A common problem when preparing whole rock material is loss of integrity of sediments during grinding and polishing. Poorly indurated sedimentary rocks, and those containing swelling clays, are a particular problem. This applies to many petroleum exploration samples requiring reflectance analysis. Without adequate impregnation and/or use of non-aqueous polishing methods the sediments disaggregate and become recessed below the surface of the pellet. In this situation the mineral matter and organic matter cannot be successfully polished. The use of relief in this context is ambiguous because the term is also traditionally used to describe a localised polishing effect, whereby soft constituents are cut back more than adjacent hard constituents. This results in a difference in level, although both soft and hard materials in this context may have a good fine polish. Excessive relief causes oblique reflection of the incident light beam, and is consequently undesirable. The proposed revision uses erosion to more accurately convey disaggregation and loss of rock material at the polished surface, in items 1 to 3 of the preparation quality assessment. The term relief is recommended to be included in items A to C as a descriptor of polish quality.
Keywordsdispersed organic matter; gas; hydrocarbons; oil; thermal maturity; vitrinite reflectance:;
Ballot Item Approved as D7708-2014 and Pending Publication