Stress state analysis in the vicinity of the hydraulic fracturing tool located near the bottom of the well

ABSTRACT

Hydraulic fracturing is a widely used method in the mining industry. In the case of underground workings, the formation of parallel fractures across the borehole axis is of great particular interest for many geotechnical issues, for example, improving the production of coal seam gas or making an impermeable screen in massif to eliminate a water inflow. The article presents a hydofrac tool’s scheme with one inflatable packer promoting the creation of transverse crack. We observe in the laboratory the behaviour of the packer to estimate the displacement of its sliding end when the pressure was applied. These data were used to assess the possibility to form a fracture in the desired direction. In addition, numerical studies of the stress state caused by loading, created with the help of the downhole tool, have been carried out. Analysis of parameters necessary for the formation of an initial crack on the borehole wall is presented. Results show that the using of the borehole tool equipped with an anchoring module allows to create conditions for the appearance of a transverse initiating crack. It has been established that a decrease in the length of the anchor leads to an increase in the tensile axial stresses.

KEYWORDS:

• Hydraulic fracturing
• underground workings
• borehole
• downhole tool
• anchor
• mathematical modelling

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by RFBR and Novosibirsk region according to the research project № 17-45-540686.