Figure 5
Photomicrographs showing the results of reflected light organic petrography of an as-received drill cuttings (ARcutt) sample from 2155 m depth in white light (a,c,e,g; images on the left column) and same view in fluorescence light (b,d,f,h; images on the right column). Three major sources of contamination are identified in the cuttings sample: cavings from overlying formations, clay-like matter from drilling mud, and possibly volatile, oil-based invert emulsion drilling fluids. (a,b) Caved fragment of organic-rich shale from overlying source rock displaying low maturity, as evidenced by the presence of brightly fluorescing liptinitic (L) particles (b). (c,d) Flocculation of drilling mud in the form of clay-like aggregates. (e,f) Fine-grained, shaley, organic-rich fragment, possibly caved from overlying source rocks (right side of image) shown next to the original Montney fragment (left side of image). (g,h) A microscopic view of Montney siltstone showing possible staining from diesel-based invert emulsion drilling fluids, apparent under fluorescence light (right image).
