Effect of Hydrothermal Treatment and Prolonged Extraction on the Generation of Hydrocarbons from High-Carbon Low-Permeability Rocks from Domanik Deposits

The effect of hydrothermal treatment of high-carbon low-permeability Domanik rock on the efficiency of recovering hydrocarbons from this rock by prolonged four-step extraction for 20, 68, 116, and 220 h with a mixture of organic solvents (chloroform, toluene, and isopropyl alcohol) was studied. As compared to the extraction from the untreated rock, the hydrothermal treatment at 300°С in a СО₂ medium allows recovery of a 6 times larger amount of the extract in the first step (in 20 h). In the second extraction step (68 h), the extract yield decreases by a factor of 8, but the relative content of saturated hydrocarbons in the extract increases by a factor of more than 3 compared to the first step, whereas the relative content of asphaltenes, resins, and aromatic compounds decreases. In the third extraction step (116 h), the extract yield is as low as 0.16%, the content of resins in it drastically decreases, whereas the content of asphaltenes increases to 52%. The extract of the fourth step (220 h) consists to 80.77% of asphaltenes. From the initial rock, the maximal yield of the extract enriched in saturated hydrocarbons with the minimal content of asphaltenes was observed after the second extraction step. In the course of prolonged extraction, the yield of petroleum fractions from the initial rock increases by a factor of almost 4, and in combination with the preliminary hydrothermal treatment, by a factor of 7. This fact demonstrates the possibility of generating an additional amount of hydrocarbons. Changes were revealed in the structural-group, hydrocarbon, elemental, and microelemental composition of petroleum fractions recovered from the low-permeability Domanik rock, depending on the extraction time and transformations of the organic matter of this rock in the course of hydrothermal treatment.