--> Dolomite Outcrop Analogues as a Key to Understand the Development of Super-K Layers in a Giant Carbonate Reservoir (Upper Khuff Formation, Middle-East)

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Dolomite Outcrop Analogues as a Key to Understand the Development of Super-K Layers in a Giant Carbonate Reservoir (Upper Khuff Formation, Middle-East)

F. Gisquet, M. Floquet, B. Caline, A. Virgone and J. Borgomano

Carbonate Group, Total, Pau, France
CEREGE, Aix-Marseille University, Marseille, France
R&D, Total, Pau, France

September 9, 2016 Friday 9:30 A.M. AAPG/SEG International Conference & Exhibition, Cancun, Mexico

Abstract

Abstract

The Permo-Triassic Upper Khuff Fm hosts a giant carbonate reservoir well known almost all over the Middle-East. The reservoir corresponds to a several hundred meters thick alternation of limestone, dolomite and anhydrite bodies. Super-K layers have been identified within the reservoir by production logging tool pikes and matrix permeability over 1000 mD. These highly permeable intervals are made of several-m thick and several-km in length dolomite bodies.

Because super-K layers represent fluid flow heterogeneities below the seismic resolution, outcrop analogues have been used to better understand the processes responsible for the development of dolomite bodies on extended area. The Upper Jurassic carbonate platform of SE France allows observing and studying at the best, different types of dolomite bodies, fault-related or associated to stratigraphic surfaces.

The objectives of this work focus on:

  • the stratigraphic architectures of carbonate outcrops and subsurface reservoirs;
  • the relationships between the sedimentary processes and dolomite bodies development in the carbonate outcrops and subsurface reservoir;
  • the origin, geometry and development of super-k layers in the subsurface reservoirs.
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    Results of this study show that most of the highly porous/permeable bodies are found below major emersion surfaces. Emersions and linked meteoric dissolution were responsible for secondary porosity creation (vuggy and moldic). Then, subsequent brines reflux during the deposition of inner shelf facies above emersion surfaces, has created dolomitisation front resulting in highly porous/permeable bodies.

    Super-K layers are developed within the dolomite bodies during burial, due to the dissolution of residual anhydrite or calcite. Such mesogenetic dissolution was probably related to the genesis of humic acid during or just before hydrocarbon filling and is considered as the final step for the stratabound super-K development.

    Saddle dolomite is locally found within a super-K layer located in a well close to a major basement-rooted fault. Zebras and exotic minerals associated to the saddle dolomite argue for fluid deriving from the basement. As a late burial event, saddle dolomite invaded and partly cemented the super-K layer. To conclude, super-K layers in the Upper Khuff Fm result from the combination of shallow burial (meteoric dissolution and reflux dolomitisation) and deep burial (sulfate/calcite dissolution) diagenesis.

    AAPG Datapages/Search and Discovery Article #90260 © 2016 AAPG/SEG International Conference & Exhibition, Cancun, Mexico, September 6-9, 2016