Abstract: Vitrinite Reflectance: To Increase the Value in Exploration, Consider Special Sampling, Give Sample Background to the Analyst, and Ask for Information, Not Just Numbers

Neely H. Bostick

Examples show that you get significantly increased value from vitrinite reflectance if you consider special samples, provide background to the analyst (not just samples), and ask for information (not just raw numbers).

Samples: (1) Shallow samples (to establish gradient control and help estimate eroded overburden); (2) Coals or "ordinary" siltstones (to establish the range of vitrinite types); (3) Hand-picked vitrain; (4) Sidewall core.

Answer background questions: (1) Are samples core, cuttings (washed or unwashed), outcrop, etc.? (2) Was lignitic drilling additive (eg., LIGCON, MILCO, etc.) used? If possibly so, provide unwashed cuttings to check. (3) The history of well casing? (4) Is there a logical maturation relationship among samples? If samples are given "blind", will you pay for later for re-analysis with the logical relationships furnished? (5) Lithology? oil-bearing? (6) Signs that solid bitumens may be present?

Ask for information (not just numbers): (1) Is there an indication of sample "quality"--ease of locating and recognizing first-cycle vitrinite? (2) Does a reflectogram represent all organic grains or just "first cycle vitrinite"? If just a reflectance number is given, what does it mean? (3) Are liptinite and sclerotinite reflectance given to help identify primary vitrinite? (4) Is lignite (leonardite) from drilling mud seen? Does it contain inertinite that will hamper identification of primary vitrinite? (5) Does vitrinite or resinite have low-reflecting rims indicative of sample weathering? (6) Are pyrite grains in vitrinite "rusted" from weathering? (7) Do some grains have high-reflecting rims--damage from overheating when cuttings were dried? (8) Is analysis made using whole-rock c ips, hand-picked vitrain, or organic grains concentrated by processing? (9) Does the analyst report oil films (which significantly lower reflectance)? (10) Does vitrinite contain cell resin (which gives low reflectance)? (11) Does the analyst suspect that some "vitrinite" is solid bitumen or dead oil? (12) Could you request special detailed analysis of a few core samples? Could they be analyzed for low-reflecting saprovitrinite by fluorescence or photoalteration?

AAPG Search and Discovery Article #90986©1994 AAPG Annual Convention, Denver, Colorado, June 12-15, 1994