Bed load proppant transport during slickwater hydraulic fracturing: Insights from comparisons between published laboratory data and correlations for sediment and pipeline slurry transport

Journal of Petroleum Science and Engineering

Zhou

Feng

et al. 2020

As proven from field practices in North America and Northwest China, temporary plugging and diverting acid fracturing is an indispensable technology to enhance stimulation effect and hydrocarbon production of complex carbonate reservoirs. It's well-known that the key to the success of this technology lies in creating a temporary plugging within the previously created fractures. Consequently, many scholars have conducted laboratory experiments to investigate the plugging behavior of fibers and particulates. However, the current devices nearly have certain limitations in simulating temporary plugging experiments. Aiming at this problem, this paper introduced the fracture temporary plugging evaluation system with large fracture size, and high-pressure resistance, which can meet the requirement of temporary plugging experiment. In addition, 3D printing technology was used to reproduce the roughness of acid-etched fracture surface, improving the experimental accuracy. Based on the device, a series of experiments were performed to study the effect of carrier fluids type, the injection rate, the fracture width, and the fracture morphology on plugging behavior of fibers and particulates. Experimental results show that the plugging effect of HPG fracturing fluid is better than that of slick water. Moreover, the effect of temporary plugging deteriorates with the decrease of injection rate, which can be attributed to the fact that high injection rate increases the probability of bridging and plugging. When it comes to the fracture width, only fibers have favorable plugging effect under the condition of 2 mm fracture width. However, a single type of temporary plugging agent (only fibers or particulates) cannot achieve effective plugging under the condition of 4 mm fracture width. The combination of fibers and particulates can obtain favorable plugging effect. When the fracture width increases to 6 mm, it's difficult to obtain favorable plugging effect if the diameter of particulates is less than 50% of fracture width. Hence, it is recommended to add big particulates whose diameters are at least 50% of the fracture width to improve the plugging effect. Moreover, the fracture surface morphology affects the formation time of temporary plugging, but does not affect whether temporary plugging is formed or not. This study deepens the understanding the plugging behavior of fibers and particulates within acid-etched fracture and provides fundamental for field treatment design.

Section: The Effect Of Carrier Fluids Typementioning

confidence: 99%

Experimental study on plugging behavior of degradable fibers and particulates within acid-etched fracture

Journal of Petroleum Science and Engineering

Zhou

Feng

et al. 2020

“…The length of a primary fracture in a conventional slot system is generally less than 2 m (e.g., 1.22 m used by Sahai et al [18] and 0.381 m used by Tong and Mohanty [19]), and the length of a secondary fracture is less than 1 m (e.g., 0.19 m used by Tong and Mohanty [19] and 0.9 m used by Pan et al [22]). According to McClure [33], under this condition, finer proppants may travel out of the slot before they settle to the bottom, and a real proppant distribution may not be recorded due to an adequate transport distance. Thirdly, few experiments combined numerical simulations to analyze the experimental results, especially the proppant transport trajectories, which cannot be precisely captured through experimental techniques.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

Energies

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.

“…The mechanism of the proppant from the primary fracture into the secondary fracture was also analyzed. McClure [7] analyzed in detail the formation process of the equilibrium proppant height (EPH). As the proppants settle at the bottom of the fractures, Energies 2020, 13, 4912 2 of 17 the height of the proppant bed gradually grows to EPH during transportation [7].…”

Section: Introductionmentioning

confidence: 99%

“…McClure [7] analyzed in detail the formation process of the equilibrium proppant height (EPH). As the proppants settle at the bottom of the fractures, Energies 2020, 13, 4912 2 of 17 the height of the proppant bed gradually grows to EPH during transportation [7]. The velocity of the mixture of water and proppants above the proppant bed in the fractures is called the equilibrium mixture velocity (EMV) when the EPH is reached.…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2020

Energies

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.