Organic petrography and pore structure characterization of low-mature and gas-mature marine organic-rich mudstones: Insights into porosity controls in gas shale systems

Abstract

petrography and pore structure characterization of low-mature and gas-mature marine organic-rich mudstones: Insights into porosity controls in gas shale systems, Marine and Petroleum Geology (2019),

Effect of organic matter composition on source rock porosity during confined anhydrous thermal maturation: Example of Kimmeridge-clay mudstones

“…Previous XRD analyses show that the studied samples contain similar mineralogy with 7.8-19.7 wt% of quartz, 13.8-17.6 wt% of carbonates, 52.5-54.6 wt% of clay and less than 10 wt% of pyrite, albite and gypsum (Cavelan et al, 2019). Three samples were collected in Marton borehole between 128.15 to 128.78 meters deep and three samples in Ebberston hole between 69.98 to 70.28 meters deep ( Fig.2).…”

“…The studied samples were collected from the well-documented cycle I of Marton and Ebberston boreholes in the Cleveland Basin (Fig.1, Boussafir et al, 1995a, b;Desprairies et al, 1995;Lallier-Vergès et al, 1995;Ramanampisoa and Disnar, 1994) and are low-mature (Rc < 0.50%, Ramanampisoa and Disnar, 1994). This cycle (Oschmann, 1988) is characterized by OM contents ranging from 1 to 11 wt% in Marton and from 3 to 18 wt% in Ebberston (Fig.2, (Boussafir and Lallier-Vergès, 1997;Cavelan et al, 2019;. These changes occur in parallel with variations in the organic productivity and the oxygenation of the dispositional environment (Boussafir et al, 1995a, b;Boussafir and Lallier-Vergès, 1997;Lallier-Vergès et al, 1995).…”

“…Cleveland Basin, Northeast England (Yorkshire, modified from Cavelan et al, 2019;Herbin et al, 1995). Cavelan et al, 2019;Herbin et al, 1995;Powell, 2010).…”

“…OM-hosted pores inherited from the original structure of cellulose, lignaceous debris or between adjacent cells of colonial algae are sometimes present (Löhr et al, 2015;Reed, 2017), but pores are rarely observed in type II OM in the immature stage (Bernard et al, 2012a;Cavelan et al, 2019;Katz and Arango, 2018;Kuila et al, 2014). However, pores are frequently observed in thermally mature mudstones (Bernard et al, 2012b;Cavelan et al, 2019;Curtis et al, 2012;Katz and Arango, 2018;Ko et al, 2018Ko et al, , 2016Kuila et al, 2014;Loucks et al, 2012Loucks et al, , 2009.…”

“…OM-hosted pores inherited from the original structure of cellulose, lignaceous debris or between adjacent cells of colonial algae are sometimes present (Löhr et al, 2015;Reed, 2017), but pores are rarely observed in type II OM in the immature stage (Bernard et al, 2012a;Cavelan et al, 2019;Katz and Arango, 2018;Kuila et al, 2014). However, pores are frequently observed in thermally mature mudstones (Bernard et al, 2012b;Cavelan et al, 2019;Curtis et al, 2012;Katz and Arango, 2018;Ko et al, 2018Ko et al, , 2016Kuila et al, 2014;Loucks et al, 2012Loucks et al, , 2009. It has been well-documented that changes in the abundance, size and shape of the OM pores during burial appears to be mainly stimulated by oil and primary and/or secondary gas generation from oil-prone kerogen (Bernard et al, 2012a, b;Cardott et al, 2015;Chalmers and Bustin, 2008;Chen and Xiao, 2014;Curtis et al, 2012;Katz and Arango, 2018;Ko et al, 2018Ko et al, , 2016Loucks et al, 2012;Mastalerz et al, 2013;Milliken et al, 2013).…”