## 3 Results and Discussion
### Investigation of the Mechanism of Sediment Formation in Sediment-Gelling Compositions
The authors of [15; 16; 17; 18] studied the rheological properties of some developed polymer compositions. These polymeric compositions have been developed as water barriers and sand-reinforcing agents for oil and gas production wells. The influence of various factors on the rheology of compositions was studied, and their changes were evaluated in a wide range of temperatures (25-110 \({}^{\circ}\)C), shear rates (0-500 s\({}^{-1}\)), saline solution percentages (0-15%), types of cross-linking agents and concentrations of (0-3%), and polymer concentrations (6-50%). It has been established that an increase in the shear rate from 0 s\({}^{-1}\) to 100 s leads to a decrease in shear and a decrease in the viscosity of dilute solutions (6-13%) from 25 cP to \(\sim\)3 cP at 80 \({}^{\circ}\)C.  
With regard to statistical analysis of the results of studies of the rheological characteristics of sediment-gelling compositions, as noted in [12], the main disadvantage of technologies using selective sediment-forming reagents is that they do not take into account the physical properties of the working fluids used, which leads to low water isolation of highly permeable aquifers [1] and insufficient impact on the low-permeability oil-bearing layer. Therefore, to determine the injection rates of SGCs in NBHZ, the expected pressures and filtration conditions in porous media and knowledge of the rheological and filtration characteristics of SGCs is necessary. Our study of the rheological properties of SGCs depending on the concentrations of the polymer and alkali and the type of solvent was carried out on the rotational viscometer Reotest 2.1 according to the standard procedure, with thermostating at a temperature of 30 \({}^{\circ}\)C [1]. SGCs of the following composition were taken as samples for the study: ionomer \"L\" or technical PAA of ammonia purification with a molecular weight of 1.35 \(\times\) 10\({}^{6}\); sodium hydroxide (NaOH); and a solvent. The concentration of PAA and NaOH in the SGCs varied from 0.05 to 0.15% and from 0.1 to 0.75%, respectively, and the concentration of the ionomer \"L\" and NaOH changed from 0.075 to 1% and from 0.1 to 1%. As solvents, similar to [1,2], distilled, fresh, sea, formation, and combined formation water were chosen, respectively. On the basis of the experimental data obtained from the viscometer, the flow curves were plotted as a dependence of the shear stress (\(\tau\)) on the shear rate (\(\dot{\gamma}\)). The parameters of this dependence were determined by the methods of mathematical statistics based on the processing of flow curves according to the power law of Ostwald-de Waele [9,13]. It is known that the media, which are characterized by flow curves passing through the origin, are called pseudoplastic, and their rheology is described by the Ostwald-de Waele power model. This model is expressed as follows:  
\[\tau=k\times\dot{\gamma}^{n}, \tag{4}\]  
where \(\tau\) is the shear stress, Pa; \(k\) is the consistency coefficient, Pa-s\({}^{n}\), where the shear rate gradient is s\({}^{-1}\); and n is the current index. The parameters of these dependences, in turn, depend on the concentrations of the alkali and polymer as well as on the temperature. The data obtained are summarized in Table 2.