In-situ stress variations and hydraulic fracture propagation in layered rock — observations from a mineback experiment

1984 ◽  
Vol 21 (5) ◽  
pp. A165
Keyword(s):  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Layered Rock ◽  
Hydraulic Fracture Propagation ◽  
Stress Variations

scholarly journals Hydraulic Fracture Propagation under Varying In-situ Stress Conditions of Reservoirs

2017 ◽  
Vol 191 ◽  
pp. 410-418 ◽  
Author(s):  
P.L.P. Wasantha ◽  
H. Konietzky
Keyword(s):  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Stress Conditions ◽  
Hydraulic Fracture Propagation

Investigation of the influence of natural fractures and in situ stress on hydraulic fracture propagation using a distinct-element approach

2015 ◽  
Vol 52 (7) ◽  
pp. 926-946 ◽  
Author(s):  
N. Zangeneh ◽  
E. Eberhardt ◽  
R.M. Bustin
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Distinct Element ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Natural Fractures ◽  
Geological Conditions ◽  
Hydraulic Fracture Propagation

Hydraulic fracturing is the primary means for enhancing rock mass permeability and improving well productivity in tight reservoir rocks. Significant advances have been made in hydraulic fracturing theory and the development of design simulators; however, these generally rely on continuum treatments of the rock mass. In situ, the geological conditions are much more complex, complicated by the presence of natural fractures and planes of weakness such as bedding planes, joints, and faults. Further complexity arises from the influence of the in situ stress field, which has its own heterogeneity. Together, these factors may either enhance or diminish the effectiveness of the hydraulic fracturing treatment and subsequent hydrocarbon production. Results are presented here from a series of two-dimensional (2-D) numerical experiments investigating the influence of natural fractures on the modeling of hydraulic fracture propagation. Distinct-element techniques applying a transient, coupled hydromechanical solution are evaluated with respect to their ability to account for both tensile rupture of intact rock in response to fluid injection and shear and dilation along existing joints. A Voronoi tessellation scheme is used to add the necessary degrees of freedom to model the propagation path of a hydraulically driven fracture. The analysis is carried out for several geometrical variants related to hypothetical geological scenarios simulating a naturally fractured shale gas reservoir. The results show that key interactions develop with the natural fractures that influence the size, orientation, and path of the hydraulic fracture as well as the stimulated volume. These interactions may also decrease the size and effectiveness of the stimulation by diverting the injected fluid and proppant and by limiting the extent of the hydraulic fracture.

scholarly journals Numerical Investigation of Influence of In-Situ Stress Ratio, Injection Rate and Fluid Viscosity on Hydraulic Fracture Propagation Using a Distinct Element Approach

Energies ◽  
2016 ◽  
Vol 9 (3) ◽  
pp. 140 ◽  
Author(s):  
Bo Zhang ◽  
Xiao Li ◽  
Zhaobin Zhang ◽  
Yanfang Wu ◽  
Yusong Wu ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Stress Ratio ◽  
Distinct Element ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Injection Rate ◽  
Fluid Viscosity ◽  
Element Approach ◽  
Hydraulic Fracture Propagation

The Impact of Layering and Permeable Frictional Interfaces on Hydraulic Fracturing in Unconventional Reservoirs

2021 ◽  
pp. 1-14
Author(s):  
Qian Gao ◽  
Ahmad Ghassemi
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
In Situ Stress ◽  
Height Growth ◽  
Interface Element ◽  
Hydraulic Fractures ◽  
Hydraulic Fracture Propagation ◽  
Fracture Height

Summary The impacts of formation layering on hydraulic fracture containment and on pumping energy are critical factors in a successful stimulation treatment. Conventionally, it is considered that the in-situ stress is the dominant factor controlling the fracture height. The influence of mechanical properties on fracture height growth is often ignored or is limited to consideration of different Young’s moduli. Also, it is commonly assumed that the interfaces between different layers are perfectly bounded without slippage, and interface permeability is not considered. In-situ experiments have demonstrated that variation of modulus and in-situ stress alone cannot explain the containment of hydraulic fractures observed in the field (Warpinski et al. 1998). Enhanced toughness, in-situ stress, interface slip, and energy dissipation in the layered rocks should be combined to contribute to the fracture containment analysis. In this study, we consider these factors in a fully coupled 3D hydraulic fracture simulator developed based on the finite element method. We use laboratory and numerical simulations to investigate these factors and how they affect hydraulic fracture propagation, height growth, and injection pressure. The 3D fully coupled hydromechanical model uses a special zero-thickness interface element and the cohesive zone model (CZM) to simulate fracture propagation, interface slippage, and fluid flow in fractures. The nonlinear mechanical behavior of frictional sliding along interface surfaces is considered. The hydromechanical model has been verified successfully through benchmarked analytical solutions. The influence of layered Young’s modulus on fracture height growth in layered formations is analyzed. The formation interfaces between different layers are simulated explicitly through the use of the hydromechanical interface element. The impacts of mechanical and hydraulic properties of the formation interfaces on hydraulic fracture propagation are studied. Hydraulic fractures tend to propagate in the layer with lower Young’s modulus so that soft layers could potentially act as barriers to limit the height growth of hydraulic fractures. Contrary to the conventional view, the location of hydraulic fracturing (in softer vs. stiffer layers) does affect fracture geometry evolution. In addition, depending on the mechanical properties and the conductivity of the interfaces, the shear slippage and/or opening along the formation interfaces could result in flow along the interface surfaces and terminate the fracture growth. The frictional slippage along the interfaces can serve as an effective mechanism of containment of hydraulic fractures in layered formations. It is suggested that whether a hydraulic fracture would cross a discontinuity depends not only on the layers’ mechanical properties but also on the hydraulic properties of the discontinuity; both the frictional slippage and fluid pressure along horizontal formation interfaces contribute to the reinitiation of a hydraulic fracture from a pre-existing flaw along the interfaces, producing an offset from the interception point to the reinitiation point.

scholarly journals Laboratory Investigation on the -Effect of In-Situ Stresses on Hydraulic Fracture Containment

1982 ◽  
Vol 22 (03) ◽  
pp. 333-340 ◽  
Author(s):  
Norman R. Warpinski ◽  
James A. Clark ◽  
Richard A. Schmidt ◽  
Clarence W. Huddle
Keyword(s):  
Pore Pressure ◽  
Hydraulic Fracture ◽  
Laboratory Experiments ◽  
In Situ Stress ◽  
Enhanced Production ◽  
In Situ Stresses ◽  
Extensive Growth ◽  
Stress Variations ◽  
Fracture Growth

Abstract Laboratory experiments have been conducted to determine the effect of in-situ stress variations on hydraulic fracture containment. Fractures were initiated in layered rock samples with prescribed stress variations, and fracture growth characteristics were determined as a function of stress levels. Stress contrasts of 300 to 400 psi (2 to 3 MPa) were found sufficient to restrict fracture growth in laboratory samples of Nevada tuff and Tennessee and Nugget sandstones. The required stress level was found not to depend on mechanical rock properties. However, permeability and the resultant pore pressure effects were important. Tests conducted at biomaterial interfaces between Nugget and Tennessee sandstones show that the resultant stresses set up near the interface because of the applied overburden stress affect the fracture behavior in the same way as the applied confining stresses. These results provide a guideline for determining the in-situ stress contrast necessary to contain a fracture in a field treatment. Introduction An under-standing of the factors that influence and control hydraulic fracture containment is important for the successful use of hydraulic fracturing technology in the enhanced production of natural gas from tight reservoirs. Optimally, this understanding would provide improved fracture design criteria to maximize fracture surface area in contact with the reservoir with respect to volume injected and other treatment parameters. In formations with a positive containment condition (i.e., where fracturing out of zone is not anticipated), long penetrating fractures could be used effectively to develop the resource. For the opposite case, the options would beto use a small treatment so that large volumes are not wasted in out-of-zone fracturing and to accept a lower productivity improvement, orto reject the zone as uneconomical. These decisions cannot be made satisfactorily unless criteria for vertical fracture propagation are developed and techniques for readily measuring the important parameters are available. Currently, both theoretical and experimental efforts are being pursued to determine the important parameters and their relative effects on fracture growth. Two modes of fracture containment are possible. One is the situation where fracture growth is terminated at a discrete interface. Examples of this include laboratory experiments showing fracture termination at weak or unbonded interfaces and theoretical models that predict that fracture growth will terminate at a material property interface. The other mode may occur when the fracture propagates into the bounding layer, but extensive growth does not take place and the fracture thus is restricted. An example is the propagation of the fracture into a region with an adverse stress gradient so that continued propagation results in higher stresses on the fracture, which limits growth, as suggested by Simonson et al. and as seen in mineback experiments. Another example is the possible restriction caused by propagation into a higher modulus region where the decreased width results in increased pressure drop in the fracture, which might inhibit extensive growth into that region relative to the lower modulus region. Other parameters, such as natural fractures, treatment parameters, pore pressure, etc., may affect either of these modes. Laboratory and mineback experiments have shown that weak interfaces and in-situ stress differences are the most likely factors to contain the fracture, and weak interfaces are probably effective only at shallow depths. Thus, our experiments are being performed to determine the effect of in-situ stresses on fracture containment, both in a uniform rock sample and at material properly interfaces. SPEJ P. 333^

In-situ stresses controlling hydraulic fracture propagation and fracture breakdown pressure

2018 ◽  
Vol 164 ◽  
pp. 164-173 ◽  
Author(s):  
Yushuai Zhang ◽  
Jincai Zhang ◽  
Bin Yuan ◽  
Shangxian Yin
Keyword(s):  
Hydraulic Fracture ◽  
Fracture Propagation ◽  
Breakdown Pressure ◽  
In Situ Stresses ◽  
Hydraulic Fracture Propagation
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