Modeling of Proppant Distribution During Fracturing of Multiple Perforation Clusters in Horizontal Wells

2021 ◽  
Author(s):  
Konstantin Sinkov ◽  
Xiaowei Weng ◽  
Olga Kresse
Keyword(s):  
Transport Model ◽  
Dynamic Pressure ◽  
Formation Rate ◽  
Network Models ◽  
Fracture Network ◽  
Low Flow ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Pumping Rate ◽  
Proppant Transport

Abstract Uniformity of proppant distribution among multiple perforation clusters affects treatment efficiency in multistage fractured wells stimulated using the plug-and-perf technique. Multiple physical phenomena taking place in the well and perforation tunnels can cause uneven proppant distribution among multiple clusters. The problem has been studied in the recent years with experimental and computational fluid dynamics (CFD) methods, which provide useful insights but are impractical for routine designs. Simplified models that incorporated the proppant transport efficiency (PTE) correlation derived from the CFD results in a hydraulic fracture model have been also presented in literature. In this paper, we present a numerical model that simulates the transient proppant slurry flow in the wellbore, considering proppant transport and settling including bed formation, rate- and concentration-dependent pressure drop, PTE, and dynamic pressure coupling with the hydraulic fractures. The model is efficient and is designed to be an independent wellbore transport model so it can be integrated with any fracture models, including fully 3D and/or complex fracture network models, for practical design optimization. The model predictions are compared and found to agree with previously published studies. Parametric studies demonstrate sensitivity of proppant distribution to grain size, fluid viscosity, and pumping rate for fixed perforation designs. Analysis of the simulation results shows that the dominant cause of uneven proppant distribution is proppant inertia. Possible slurry stratification is less important, except for the cases with relatively low flow rates and near toe clusters. Accordingly, proppant distribution is less sensitive to perforation phasing than to the number of perforations in clusters. Alterations of the number of perforations per cluster within a stage enable achieving more even proppant distribution.

Numerical Simulation Study of Proppant Transport in Cross Fractures

2022 ◽  
Author(s):  
Cong Lu ◽  
Li Ma ◽  
Jianchun Guo
Keyword(s):  
Hydraulic Fracturing ◽  
Transport Model ◽  
Injection Rate ◽  
Natural Fracture ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Natural Fractures ◽  
Fracturing Fluid ◽  
Proppant Transport ◽  
Approach Angle

Abstract Hydraulic fracturing technology is an important means to stimulate unconventional reservoirs, and the placement morphology of proppant in cross fractures is a key factor affecting the effect of hydraulic fracturing. It is very important to study the proppant transport law in cross fractures. In order to study the proppant transportation law in cross fractures, based on the CFD-DEM method, a proppant transport model in cross fractures was established. From the two aspects of the flow field in the fractures and the morphology of the proppant dune, the influence of the natural fracture approach angle, the fracturing fluid viscosity and injection rate on the proppant transport is studied. Based on the principle of hydropower similarity, the conductivity of proppant dune under different conditions is quantitatively studied. The results show that the natural fracture approach angle affects the distribution of proppant and fracturing fluid in natural fractures, and further affects the proppant placement morphology in hydraulic fractures and natural fractures. When the fracturing fluid viscosity is low and the displacement is small, the proppant forms a "high and narrow" dune at the entrance of the fracture. With the increase of the fracturing fluid viscosity and injection rate, the proppant settles to form a "short and wide" placement morphology. Compared with the natural fracture approach angle, the fracturing fluid viscosity and injection rate have a more significant impact on the conductivity of proppant dune. This paper investigated the proppant transportation in cross fractures, and quantitatively analyzes the conductivity of proppant dunes with different placement morphology. The results of this study can provide theoretical guidance for the design of hydraulic fracturing.

scholarly journals Hydraulic Fracturing in Enhanced Geothermal Systems—Field, Tectonic and Rock Mechanics Conditions—A Review

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5725
Author(s):  
Rafał Moska ◽  
Krzysztof Labus ◽  
Piotr Kasza
Keyword(s):  
Hydraulic Fracturing ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Enhanced Geothermal Systems ◽  
Seismic Velocities ◽  
Geothermal Systems ◽  
Principal Stresses ◽  
Pumping Rate ◽  
Work Related ◽  
Stimulation Method

Hydraulic fracturing (HF) is a well-known stimulation method used to increase production from conventional and unconventional hydrocarbon reservoirs. In recent years, HF has been widely used in Enhanced Geothermal Systems (EGS). HF in EGS is used to create a geothermal collector in impermeable or poor-permeable hot rocks (HDR) at a depth formation. Artificially created fracture network in the collector allows for force the flow of technological fluid in a loop between at least two wells (injector and producer). Fluid heats up in the collector, then is pumped to the surface. Thermal energy is used to drive turbines generating electricity. This paper is a compilation of selected data from 10 major world’s EGS projects and provides an overview of the basic elements needed to design HF. Authors were focused on two types of data: geological, i.e., stratigraphy, lithology, target zone deposition depth and temperature; geophysical, i.e., the tectonic regime at the site, magnitudes of the principal stresses, elastic parameters of rocks and the seismic velocities. For each of the EGS areas, the scope of work related to HF processes was briefly presented. The most important HF parameters are cited, i.e., fracturing pressure, pumping rate and used fracking fluids and proppants. In a few cases, the dimensions of the modeled or created hydraulic fractures are also provided. Additionally, the current state of the conceptual work of EGS projects in Poland is also briefly presented.

scholarly journals Review of pseudo-three-dimensional modeling approaches in hydraulic fracturing

2021 ◽  
Author(s):  
Hai T. Nguyen ◽  
Jang Hyun Lee ◽  
Khaled A. Elraies
Keyword(s):  
Hydraulic Fracture ◽  
Oil And Gas ◽  
Three Dimensional ◽  
Network Models ◽  
Fracture Network ◽  
Injection Rate ◽  
Height Growth ◽  
Early Developmental Stage ◽  
Hydraulic Fractures ◽  
Equilibrium Height

AbstractIn the field of hydraulic fracture modeling, the pseudo-three-dimensional (P3D) approach is an efficient and practical computational tool serving as a compromise between two-dimensional and planar three-dimensional models. This review discusses the P3D modeling approach from its early developmental stage in the 1980s to the present. The evolution of P3D modeling is drawn over time based on the major differences in the governing formulation and assumptions considered by each model. The problems of equilibrium height growth and vertical viscous fluid resistance (i.e., non-equilibrium height growth) emphasize the primary differences among these models. Besides, the P3D-based complex fracture network models for shale oil and gas reservoirs accounting for the interaction between preexisting natural fractures and induced hydraulic fractures are discussed. Finally, in the application section, several simulations are reported to demonstrate the validation of the P3D numerical algorithm by comparing it with the Perkins–Kern–Nordgren (PKN) large and small asymptotic solutions, as well as the effect of time-dependent variable injection rates on the hydraulic fracture propagation. The results showed a good matching between P3D and PKN solutions and a significant effect of the wellbore variable injection rate on the evolution of the fracture length.

scholarly journals Slurry flow, gravitational settling and a proppant transport model for hydraulic fractures

2014 ◽  
Vol 760 ◽  
pp. 567-590 ◽  
Author(s):  
E. V. Dontsov ◽  
A. P. Peirce
Keyword(s):  
Boundary Layer ◽  
Approximate Solution ◽  
Hydraulic Fracturing ◽  
Transport Model ◽  
Fluid Velocity ◽  
Spherical Particles ◽  
Hydraulic Fractures ◽  
Gravitational Settling ◽  
Proppant Transport ◽  
Two Dimensional Flow

AbstractThe goal of this study is to analyse the steady flow of a Newtonian fluid mixed with spherical particles in a channel for the purpose of modelling proppant transport with gravitational settling in hydraulic fractures. The developments are based on a continuum constitutive model for a slurry, which is approximated by an empirical formula. It is shown that the problem under consideration features a two-dimensional flow and a boundary layer, which effectively introduces slip at the boundary and allows us to describe a transition from Poiseuille flow to Darcy’s law for high proppant concentrations. The expressions for both the outer (i.e. outside the boundary layer) and inner (i.e. within the boundary layer) solutions are obtained in terms of the particle concentration, particle velocity and fluid velocity. Unfortunately, these solutions require the numerical solution of an integral equation, and, as a result, the development of a proppant transport model for hydraulic fracturing based on these results is not practicable. To reduce the complexity of the problem, an approximate solution is introduced. To validate the use of this approximation, the error is estimated for different regimes of flow. The approximate solution is then used to calculate the expressions for the slurry flux and the proppant flux, which are the basis for a model that can be used to account for proppant transport with gravitational settling in a fully coupled hydraulic fracturing simulator.

Numerical Study on Proppant Transport in Hydraulic Fractures Using a Pseudo-3D Model for Multilayered Reservoirs

SPE Journal ◽  
2021 ◽  
pp. 1-16
Author(s):  
Xi Zhang ◽  
Lifeng Yang ◽  
Dingwei Weng ◽  
Zhen Wang ◽  
Robert G. Jeffrey
Keyword(s):  
Hydraulic Fracture ◽  
Transport Model ◽  
Numerical Study ◽  
Soft Rock ◽  
Injection Pressure ◽  
Field Measurements ◽  
Fracture Plane ◽  
Hydraulic Fractures ◽  
Fracture Aperture ◽  
Proppant Transport

Summary In this paper, we incorporated a kinematic proppant transport model for spherical suspensions in hydraulic fractures developed by Dontsov and Peirce (2014) in a pseudo-3D hydraulic-fracture simulator for multilayered rocks to capture a different proppant transport speed than fluid flow and abridged fracture channel by highly concentrated suspensions. For pressure-driven proppant transport, the bridges made of compact proppant particles can lead to both proppant distribution discontinuity and increased fracture aperture and height because of the higher pressure. The model is applied to growth of a fracture from a vertical well, which can contain thin-bedded intervals and more than one opened hydraulic-fracture interval, because the fracture plane extends in height through layers with contrasts in stress and material properties. Three numerical examples demonstrate that a loss of vertical connectivity can occur among multiple fracture sections, and proppant particles are transported along the more compliant layers. The proppant migration within a narrow fracture in a thin soft rock layer can result in bridging and formation of a proppant plug that strongly limits fluid speed. This generates an increase of injection pressure associated with fracture screenout, and these screenout events can emerge at different places along the fracture. Next, because of the lack of pretreatment geomechanical data, the values of layer stress and leakoff coefficient are adjusted for a field case so that the varying bottomhole pressure and fracture length are in line with the field measurements. This paper provides a useful illustration for hydraulic-fracturing treatments with proppant transport affected by and interacting with reservoir lithological complexities.

Propagation, proppant transport and the evolution of transport properties of hydraulic fractures

2018 ◽  
Vol 855 ◽  
pp. 503-534 ◽  
Author(s):  
Jiehao Wang ◽  
Derek Elsworth ◽  
Martin K. Denison
Keyword(s):  
Preferential Flow ◽  
Fluid Pressure ◽  
Fracture Propagation ◽  
Hydraulic Fractures ◽  
Fracture Aperture ◽  
Fluid Viscosity ◽  
Fracture Conductivity ◽  
Proppant Transport ◽  
Fracture Closure ◽  
Proppant Embedment

Hydraulic fracturing is a widely used method for well stimulation to enhance hydrocarbon recovery. Permeability, or fluid conductivity, of the hydraulic fracture is a key parameter to determine the fluid production rate, and is principally conditioned by fracture geometry and the distribution of the encased proppant. A numerical model is developed to describe proppant transport within a propagating blade-shaped fracture towards defining the fracture conductivity and reservoir production after fracture closure. Fracture propagation is formulated based on the PKN-formalism coupled with advective transport of an equivalent slurry representing a proppant-laden fluid. Empirical constitutive relations are incorporated to define rheology of the slurry, proppant transport with bulk slurry flow, proppant gravitational settling, and finally the transition from Poiseuille (fracture) flow to Darcy (proppant pack) flow. At the maximum extent of the fluid-driven fracture, as driving pressure is released, a fracture closure model is employed to follow the evolution of fracture conductivity with the decreasing fluid pressure. This model is capable of accommodating the mechanical response of the proppant pack, fracture closure of potentially contacting rough surfaces, proppant embedment into fracture walls, and most importantly flexural displacement of the unsupported spans of the fracture. Results show that reduced fluid viscosity increases the length of the resulting fracture, while rapid leak-off decreases it, with both characteristics minimizing fracture width over converse conditions. Proppant density and size do not significantly influence fracture propagation. Proppant settling ensues throughout fracture advance, and is accelerated by a lower viscosity fluid or greater proppant density or size, resulting in accumulation of a proppant bed at the fracture base. ‘Screen-out’ of proppant at the fracture tip can occur where the fracture aperture is only several times the diameter of the individual proppant particles. After fracture closure, proppant packs comprising larger particles exhibit higher conductivity. More importantly, high-conductivity flow channels are necessarily formed around proppant banks due to the flexural displacement of the fracture walls, which offer preferential flow pathways and significantly influence the distribution of fluid transport. Higher compacting stresses are observed around the edge of proppant banks, resulting in greater depths of proppant embedment into the fracture walls and/or an increased potential for proppant crushing.

scholarly journals Fractal Characterization of Complex Hydraulic Fractures in Oil Shale via Topology

Energies ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1123
Author(s):  
Qiang He ◽  
Bo He ◽  
Fengxia Li ◽  
Aiping Shi ◽  
Jiang Chen ◽  
...  
Keyword(s):  
Fractal Dimension ◽  
Stress Ratio ◽  
Fractal Theory ◽  
Horizontal Stress ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Fracture Networks ◽  
Change Rate ◽  
Complex Fracture

The formation of complex fracture networks through the fracturing technology is a crucial operation used to improve the production capacity of tight gas/oil. In this study, physical simulation experiments of hydraulic fracturing were conducted with a true triaxial test system on cubic shale oil samples from the Yanchang Formation, China. The fractures were scanned by CT both before and after the experiments and then reconstructed in 3D. The complexity of fracture networks was investigated quantitatively by the fractal theory with topology. Finally, the effect of the horizontal stress ratio, fluid viscosity, and natural fractures on the complexity of the fracture networks was discussed. The results indicate that the method based on fractal theory and topology can effectively characterize the complexity of the fracture network. The change rates of the fractal dimension (K) are 0.45–3.64%, and the fractal dimensions (DNH) of the 3D fracture network after fracturing are 1.9522–2.1837, the number of connections per branch after fracturing (CB) are 1.57–2.0. The change rate of the fractal dimension and the horizontal stress ratio are negatively correlated. However, the change rate of the fractal dimension first increases and then decreases under increasing fluid viscosities, and a transition occurs at a fluid viscosity of 5.0 mPa·s. Whether under different horizontal stress ratios or fluid viscosities, the complexity of the fracture networks after fracturing can be divided into four levels according to DNH and CB. Complex fracture networks are more easily formed under a lower horizontal stress ratio and a relatively low fluid viscosity. A fracturing fluid viscosity that is too low or too high limits the formation of a fracture network.

Numerical Investigation of Proppant Transport and Placement Along Opened Bedding Interfaces

2021 ◽  
Author(s):  
Jun Xie ◽  
Jizhou Tang ◽  
Sijie Sun ◽  
Yuwei Li ◽  
Yi Song ◽  
...  
Keyword(s):  
Fluid Flow ◽  
Volume Fraction ◽  
Transport Model ◽  
Fluid Velocity ◽  
Fracture Propagation ◽  
Propagation Model ◽  
Fluid Viscosity ◽  
Fracture Width ◽  
Proppant Transport ◽  
Penny Shaped Crack

Abstract Slurry, as a proppant-laden fluid for hydraulic fracturing, is pumped into initial perforated cracks to generate a conductive pathway for hydrocarbon movement. Recently, numerous studies have been done to investigate mechanisms of proppant transport within vertical fractures. However, the distribution of proppant during stimulation becomes much more complicated if bedding planes (BPs), natural fractures (NFs) or other discontinuities pervasively distributed throughout the formation. Thus, how to capture the transport and placement mechanisms of proppant particles in the opened BPs becomes a significant issue. In this paper, we propose a closed-form continuous proppant transport model based on the conservation of total proppant volume and sedimentation of proppant particles. This model enables to integrate with the fluid flow section of a 3-D hydro-mechanical coupled fracture propagation model and then predict the distribution of proppant velocity and slurry volume fraction within a dynamic fracture network. Stokes’ law is applied to determine the sedimentation velocity. In the fracture propagation model, rock deformation is governed by the analytical solution of penny-shaped crack to determine fracture width. Fluid flow is characterized by finite differentiation scheme and then the fluid velocity is obtained. These two parameters above are inputs for the proppant transport model and both slurry viscosity and density are updated in this step. Afterwards, both fracture width and fluid velocity would be altered in the fracture model. Analysis of the proppant distribution within crossing-shaped fracture is conducted to study mechanisms of proppant transport along opened BPs. From our numerical analysis, we find that the distribution of proppant concentration is independent with the fluid viscosity, but highly dependent on the volume fraction of pumping slurry, under a given pumping pressure. Due to the difference of viscosity and proppant volume fraction at locations of upper and lower BPs, we observe that two symmetric BPs are unevenly opened, with different channel length along BP. Moreover, the width of opened upper BP is much smaller than that of opened lower BP as a result of discrepancy of proppant sedimentation. Last but not the least, a criterion of flow bed mobilization is established for dynamically tracking the sedimentation along the BP. Then the effect of different parameters (such as proppant size, proppant density, fluid viscosity, injection rate) on proppant distribution along opened BPs is also studied. Our model fully considers the proppant transport and settlement, proppant bed formation and interaction between fracture and proppant, which helps to predict the influence of proppant during fracturing treatment. Additionally, our model is also capable of dynamically tracking the settlement of proppant along opened BPs.

New Wellbore Proppant Transport Model Improves Prediction of Multiple Fracture Propagation in Horizontal Wells

2021 ◽  
Author(s):  
Konstantin Sinkov ◽  
Kaustubh Shrivastava ◽  
Olga Kresse ◽  
Safdar Abbas ◽  
Egor Knyazev ◽  
...  
Keyword(s):  
Transport Model ◽  
Mutual Influence ◽  
Coupled Model ◽  
Injection Rate ◽  
Diagnostic Methods ◽  
Analytical Models ◽  
Hydraulic Fractures ◽  
Transient Pressure ◽  
Multiple Fractures ◽  
Proppant Transport

Abstract Completion optimization in hydraulic fracturing operations requires understanding the interaction between simultaneously propagating multiple fractures and the distribution of fluid and proppant among the fractures during the treatment. Diagnostic methods often reveal that propagation of fractures within single stage is quite uneven. Nonuniform growth is caused by a complex interplay between fracture mechanics and hydrodynamics of proppant transport in wellbore and perforations. A recently developed numerical model simulates the transient proppant slurry flow in the wellbore, considering proppant transport and settling, including bed formation, fluid rheology, perforation erosion, rate- and concentration-dependent pressure drop, and variable efficiency of proppant transport through perforations. The model is numerically coupled to an advanced fracture simulator that models fracture growth, fluid flow, proppant transport inside complex hydraulic fracture networks, and mechanical interaction between adjacent hydraulic fractures. The coupled model enables comprehensive simulations and captures the mutual influence of the transport of proppant in the wellbore and the propagation of fractures. Integration of the model into the proprietary stimulation-to-production workflow allows leveraging available data and applying the model to optimization of completion strategy and design. The coupled model is shown to agree with the results of analytical models in special limiting cases. It also qualitatively reproduces patterns of proppant distribution observed in the field with the help of various fracturing monitoring techniques. Parametric studies demonstrate that the combined influence of proppant inertia causing higher concentration of proppant in toe clusters, erosion of perforations, and transient pressure response of fractures leads to the nonuniform and transient distribution of the injection rate among fractures. Simulation results show that the nonuniform proppant transport efficiency induced by proppant inertia and broad proppant size distribution can be superposed on the stress shadow effect and lead to the uneven growth of fractures within a stage. The integrated model is efficient and allows routine optimization of fracturing treatment designs. An example of the design optimization illustrating wellbore proppant transport effects on treatment dynamics and showing the value of the coupled wellbore-fractures simulations is also provided.

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