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

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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An Analytical Model for Fracture Initiation from a Particular Radial Borehole in Hydraulic Fracturing Guided by Multiradial Boreholes

Geofluids ◽

10.1155/2021/6657788 ◽

2021 ◽

Vol 2021 ◽

pp. 1-18

Author(s):

Yuxin Chen ◽

Yunhong Ding ◽

Chong Liang ◽

Dawei Zhu ◽

Yu Bai ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Analytical Model ◽

Fracture Initiation ◽

Hydraulic Fractures ◽

Large Radius ◽

Intersection Angle ◽

Biot Coefficient ◽

Depth Difference ◽

Wellbore Pressure ◽

The Impact

Radial drilling-fracturing, the combination of the hydraulic fracturing and radial borehole, is a technology that can guide the hydraulic fractures to directionally propagate and efficiently develop low permeability reservoir. In this paper, an analytical model of two radial boreholes (a basic research unit) is established to predict fracture initiation pressure (FIP) from one particular radial borehole and the interference between radial boreholes when the hydraulic fracturing is guided by multi-radial boreholes. The model is based on the stress superposition principle and the maximum tensile stress criterion. The effects of in situ stress, wellbore pressure, and fracturing fluid percolation are considered. Then, sensitivity analysis is performed by examining the impact of the intersection angle between radial boreholes, the depth difference between radial boreholes, the radius of radial boreholes, Biot coefficient, and the number of radial boreholes. The results show that FIP declines with the increase of radial boreholes number and the decrease of intersection angle and depth difference between radial boreholes. Meanwhile, the increase of radial borehole number and the reduction of intersection angle and depth difference strengthen the interference between radial boreholes, which conduce to the formation of the fracture network connecting radial boreholes. Besides, FIP declines with the increase of radial borehole radius and the decrease of Biot coefficient. Large radius and low Biot coefficient can enlarge the influence range of additional stress field produced by radial boreholes, enhance the mutual interference between radial boreholes, and guide fracture growth between radial boreholes. In hydraulic fracturing design, in order to reduce FIP and strengthen the interference between radial boreholes, the optimization design can be carried out by lowering intersection angle, increasing radius and number of boreholes, and reducing the depth difference between boreholes when the conditions permit. The research clarifies the interference between radial boreholes and provides the theoretical basis for optimizing radial boreholes layout in hydraulic fracturing guided by multi-radial boreholes.

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Digital Fracture Characterization at Hydraulic Fracturing Test Site HFTS-Midland: Fracture Clustering, Stress Effects and Lithologic Controls

10.2118/204174-ms ◽

2021 ◽

Author(s):

Debotyam Maity ◽

Jordan Ciezobka

Keyword(s):

Hydraulic Fracturing ◽

Hydraulic Fracture ◽

Test Site ◽

Fracture Morphology ◽

Rock Properties ◽

Hydraulic Fractures ◽

Strong Positive Correlation ◽

Fracture Roughness ◽

Fracture Characterization ◽

Stress Effects

Abstract In this case study, we apply a novel fracture imaging and interpretation workflow to take a systematic look at hydraulic fractures captured during thorugh fracture coring at the Hydraulic Fracturing Test Site (HFTS) in Midland Basin. Digital fracture maps rendered using high resolution 3D laser scans are analyzed for fracture morphology and roughness. Analysis of hydraulic fracture faces show that the roughness varies systematically in clusters with average cluster separation of approximately 20' along the core. While isolated smooth hydraulic fractures are observed in the dataset, very rough fractures are found to be accompanied by proximal smoother fractures. Roughness distribution also helps understand the effect of stresses on fracture distribution. Locally, fracture roughness seems to vary with fracture orientations indicating possible inter-fracture stress effects. At the scale of stage lengths however, we see evidence of inter-stage stress effects. We also observe fracture morphology being strongly driven by rock properties and changes in lithology. Identified proppant distribution along the cored interval is also correlated with roughness variations and we observe strong positive correlation between proppant concentrations and fracture roughness at the local scale. Finally, based on the observed distribution of hydraulic fracture properties, we propose a conceptual spatio-temporal model of fracture propagation which can help explain the hydraulic fracture roughness distribution and ties in other observations as well.

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Proppant Transport in Hydraulic Fractures by Creating a Capillary Suspension

10.2118/208624-stu ◽

2021 ◽

Author(s):

Ayomikun Bello

Keyword(s):

Hydraulic Fracturing ◽

Significant Risk ◽

High Viscosity ◽

Hydraulic Fractures ◽

Main Task ◽

Low Viscosity ◽

Fracturing Fluids ◽

Geological Conditions ◽

Fracture Development ◽

The Impact

Abstract Slick water fracturing fluids with high viscosity and minimal friction pressure losses are commonly employed in hydraulic fracturing nowadays. At the same time, high injection rates can be used to perform hydraulic fracturing to get the calculated fracture sizes. The conventional algorithm for conducting a standard proppant hydraulic fracturing includes performing a pressure test using a linear gel without a trial proppant pack to determine the quality of communication with the formation and the initial parameters of the fracture; and performing a mini-hydraulic fracturing on a cross-linked gel with a trial proppant pack (1000 - 2000 kg) to assess the parameters of the fracture development used to correct the design of the main hydraulic fracturing operation. However, in complex geological conditions associated with the presence of small clay barriers between the target formation and above or below the water-saturated layers, as well as in low-productive formations, this conventional method of conducting hydraulic fracturing operations using high-viscosity fluids is not always suitable. Hydraulic fracturing in thin-layer formations is associated with a significant risk of the tightness established by the fracture being broken, as well as fluids contained in the underlying or overlying layers being involved in the drainage process. Hydraulic fracturing in low-productive formations creates fractures that are similar in shape to radial fractures, reducing the efficiency and profitability of the impact due to inefficient use of materials and reagents. The main task in this situation is to limit the height of the fracture development and increase their length. It is necessary to use low-viscosity fracturing fluids with a high ability to transfer proppants to reduce the specific pressure in the fracture and control the height of the rupture. The goal of this research is to develop such fluid.

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Geomechanical modeling of hydraulic fractures interacting with natural fractures — Validation with microseismic and tracer data from the Marcellus and Eagle Ford

Interpretation ◽

10.1190/int-2014-0274.1 ◽

2015 ◽

Vol 3 (3) ◽

pp. SU71-SU88 ◽

Cited By ~ 29

Author(s):

Yamina E. Aimene ◽

Ahmed Ouenes

Keyword(s):

Hydraulic Fracturing ◽

Tracer Tests ◽

Material Point ◽

Propagation Path ◽

Hydraulic Fractures ◽

Natural Fractures ◽

Differential Stress ◽

Eagle Ford ◽

Microseismic Data ◽

The Impact

We have developed a new geomechanical workflow to study the mechanics of hydraulic fracturing in naturally fractured unconventional reservoirs. This workflow used the material point method (MPM) for computational mechanics and an equivalent fracture model derived from continuous fracture modeling to represent natural fractures (NFs). We first used the workflow to test the effect of different stress anisotropies on the propagation path of a single NF intersected by a hydraulic fracture. In these elementary studies, increasing the stress anisotropy was found to decrease the curving of a propagating NF, and this could be used to explain the observed trends in the microseismic data. The workflow was applied to Marcellus and Eagle Ford wells, where multiple geomechanical results were validated with microseismic data and tracer tests. Application of the workflow to a Marcellus well provides a strain field that correlates well with microseismicity, and a maximum energy release rate, or [Formula: see text] integral at each completion stage, which appeared to correlate to the production log and could be used to quantify the impact of skipping the completion stages. On the first of two Eagle Ford wells considered, the MPM workflow provided a horizontal differential stress map that showed significant variability imparted by NFs perturbing the regional stress field. Additionally, a map of the strain distribution after stimulating the well showed the same features as the interpreted microseismic data: three distinct regions of microseismic character, supported by tracer tests and explained by the MPM differential stress map. Finally, the workflow was able to estimate, in the second well with no microseismic data, its main performance characteristics as validated by tracer tests. The field-validated MPM geomechanical workflow is a powerful tool for completion optimization in the presence of NFs, which affect in multiple ways the final outcome of hydraulic fracturing.

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A Two-Phase Model for Analysis of Blood Flow and Rheological Properties in the Elastic Microvessel

ASME 2016 14th International Conference on Nanochannels, Microchannels, and Minichannels ◽

10.1115/icnmm2016-8103 ◽

2016 ◽

Author(s):

Xiaohui Lin ◽

Chibin Zhang ◽

Changbao Wang ◽

Wenquan Chu ◽

Zhaomin Wang

Keyword(s):

Two Phase Flow ◽

Volume Fraction ◽

Transport Model ◽

Planck Equation ◽

Navier Stokes ◽

Phase Flow ◽

Two Phase ◽

Navier Stokes Equation ◽

Experimental Values ◽

The Impact

The blood in microvascular is seemed as a two-phase flow system composed of plasma and red blood cells (RBCs). Based on hydrodynamic continuity equation, Navier-Stokes equation, Fokker-Planck equation, generalized Reynolds equation and elasticity equation, a two-phase flow transport model of blood in elastic microvascular is proposed. The continuous medium assumption of RBCs is abandoned. The impact of the elastic deformation of the vessel wall, the interaction effect between RBCs, the Brownian motion effect of RBCs and the viscous resistance effect between RBCs and plasma on blood transport are considered. Model does not introduce any phenolmeno-logical parameter, compared with the previous phenolmeno-logical model, this model is more comprehensive in theory. The results show that, the plasma velocity distribution is cork-shaped, which is apparently different with the parabolic shape of the single-phase flow model. The reason of taper angle phenomenon and RBCs “Center focus” phenomenon are also analyzed. When the blood vessel radius is in the order of microns, blood apparent viscosity’s Fahraeus-Lindqvist effect and inverse Fahraeus-Lindqvist effect will occur, the maximum of wall shear stress will appear in the minimum of diameter, the variations of blood apparent viscosity with consider of RBCs volume fraction and shear rate calculated by the model are in good agreement with the experimental values.

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

Journal of Fluid Mechanics ◽

10.1017/jfm.2014.606 ◽

2014 ◽

Vol 760 ◽

pp. 567-590 ◽

Cited By ~ 54

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.

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Experimental Investigation on the Initiation of Hydraulic Fractures from a Simulated Wellbore in Laminated Shale

Lithosphere ◽

10.2113/2021/4152918 ◽

2021 ◽

Vol 2021 (Special 4) ◽

Author(s):

Yang Liu ◽

Congrui Chen ◽

Tianshou Ma ◽

Gongsheng Zhu ◽

Nian Peng ◽

...

Keyword(s):

Hydraulic Fracturing ◽

Fracture Initiation ◽

Bedding Plane ◽

Injection Rate ◽

Growth Patterns ◽

Hydraulic Fractures ◽

Fracture Surfaces ◽

Shale Rock ◽

The Impact ◽

Borehole Size

Abstract Understanding the formation mechanisms of complex fracture networks is vitally important for hydraulic fracturing operations in shale formation. For this purpose, a hydraulic fracturing experiment under a core-plunger scale is conducted to investigate the impact of the bedding plane angle, borehole size, and injection rate on fracture initiation behaviors of laminated shale rock. The results on rock properties demonstrate that the anisotropic characteristics of shale rock are reflected not only in elastic modulus but also in tensile strength. The results of fracturing experiments show that the bedding plane dip angle and borehole size have significant effects on fracture initiation behaviors, in that fracture initiation pressure (FIP) decreases with the increase of those two factors. The impact of injection rate, by contrast, has no obvious variety regulation. The above data is further used to validate our previously proposed fully anisotropic FIP model, which shows better agreement with experimental results than those using other models under various parameter combinations. Finally, a postfracturing analysis is performed to identify the fracture growth patterns and the microstructures on the fracture surfaces. The results show that the hydraulic fractures (HFs) always grow along mechanically favorable directions, and the potential interaction between HFs and bedding planes mainly manifests as fracture arrest. Meanwhile, the roughness of fracture surfaces is physically different from each other, which in turn results in the difficulties of fluid flow and proppant migration. The findings of this study can help for a better understanding of the fracture initiation behavior of laminated shale rock and the corresponding fracture morphology.

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Numerical Simulation Study of Proppant Transport in Cross Fractures

10.2118/205255-ms ◽

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.

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The Impact of Oriented Perforations on Fracture Propagation and Complexity in Hydraulic Fracturing

Processes ◽

10.3390/pr6110213 ◽

2018 ◽

Vol 6 (11) ◽

pp. 213 ◽

Cited By ~ 9

Author(s):

Liyuan Liu ◽

Lianchong Li ◽

Derek Elsworth ◽

Sheng Zhi ◽

Yongjun Yu

Keyword(s):

Hydraulic Fracturing ◽

Hydraulic Fracture ◽

Fracture Propagation ◽

Hydraulic Fractures ◽

Fracturing Fluid ◽

Stress Criterion ◽

Damage And Fracture ◽

Fracturing Process ◽

Heterogeneous Rock ◽

The Impact

To better understand the interaction between hydraulic fracture and oriented perforation, a fully coupled finite element method (FEM)-based hydraulic-geomechanical fracture model accommodating gas sorption and damage has been developed. Damage conforms to a maximum stress criterion in tension and to Mohr–Coulomb limits in shear with heterogeneity represented by a Weibull distribution. Fracturing fluid flow, rock deformation and damage, and fracture propagation are collectively represented to study the complexity of hydraulic fracture initiation with perforations present in the near-wellbore region. The model is rigorously validated against experimental observations replicating failure stresses and styles during uniaxial compression and then hydraulic fracturing. The influences of perforation angle, in situ stress state, initial pore pressure, and properties of the fracturing fluid are fully explored. The numerical results show good agreement with experimental observations and the main features of the hydraulic fracturing process in heterogeneous rock are successfully captured. A larger perforation azimuth (angle) from the direction of the maximum principal stress induces a relatively larger curvature of the fracture during hydraulic fracture reorientation. Hydraulic fractures do not always initiate at the oriented perforations and the fractures induced in hydraulic fracturing are not always even and regular. Hydraulic fractures would initiate both around the wellbore and the oriented perforations when the perforation angle is >75°. For the liquid-based hydraulic fracturing, the critical perforation angle increases from 70° to 80°, with an increase in liquid viscosity from 10−3 Pa·s to 1 Pa·s. While for the gas fracturing, the critical perforation angle remains 62° to 63°. This study is of great significance in further understanding the near-wellbore impacts on hydraulic fracture propagation and complexity.

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Sand Transportations and Deposition Characteristics in Multiphase Flows in Pipelines

Journal of Energy Resources Technology ◽

10.1115/1.4006433 ◽

2012 ◽

Vol 134 (3) ◽

Cited By ~ 33

Author(s):

S. Al-lababidi ◽

W. Yan ◽

H. Yeung

Keyword(s):

Multiphase Flow ◽

Water Flow ◽

Oil And Gas ◽

Volume Fraction ◽

Management Strategies ◽

Sand Transport ◽

Transport Velocity ◽

Sand Particles ◽

Phase Water ◽

Slurry Transport

Sand management strategies become an important study to be performed as part of multiphase flow assurance assessments during oil and gas project life and especially for subsea multiphase flow network. This paper presents experimental works to investigate the sand transport characteristics and identify the sand minimum transport condition (MTC) in sand–water and sand–air–water flows in a horizontal and + 5 deg inclined pipelines. The used sand volume fraction, Cv, ranged from 1.61 × 10−5 up to 5.38 × 10−4. The sand minimum transport velocity in single-phase water flow was obtained visually and then compared with that calculated by previous correlations for slurry transport. It was found that in sand–water flow, the pipeline inclination had negligible effect on the minimum sand transport velocity. However, the transport characteristics of sand particles were found changed significantly by changing the pipe inclination, which could result in the change of air–water flow regime. It was observed that sand particles transport more efficiently in terrain slug than stratified wavy flow in +5 deg inclined pipes. The sand transport and settling boundary for different air–water flow regimes were generated for horizontal and +5 deg inclined pipeline.

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