Numerical Solution of Sand Transport in Hydraulic Fracturing

Abstract Hydraulic fracturing stimulation of unconventional wells employing large volumes of sand in low viscosity fluids provides propped fracture conductivity in less than 25% of the created fracture area, primarily because of poor sand transport mechanics. The remaining unpropped area is at best only marginally productive using the conventional sand/slickwater hydraulic fracturing process alone. Near-neutrally buoyant proppants (NBPs, ASG 1.055) have proven to be highly effective in accessing production from fracture area that is otherwise left unpropped. Fracture models illustrate the propped fracture area of designs incorporating NBPs is improved to over 85% of the created fracture area. Production simulations of typical slickwater and sand frac designs supplemented with NBPs at 3% by weight of sand distributed evenly throughout the slurry stages show cumulative production increases of 20% to greater than 50% compared to the large volume slickwater/sand treatments without NBPs. Efforts have been directed to justification of the incremental expense involved with the NBP applications and assessment of the associated value-added economic metrics, including the value of the realized incremental production vs. time, the payback time for recovery of the incremental costs, and Return on Investment (ROI). For example, in a 2018 trial of NBP wells in the Middle Bakken formation of North Dakota, the production uplift observed for NBP wells achieved payback of the incremental costs in an average of 26 days; the 1-year cumulative oil production of the NBP wells averaged 69,632 barrels greater than control wells, resulting in a 25% uplift compared to the offset control wells. The Year 1 Return on Investment (ROI) for the drilling and completion costs of the first Middle Bakken well with NBP was 97% versus 64% for the sand-only control wells. Controlled multi-stage horizontal completions of wells with sand-only have been evaluated against wells utilizing NBPs in the application have been executed within several unconventional plays, including the Permian and Williston basins. The performance of the NBP wells have consistently validated the production uplift predictions of the production simulation models. The case studies analyzed herein expand the economic assessment of the NBP stimulation designs by including production analyses quantitative comparison of Net Present Value, production decline rates, and projected EURs of the NBP wells and non-NBP offset wells.

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Development and implementation of a numerical solution for modelling the hydraulic fracturing process as part of an integrated geomechanical modelling system

10.3997/2214-4609.202150101 ◽

2021 ◽

Author(s):

M.S Eryashkin ◽

F.F Khusnutdinov ◽

S.V Chaynikov ◽

E.V Danilov ◽

A.V Abramovich ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Numerical Solution ◽

Fracturing Process ◽

Modelling System

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Impacts of Fracture Roughness and Near-wellbore Tortuous on Proppant Transport Within Hydraulic Fractures

10.21203/rs.3.rs-1118961/v1 ◽

2021 ◽

Author(s):

Di Wang ◽

Bingyang Bai ◽

Bin Wang ◽

Dongya Wei ◽

Tianbo Liang

Keyword(s):

Hydraulic Fracturing ◽

Analytical Model ◽

Volume Fraction ◽

Transport Model ◽

Sand Transport ◽

Hydraulic Fractures ◽

Fracture Roughness ◽

Transport Velocity ◽

Sand Bank ◽

The Impact

Abstract For unconventional reservoirs hydraulic fracturing design, a greater fracture length is a prime factor to optimize. However, core observation results from Hydraulic Fracturing Test Site (HFTS) show the propped fractures are far less or shorter than expected which suggests the roughness and tortuous of hydraulic fractures are crucial to sand transport. In this study a transport model of sands is first built based on experimental measurements on the height and transport velocity of sand bank in fractures with predetermined width and roughness. The fracture roughness is quantified by using surface height integral. Then, three-dimensional simulations are conducted with this modified model to further investigate the impact of fractures tortuous on sand transport, from which an analytical model is established to estimate the propped length of hydraulic fractures at a certain pumping condition. Experiments results show that height of sand bank in roughness fracture is 20-50% higher than that in smooth. The height of sand bank decreases with the reduction of slurry velocity and increases with the sand diameters increasing. Sand sizes do little effect on the transport velocity of sand bank but the increase in slurry velocity and sand volume fraction can dramatically enhance the migration velocity of sand bank. The appearance of tortuous decreases the horizontal velocity of suspended particles and results in a higher sand bank compared with that in straight fractures. When the sand bank gets equilibrium at the tortuous position, it is easy to produce vortices. So, there is a significant height of sand bank change at the tortuous position. Moreover, sand plugging can occur at the entrance of the fractures, making it difficult for the sand to transport deep in fractures. This study explains why the propped length of fractures in HFTS is short and provides an analytical model that can be easily embedded in the fracturing simulation to fast calculate dimensions of the propped fractures network to predict length and height of propped fractures during fracturing.

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