“…The common method to improve the permeability of low-permeability reservoirs is reservoir stimulation, including the hydraulic fracturing method [ [10] , [11] , [12] , [13] , [14] ], pressure-relief method [ [15] , [16] , [17] ], chemical stimulation method [ [18] , [19] , [20] ], high/low-thermal shock method [ 21 , 22 ] and blasting method [ 23 , 24 ], which have been applied in unconventional oil/gas development fields. For the LPSUD, reservoir stimulation methods of blasting-enhanced permeability (BEP) [ 25 , 26 ] and acidizing-enhanced permeability (AEP) [ [27] , [28] , [29] , [30] ] have carried out several pilot tests in China and the injection rate of wells has improved by 118% [ 31 ]. Fig.…”
“…The common method to improve the permeability of low-permeability reservoirs is reservoir stimulation, including the hydraulic fracturing method [ [10] , [11] , [12] , [13] , [14] ], pressure-relief method [ [15] , [16] , [17] ], chemical stimulation method [ [18] , [19] , [20] ], high/low-thermal shock method [ 21 , 22 ] and blasting method [ 23 , 24 ], which have been applied in unconventional oil/gas development fields. For the LPSUD, reservoir stimulation methods of blasting-enhanced permeability (BEP) [ 25 , 26 ] and acidizing-enhanced permeability (AEP) [ [27] , [28] , [29] , [30] ] have carried out several pilot tests in China and the injection rate of wells has improved by 118% [ 31 ]. Fig.…”
“…1 Most of the existing sandstone acid rock reaction mathematical models are based on the study of sandstone reaction kinetics, 12 and according to the treatment of sandstone reservoir mineral composition, the acid rock reaction mathematical models can be roughly classified into four major categories: set total parameter model, 13 one acid and two minerals model, two acids and three minerals model, 14 and geochemical model. 15,16 As for the numerical methods, sandstone acid flow reaction models mostly adopt the finite difference method. 17 In 1991, Bryant et al 18 first introduced the secondary reaction into the mathematical model of acid rock reaction, considering the reaction of fluorosilicic acid with silicate, and established a more mature and nowadays more commonly used mathematical model of two-acid and three-mineral sandstone reaction.…”
Section: Introductionmentioning
confidence: 99%
“…In more than half a century of research, experts at home and abroad have been devoted to constructing mathematical models that can truly reflect the acid rock reaction process in sandstone reservoirs 1 . Most of the existing sandstone acid rock reaction mathematical models are based on the study of sandstone reaction kinetics, 12 and according to the treatment of sandstone reservoir mineral composition, the acid rock reaction mathematical models can be roughly classified into four major categories: set total parameter model, 13 one acid and two minerals model, two acids and three minerals model, 14 and geochemical model 15,16 . As for the numerical methods, sandstone acid flow reaction models mostly adopt the finite difference method 17 …”
Acidification, as an effective measure to remove blockages and restore oil well productivity, has received widespread concern. However, conventional acid systems can only be used to unblock near‐wellbore zones and are difficult to act on far‐wellbore reservoirs. In this article, scanning electron microscope, energy‐dispersive X‐ray spectroscope, and X‐ray diffractometer were used to analyze the blockages in the Bai 823 well area, and it was determined that their main components were CaCO3 and FeCO3, which provided the basis for the construction of the unblocking formula. Then, the acid dissolution experiments on the plugging materials showed that the dissolution rate of 10% HCl can reach more than 85% for the scale sample; the acid dissolution experiments on the rock sample showed that the autogenous mud acid has better dissolution performance and better retardation performance for the rock sample, and the effective action time is longer, so it can be used for deeper unplugging of the reservoir. Finally, the process parameters such as the optimal acid concentration, acid dosage, and discharge volume were optimized by establishing the fracture‐matrix acid flow reaction model. Research results indicate that the autogenous mud acid can act on the blockage in the far‐wellbore area to improve the acidification effect.
“…As most studies are focused on CAs' application for the EOR, duration of experiments is on the order of several days or even months, whereas a residence time of acid during the normal well stimulation is about 3-6 h [43]. In addition, core samples are usually aged in dead crude oil, which is unique for every field, therefore a unique wettability state occurs in every study.…”
Chelating agents’ application for well stimulation is gaining more and more interest, as they can perform under harsh conditions. However, the mutual influence of surfactants and chelating agents on the wettability alteration of hydrophobic carbonate rock under conditions of high-temperature well stimulation is relatively unexplored. This paper aims to study interfacial processes on the surface of hydrophobic rock in the presence of the EDTA-based chelating agent and surfactants of different classes. Cationic (cetyltrimethylammonium bromide, CTAB, and cetylpyridinium bromide, CPB), anionic (sodium dodecyl sulfate, SDS), and amhoteric (alkyldimethyl aminooxide, AO) surfactants were studied. Wettability alteration of model hydrophobic rock was studied under conditions specific to well stimulation. It was shown that chelating agent (CA) alone and its mixture with SDS could not lead to sufficient wettability alteration. CTAB, CPB, and AO were able to change the wettability effectively. A synergistic effect between CA and these surfactants was observed and a possible mechanism was proposed. AO was selected as the most promising surfactant. The influence of surfactant on the CA’s dissolution capacity towards carbonate rock was investigated; dissolution capacity strongly depends on wettability alteration. Finally, the effect of CA, AO, and their mixture on the wettability of aged reservoir rock was studied and the absence of negative effects was proven.
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