We used the pyrolysis parameter HI as a thermal maturation proxy to qualitatively confirm the synthetic maturation of kerogen samples from formations A and B. Figure shows the variation of HI as a function of heat-treatment temperature. It is observed that the hydrogen index of kerogen samples decreases as the heat-treatment temperature increases in both formations A and B confirming that synthetic maturation increases the thermal maturity of the kerogen samples. We performed XPS measurements on the kerogen samples from Formations A and B at different thermal maturities. Figure shows an example of XPS measurements, obtained for a non-heated kerogen sample from Formation A. Similar results were obtained for samples prepared at different thermal maturity levels for both formations. The XPS measurements confirmed the presence of carbon, oxygen, nitrogen, sulfur and traces of fluorine in Formations A and B. The results of XPS measurements were used to estimate oxygen to carbon (O/C) ratio. Figure shows the variation in O/C ratio with heat-treatment temperature. Formation B (i.e., type II/III kerogen) has higher O/C ratio than Formation A, which contains type II kerogen. We observe that the O/C ratio decreases as heat-treatment temperature increases in both formations A and B. This observation can be explained by the decrease in O/C ratio during catagenesis of kerogen samples as they become thermally mature.