Comparison of Geochemical Characteristics of Products from Thermal Simulation Experiments of Hydrocarbon Generation at Different Heating Rates in the Semiclosed System

Abstract

Based on the thermal simulation experiment in a semiclosed system, the products of continental type II of the Chang 7 shale under slow and fast heating rates were studied. The results show that the yield of hydrocarbon gases (C1–C5) increases under the fast heating rate. Under the slow heating rate, the heavy hydrocarbon gas (C2–C5) begins to crack when the temperature exceeds 400 °C. The H2S and H2 have similar variation rules with hydrocarbon gases. Under the slow heating rate, the expelled oil is larger than that of the fast heating rate. C15+ constitutes the main component of retained oil, and the yield of retained oil at the fast heating rate is larger than that of the slow heating rate, which is different from the expelled oil. After 380 °C, the slow heating rate leads to the cracking of C15+, so the amount of C15+ generated by the fast heating rate is larger than that of the slow heating rate. After 340 °C, the proportion of expelled oil to total expelled hydrocarbons at a slow heating rate is larger than that of the fast heating rate. This study confirms that the fast heating rate can lead to a retardation effect, making the slow heating rate more favorable for the generation and discharge of hydrocarbons. The experimental results verify the compensation effect of time on temperature in the process of hydrocarbon generation.