main orientation, internal architecture…) and intercalated structural blocks (degree of fracturing, main fracture trends, dyke occurrence…). Particular attention has been given to fault ranking. When seismic and image log interpretations are compared, a good correlation is observed in terms of fault zones orientations, fault zones ranking (i.e. thickness versus throw), spatial distribution of deformation and structural inheritance. This approach permits to describe a first order structural network which can be considered as the reservoir backbone. In addition, detailed analyses on image log provide relevant input for reservoir modeling.

Spacial Distribution of Fluid Flow Paths in Fractured Granites - Application to EGS

Two fractured variscan granites have been selected to investigate present and past percolated networks. The first case study is the geothermal site at Soultz-sous-Forets (Rhine Graben). Borehole seismic (VSP) has been used to map in 3D some generally per