Microscopic and sedimentologic evidence for the generation and migration of hydrocarbons in Toarcian source rocks of different maturities

Oil retention and porosity evolution in organic-rich shales

“…These six wells represent a 70 maturity sequence from 0.48 to 1.45% Ro (Jochum et al, 1995;Bernard et al, 2013), with only minor 71 variations in organic geochemical composition and mineralogy (Littke et al, 1988;Rullkötter and Marzi, 72 1988), although the maturation history has been a matter of dispute (Gasparik et al, 2014). Here we base the 73 interpretation of our results on the assumption that the organic matter was never deeply buried (<1800 m; 74 Figure 1B) but thermally altered by a deep seated igneous intrusion (Littke et al, 1988;Düppenbecker, 1992; 75 Jochum et al, 1995;Gasparik et al, 2014), the Vlotho Massif, of Turonian age (93.6-88.6 Ma). Thus, the 76 compaction of the Posidonia Shale has not proceeded since that time.…”

“…The Posidonia Shale is one of the most widespread and economically important source rocks of Western 62 Europe (Littke et al, 1988 Figure 1A). These six wells represent a 70 maturity sequence from 0.48 to 1.45% Ro (Jochum et al, 1995;Bernard et al, 2013), with only minor 71 variations in organic geochemical composition and mineralogy (Littke et al, 1988;Rullkötter and Marzi, 72 1988), although the maturation history has been a matter of dispute (Gasparik et al, 2014).…”

“…Those results are in line with the hypothesis that the studied wells have never been deeply 221 buried (<1800m; Figure 1B) and that compaction of Posidonia Shale in the Hils Syncline area has not 222 proceeded since the initiation of thermal maturation by the deep seated igneous intrusion, Vlotho Massif 223 (Düppenbecker, 1992). 224 Given that lateral facies variations between the studied Posidonia wells are only minor (Littke et al, 1988;225 Rullkötter and Marzi, 1988), the oil-mature Harderode well is treated as the less mature precursor of the 246 In the investigated Posidonia Shale, a discrepancy in estimated maturity exists between Tmax and Ro values, 247 something which has been reported previously (Price and Baker, 1985;Peters, 1986) The appearance of secondary organic pores in the Barnett Shale is reported as being at 0.85% Ro, as 257 compiled in Table 3. Other shales that span immature to overmature levels, show the occurrence of secondary (Table 4).…”

Comparison of Methods for the Determination of the Pore System of a Potential German Gas Shale

“…The thermal maturity levels of four core samples examined from the western part of the Hils Syncline vary between 0.49% VRr and 1.42% VRr (Table 4) and agree well with the data of Littke et al (1988). The maturity determined appears to increase toward the northwest (Jochum et al 1991).…”

“…Detailed descriptions of the cores, and of their sedimentological and geochemical features, have been published (e.g. Mann, 1987;Littke et al, 1988;Rullkötter et al, 1988). In the following text the samples are designated by abbreviations related to their drill locations, i.e.…”