Abstract
The proppant transportation is a typical two-phase flow process in a complex cross fracture network during hydraulic fracturing. In this paper, the proppant transportation in cross fractures is investigated by the computational fluid dynamics (CFD) method. The Euler–Euler two-phase flow model and the kinetic theory of granular flow (KTGF) are adopted. The dimensionless controlling parameters are derived by dimensional analysis. The equilibrium proppant height (EPH) and the ratio of the proppant mass (RPM) in the secondary fracture to that in the whole cross fracture network are used to describe the movement and settlement of proppants in the cross fractures. The main features of the proppant transportation in the cross fractures are given, and several relative suggestions are presented for engineering application in the field. The main controlling dimensionless parameters for relative EPH are the proppant Reynolds number and the inlet proppant volume fraction. The dominating dimensionless parameters for RPM are the relative width of the primary and the secondary fracture. Transportation of the proppants with a certain particle size grading into the cross fractures may be a good way for supporting the hydraulic fractures.
Highlights
Unconventional energy resources such as low permeability, shale, and tight oil and gas reservoirs account for a larger and larger proportion in the present oil and gas exploration [1,2,3,4]
McClure [7] analyzed in detail the formation process of the equilibrium proppant height (EPH)
The proppants first stack at a certain distance after entering entering the primary fracture
Summary
Unconventional energy resources such as low permeability, shale, and tight oil and gas reservoirs account for a larger and larger proportion in the present oil and gas exploration [1,2,3,4]. The hydraulic fractures are the main flow channel for these fluid resources due to the natural poor flow capability of the porous media, and it is of great importance to know the effective support range and the distribution of proppants in cross fractures. Alotaibi and Miskimins [5] designed a cross fracture system with one primary fracture, three secondary fractures, and two tertiary fractures. They found that the proppants were able to flow into the subsidiary fractures and form a proppant bed. The transportation distance of the proppant in the subsidiary fractures is important for the production. The mechanism of the proppant from the primary fracture into the secondary fracture was analyzed. As the proppants settle at the bottom of the fractures, Energies 2020, 13, 4912; doi:10.3390/en13184912 www.mdpi.com/journal/energies
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