Fracture stimulation fundamentals

Britt, Larry K.

doi:10.1016/j.jngse.2012.06.006

Cited by 41 publications

(18 citation statements)

References 20 publications

(35 reference statements)

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“…Injecting pressure is higher than the fracture initiation pressure; the access to each selected zone is ensured by pressurizing a wellbore interval, previously isolated by means of retrievable plugs (Nolen-Hoeksema, 2013). Due to the formation breakdown, a network of fractures and cracks develops depending on the stress state of the formation (for a review, see Britt 2012). During the first injection phase, the fracturing fluid does not usually contain a gelling agent, which is added to its formulation once the development of fractures and cracks has started; the scope of the gelling agent is to increase the fluid viscosity, forming hydrogels which can carry the proppant (Kreipl & Kreipl, 2017).…”

Section: Introductionmentioning

confidence: 99%

Non‐Newtonian Backflow in an Elastic Fracture

Chiapponi

Ciriello

Longo

et al. 2019

Water Resources Research

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Backflow phenomenon, as a consequence of hydraulic fracturing, is of considerable technical and environmental interest. Here, backflow of a non-Newtonian fluid from a disk-shaped elastic fracture is studied theoretically and experimentally. The fracture is of constant aperture h and the outlet section at constant pressure p e . We consider a shear-thinning power-law fluid with flow behavior index n. Fracture walls are taken to react with a force proportional to h , with a positive elasticity exponent; for = 1 linear elasticity holds. Constant overload f 0 , acting on the fracture, is also embedded in the model. A transient closed-form solution is derived for the (i) fracture aperture, (ii) pressure field, and (iii) outflow rate. The particular case of a Newtonian fluid (n = 1) is explicitly provided. For p e = 0 and f 0 = 0, the residual aperture and outflow rate scale asymptotically with time t as t −n/(n+ +1) and t −(2n+ +1)/(n+ +1) , respectively, thus generalizing literature results for n = 1 and/or = 1. For nonzero exit pressure and/or overload, the fracture aperture tends asymptotically to a constant value depending on , n, p e , f 0 , and other geometrical and physical parameters. The results are provided in dimensionless and dimensional form, including the time to achieve a given percentage of fluid recovery. In addition, an example application (with values of parameters derived from field scale applications) is included to further characterize the influence of fluid rheology. Experimental tests are conducted with Newtonian and shear-thinning fluids and different combinations of parameters to validate the model. Experimental results match well the theoretical predictions, mostly with a slight overestimation.

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Section: Introductionmentioning

confidence: 99%

Non‐Newtonian Backflow in an Elastic Fracture

Chiapponi

Ciriello

Longo

et al. 2019

Water Resources Research

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Section: Introductionmentioning

confidence: 99%

“…Hydraulic fracturing is a widely applied technology in the extraction of shale gas [1][2][3]. This technology improves the permeability of shale reservoirs by pumping a high-pressure fracturing fluid into the borehole and fracturing the tight formation [2][3][4]. Water is the main fracturing fluid used, and the effects of water-based fluids on fracture behaviors have been well investigated [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of Fracture Network Evolution during Nitrogen Fracturing Processes in Shale Reservoirs

et al. 2018

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This paper develops a numerical model to study fracture network evolution during the nitrogen fracturing process in shale reservoirs. This model considers the differences of incompressible and compressible fluids, shear and tensile failure modes, shale heterogeneity, and the strength and permeability of both shale matrix and bedding planes through the coupling of mechanical-seepage-damage during fracturing fluid injection. The results show that nitrogen fracturing has a lower breakdown pressure and larger seepage zone than hydraulic fracturing under the same injection pressure. Tensile failure was identified as the major reason for the initiation and propagation of fractures. Ignoring the effect of bedding planes, the fracture initiation pressure, breakdown pressure, and fracturing effectiveness reached their maxima when the stress ratio is 1. Under the same strength ratio, the propagation path of the fractures was controlled by the stronger effect that was casused by the bedding angle and stress ratio. With increasing the strength ratio, the fracture number and shearing of the bedding plane increased significantly and the failure pattern changed from tensile-only mode to tensile-shear mode. These analyses indicated that the fracture network of bedding shale was typically induced by the combined impacts of stress ratio, bedding angle and strength ratio.Energies 2018, 11, 2503 2 of 22 more effective if N 2 is applied for the hydraulic fracturing [22,23]. Different fracturing fluids lead to the different pore pressure distributions during fluid flow due to the various properties such as viscosity and compressibility. According to the principle of effective stress, the difference in pore pressure distribution induces the difference in the stress distribution in rocks, which plays an important role in fracturing behavior during the fracturing process [24][25][26][27]. Lower breakdown pressure, larger seepage zone and more complex fracture network were observed during nitrogen fracturing [24][25][26][27]. However, these studies were performed on simple rock samples and the influence of other factors during nitrogen fracturing has not been well evaluated. It is essential to investigate fracture network evolution during the nitrogen fracturing process.Several numerical models have been developed to investigate fracture behaviors during the hydraulic fracturing process. These models include the boundary element method [28], finite element method [29][30][31], and discrete element method [32,33]. Wang et al. [29] applied a new mathematical model to investigate fracture network evolution of multi-stranded fractures with pre-existing natural fractures. Shalev and Lyakhovsky [31] studied the damage evolution and seismicity phenomenon in hydraulic fracturing using an improved damage model based on the finite element method. However, there are still only a few studies on a numerical model for nitrogen fracturing and the comparison between water fracturing and nitrogen fracturing. On the other hand, shale reservoirs occur at di...

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“…Sweep efficiency is a measure of 50 the effectiveness of heat, gas or oil recovery process that depends on the volume of the 51 reservoir contacted by an injected fluid. In the petroleum industry, hydraulic fracturing 52 techniques have been used for over 60 years to increase hydraulic communication and 53 stimulate oil and gas production (Britt, 2012). Artificial (stimulated) hydraulic fractures 54 are usually initiated by injecting fluids into the borehole to increase the pressure to the 55 point where the minimal principal stress in the rock becomes tensile.…”

Section: Introduction 48mentioning

confidence: 99%

“…Hydraulic fracturing activities often involve injection of a fracturing fluid with proppants 59 in order to better propagate fractures and to keep them open (Britt, 2012). The design of 60 fracturing treatment should involve the optimization of operational parameters, such as 61 the viscosity of the fracturing fluid, injection rate and duration, proppant concentration, 62 etc., so as to create a fracture geometry that favors increased sweep efficiency.…”

Section: Introduction 48mentioning

confidence: 99%

Surrogate-based optimization of hydraulic fracturing in pre-existing fracture networks

Chen

Sun

et al. 2013

Computers & Geosciences

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25Hydraulic fracturing has been used widely to stimulate production of oil, natural 26 gas, and geothermal energy i n formations with low natural permeability. Numerical 27 optimization of fracture stimulation often requires a large number of evaluations of 28 forward hydraulic fracturing models, which are computationally expensive and even 29 prohibitive in some situations. Moreover, there are a variety of uncertainties associated 30 with the pre-existing fracture distributions and rock mechanical properties, which require 31 evaluation of their impact on the optimal treatment. In this study, a surrogate-based 32 approach is developed for efficient optimization of hydraulic fracturing well design in the 33 presence of natural-system uncertainty. The fractal dimension is derived from the 34 simulated fracturing network as the objective for maximizing energy recovery sweep 35 efficiency. The surrogate model mapping the input parameters to the fractal dimension is 36 constructed using training data generated by high-fidelity fracturing models, and it 37 provides fast approximation of the objective functions. A suite of surrogate models 38 constructed using different fitting methods is evaluated and validated for fast predictions. 39Global sensitivity analysis is conducted to gain insights into the impact of the input 40 variables on the output of interest, and further used for parameter screening. The high 41 efficiency o f the surrogate-based approach is demonstrated for three optimization 42 scenarios with different, uncertain ambient conditions. Our results suggest the critical 43 importance of c onsidering uncertain pre-existing fracture networks in optimization 44 studies of hydraulic fracturing. 45

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Fracture stimulation fundamentals

Cited by 41 publications

References 20 publications

Non‐Newtonian Backflow in an Elastic Fracture

Non‐Newtonian Backflow in an Elastic Fracture

Numerical Study of Fracture Network Evolution during Nitrogen Fracturing Processes in Shale Reservoirs

Surrogate-based optimization of hydraulic fracturing in pre-existing fracture networks

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