Maturação artificial: hidropirólise em menor escala

Abstract

Hydrous pyrolysis is a type of experiment that involves the heating of samples in a closed reactor system with the addition of liquid water. In it, certain amounts of gravel-sized source rocks are added to the system along with an appropriate amount of liquid water to ensure that these rocks are completely submerged before, during, and after the experiment, because contact with water is required for oil to form from thermal cracking reactions of kerogen and bitumen, by providing hydrogen atoms that are necessary for these reactions to occur. This oil accumulates on the water surface of the system after the experiment and is chemically similar to oils obtained from natural sources, allowing the use of hydrous pyrolysis to correctly simulate and understand the process of oil generation, expulsion, and migration. Since there are four stages of petroleum formation (pre-oil, incipient-oil, primary-oil, and post-oil generation), different experimental conditions are used to ensure that all stages are covered to correctly simulate oil and gas formation from a particular source rock. These conditions involve high temperatures (280-365°C) and pressures (due to the water at high temperatures in the system), along with an experiment duration of 72 hours. Typically, 1-liter reactors are used in hydrous pyrolysis experiments; however, in this work, a 250-milliliter reactor was also used to compare the amount of products generated and to verify if it is possible to adapt normal hydrous pyrolysis experiments into this smaller reactor, since an amount four times smaller of rocks and water (or a 5% wt. NaCl solution) are used, allowing more experiments to be conducted, especially in cases where the amount of rocks available is very low. After comparing product (oil and gas) yields, bitumen extracted from recovered rocks and mineral characteristics from rocks used in both reactors and with results reported by Spigolon et al. (2015), there were no significant differences with the use of a smaller reactor, indicating that using a lower-capacity reactor does not interfere with the ability of hydrous pyrolysis to simulate petroleum formation and expulsion. Since using a 250-milliliter reactor results in almost the same amount of products, it is an improvement, especially because it reduces the amount of sample required to conduct all the necessary experiments, it is easier to handle and requires less labor due to its lower total weight.