Carbonate Sedimentology

Carbonate Sedimentology

Carbonate sedimentology represents one of the main services that Oolithica provides.  We have extensive experience of carbonate and carbonate – evaporite petroleum systems throughout North Africa, Europe, the Middle East, Pakistan and the Far East.

Carbonate reservoir fairways are often complex, despite their relatively simple mineralogy, and sedimentological studies are critical to accurate reservoir delineation, description and management.  The studies we perform are generally of a integrated multi-disciplinary nature, and may comprise some or all of the following elements:

  • Detailed description of core and/or outcrop sections (typically presented as a graphic log of lithology, estimated clay content, grain size, sedimentary and biogenic structures, bounding surfaces, cycle stacking patterns and hierarchy, diagenetic features, and visual assessment of porosity, pore types and hydrocarbon shows, together with preliminary palaeo-environmental interpretations); core logs are commonly prepared at 1:50 scale, whereas outcrop reconnaissance logs are often recorded at a larger 1:200 scale

  • Acquisition of outcrop spectral gamma data to provide ties into the subsurface

  • Determination of core-to-log depth shifts

  • Sampling for subsequent analysis (including sampling of ditch cuttings where core is not available)

  • A phased analytical programme, typically commencing with thin section petrography, microfacies analysis, diagenetic sequencing and initial characterization of pore systems as seen in thin section

  • Revision/refinement of provisional sedimentological logs and depositional interpretations based on thin-section observations and the integration of additional datasets such as image logs

  • Establishment of a 1D sequence stratigraphic framework and comparison with adjacent reference sections / offset wells, leading to the development of a wider 3D sequence stratigraphic framework

  • Targeted follow-up analyses (typically SEM, CL, ICP and/or XRF elemental analyses, C/O/Sr isotope analysis, fluid inclusion microthermometry) aimed at further refinement of the diagenetic sequence and improved pore characterisation

  • Definition of reservoir layering schemes and characterization of flow units based on the integration of sedimentological observations with wireline, petrophysical and engineering datasets

  • Construction of predictive facies and reservoir property maps

 

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Sedimentological log of an outcrop section in the Cotswolds

 

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Outcrop Gamma Ray Logs superimposed onto limestone quarry face showing how spectral gamma can highlight subtle lithological variations and enable the correlation of outcrops with subsurface well sections.

 

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Example well summary chart integrating wireline logs and cuttings petrography