Abstract
Directional rupture is one of the most important and common problems in rock breaking engineering. The purpose of directional rock breaking can be effectively realized by using multihole linear codirectional hydraulic fracturing. In this paper, realistic failure process analysis (RFPA) software is used to verify the experimental results of multihole linear codirectional hydraulic fracturing and investigate its basic law. The following results are demonstrated: (1) RFPA software can be very helpful to study the basic law of multihole linear codirectional hydraulic fracturing; (2) the process of multihole linear codirectional hydraulic fracturing can be divided into four stages: water injection boost, fracture initiation, stable fracture propagation, and fracture connection; and (3) multihole linear codirectional hydraulic fractures propagate along the direction of borehole distribution. Multihole codirectional hydraulic fracturing is influenced by the angle between the direction of the hole distribution and maximum principal stress, the difference of the principal stress, and the spacing of the boreholes. The smaller the angle, the difference value of the principal stress, and the hole spacing, the better the multihole codirectional hydraulic fracturing effect.
Highlights
The results indicate the following: (1) When the values of θ are 0°, 15°, and 45°, the initial initiation fractures are mainly affected by the macroscopic in situ stress field and expand along the direction of the maximum principal stress at first
(2) When the value of θ is 15° and 45°, the initial fracture of each borehole expands along the direction of the maximum principal stress under the action of the macroscopic stress field
A numerical simulation method is used to study the basic law of multihole linear codirectional hydraulic cracking
Summary
Directional hydraulic fracturing technology has made a significant difference in the control of coal seam hard top roof [1,2,3,4], the weakening and falling of hard top coal [5, 6], the control of rock burst [7,8,9], gob retaining roadway, and the increased permeability of methane-bearing coal seam and shale oil and gas layer [10,11,12]. Research on fracture initiation and propagation rules of the directional hydraulic fracturing controlled by multiholes is still in the stage of exploration and improvement and needs to be further studied. The more guide holes, the better the effect of directional propagation and the larger the directional propagation range of hydraulic fracturing [23, 24, 29, 30]. Few studies have been conducted on the effects of in situ stress, fracturing hole arrangement, and space between holes on the initiation and propagation of hydraulic fracture. The influence of the layout, number of fracturing holes, and in situ stress on the effect of multihole linear codirectional hydraulic fracturing is studied, which is helpful to guide the engineering practice
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