Effect of Fracture Heterogeneity on Proppant Transport and Settling Mechanism PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Effect of Fracture Heterogeneity on Proppant Transport and Settling Mechanism PDF full book. Access full book title Effect of Fracture Heterogeneity on Proppant Transport and Settling Mechanism by Dhurgham Abdulameer Kadhim. Download full books in PDF and EPUB format.
Author: Dhurgham Abdulameer Kadhim
Publisher:
ISBN:
Category :
Languages : en
Pages : 104
Get Book Here
Book Description
"Proppant transport modeling through fractures with slickwater fluid systems assumes uniform and homogeneous fracture widths by implying constant fluid behavior at wall boundaries. Hydraulic fracturing mineback operations have demonstrated that induced fractures are heterogeneous and varying in width. This work investigates the impact of fracture width heterogeneity, roughness, and leak-off on ceramic proppant transport and settling, using proppant distribution concepts of Equilibrium Dune Level (EDL) and equilibrium Dune Length (EDX). Experimental work was conducted to investigate the impact of fracture width heterogeneity by varying fracture width along two plexiglass sheets. To mimic actual hydraulic fractures, the injection side was designed as the largest width, and the width of the opposite end was reduced. The ratio between the injection and tip side widths was varied to study the effect of changing fracture width. One ratio was used as a base to study the effect of varying wall roughness and leak-off on the proppant placement. Results of this work demonstrate the impacts of reservoir heterogeneity, wall roughness, and leak off on proppant conveyance and distribution. Fracture width and wall roughness have a significant effect on proppant distribution along a fracture. Increasing width heterogeneity and roughness provide a better proppant distribution and thus better fracture propped conductivity. The effect of leak-off on proppant distribution was monitored, and it showed that proppant followed water movement. Consequently, average water volume that left the slot was affected by proppant distribution"--Abstract, page iii.
Author: Dhurgham Abdulameer Kadhim
Publisher:
ISBN:
Category :
Languages : en
Pages : 104
Get Book Here
Book Description
"Proppant transport modeling through fractures with slickwater fluid systems assumes uniform and homogeneous fracture widths by implying constant fluid behavior at wall boundaries. Hydraulic fracturing mineback operations have demonstrated that induced fractures are heterogeneous and varying in width. This work investigates the impact of fracture width heterogeneity, roughness, and leak-off on ceramic proppant transport and settling, using proppant distribution concepts of Equilibrium Dune Level (EDL) and equilibrium Dune Length (EDX). Experimental work was conducted to investigate the impact of fracture width heterogeneity by varying fracture width along two plexiglass sheets. To mimic actual hydraulic fractures, the injection side was designed as the largest width, and the width of the opposite end was reduced. The ratio between the injection and tip side widths was varied to study the effect of changing fracture width. One ratio was used as a base to study the effect of varying wall roughness and leak-off on the proppant placement. Results of this work demonstrate the impacts of reservoir heterogeneity, wall roughness, and leak off on proppant conveyance and distribution. Fracture width and wall roughness have a significant effect on proppant distribution along a fracture. Increasing width heterogeneity and roughness provide a better proppant distribution and thus better fracture propped conductivity. The effect of leak-off on proppant distribution was monitored, and it showed that proppant followed water movement. Consequently, average water volume that left the slot was affected by proppant distribution"--Abstract, page iii.
Author: Christopher Allen Johnson Blyton
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
Current hydraulic fracturing practice in unconventional resource development typically involves multiple fracturing stages, each consisting of the simultaneous creation of several fractures from a horizontal well. A large mass of proppant, often millions of pounds per well, is injected with the fluid to provide post-closure conductivity. Despite the large quantity of proppant used and its critical importance to well productivity, simple models are often applied to determine its placement in fractures. Propped or effective fracture lengths indicated by modeling may be 100 to 300% larger than the lengths inferred from production data. A common assumption is that the average proppant velocity due to pressure driven flow is equal to the average carrier fluid velocity, while the settling velocity calculation uses Stokes' law. To more accurately determine the placement of proppant in a fracture, it is necessary to rigorously account for many effects not included in the above assumptions. In this study, the motion of particles flowing with a fluid between fracture walls has been simulated using a coupled computational fluid dynamics and discrete element method (CFD-DEM) that rigorously accounts for the both aspects of the problem. These simulations determine individual particle trajectories as particle to particle and particle to wall collisions occur and include the effect of fluid flow. The results show that the proppant concentration and the ratio of proppant diameter to fracture width govern the relative velocity of proppant and fluid. Proppant settling velocity has been examined for small fracture widths to delineate the effect of several independent variables, including concentration. Simulations demonstrate that larger concentration increases the average settling velocity, in apparent contrast with much of the available literature, which indicates that increased concentration reduces settling velocity. However, this is due to the absence of displacement driven counter current fluid flow. This demonstrates that proppant settling in a hydraulic fracture is more complex than usually considered. A proppant transport model developed from the results of the direct numerical simulations and existing correlations for particle settling velocity has been incorporated into a fully three-dimensional hydraulic fracturing simulator. This simulator couples fracture geomechanics with fluid flow and proppant transport considerations to enable the fracture geometry and proppant distribution to be determined rigorously. Two engineering fracture design parameters, injection rate and proppant diameter, have been varied to show the effect on proppant placement. This allows for an understanding of the relative importance of each and optimization of the treatment to a particular application. The presence of natural fractures in unconventional reservoirs can significantly contribute to well productivity. As proppant is transported along a hydraulic fracture, the presence of a dilated natural fracture forms a fluid accepting branch and may result in proppant entry. The proportion of proppant transported into a branch at steady state has been determined using the CFD-DEM approach and is presented via a dimensionless 'particle transport coefficient' through normalization by the proportion of fluid flowing into the branch. Reynolds number at the inlet, branch aperture and the angle of orientation between the main slot and branch, particle size and concentration each affect the transport coefficient. A very different physical process, which controls particle transport into a branch under certain conditions, is the formation of a stable particle bridge preventing subsequent particle transport into the branch. This phenomenon was observed in several simulation cases. The complete set of equations for a three-dimensional formulation of rectangular displacement discontinuity elements has been used to determine the width distribution of a hydraulic fracture and dilated natural fracture. The widths have been determined for several combinations of stress anisotropy, net pressure, hydraulic fracture height and length. The effect of the length, height and orientation of the natural fracture and the elastic moduli of the rock have also been examined. Of the cases examined, many show that natural fracture dilation does not occur. Further, of those cases where dilation is apparent, the proppant transport efficiency corresponding to the natural fracture width is significantly less than one and in many cases zero due to size exclusion. The location and orientation of the natural fracture do not significantly affect its width, while its length and the elastic moduli of the rock substantially change the width.
Author: Sahil Malhotra
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
This dissertation presents an experimental investigation of fluid flow, proppant settling and horizontal proppant transport in hydraulic fractures. The work is divided into two major sections: investigation of proppant settling in polymer-free surfactant-based viscoelastic (VES) fluids and development of a new method of proppant injection, referred to as Alternate-Slug fracturing. VES fluid systems have been used to eliminate polymer-based damage and to efficiently transport proppant into the fracture. Current models and correlations neglect the important influence of fracture walls and fluid elasticity on proppant settling. Experimental data is presented to show that elastic effects can increase or decrease the settling velocity of particles, even in the creeping flow regime. Experimental data shows that significant drag reduction occurs at low Weissenberg number, followed by a transition to drag enhancement at higher Weissenberg numbers. A new correlation is presented for the sphere settling velocity in unbounded viscoelastic fluids as a function of the fluid rheology and the proppant properties. The wall factors for sphere settling velocities in viscoelastic fluids confined between solid parallel plates (fracture walls) are calculated from experimental measurements made on these fluids over a range of Weissenberg numbers. Results indicate that elasticity reduces the retardation effect of the confining walls and this reduction is more pronounced at higher ratios of the particle diameter to spacing between the walls. Shear thinning behavior of fluids is also observed to reduce the retardation effect of the confining walls. A new empirical correlation for wall factors for spheres settling in a viscoelastic fluid confined between two parallel walls is presented. An experimental study on proppant placement using a new method of fracturing referred to as Alternate-Slug fracturing is presented. This method involves alternate injection of low viscosity and high viscosity fluids into the fracture, with proppant pumped in the low viscosity fluid. Experiments are conducted in Hele-Shaw cells to study the growth of viscous fingers over a wide range of viscosity ratios. Data is presented to show that the viscous finger velocities and mixing zone velocities increase with viscosity ratio up to viscosity ratios of about 350 and the trend is consistent with Koval's theory. However, at higher viscosity ratios the mixing zone velocity values plateau signifying no further effect of viscosity contrast on the growth of fingers and mixing zone. The plateau in the velocities at high viscosity ratios is caused by an increase in the thickness of the displacing fluid and a reduction in the thin film of the displaced fluid on the walls of the Hele-Shaw cell. Fluid elasticity is observed to retard the growth of fingers and leads to growth of multiple thin fingers as compared to a single thick dominant finger in less elastic fluids. Observations show the shielding effect is reduced by fluid elasticity. Elastic effects are observed to reduce the thickness of thin film of displaced fluid on the walls of Hele-Shaw cell. The dominant wave number for the growth of instabilities is observed to be higher in more elastic fluids. At the onset of instability, the interface breaks down into a greater number of fingers in more elastic fluids. Experiments are performed in simulated fractures (slot cells) to show the proppant distribution using alternate-slug fracturing. Observations show alternate-slug fracturing ensures deeper placement of proppant through two primary mechanisms: (a) proppant transport in viscous fingers formed by the low viscosity fluid and (b) an increase in drag force in the polymer slug leading to better entrainment and displacement of any proppant banks that may have formed. The method offers advantages of lower polymer costs, lower pumping horsepower, smaller fracture widths, better control of fluid leak-off and less gel damage compared to conventional gel fracs.
Author: Vivekvardhan Reddy Kesireddy
Publisher:
ISBN:
Category :
Languages : en
Pages : 91
Get Book Here
Book Description
"Water fracs have become an essential part of unconventional reservoirs to create deeper fracture networks. Proppant transport in water fracs is challenging in terms of fluids ability to carry the proppant deeper into these fracture networks. This experimental study investigates the impact of the flow rates, fracture widths and complexity controlling the ability of proppant to flow into complex fracture networks. This research attempts to nullify the knowledge gap in understanding width heterogeneity in primary and secondary fractures. This study speaks for settling pattern and proppant transport through a slot flow model with a unique approach to understand stage wise distribution of proppant. The slurry was injected in multiple fracture pore volumes at required flow rates to monitor the stage-wise development of proppant bed. Study illustrates proppant transport in terms of proppant bed heights, equilibrium dune levels and proppant area fractions. Results represents proppant transport for fracture widths, which are comparable to proppant diameter. Two different configurations of apparatus were used to investigate heterogeneity in width in complex fracture networks. Results describe stepwise distribution of ceramic proppant under the influence of flow rates, fracture width and complexity. The bed height gradually builds up in the slot with each injection to achieve an equilibrium bed height. Injection slurry velocities primarily affect proppant transport affecting its distribution in fractures. The fracture width showed a significant impact on proppant transport. Width heterogeneity in complex fracture systems provide better proppant distribution in complex fracture networks. Heterogeneity of width in the fracture caused increased settling and more proppant surface area fractions. The results help in optimizing the proppant flow patterns into complex fracture networks"--Abstract, page iii.
Author: Songyang Tong
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
During hydraulic fracturing treatments, proppants - usually sand - are placed inside fractures to improve fracture conductivity. However, a large portion of the generated hydraulic fractures often remain unpropped after fracturing treatments. There are two primary reasons for this poor proppant placement. First, proppants settle quickly in common fracturing fluids (e.g., slickwater), which results in unpropped sections at the tip or top of the fracture. Second, a large number of the microfractures are too narrow to accommodate any common commercial proppant. Such unpropped fractures hold a large potential flow capacity as they exhibit a large contact area with the reservoir. However, their potential flow capacity is diminished during production due to closing of unpropped fractures because of closure stress. In this study, fractures are categorized as wider fractures, which are accessible to proppant, and narrower fractures, which are inaccessible to proppant. For wider fractures, proppant transport is important as proppant is needed for keeping them open. For narrower fractures, a chemical formulation is proposed as there is less physical restriction for fluids to flow inside across them. The chemical formulation is expected to improve fracture conductivity by generating roughness on fracture surfaces. This dissertation uses experiments and simulations to investigate proppant transport in a complex fracture network with laboratory-scale transparent fracture slots. Proppant size, injection flow rate and bypass fracture angle are varied and their effects are systematically evaluated. Based on experimental results, a straight-line relationship can be used to quantify the fraction of proppant that flows into bypass fractures with the total amount of proppant injected. A Computational Fluid Dynamics (CFD) model is developed to simulate the experiments; both qualitative and quantitative matches are achieved with this model. It is concluded that the fraction of proppant which flows into bypass fractures could be small unless a significant amount of proppant is injected, which indicates the inefficiency of slickwater in transporting proppant. An alternative fracturing fluid - foam - has been proposed to improve proppant placement because of its proppant carrying capacity. Foam is not a single-phase fluid, and it suffers liquid drainage with time due to gravity. Additionally, the existence of foam bubbles and lamellae could alter the movement of proppants. Experiments and simulations are performed to evaluate proppant placement in field-scale foam fracturing application. A liquid drainage model and a proppant settling correlation are developed and incorporated into an in-housing fracturing simulator. Results indicate that liquid drainage could negatively affect proppant placement, while dry foams could lead to negligible proppant settling and consequently uniform proppant placement. For narrower fractures, two chemical stimulation techniques are proposed to improve fracture conductivity by increasing fracture surface roughness. The first is a nanoparticle-microencapsulated acid (MEA) system for shale acidizing applications, and the second is a new technology which can generate mineral crystals on the shale surface to act as in-situ proppants. The MEA could be released as the fracture closes and the released acid could etch the surface of the rock locally, in a non-uniform way, to improve fracture conductivity (up to 40 times). Furthermore, the in-situ proppant generation technology can lead to crystal growth in both fracking water and formation brine conditions, and it also improves fracture conductivity (up to 10 times) based on core flooding experiments
Author: Endrina Rivas
Publisher:
ISBN:
Category :
Languages : en
Pages :
Get Book Here
Book Description
Hydraulic fracturing is a stimulation technique in which fluid is injected at high pressure into low-permeability reservoirs to create a fracture network for enhanced production of oil and gas. It is the primary purpose of hydraulic fracturing to enhance well production. The three main mechanisms during hydraulic fracturing for oil and gas production which largely impact the reservoir production are: (1) fracture propagation during initial pad fluid injection, which defines the extent of the fracture; (2) fracture propagation during injection of proppant slurry (fluid mixed with granular material), creating a propped reservoir zone; and (3) shear dilation of natural fractures surrounding the hydraulically fractured zone, creating a broader stimulated zone. The thesis has three objectives that support the simulation of mechanisms that lead to enhanced production of a hydraulically-fractured reservoir. The first objective is to develop a numerical model for the simulation of the mechanical deformation and shear dilation of naturally fractured rock masses. In this work, a two-dimensional model for the simulation of discrete fracture networks (DFN) is developed using the extended finite element method (XFEM), in which the mesh does not conform to the natural fracture network. The model incorporates contact, cohesion, and friction between blocks of rock. Shear dilation is an important mechanism impacting the overall nonlinear response of naturally fractured rock masses and is also included in the model--physics previously not simulated within an XFEM context. Here, shear dilation is modeled through a linear dilation model, capped by a dilation limiting displacement. Highly nonlinear problems involving multiple joint sets are investigated within a quasi-static context. An explicit scheme is used in conjunction with the dynamic relaxation technique to obtain equilibrium solutions in the face of the nonlinear constitutive models from contact, cohesion, friction, and dilation. The numerical implementation is verified and its convergence illustrated using a shear test and a biaxial test. The model is then applied to the practical problem of the stability of a slope of fractured rock. The second objective is to develop a numerical model for the simulation of proppant transport through planar fractures. This work presents the numerical methodology for simulation of proppant transport through a hydraulic fracture using the finite volume method. Proppant models commonly used in the hydraulic fracturing literature solve the linearized advection equation; this work presents solution methods for the nonlinear form of the proppant flux equation. The complexities of solving the nonlinear and heterogeneous hyperbolic advection equation that governs proppant transport are tackled, particularly handling shock waves that are generated due to the nonlinear flux function and the spatially-varying width and pressure gradient along the fracture. A critical time step is derived for the proppant transport problem solved using an explicit solution strategy. Additionally, a predictor-corrector algorithm is developed to constrain the proppant from exceeding the physically admissible range. The model can capture the mechanisms of proppant bridging occurring in sections of narrow fracture width, tip screen-out occurring when fractures become saturated with proppant, and flushing of proppant into new fracture segments. The results are verified by comparison with characteristic solutions and the model is used to simulate proppant transport through a KGD fracture. The final objective is to develop a numerical model for the simulation of proppant transport through propagating non-planar fractures. This work presents the first monolithic coupled numerical model for simulating proppant transport through a propagating hydraulic fracture. A fracture is propagated through a two-dimensional domain, driven by the flow of a proppant-laden slurry. Modeling of the slurry flow includes the effects of proppant bridging and the subsequent flow of fracturing fluid through the packed proppant pack. This allows for the simulation of a tip screen-out, a phenomenon in which there is a high degree of physical interaction between the rock deformation, fluid flow, and proppant transport. Tip screen-out also leads to shock wave formation in the solution. Numerical implementation of the model is verified and the model is then used to simulate a tip screen-out in both planar and non-planar fractures. An analysis of the fracture aperture, fluid pressure, and proppant concentration profiles throughout the simulation is performed for three different coupling schemes: monolithic, sequential, and loose coupling. It is demonstrated that even with time step refinement, the loosely-coupled scheme fails to converge to the same results as the monolithic and sequential schemes. The monolithic and sequential algorithms yield the same solution up to the onset of a tip screen-out, after which the sequential scheme fails to converge. The monolithic scheme is shown to be more efficient than the sequential algorithm (requiring fewer iterations) and has comparable computational cost to the loose coupling algorithm. Thus, the monolithic scheme is shown to be optimal in terms of computational efficiency, robustness, and accuracy. In addition to this finding, a robust and more efficient algorithm for injection-rate controlled hydraulic fracturing simulation based on global mass conservation is presented in the thesis.
Author: Yanan Ding
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Get Book Here
Book Description
In addition to conventional enhanced oil recovery (EOR) technologies, extensive efforts have been made to explore new approaches to sustain the increasing global oil and gas consumption while lowering the operational costs. In recent decades, nanoparticles (NPs) have seen their promising potentials in recovering hydrocarbons from numerous laboratory experiments and field pilots. Also, hydraulic fracturing techniques have unlocked a significant quantity of hydrocarbon resources from unconventional reservoirs. Solid particle transport including NP transport, dispersion, and distribution in hydrocarbon reservoirs, proppant placement within hydraulic fractures, and sand production is critical to the efficient and effective hydrocarbon exploitation. Considering the petrophysical complexity as well as the intricate interactions among particles, fluids, and rock matrix, it is, therefore, an extremely challenging task to accurately predict the associated transport and placement behaviour of solid particles in a hydrocarbon reservoir. Theoretically, a robust and pragmatic method has been developed and validated to analytically determine the dynamic dispersion coefficients for particles flowing in a parallel-plate fracture with instantaneous point source as well as uniform and volumetric line sourcess, in which particle gravity settling effect has been considered. It is found that the point source and the uniform line source are respectively the most and least sensitive to the gravity effect. An increase of particle size larger than its critical value decreases the asymptotical dispersion coefficient for all the source conditions, while gravity settling promotes the dispersion phenomenon during the early-stage of point source condition. Particle-tracking simulations have been performed and validated on polydisperse dense particle transport in a randomly-orientated fracture with spatially variable apertures. The simulated results indicate that the mass breakthrough efficiency of particles and particle plume distribution in a randomly-orientated rough fracture are significantly influenced by different factors when particle gravity settling occurs. In addition, particle attachment consisting of reversible and irreversible adsorptions on an aperture surface is quantified applying the Derjaguin-Landau-Verwey-Overbeek (DLVO) kinetics. With sensitivity analysis performed, the impacts of different factors on particle attachment are found to vary with each other through non-unique patterns. By integrating the Perkins-Kern-Nordgren-Carter (PKN-C) fracture propagation model and the particle tracking algorithm, a novel Eulerian-Lagrangian (E-L) model has been developed and validated to simulate field-scale proppant transport during hydraulic fracturing operations. Such an E-L model incorporates pertinent empirical correlations determined from regressing experimental measurements regarding the proppant settling velocity and the drag/lift forces, which is applicable to both the Newtonian and non- Newtonian fluid conditions. The non-Newtonian fluid is usually found to yield a less "heel-biased" pattern of proppant distribution in a hydraulic fracture, e.g., a larger slurry coverage together with a longer proppant dune, while distinct patterns of the dominant factors are observed and evaluated.
Author: Antonio A. Munjiza
Publisher: John Wiley & Sons
ISBN: 0470020172
Category : Technology & Engineering
Languages : en
Pages : 348
Get Book Here
Book Description
The combined finite discrete element method is a relatively new computational tool aimed at problems involving static and / or dynamic behaviour of systems involving a large number of solid deformable bodies. Such problems include fragmentation using explosives (e.g rock blasting), impacts, demolition (collapsing buildings), blast loads, digging and loading processes, and powder technology. The combined finite-discrete element method - a natural extension of both discrete and finite element methods - allows researchers to model problems involving the deformability of either one solid body, a large number of bodies, or a solid body which fragments (e.g. in rock blasting applications a more or less intact rock mass is transformed into a pile of solid rock fragments of different sizes, which interact with each other). The topic is gaining in importance, and is at the forefront of some of the current efforts in computational modeling of the failure of solids. * Accompanying source codes plus input and output files available on the Internet * Important applications such as mining engineering, rock blasting and petroleum engineering * Includes practical examples of applications areas Essential reading for postgraduates, researchers and software engineers working in mechanical engineering.
Author: D. Mader
Publisher: Elsevier
ISBN: 0080868843
Category : Technology & Engineering
Languages : en
Pages : 1277
Get Book Here
Book Description
Many aspects of hydraulic proppant fracturing have changed since its innovation in 1947. The main significance of this book is its combination of technical and economical aspects to provide an integrated overview of the various applications of proppants in hydraulic fracturing, and gravel in sand control. The monitoring of fractures and gravel packs by well-logging and seismic techniques is also included.The book's extensive coverage of the subject should be of special interest to reservoir geologists and engineers, production engineers and technologists, and well log analysts.
Author: Dongkeun Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 390
Get Book Here
Book Description
Hydraulic fracturing in unconsolidated or poorly consolidated formations has been used as a technique for well stimulation and for sand control. Although a large number of hydraulic fracturing operations have been performed in soft formations, the exact mechanisms of failure and fracture propagation remain an unresolved issue. Conventional hydraulic fracturing models based on the theory of linear elastic fracture mechanics (LEFM) consistently predict lower net fracturing pressure, smaller fracture widths and longer fracture lengths in soft formations than observed in the field. Operators who want to design and analyze frac-pack treatments routinely use a hard rock model and need to calibrate and often manipulate input parameters beyond a physically reasonable range to match the net fracturing pressure and well performance data. In this dissertation, we have developed a fully-coupled, three-dimensional hydraulic fracture model for poro-elasto-plastic materials and fluid flow coupled with proppant transport. A computational framework for fluid-structure interaction (FSI) based on finite volume method was developed for modeling of hydraulic fracturing and proppant placement in soft formations. Two separate domains, a fracture and a reservoir domain, are discretized individually, separate equations are solved in the two domains, and their interactions are modeled. The model includes the fully coupled process of power-law fluid flow inside the fracture with proppant transport, fluid leak-off from the fracture into the porous reservoir, pore pressure diffusion into the reservoir, inelastic deformation of the poro-elasto-plastic reservoir, and fracture propagation using a cohesive zone model along with a dynamic meshing procedure. Fully-coupled processes between the two domains, and pressure, flow and displacement coupling within each domain are modeled by an iterative and segregated solution procedure, where each component of the field variable is solved separately, consecutively, and iteratively. We verified the essential components of the model by comparing our simulation results with several well-known analytical solutions (elastoplastic deformation and failure problem, KGD model in a 2-D elastic domain, and KGD model in storage-toughness dominated regime). We applied the model to design and analyze frac-pack operations conducted in a Gulf of Mexico oilfield. Our model is capable of capturing the high net fracturing pressure commonly observed during frac-packing operations without adjusting any input parameters. The model shows quantitatively that plasticity causes lower stress concentration around the fracture tip which shields the tip of the propagating fracture from the fracturing pressure, and retards fracture growth. Our model predicts shorter fracture lengths and wider widths compared to a hard rock model. Shear failure around the fracture and ahead of the tip are modeled. Low cohesion sands tend to fail in shear first then in tension if sufficient pore pressure builds up. We investigated the effect of fluid viscosity, injection rate, and proppant diameter on fracture growth and proppant placement using sensitivity studies. Higher apparent fluid viscosity and injection rate results in wider fractures with better proppant placement, when the fracture is expected to be contained within the payzone. Utilizing larger diameter of proppant leads to settling-dominant proppant placement resulting in the formation of a proppant bank at the bottom of the induced fracture. The new frac-pack model for the first time allows operators to design and analyze hydraulic fracturing stimulations in soft, elastoplastic formations when complex fracturing fluids are used. Our results also provide guidelines for the selection of fracturing fluid rheology, proppant size, and injection rates.
