In the last decade, the negative impact of hydraulic fracturing fluids on the reservoir properties has been noted, which has led to the new trend of improving characteristics and developing new hydraulic fracturing fluids. As an alternative option to the traditionally used cross-linked fluids based on guar solution, in our laboratory we have tested fluids having a branched spatial structure, which allowed them to hold and transport proppants, despite the low viscosity of this kind of fluids (100–200 mPa·s measured at 100 s⁻¹). Existing theoretical models of hydraulic fracture (HF) propagation have some limitations in predicting the influence of fracturing fluids on reservoir properties. Unfortunately, in situ experiments in the target reservoir are difficult and expensive. Thus, laboratory experiments can be considered as a reasonable alternative for testing new fluids, since they can provide comprehensive information about the properties of the created HF before the application of a new hydraulic fracturing technique in the field conditions. This paper presents the results of an experimental study of hydraulic fracturing of granite samples in laboratory conditions. The injection of water- and oil-based unconventional fracturing fluids was performed to study the influence of fluid rheology on the dynamics of the hydraulic fracture propagation process and parameters of the created HF. We have found that the fracturing fluid viscosity affects the parameters of the created HF, such as aperture, propagation velocity, breakdown pressure, and HF surface tortuosity. The obtained relationships can be taken into account for Hydraulic Fracture modelling, which may increase the efficiency of the hydraulic fracturing in the field conditions.

: Despite their efficiency, existing methods to dispose of drilling fluids used in the construction of oil and gas wells (chemical treatment of spent solutions, thermal method, thickening) are often expensive and unsustainable. Basidiomycota are natural xylotroph destructors that process lignocellulosic substrate – one of the most stable biopolymers in nature. Prospects for using enzyme preparations based on Basidiomycota as biodestructors of organic substances are evident due to the high efficiency and zero-waste production. The aim was to obtain an enzyme preparation based on the Trametes hirsute MT-17.24 Basidiomycota strain and evaluate its ability to biodegrade polyanionic cellulose, used as a viscosifier for drilling fluids in the construction and repair of oil and gas wells. Screening of cellulase activity of the following strains was carried out: Fomitopsis pinicola MT-5.21, Fomes fomentarius MT-4.05, Lactarius necator, Schizophyllum commune MT-33.01, Trametes versicolor It-1, Trametes hirsute MT-17.24, Trametes hirsuta MT-24.24. To obtain the enzyme preparation, the T. hirsuta MT-17.24 strain was selected, which demonstrated the highest coefficient of cellulase activity (10.9). A medium for solid-phase cultivation of this strain was selected. Enzymatic activity of the enzyme preparation was studied on a model drilling fluid. A 10-hour experiment showed that the use of a 1% enzyme preparation leads to a decrease in the plastic viscosity of the drilling fluid from 16 to 8 mPa·s. The research results demonstrate the efficiency of enzyme preparations based on Basidiomycota in the biodestruction of polyanionic cellulose.