... al., 1994], [Diessel and Gammidge, 1998] and [Gurba and Ward, 1998]), and some of the R o val... more ... al., 1994], [Diessel and Gammidge, 1998] and [Gurba and Ward, 1998]), and some of the R o values obtained for the coals used in this study indicate suppression of as much as 0.2% (Sykes et al., 1999). T max values are also suppressed in very hydrogen-rich coals, including ...
For coal or terrestrial (Type III) organic matter to act as a source rock for petroleum, two sepa... more For coal or terrestrial (Type III) organic matter to act as a source rock for petroleum, two separate criteria must be met. The coal must be capable of (1) generating hydrocarbons in response to thermal stress (catagenesis) and (2) releasing those hydrocarbons to a porous migration conduit or reservoir (expulsion or primary migration). While there is little doubt that coal is an effective source for methane, liquid hydrocarbons (oil) have been only rarely attributed to a coal source. This is in spite of the observation that virtually every high volatile bituminous coal (i.e. in the oil window) contains significant amounts of solvent extractable hydrocarbons, typically up to 24,000 ppm or 30 mg hydrocarbons/g organic carbon (assuming a carbon content of 80%). Thus one is left to conclude that the limiting factor is not the ability to generate hydrocarbons, but rather primary migration out of the rock. In order to be an effective source, the organic matter in a rock must have chemical properties such that it can produce a quantity of bitumen that exceeds the expulsion threshold. Empirical evidence suggests that inertinite (or fusinite) falls well below 30 mg/g and vitrinite typically yields values that are up to this limit but rare above it. Liptinitic macerals such as resinite and sporinite are enriched in hydrogen and have a higher capacity to generate hydrocarbons. As a result, coals that are rich in liptinites will exceed the bitumen saturation threshold at maturity and be capable of expelling liquid hydrocarbons if a physical migration route is available.
Many Cretaceous–Cenozoic coaly source rocks in Australasian and southeast Asian basins were depos... more Many Cretaceous–Cenozoic coaly source rocks in Australasian and southeast Asian basins were deposited in coastal plain environments, yet the effect of early diagenetic marine influence on their oil potential is not well understood. An integrated organic geochemical and petrographic study of humic coals from the Eocene Mangahewa Formation (Taranaki Basin, New Zealand) was undertaken with coals predominantly from raised mire petrofacies, with subordinate proportions from planar mires. The total S content of 0.63–4.4% (dry, ash-free) indicated very slight to strong degrees of marine influence. Other than minor addition of inferred mangrove derived suberinite and associated liptodetrinite, the degree of marine influence had no obvious effect on maceral or plant tissue abundance. However, hydrogen index (HI) values were up to ca. 150% (109 mg HC/g TOC) higher, and total (C6+) oil potential, up to ca.140% (43 mg/g TOC) higher among the more strongly marine influenced coals. Correlations o...
The geochemistry of Recent sediments from Pigeon Lake, Alberta was studied using Rock-Eval-6 in c... more The geochemistry of Recent sediments from Pigeon Lake, Alberta was studied using Rock-Eval-6 in conjunction with Instrumental Neutron Activation Analyses 137 Cs isotope. The results of this study indicate that the variations in Rock-Eval parameters within the sedimentary column are correlated with the concentration of lithophile elements. These variations appear to be controlled by a balance between a number of interrelated processes concerned with both the nature of the deposited biomass and the depositional conditions. Two marker horizons were identified showing an abrupt decrease in Rock-Eval parameters (TOC, S2, and HI) and an increase in concentration of lithophile elements, indicating the clastic nature of the sediments with low autochthonous organic contents. This is attributed to significant natural events such as a storm or flood, which result in a rapid increase in the rate of erosion and subsequently in a high clastic input to the lake. Two cycles showing high organic content were also identified. The first cycle (productivity cycle) corresponds to the increase in algal productivity of the lake due to agricultural activities in the lake's catchment. In the second cycle (diagenetic cycle), the downward decrease of organic matter is interpreted as the result of selective degradation of organic matter during early diagenesis. The estimated sedimentation rates based on the established marker horizons and 137 Cs isotope indicate higher sedimentation in the deeper part of the lake prior to the productivity cycle. However, the sedimentation rates increased towards the littoral zone coinciding with an increase in productivity and subsequently the rise in growth of macrophytes in the nearshore area.
... al., 1994], [Diessel and Gammidge, 1998] and [Gurba and Ward, 1998]), and some of the R o val... more ... al., 1994], [Diessel and Gammidge, 1998] and [Gurba and Ward, 1998]), and some of the R o values obtained for the coals used in this study indicate suppression of as much as 0.2% (Sykes et al., 1999). T max values are also suppressed in very hydrogen-rich coals, including ...
For coal or terrestrial (Type III) organic matter to act as a source rock for petroleum, two sepa... more For coal or terrestrial (Type III) organic matter to act as a source rock for petroleum, two separate criteria must be met. The coal must be capable of (1) generating hydrocarbons in response to thermal stress (catagenesis) and (2) releasing those hydrocarbons to a porous migration conduit or reservoir (expulsion or primary migration). While there is little doubt that coal is an effective source for methane, liquid hydrocarbons (oil) have been only rarely attributed to a coal source. This is in spite of the observation that virtually every high volatile bituminous coal (i.e. in the oil window) contains significant amounts of solvent extractable hydrocarbons, typically up to 24,000 ppm or 30 mg hydrocarbons/g organic carbon (assuming a carbon content of 80%). Thus one is left to conclude that the limiting factor is not the ability to generate hydrocarbons, but rather primary migration out of the rock. In order to be an effective source, the organic matter in a rock must have chemical properties such that it can produce a quantity of bitumen that exceeds the expulsion threshold. Empirical evidence suggests that inertinite (or fusinite) falls well below 30 mg/g and vitrinite typically yields values that are up to this limit but rare above it. Liptinitic macerals such as resinite and sporinite are enriched in hydrogen and have a higher capacity to generate hydrocarbons. As a result, coals that are rich in liptinites will exceed the bitumen saturation threshold at maturity and be capable of expelling liquid hydrocarbons if a physical migration route is available.
Many Cretaceous–Cenozoic coaly source rocks in Australasian and southeast Asian basins were depos... more Many Cretaceous–Cenozoic coaly source rocks in Australasian and southeast Asian basins were deposited in coastal plain environments, yet the effect of early diagenetic marine influence on their oil potential is not well understood. An integrated organic geochemical and petrographic study of humic coals from the Eocene Mangahewa Formation (Taranaki Basin, New Zealand) was undertaken with coals predominantly from raised mire petrofacies, with subordinate proportions from planar mires. The total S content of 0.63–4.4% (dry, ash-free) indicated very slight to strong degrees of marine influence. Other than minor addition of inferred mangrove derived suberinite and associated liptodetrinite, the degree of marine influence had no obvious effect on maceral or plant tissue abundance. However, hydrogen index (HI) values were up to ca. 150% (109 mg HC/g TOC) higher, and total (C6+) oil potential, up to ca.140% (43 mg/g TOC) higher among the more strongly marine influenced coals. Correlations o...
The geochemistry of Recent sediments from Pigeon Lake, Alberta was studied using Rock-Eval-6 in c... more The geochemistry of Recent sediments from Pigeon Lake, Alberta was studied using Rock-Eval-6 in conjunction with Instrumental Neutron Activation Analyses 137 Cs isotope. The results of this study indicate that the variations in Rock-Eval parameters within the sedimentary column are correlated with the concentration of lithophile elements. These variations appear to be controlled by a balance between a number of interrelated processes concerned with both the nature of the deposited biomass and the depositional conditions. Two marker horizons were identified showing an abrupt decrease in Rock-Eval parameters (TOC, S2, and HI) and an increase in concentration of lithophile elements, indicating the clastic nature of the sediments with low autochthonous organic contents. This is attributed to significant natural events such as a storm or flood, which result in a rapid increase in the rate of erosion and subsequently in a high clastic input to the lake. Two cycles showing high organic content were also identified. The first cycle (productivity cycle) corresponds to the increase in algal productivity of the lake due to agricultural activities in the lake's catchment. In the second cycle (diagenetic cycle), the downward decrease of organic matter is interpreted as the result of selective degradation of organic matter during early diagenesis. The estimated sedimentation rates based on the established marker horizons and 137 Cs isotope indicate higher sedimentation in the deeper part of the lake prior to the productivity cycle. However, the sedimentation rates increased towards the littoral zone coinciding with an increase in productivity and subsequently the rise in growth of macrophytes in the nearshore area.
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