Negative values of contact angle cosine lead to negative capillary pressure at the oil-water interface in pores, which makes the pore unswept by water during waterflooding [19; 20]. All these factors result in the alteration of relative permeability curves, which is well described by several researchers [21; 22]. Generally, oil-wetness leads to lower oil permeability at a given saturation, a higher value of residual oil saturation, and an intersection point shift to higher water saturation values. Thus, the wettability of oil-containing carbonate rock should be altered to the water-wet state. However, in gas reservoirs, a hydrophobic or gas-wetting state in the near well-bore zone is expected [23; 24] to reduce liquid mobility. Wetthality alteration is usually achieved by using surface active agents (surfactants). A huge number of papers are devoted to surfactant-assisted wettability alteration. An excellent review of recent works was given by [PERSON] et al. [25]. Cationic surfactants are known to cause the highest degree of wettability alteration. The possible mechanism includes ionic pairing between positively charged ionic headgroup and negatively charged carboxylic groups of adsorbed oil compounds with its following desorption [26]. Desorbed oil compounds are then solubilized in surfactant's micelles, and this process does not allow such compounds to adsorb again [27]. However, surfactants themselves can also adsorb on the rock surface and cause wettability alteration to both hydrophobic or hydrophilic state, depending on the type of layer which is formed on the surface [28; 29]. Therefore, the process of surfactant-induced wettability alteration is very complex and requires thorough investigation for each specific case. Chelating agents (CA) are a novel class of reagents, which has recently been investigated as promising EOR and well-stimulation reagents. These chemicals also alter wettability of carbonate minerals at moderate or high temperatures [30; 31]. The positive effect of CAs on oil recovery was demonstrated at the core scale several times [32; 33]. Calcium or magnesium ions leaching from the surface are believed to be the reason for wettability alteration by CAs [34]. Therefore, the surface of the carbonate becomes more negatively charged, which leads to the spontaneous desorption of negatively charged oil constituents. The presence of surfactants, such as crucamidopropylbetaine [35; 36] or ethoxylated quaternary ammonium Gemini surfactant [37; 38], enhanced wettability alteration by CAs. Application of CAs as well-stimulation fluids is based on their ability to dissolve carbonate minerals, which are usually insoluble in water by surface complexation [39]. CAs were proposed for the stimulation of high-temperature wells [40], which are problematic for the use of conventional HCl-containing fluids. Low corrosivity, low reaction rate, and a good compatibility with crude oil ensured the applicability of CAs. It should be noted that dynamic wettability alteration, i.e., desorption of oil components from pore walls during treatment, and eventual water-wetness play a crucial role in well stimulation effectiveness [41]. The effect of hydrochloric acid on carbonate rock wettability is widely known [42]; however, the wettability alteration of hydrophobic carbonate rock by surfactant-containing solutions of CAs has not been studied thoroughly. 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. Ambient conditions, which are the best choice for routine experiments, do not represent well conditions properly. All these circumstances hinder comparison of results obtained by different researchers and their application for the development of CAs-based well stimulation fluids.