Facilitation Effects of Acidic Chlorinated Salts on Reservoir Unblocking During In Situ Conversion of Huadian Oil Shale  
[PERSON]  
1 School of Engineering and Technology, China University of Geosciences, Beijing 100083, China; [EMAIL_ADDRESS] (S.X. ); [EMAIL_ADDRESS] (H.W. )1 School of Engineering and Technology, China University of Geosciences, Beijing 100083, China; [EMAIL_ADDRESS] (S.X. ); [EMAIL_ADDRESS] (H.W. and reduce the fluidity of crude oil. Thus, the large amount of precipitated asphaltene products and its thickening effect on the pyrolysis oil during the in situ conversion can seriously affect the permeability of the reservoir and cause reservoir blockage [16]. Similar phenomena have been reported multiple times in studies of laboratory experiments and field tests, which have become one of the important challenges for OS extraction. For example, [PERSON] et al. conducted core-scale experiments and found that blockage of fluid channels by heavy oil significantly affected core permeability and oil recovery [17; 18]. [PERSON] et al. performed high-temperature and high-pressure simulation experiments of OS and found that during the migration of pyrolysis products, the heavy components continuously condensed and blocked at the back location of the sample due to the low temperature (~200 \({}^{\circ}\)C). These phenomena resulted in a decrease in core permeability, leading to a significant increase in injection pressure and severely limiting pyrolysis oil production [19]. In addition, similar phenomena were observed in the pilot field tests of OS extraction conducted in the Songliao Basin, China, which seriously affected the in situ conversion process and the recovery of pyrolysis products [20]. In recent years, researchers have committed to using acid catalysts to promote the pyrolysis of kerogen and upgrade oil products, which may offer a potential solution for reservoir blockage during in situ conversion of OS. Previous studies have found that the acid catalytic metal chloride (SnCl\({}_{2}\), MoCl\({}_{5}\), ZnCl\({}_{2}\)) can promote the organic conversion to oil and gas at 350 \({}^{\circ}\)C and affects the activation energy of the solid residues [21]. The coupling effects between montmorillonite and CoCl\({}_{2}\cdot\)6H\({}_{2}\)O promoted the formation of shale oil, leading to a prominent reduction in the kerogen decomposition temperature and a decrease in the apparent activation energy [22]. Furthermore, phosphotungstic acid/boehmite (PWA/B) is used to catalyze OS pyrolysis, where the quality of catalyzed pyrolyzates could be upgraded distinctly [23]. Meanwhile, the addition of FeCl\({}_{3}\) increased the yield of subcritical water-extracted shale oil by 58.5% within 20 h and reduced the time required for maximum shale oil yield by 43%. The acidic FeCl\({}_{3}\) solution induced the decomposition of carbonate minerals in the OS matrix, providing additional mass transfer channels for the migration of bitumen products [24]. In addition, researchers prepared a catalyst named SO\({}_{3}\)H-SBA-15 by sulfonic acid grafting of existing mineral-based catalysts, which could reduce the activation energy of OS catalytic pyrolysis and promote the conversion of OS, and there was a significant effect of the amount of catalyst acid on the amount of oil produced [25]. In addition to externally added catalysts, different associated minerals in the OS matrix also play various roles in the pyrolysis of kerogen. The reported research shows that montmorillonite and gypsum promote the formation of oil products and minimize the formation of residue products, and pyrite can promote the pyrolysis and cracking of organic matter [26; 27]. However, some reported results show that carbonates have different effects on the pyrolysis of kerogen. [PERSON] et al. found that calcite appears to inhibit the formation of oil during retorting [26]. However, [PERSON] et al. and [PERSON] et al.