Estimation of kerogen porosity in source rocks as a function of thermal transformation: Example from the Mowry Shale in the Powder River Basin of Wyoming

Evolution of nanoporosity in organic-rich shales during thermal maturation

“…Valenza et al [18] reported the geochemical controls on microstructure of North American shales having maturities from approximately 0.5% to 2.7% VRo/VRb (vitrinite or bitumen reflectance), also observing a marked increase in surface area and pore volume with increasing maturity. In the case of sample LCG, its evolution of porosity indicates that porosity can undergo a reduction to some extent in the oil window stage, which is different from a monotonically growing trend as indicated by previous studies [4,18,19]. A similar reduction of pore volume or porosity around the maturation stage is also observed in naturally buried samples such as gas shales and coals, interpreted to be the result of bitumen swelling and compaction [22,38,39].…”

“…At higher maturation, pyrobitumen is produced by oil cracking to gaseous hydrocarbons [56,57]. This pyrobitumen and residual kerogen are nanoporous due to the expulsion process of hydrocarbon gas during oil cracking, which make a contribution to the total porosity of shales [6,19,40,50]. Therefore, naoporosity of oil-prone shales, in this stage, will typically shows a decrease, and then an increase.…”

“…Several measurement techniques have successfully been developed to characterize the complex pore systems such as small-angle and ultra small angle neutron scattering (SANS/ USANS), low-pressure gas adsorption, mercury injection capillary pressure (MICP), and scanning electron microscopy (SEM) [5,[13][14][15][16][17]. The geological controls of pore structure in gas shales include the total organic carbon (TOC) content, thermal maturity and mineralogy, which have preliminarily been discussed in previous works [3,4,10,18,19].…”

“…Effect of thermal maturation on porosity has recently attracted more attention because of the growing recognition that porosity in organic matter, to a large extent, is a function of thermal maturity [4,6,18,19]. The recent efforts toward understanding porosity evolution with maturation have been matched with documenting the pore networks in gas shales.…”

Main controlling factors and enrichment area evaluation of shale gas of the Lower Paleozoic marine strata in south China

“…Maturity not only controls the gas generation of shale, but also affects the reservoir properties (Curtis et al 2012;Fishman et al 2012;Loucks et al 2009;Mastalerz et al 2013;Modica and Lapierre 2012;Valenza et al 2013). The maturity of the Lower Paleozoic shale in south China is generally rather high, but it varies significantly in different regions (Nie et al 2009).…”