scholarly journals NUMERICAL AND EXPERIMENTAL MODELING OF PROPAGATION OF LONGITUDINAL FRACTURES IN MULTI-STAGE HYDRAULIC FRACTURING WITH VISCOUS FLUID

2021 ◽  
Vol 2 (4) ◽  
pp. 41-51
Author(s):  
Anton V. Panov ◽  
Igor V. Kolykhalov
Keyword(s):  
Viscous Fluid ◽  
Hydraulic Fracturing ◽  
Plastic Material ◽  
Plane Elasticity ◽  
Experimental Modeling ◽  
Hydraulic Fractures ◽  
Nonuniform Field ◽  
Fluid Viscosity ◽  
Multi Stage ◽  
Simultaneous Growth

The experimental and numerical modeling of curvilinear propagation of hydraulic fractures driven by viscous fluid is implemented. The trajectories of simultaneous growth of 2-5 fractures from the boundary of a circular opening are presented in plane elasticity. The influence of the fluid viscosity on the fracture trajectory is analyzes. The causes of initiation of main fracture and shut-down of other fractures are revealed. The attempts are made to find such conditions that simultaneous growth of a few main fractures is possible by varying lengths and orientation angles of initiation fractures in the external nonuniform field of compression. The experimental modeling of hydraulic fractures was carried out using blocks made of concrete and organic glass. There were 3 to 5 initiation fractures. The influence of the breakdown fluid viscosity on the number of the main fractures is illustrated. Hydraulic fracturing with a plastic material allowed simultaneous growth of 3 and 4 fractures within a block. The experimental modeling data and the calculation results are compared.

scholarly journals A parametric study of hydraulic fracturing interference between fracture clusters and stages based on numerical modeling

2020 ◽  
pp. 014459872095325
Author(s):  
Ang Chen ◽  
Xuyang Guo ◽  
Huiyong Yu ◽  
Lei Huang ◽  
Shanzhi Shi ◽  
...  
Keyword(s):  
Numerical Modeling ◽  
Hydraulic Fracturing ◽  
Horizontal Wells ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Shale Oil ◽  
Fracturing Fluid ◽  
Multi Stage ◽  
Study Results ◽  
Stress Contrast

Shale oil reservoirs are usually developed by horizontal wells completed with multi-stage hydraulic fractures. The fracture interference between clusters in a single stage and between consecutive stages has an impact on the stimulation quality in terms of fracture geometries and fracture widths. This study introduces a non-planar hydraulic fracture model based on the extended finite element method and its use in quantifying the effects of relevant parameters on multi-stage fracture quality in a realistic shale oil scenario. The numerical model is validated with field diagnostics based on vertical seismic profiling. Relevant parameters including stress contrast, fracturing fluid viscosity, cluster density, and fracturing in consecutive stages are quantitatively analyzed in the numerical study. Results show that effects of stress contrast on fracture quality are greater than those of fracturing fluid viscosity, while the effects are more significant in outer fractures instead of the inner fracture. Denser cluster design leads to greater inhibition for the growth of inner fractures which eventually divert them transversely. In fracturing for consecutive stages, the opening of fractures in the subsequent stages is inhibited and the fracture geometries are also altered by the inter-stage interference caused by the previous stage. Based on field data and numerical modeling, this study identifies key parameters and quantifies their effects on inter-fracture and inter-stage interference in multi-stage hydraulic fracturing in horizontal wells.

scholarly journals FEATURES OF PROPAGATION OF HYDRAULIC FRACTURES IN STRATIFIED ROCK MASS

2021 ◽  
Vol 2 (4) ◽  
pp. 190-197
Author(s):  
Evgeny N. Sher
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
External Compression ◽  
Governing Factor ◽  
Stress States ◽  
Stratified Rock ◽  
Stratified Rock Mass ◽  
Tension Strength

In hydraulic fracturing commonly used in mining, it is important to determine the shapes and sizes of created fractures. The governing factor in this case is the structure of rock mass which is often stratified. This study analyzes the influence of strengths of the layers and their stress states on the shapes of the growing fractures. Numerical modeling shows that in hydraulic fracturing with low-viscous fluids, fractures grow mostly in a layer having lower tension or compression strengths. The calculations carried out for the analyzed cases provide the values of tension strength and external compression for hydraulic fractures to grow only in one layer. It is shown that the increase in the breakdown fluid viscosity weakens this effect.

Zipper Fracturing of Horizontal Cluster Wells: Game Changing Unconventional Fracturing in UAE

2021 ◽  
Author(s):  
Yang Wu ◽  
Ole Sorensen ◽  
Nabila Lazreq ◽  
Yin Luo ◽  
Tomislav Bukovac ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
United Arab Emirates ◽  
Shale Gas ◽  
New Technology ◽  
Operational Efficiency ◽  
Gas Production ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Fracture Width ◽  
Friction Reducer

Abstract Following the increase in demand for natural gas production in the United Arab Emirates (UAE), unconventional hydraulic fracturing in the country has grown exponentially and with it the demand for new technology and efficiency to fast-track the process from fracturing to production. Diyab field has historically been a challenging field for fracturing given the high-pressure/high-temperature (HP/HT) conditions, presence of H2S, and the strike-slip to thrust faulting conditions. Meanwhile, operational efficiency is necessary for economic development of this shale gas reservoir. Hence "zipper fracturing" was introduced in UAE with modern technologies to enable both operational efficiency and reservoir stimulation performance. The introduction of zipper fracturing in UAE is considered a game changer as it shifted the focus from single-well fracturing to multiple well pads that allow for fracturing to take place in one well while the adjacent well is undergoing a pumpdown plug-and-perf operation using wireline. The overall setup of the zipper surface manifold allowed for faster transitions between the two wells; hence, it also rendered using large storage tanks a viable option since the turnover between stages would be short. Thus, two large modular tanks were installed and utilised to allow 160,000 bbl of water storage on site. Similarly, the use of high-viscosity friction reducer (HVFR) has directly replaced the common friction reducer additive or guar-based gel for shale gas operation. HVFR provides higher viscosity to carry larger proppant concentrations without the reservoir damage, and the flexibility and simplicity of optimizing fluid viscosity on-the-fly to ensure adequate fracture width and balance near-wellbore fracture complexity. Fully utilizing dissolvable fracture plugs was also applied to mitigate the risk of casing deformation and the subsequent difficulty of milling plugs after the fracturing treatment. Furthermore, fracture and completion design based on geologic modelling helped reduce risk of interaction between the hydraulic fractures and geologic abnormalities. With the application of advanced logistical planning, personnel proficiency, the zipper operation field process, clustered fracture placement, and the pump-down plug-and-perforation operation, the speed of fracturing reached a maximum of 4.5 stages per day, completing 67 stages in total between two wells placing nearly 27 million lbm of proppant across Hanifa formation. The maximum proppant per stage achieved was 606,000 lbm. The novelty of this project lies in the first-time application of zipper fracturing, as well as the first application of dry HVFR fracturing fluid and dissolvable fracturing plugs in UAE. These introductions helped in improving the overall efficiency of hydraulic fracturing in one of UAE's most challenging unconventional basins in the country, which is quickly demanding quicker well turnovers from fracturing to production.

Numerical Investigation Into the Simultaneous Growth of Two Closely Spaced Fluid-Driven Fractures

SPE Journal ◽  
2018 ◽  
Vol 24 (01) ◽  
pp. 274-289 ◽  
Author(s):  
Xiyu Chen ◽  
Jinzhou Zhao ◽  
Wenyi Yan ◽  
Xi Zhang
Keyword(s):  
Fracture Surface ◽  
Viscous Dissipation ◽  
Treatment Success ◽  
Displacement Discontinuity ◽  
Hydraulic Fractures ◽  
Single Fracture ◽  
Fluid Viscosity ◽  
Initial Fracture ◽  
Fracture Growth ◽  
Simultaneous Growth

Summary Multistage, multicluster hydraulic fracturing is a widespread method used in the petroleum industry to enhance the hydrocarbon production of low-permeability unconventional reservoirs. The core for fracturing-treatment success is achieving the simultaneous propagation of multiple closely spaced hydraulic fractures to enlarge the fracture surface. To better understand this coupled elasto-hydrodynamics mechanics, a 2D model comprising a combination of a displacement discontinuity method for elasticity and a finite volume method for lubrication is presented in this paper. Furthermore, a universal tip asymptotic solution, reflecting the unique multiscale tip behavior for fluid-driven fractures, is adopted as a propagation criterion to locate the fracture front. Numerical examples are fully implemented to investigate the competition in the growth of two closely spaced fluid-driven fractures at different initial lengths. Parametric studies reveal that the competition between simultaneous and single fracture growth is governed by dimensionless toughness, which represents the energy ratio of fracture-surface creation to fluid viscous dissipation. The simultaneous growth will be promoted when the fluid viscous dissipation is dominant, while, with increasing rock toughness, the tendency for single-fracture growth will increase correspondingly. Numerical results also demonstrate that initial fracture geometric settings play an important role in this competition. A large initial length offset between two fractures will generate preferential growth for the longer fracture, even in the viscosity-dominated regime. Furthermore, this paper provides dimensionless parameters characterizing fracture deflection caused by fracture interaction. The paper concludes by identifying the controlling parameters and their field applications, emphasizing that high injection rate, high fluid viscosity, and small initial fracture-size offset are beneficial to promoting the simultaneous growth at early time, which is important in enhancing reservoir permeability.

scholarly journals Heterogeneity analysis of shale reservoir based on multi-stage pumping data

2019 ◽  
Vol 11 (1) ◽  
pp. 1182-1193
Author(s):  
Wenbao Zhai ◽  
Jun Li ◽  
Zhaowei Chen ◽  
Gonghui Liu ◽  
Yingcao Zhou
Keyword(s):  
Hydraulic Fracturing ◽  
Nonlinear Behavior ◽  
Hydraulic Fractures ◽  
Intrinsic Mode Functions ◽  
Heterogeneity Index ◽  
Reservoir Volume ◽  
Multi Stage ◽  
Shale Reservoir ◽  
Heterogeneity Analysis ◽  
Degree Of Heterogeneity

Abstract Heterogeneity analysis of conventional data, such as geophysical log data, has been still limited to the application of near-wellbore zone, which makes it difficult to optimize the hydraulic fracturing design and may render suboptimal performance. However, the fluctuation of multi-stage pumping data, manifesting nonlinear behavior of physical properties with shale reservoir during hydraulic fractures propagation stage, is usually ignored. In this study, the empirical mode decomposition technique (EMDT) was introduced and applied to the multi-stage pumping data to determine the respective Intrinsic Mode Functions (IMF). By using a relationship between the IMF number and its mean wavenumber, the heterogeneity index associated with far-wellbore shale reservoir was determined. The results indicate that the heterogeneity index from multi-stage pumping data is good coincided with the effective stimulation reservoir volume (ESRV) obtained from micro-seismic events. Not only that, but it also reveals that there is a strong correlation of heterogeneity index, IMF number, ESRV, and degree of heterogeneity within shale reservoir. This work has demonstrated that heterogeneity index analysis combined with EMDT has been significantly important and essential to quantify the degree of heterogeneity within far-wellbore shale reservoir from multi-stage pumping data, which contributes to optimizing the hydraulic fracturing design and improving good optimal performance.

Application of multi-stage hydraulic fracturing in the development of Achimov sediments at the Urengoy oil and gas condensate field

2020 ◽  
pp. 38-48
Author(s):  
E. V. Panikarovskii ◽  
V. V. Panikarovskii ◽  
M. M. Mansurova ◽  
M. V. Listak
Keyword(s):  
Hydraulic Fracturing ◽  
Oil And Gas ◽  
Gas Condensate ◽  
Hydraulic Fractures ◽  
High Permeability ◽  
Main Method ◽  
Reservoir Rocks ◽  
New Methods ◽  
Multi Stage ◽  
Oil Gas

The development of deep-lying Achimov deposits makes it possible to extract additional volumes of gas and gas condensate in the fields with decreasing production, as well as implement strategies to introduce new methods to increase oil, gas and condensate production. The decrease in well productivity during the development of gas condensate fields requires the use of new methods of intensification of production. The main method for increasing the productivity of Achimov wells is hydraulic fracturing. The choice of hydraulic fracturing technology for low-permeability Achimov deposits is especially important for creating large hydraulic fractures and high permeability, as well as maintaining the filtration characteristics of reservoir rocks. Multi-stage hydraulic fracturing is the most effective method of intensifying gas and gas condensate production in the development of the Achimov deposits.

scholarly journals The Role of Rock Matrix Permeability in Controlling Hydraulic Fracturing in Sandstones

2021 ◽  
Author(s):  
Marco Fazio ◽  
Peter Ibemesi ◽  
Philip Benson ◽  
Diego Bedoya-González ◽  
Martin Sauter
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Space ◽  
Hydraulic Fractures ◽  
Low Permeability ◽  
Fluid Viscosity ◽  
Rock Matrix ◽  
Porous Rock ◽  
Sleeve Fracture ◽  
Matrix Permeability ◽  
Fracturing Process

AbstractA concomitant effect of a hydraulic fracturing experimenting is frequently fluid permeation into the rock matrix, with the injected fluid permeating through the porous rock matrix (leak-off) rather than contributing to the buildup of borehole pressure, thereby slowing down or impeding the hydro-fracturing process. Different parameters, such as low fluid viscosity, low injection rate and high rock permeability, contribute to fluid permeation. This effect is particularly prominent in highly permeable materials, therefore, making sleeve fracturing tests (where an internal jacket separates the injected fluid in the borehole from the porous rock matrix) necessary to generate hydraulic fractures. The side effect, however, is an increase in pressure breakdown, which results in higher volume of injected fluid and in higher seismic activity. To better understand this phenomenon, we report data from a new comparative study from a suite of micro-hydraulic fracturing experiments on highly permeable and on low-permeability rock samples. Experiments were conducted in both sleeve fracture and direct fluid fracture modes using two different injection rates. Consistent with previous studies, our results show that hydraulic fracturing occurred only with low permeation, either due to the intrinsic low permeability or due to the presence of an inner silicon rubber sleeve. In particular, due to the presence of quasi-impermeable inner sleeve or borehole skin in the sleeve fracturing experiment, fracturing occurs, with the breakdown pressure supporting the linear elastic approach considering poroelastic effects, therefore, with low stress drop and consequently low microseismicity. Rock matrix permeability also controls the presence of precursory Acoustic Emission activity, as this is linked to the infiltration of fluids and consequent expansion of the pore space. Finally, permeability is shown to mainly control fracturing speed, because the permeation of fluid into the newly created fracture via the highly permeable rock matrix slows down its full development. The application of these results to the field may help to reduce induced seismicity and to conduct well stimulation in a more efficient way.

The effect of gravity on the shape and direction of vertical hydraulic fractures

2020 ◽  
Vol 60 (2) ◽  
pp. 668
Author(s):  
Saeed Salimzadeh
Keyword(s):  
Hydraulic Fracturing ◽  
Shale Gas ◽  
Hydraulic Fracture ◽  
Hydraulic Fractures ◽  
Fluid Viscosity ◽  
Gas Reservoirs ◽  
Unconventional Gas Reservoirs ◽  
Fracture Fluid ◽  
Fracture Opening

Australia has great potential for shale gas development that can reshape the future of energy in the country. Hydraulic fracturing has been proven as an efficient method to improve recovery from unconventional gas reservoirs. Shale gas hydraulic fracturing is a very complex, multi-physics process, and numerical modelling to design and predict the growth of hydraulic fractures is gaining a lot of interest around the world. The initiation and propagation direction of hydraulic fractures are controlled by in-situ rock stresses, local natural fractures and larger faults. In the propagation of vertical hydraulic fractures, the fracture footprint may extend tens to hundreds of metres, over which the in-situ stresses vary due to gravity and the weight of the rock layers. Proppants, which are added to the hydraulic fracturing fluid to retain the fracture opening after depressurisation, add additional complexity to the propagation mechanics. Proppant distribution can affect the hydraulic fracture propagation by altering the hydraulic fracture fluid viscosity and by blocking the hydraulic fracture fluid flow. In this study, the effect of gravitational forces on proppant distribution and fracture footprint in vertically oriented hydraulic fractures are investigated using a robust finite element code and the results are discussed.

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.

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