STUDY OF HYDRAULIC FRACTURING OF AN X-SHAPED SYSTEM OF BOREHOLES IN LABORATORY CONDITIONS
DOI:
https://doi.org/10.25635/2313-1586.2023.02.047Keywords:
Hydraulic fracturing, laboratory experiment, test bench, physical modeling, fracture, stress state, computed tomographyAbstract
The paper presents the results of laboratory studies of the development of a hydraulic fracture created in two intersecting boreholes in a non-uniform stress field. The experiment was carried out in artificial cubic blocks of sandcrete, as well as its mixture with a 2 mm coal fraction. The boreholes were drilled without percussion, one of them was vertical. To supply the working fluid to the resulting X-shaped loading interval, a special tool with compression packers made of polyurethane was used.
The internal structure of the blocks and the trajectories of the formed cracks were studied by the method of computed tomography, based on the attenuation of X-ray radiation from rocks and inclusions of different density. After hydraulic fracturing was completed, the opening of fractures in various materials was estimated, as well as particular features of its propagation depending on the geometric parameters of the problem and the compressive stress field.
It has been established that in a uniform stress field, boreholes are highly likely to be united by a single longitudinal fracture located in a plane intersecting the axes of the boreholes, regardless of the angle between them.
In the case of the presence of the maximum compressive stress directed perpendicular to this plane, in stronger blocks a fracture is formed on the wall of one of the boreholes in the direction of this stress. In sandcrete blocks with the addition of coal fraction, the boreholes are also connected by a single fracture; however, with an increase in the distance between them, the fracture is reoriented in the direction of the maximum compressive stress.
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