Colorado Green River Formation oil shale as viewed by pulsed n.m.r.

Abstract

Wideband proton pulsed n.m.r. techniques have been applied to selected Colorado Green River Formation oil shales. Among the various parameters generated by this technique, one correlates with total organic matter contents and another correlates with Fischer assay oil yields. The free induction decay (FID) amplitude quantitatively measures total oil shale proton contents when 1. (1) the amplitude is extrapolated up to the midpoint of the radio frequency pulse, and 2. (2) an adequate trigger repetition rate ( t r ) is used. A 1 s value of t r , within experimental precision, masks the crystalline inorganic protons. The maximum FID amplitude with a 1 s t r correlates with the total organic matter content. T 1 decays for the organic matter have two relaxation components. The fast component has relaxation times ⪡ 5 ms. Maximum FID amplitudes using a 1 s t r , reduced by the fraction of protons with the fast T 1 decays, correlate directly with Fischer assay oil yields. This T 1 correction factor, thus, reflects the organic matter unrecoverable as oil by the Fischer assay. The reported procedure cannot alone resolve oil-shale free and clay interlayer water protons from the organic protons. This work, along with literature references, shows these protons to be present in minor quantities as compared to the organic proton content of commercial oil shales. If such protons should be present in significant quantities, their concentration can be greatly reduced by finely crushing the oil shale and drying at 110 °C overnight.