Laboratory Testing on Proppant Transport in Complex-Fracture Systems

et al. 2020

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.

Section: Resultsmentioning

confidence: 98%

Proppant Transportation in Cross Fractures: Some Findings and Suggestions for Field Engineering

et al. 2020

“…They also pointed out that, rather than the fluid velocity, the degree of dune development in the primary slot heavily determines the proppants into the secondary and tertiary slots. Li et al [21] and Pan et al [22] extended previous conclusions and formulated correlations of dune geometries using a variety of parameters such as fluid viscosity, sand concentration, and branch angle. Furthermore, Ma et al [23] characterized slurry velocity field in the slot configuration to quantify the relationships between the governing parameters which affect proppant placement efficiency through intersections.…”

Section: Introductionmentioning

confidence: 86%

“…As slickwater fracturing was applied widely to the stimulation of shale-gas formations, much attention was paid to the proppant transport in the complex fracture network. Similarly, proppant transport in the fracture network is performed in a configuration in which multiple slots are joined together [18][19][20][21][22][23]. There are two types of slot intersection patterns for the experimental fracture network.…”

Section: Introductionmentioning

confidence: 99%

“…There are two types of slot intersection patterns for the experimental fracture network. One is the T-shaped pattern, in which the branch slot, served as the secondary fracture, intersects orthogonally with the primary slot, taken as the primary fracture [18,20]; the other is the V-shaped pattern, in which the secondary slot intersects with the primary slot at a specified angle [19,[21][22][23].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Experimental and Numerical Study on Proppant Transport in a Complex Fracture System

et al. 2020

Slickwater fracturing can create complex fracture networks in shale. A uniform proppant distribution in the network is preferred. However, proppant transport mechanism in the fracture network is still uncertain, which restricts the optimization of sand addition schemes. In this study, slot flow experiments are conducted to analyze the proppant placement in the complex fracture system. Dense discrete phase method is used to track the particle trajectories to study the transport mechanism into the branch. The effects of the pumping rate, sand ratio, sand size, and branch angle and location are discussed in detail. Results demonstrate that: (1) under a low pumping rate or coarse proppant conditions, the dune development in the branch depends on the dune geometry in the primary fracture, and a high proportion of sand can transport into the branch; (2) using a high pumping rate or fine proppants is beneficial to the uniform placement in the fracture system; (3) sand ratio dominates the proppant placement in the branch and passing-intersection fraction of a primary fracture; (4) more proppants may settle in the near-inlet and large-angle branch due to the size limit. Decreasing the pumping rate can contribute to a uniform proppant distribution in the secondary fracture. This study provides some guidance for the optimization of proppant addition scheme in the slickwater fracturing in unconventional resources.

“…low-viscosity fluid. Moreover, experiments on proppant transport in fracture networks [10,12,13] were mostly carried out to answer the debatable question of whether slickwater can transport proppants into secondary fractures or not. In addition to experimental research, computational fluid dynamics (CFD) methods were widely used to study proppant transport in fractures.…”

mentioning

confidence: 99%

Calibration of the Interaction Parameters between the Proppant and Fracture Wall and the Effects of These Parameters on Proppant Distribution

Liu

2020

Saltation and reputation (creep) dominate proppant transport rather than suspension during slickwater fracturing, due to the low sand-carrying capacity of the slickwater. Thus, the interaction parameters between proppants and fracture walls, which affect saltation and reputation, play a more critical role in proppant transport. In this paper, a calibration method for the interaction parameters between proppants and walls is built. A three-dimensional coupled computational fluid dynamics-discrete element method (CFD-DEM) model is established to study the effects of the interaction parameters on proppant migration, considering the wall roughness and unevenly distributed diameters of proppants. The simulation results show that a lower static friction coefficient and rolling friction coefficient can result in a smaller equilibrium height of the sand bank and a smaller build angle and drawdown angle, which is beneficial for carrying the proppant to the distal end of the fracture. The wall roughness and the unevenly distributed diameter of the proppants increase the collision between proppant and proppant or the wall, whereas the interactions have little impact on the sandbank morphology, slightly increasing the equilibrium height of the sandbank. low-viscosity fluid. Moreover, experiments on proppant transport in fracture networks [10,12,13] were mostly carried out to answer the debatable question of whether slickwater can transport proppants into secondary fractures or not. In addition to experimental research, computational fluid dynamics (CFD) methods were widely used to study proppant transport in fractures. The most common approach for modeling proppant transport is the Eulerian-Eulerian method in which the interaction between the particles and fluid is fully coupled [14][15][16][17][18][19]. In a recent study, Han et al. [20] used the Eulerian granular model to track proppant movement in various fractures for a better understanding of how proppant transport is influenced by fracture viscosity, proppant density, and pump rate. The second method is the Eulerian-Lagrangian model, which tracks individual particle movement with time and location with the Lagrangian framework and describes fluid flow with the Eulerian framework [21][22][23]. The discrete element method (DEM) [24] is a useful tool to simulate the behavior of particles, and it can be coupled with CFD to model the interaction between particles and the surrounding fluid. In recent years, the coupled CFD-DEM model was used to study fracturing fluid flow in fractures for its advantages of considering proppant-proppant, proppant-boundary, and proppant-fracturing fluid interactions [25][26][27][28][29][30][31][32]. Blyton et al. [26] first used the coupled CFD-DEM model to simulate the motion of particles flowing with a fluid between fracture walls, and the simulations individually determined that particle trajectories such as particle-to-particle and particle-to-wall collisions occur. Zhang et al. [28] used a two-dimensional coupled CFD-DEM model to study ...