A detailed petrographic study is the key of success for any diagenetic study. If possible, I prefer to manipulate the samples myself prior to any decision on how and where to obtain a flat disc or wafer to obtain a petrographic thin section. My petrographic experience in several geological scenarios (sedimentary carbonates and clastics, igneous and metamorphic rocks, hydrothermal precipitates) allows me to precisely select the most interesting and representative rock sections for each sample. This approach needs a profound interaction with the client, to pinpoint the needs and goals of the project.

The analytical approach to be used will depend on the nature of the sampled rocks and the goals to achieve, and will include:

1. Core description and sampling.

2. Hand sample preparation, description and recording.

3. Side Wall Core manipulation and sampling.

4. Cuttings manipulation, cleaning and sampling.

5. Photographic recording

6. High-quality thin sectioning (with or without mirror-finish polishing) from hand samples, core samples, side wall cores or cuttings.

7. Detailed petrographic studies, including rock classification (allochems, matrix, cements, ...), paragenetic sequence, precise mineral identification.

8. SEM-EDS, XRF or EPMA analyses if required, depending on client's needs.

And suggestions of further analytical techniques to be applied to fulfill the main goal of the projects.

Fluid inclusions in cement and ore minerals are ubiquitous, although the presence of "useful" fluid inclusions trapped in diagenetic minerals is always uncertain. As a consequence, a previous thorough screening is needed consisting in a very detailed petrographic study (see above) followed by a precise localization and optical characterization of fluid inclusions types within a paragenetic sequence.

A standard fluid inclusion study for diagenesis and oil systems will include:

• Very careful sample selection and cut with a low-speed saw to avoid mineral and F.I. damage.

• High-quality, double polished wafer preparation.

• Detailed fluid inclusion petrography (polarized light, UV, IR), with identification and mapping of primary, secondary and pseudo-secondary fluid inclusions, FIA's, fluid inclusion type, visual degree of filling, ...

• Careful photographic recording.

• Basic microthermometric studies, including eutectic temperature, hydrohalite melting temperature, ice melting temperature, halite (or other daughter salts) solubilization temperature, total homogenization temperature and homogenization type.

• Calculations, including electrolyte composition, total salinity, and isochore calculation

• Conclusions and recommendations.

• If oil-bearing fluid inclusions are present, a more advanced study can be performed, including:

• Paleo-fluid PVTx analysis, reconstructions and evolution (see description of methods and results below, in the fluid inclusion services).

• Paleo-fluid history (brines, gases, hydrocarbons) and sequence.

• Fluid&gas origin and processes (noble gases isotopes, halogens).

Rock geochemistry is a very powerful tool if applied correctly after a careful sedimentological and petrographic study.

This can include:

• Hand sampling

• Microsampling.

• Bulk rock chemical analysis

• Stable isotope analyses (C, O, S, D):

  • Bulk analysis

  • Bulk C&O isotope analysis for calcite/dolomite (specific attack).

  • In-situ isotope micro-analysis by ion probe.

• Sr isotope analysis

• Data reduction and interpretation.

The age of a rock, cement or even a geological process can be crucial to precisely reconstruct the events succession. During my career I used several absolute dating methods depending on the presence and preservation of the mineral phases to be dated and the goal to be achieved.

• K-Ar

• Ar-Ar

• Rb-Sr

• U-Pb

• (U-Th)/He