The Barnett Shale: Compositional fractionation associated with intraformational petroleum migration, retention, and expulsion

Abstract

9 The Marathon 1 Mesquite well was drilled in Hamilton County, 10 Texas, targeting the Barnett Shale with late oil window maturity. 11 Combining a large suite of petrologic and high-resolution organic 12 geochemical analyses on 120 core samples, we have been able to 13 document qualitatively and quantitatively the effects of petroleum 14 retention and expulsion within and from five intervals within the 15 Barnett Shale. Lithological heterogeneities control the composi-16 tion and amount of retained fluids; the sorption of oil by solid 17 organic matter is important in all intervals. Applying empirical 18 formulas, we have been able to demonstrate not only that retention 19 is primarily controlled by total organic carbon (TOC), but also 20 that the "live" or "labile" component, rather than "dead" or "inert" 21 carbon, constitutes the most active sorptive sites. Additional reten-22 tion in the micropores provided by biogenic microcrystalline 23 quartz (sponge spicules) accounts for the sweet spot defined by 24 an "oil crossover" in the 914-m (30-ft) thick second interval. The 25 fluorescing oil occurring in the axial chamber of the sponge spic-26 ules and that sorbed on organic particles are together enriched in 27 saturated hydrocarbons, whereas the dispersed oil from the adja-28 cent interval 3 is depleted in this compound class. Mass-balance 29 calculations reveal that short-distance migration of petroleum into 30 this "reservoir" interval (second) fractionates the generated oil 31 into a higher quality oil by preferential retention in the order polar 32 compounds > aromatic hydrocarbons > saturated hydrocarbons 33 within the underlying organic matter and clay-rich third interval This has to be remedied because even subtle changes in bulk fluid M51South Africa, China, Australia, and North M52Africa are key activities in service and M53research at the present time.We wish to thank D. M. Jarvie and R. J. Hill M56for their careful reviews and helpful M57comments. The editorial comments and M58suggestions by Terrilyn Olson are also M59gratefully acknowledged. Parts of this study M60were carried out during the course of the M61"GASH-Gas Shales in Europe" initiative. The M62authors wish to thank the sponsors of this M63project, especially Marathon Petroleum M64Corporation, for providing sample material. M65We are also grateful to Prof. (Bowker, 2007;Jarvie et al., 2007; Bunting and 139 Breyer, 2012) as well as in reservoir diagenesis 140 (Milliken et al., 2012 (Bowker, 2003). Rather than detrital quartz, micro-147 crystalline quartz is the major component of the sili-148 ceous Barnett facies (Loucks and Ruppel, 2007). 149 Milliken et al. (2007) interpreted the microcrystalline 150 quartz in Barnett Shale as being derived from mainly 151 agglutinated foraminifera, whereas others have 152 emphasized the importance of siliceous sponge spic-153 ules (Hickey and Henk, 2007; Slatt and O Brien, 154 2011; Abouelresh and Slatt, 2012). 155 In this paper, we (1) assess the amount and quality 156 of retained hydr...

Upper Permian Junggar and Upper Triassic Ordos lacustrine source rocks in Northwest and Central China: Organic geochemistry, petroleum potential and predicted organofacies

“…well, because retained bitumen could reduce the values of Tmax, and this is confirmed by a change to higher values after Soxhlet extraction (Han et al 2015;Kruge 1983). The uniform T max values from the Hongyanchi Formation exhibit a lower thermal maturity than Lucaogou Formation, and suggest a consistent kerogen composition of type III (Fig.…”

Oil retention and porosity evolution in organic-rich shales

“…S2 is the yield of pyrolysis products generated at a temperature up to 650 114 °C. Because the calculated amount of total-oil and the S1 value of unextracted rocks are strongly correlated 115 (Han et al, 2015), S1 has been used in the ensuing discussions as a proxy for the retained oil concentration.…”

“…For the Posidonia Shale, the density of isolated kerogen (Rexer et al, 2014) ). Thus, a weaker sorption/swelling ability can be inferred for inertinite, which might explain the weaker 170 sorption control of inert over labile kerogen (Han et al, 2015). Nevertheless, it should be noted that inert 171 kerogen is not necessarily identical to inertinite but, as opposed to labile kerogen, represents only the fraction 172 of kerogen which does not generate petroleum (Cooles et al, 1986).…”

“…Clay minerals, especially illite (Schettler and 27 Parmely, 1991), have also been documented as possessing micropore structures capable of sorbing gas 28 (Gasparik et al, 2012). In addition to sorption on particle surfaces, petroleum storage in the pores of either 29 organic (Loucks et al, 2009) or inorganic (Han et al, 2015) origin have been documented, as well as natural 30 fractures (Lopatin et al, 2003;Pollastro, 2010). 31 Organic pore development is believed to be largely due to the thermal cracking of kerogen (Jarvie et al,32 2007; Loucks et al, 2009) and/or bitumen (Bernard et al, 2012b), though primary organic pores have been 33 observed within immature organic matter as well (Löhr et al, 2015;Pommer and Milliken, 2015).…”

Unravelling maturity- and migration-related carbazole and phenol distributions in Central Graben crude oils

“…Petroleum consists of an exceedingly complex mixture of hydrocarbons and nonhydrocarbons, extending from methane to macromolecular aggregates such as asphaltenes. The relative proportions of these components are quite variable and depend initially on the type of organic matter in the parent source rock, its level of maturity at the time of expulsion, and subsequently upon secondary effects including phase behaviour (Silverman, 1965;England et al, 1987;England and Mackenzie, 1989;Larter and Mills, 1991;di Primio and Skeie, 2004), fractionation during expulsion (Han et al, 2015;Ziegs et al, 2017), biodegradation and water washing (Connan, 1984;e.g. Ahsan et al, 1998) and in-reservoir maturation (Gabrielsen et al, 1985;Horsfield et al, 1992).…”