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The thermal upgrading of kerogen into fuels has scientific and industrial importance in oil shale utilization. In this study, multiple methods were applied to clarify the pyrolysis behaviors of four kerogens from the Huadian (HD) Basin, Fushun (FS) Basin, Luozigou (LZG) Basin, and Dachanggou (DCG) Basin oil shales. Two model-free isoconversional methods and a master plot were utilized to evaluate the kinetic parameters, and the Coats–Redfern method was used to verify the estimated kinetic results. The results indicated that all studied oil shales had very good hydrocarbon generation potential. HD, FS, and LZG oil shales could be described as type I kerogen, whereas DCG oil shale was type II1kerogen with high aromatic content. HD kerogen featured a stronger polarity and contained more aliphatic structures compared with the three other samples, which induced the mass loss of its first stage at ∼38%, even larger than that of its second pyrolysis stage; the activation energies of the main pyrolysis stage of HD kerogen could also be divided clearly into two stages and in accordance with the thermogravimetric results. The thermal cracking processes of these FS, LZG, and DCG kerogens were mainly concentrated in the second pyrolysis stage, and the activation energies of FS and LZG kerogens did not show a considerable variation with conversion degrees. Moreover, DCG kerogen possessed the largest amount of aromatic structures which resulted in high yields of char, and the activation energies of the main pyrolysis stage of DCG kerogen was almost the largest, especially when the conversation rate was above 0.7. Evolution behaviors of oil and gas products at different temperatures during pyrolysis were related to the cleavage of chemical bonds in kerogen. CH4and light C2+aliphatic hydrocarbons were the typical gaseous products released from the main reaction stages of all four kerogens, and the evolving behavior of each typical gaseous product of four kerogens featured good similarity. The results showed that aliphatic and aromatic carbon contents in kerogen had a remarkable effect on its thermal characteristic and kinetic parameters, and the saturated aliphatic bonds and oxygen-containing bonds were easy to crack and had potentially low activation energy of reaction compared with those of aromatic bonds. Results of the master plot and Coats–Redfern methods verified that the Avrami–Erofeev kinetic model was the optimal model for the pyrolysis of the studied kerogens, thereby indicating that the four kerogens evolved under a similar genetic condition.

Oil shale in situ conversion processing by the downhole burner heating technology (DBHT) has been technically proven as a field pilot project in the Songliao Basin, Northeast China. In this study, the three-dimensional numerical simulations of oil shale in situ pyrolysis with the hexagonal well pattern were conducted based on the idea of DBHT and the actual oil shale reservoir in Songliao Basin to examine the temperature field and thermal processes. The effects of different well spacings (30, 35, 40, and 45 m), gas injection rates (5, 10, 15, and 20 m s−1), and fracture spacings (2.5 and 3.5 m) on the thermal evaluation process were analyzed. The relative energy efficiency and economic viability of operating an oil shale in situ retort in various cases were evaluated. The results showed that increasing well spacing could enlarge the thermal field and improve the ultimate hydrocarbon production of oil shale, but the excessive well spacing caused the heating time to be too long. An increase in the gas injection rate can significantly boost heat transmission efficiency. The energy efficiency comparison of various cases showed that smaller well spacing was conducive to making full use of energy. The results of economic efficiency estimation indicated that a high recovery of shale oil (>80%) would be very difficult to be made with economy, but optimal conditions can be developed in some cases, determined mainly by the price of shale oil. We anticipate that this study can provide new ideas for designing the oil shale in situ conversion processing.

Abstract: Gas-bearing volcanic reservoirs have been found in the deep Songliao Basin, China. Choosing proper interpretation parameters for log evaluation is difficult due to complicated mineral compositions and variable mineral contents. Based on the QAPF classification scheme given by IUGS, we propose a method to determine the mineral contents of volcanic rocks using log data and a genetic algorithm. According to the QAPF scheme, minerals in volcanic rocks are divided into five groups: Q(quartz), A (Alkaline feldspar), P (plagioclase), M (mafic) and F (feldspathoid). We propose a model called QAPM including porosity for the volumetric analysis of reservoirs. The log response equations for density, apparent neutron porosity, transit time, gamma ray and volume photoelectrical cross section index were first established with the mineral parameters obtained from the Schlumberger handbook of log mineral parameters. Then the volumes of the four minerals in the matrix were calculated using the genetic algorithm (GA). The calculated porosity, based on the interpretation parameters, can be compared with core porosity, and the rock names given in the paper based on QAPF classification according to the four mineral contents are compatible with those from the chemical analysis of the core samples.