Stimuli-responsive/rheoreversible hydraulic fracturing fluids as a greener alternative to support geothermal and fossil energy production

2015 ◽  
Vol 17 (5) ◽  
pp. 2799-2812 ◽  
Author(s):  
H. B. Jung ◽  
K. C. Carroll ◽  
S. Kabilan ◽  
D. J. Heldebrant ◽  
D. Hoyt ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Igneous Rock ◽  
Volume Expansion ◽  
Energy Production ◽  
Fracture Initiation ◽  
Stimuli Responsive ◽  
Fossil Energy ◽  
Fracturing Fluids ◽  
Initiation Pressure

A reversible CO2-triggered volume expansion significantly lowers the fracture initiation pressure in highly impermeable igneous rock as compared to conventional fracturing fluids.

Laboratory Investigation of Fracture Initiation Pressure and Orientation

1979 ◽  
Vol 19 (02) ◽  
pp. 129-144 ◽  
Author(s):  
W.L. Medlin ◽  
L. Masse
Keyword(s):  
Hydraulic Fracture ◽  
Field Data ◽  
Laboratory Experiments ◽  
Fracture Initiation ◽  
Stress Conditions ◽  
Elastic Behavior ◽  
Fracturing Fluids ◽  
Initiation Pressure ◽  
Cylindrical Cavities ◽  
Griffith Theory

Abstract The mechanics of hydraulic fracture initiation have been investigated by comparing laboratory experiments with theoretical predictions based on poro-elastic behavior. Experiments were conducted poro-elastic behavior. Experiments were conducted with 4-in. (10-cm) diameter cores containing spherical and cylindrical cavities and loaded in a triaxial cell under variable confining pressure, end load, and pore pressure. Experimental results agreed with theory for nonpenetrating fracturing fluid for limited ranges of hydrostatic confining stresses for four kinds of limestone rock. With penetrating fracturing fluids, the theory was penetrating fracturing fluids, the theory was confirmed only partially. Under nonhydrostatic stress conditions, reproducibility of measurements was too poor to evaluate the theory. Fracture orientation was controlled predominantly by stress conditions and cavity geometry. Notching of cylindrical cavities failed through notch extension only if the notch depth exceeded the value predicted approximately by a simple Griffith theory predicted approximately by a simple Griffith theory equation. Field applications of all results are discussed. Introduction This paper describes a combined theoretical/ experimental investigation of the mechanics of hydraulic fracture initiation. We considered fracture initiation pressure, fracture orientation, and mode of failure for various stress conditions and wellbore geometries. Our intention has been to consider theory applicable for both field and laboratory conditions, to test this theory with laboratory experiments, and to apply the results to interpretation of field data. The laboratory experiments were designed not to duplicate field conditions so much as to provide a critical test of the theory. Some field data are examined, but it is impractical to learn much about fracture initiation from field experiments because of the limited number of quantities that can be measured. The theory presented here is more a generalization of earlier work than a development of new theory. It provides a completely general treatment of fracture initiation in spherical and cylindrical cavities for poro-elastic materials. An extension of this theory poro-elastic materials. An extension of this theory to porous materials with nonelastic behavior already has been developed by Biot and will be referred to later. We begin by presenting theory for fracture initiation in spherical and cylindrical cavities. The theoretical results are followed by descriptions of laboratory experiments that test the equations for failure pressure in these geometries under various stress conditions, using penetrating and nonpentrating fracturing fluids. The effects of notching in cylindrical cavities then are considered, and a simple model based on Griffith crack theory is developed to explain experimental results. Field applications of all results then are discussed in detail. THEORY OF FRACTURE INITIATION The theory of hydraulic fracture initiation in rock materials has been treated in successive degrees of refinement. Cases of interest are hollow sphere and long hollow cylinder geometry with penetrating and nonpenetrating fracturing fluids. penetrating and nonpenetrating fracturing fluids. Refs. 1 through 7 cover various parts of the overall picture; Rice and Cleary give the most complete picture; Rice and Cleary give the most complete analysis. We present here an independent analysis based on Biot's theory for fluid saturated porous solids. Our analysis adds little that is new to the basic literature of fracture initiation theory. It is presented mainly to provide a way to analyze presented mainly to provide a way to analyze scaling effects between field results and our laboratory experiments. We start with Biot's stress-strain relations for a fluid saturated porous solid: (1) SPEJ P. 129

Hydraulic Fracturing Mechanical Mechanism Analyses for Soft Seams Considering Strain Softening Character

2013 ◽  
Vol 868 ◽  
pp. 319-325 ◽  
Author(s):  
Yi Lei ◽  
Wen Bin Wu
Keyword(s):  
Plastic Deformation ◽  
Elastic Modulus ◽  
Internal Friction ◽  
Hydraulic Fracturing ◽  
Poisson’S Ratio ◽  
Strain Softening ◽  
Fracture Initiation ◽  
Poisson's Ratio ◽  
Angle Of Internal Friction ◽  
Initiation Pressure

Mathematical model based on elasticity is not suitable for soft seam hydraulic fracturing mechanism study because its intensity is small, Poisson's ratio is relatively large, and its prone to plastic deformation. Based on plastic mechanics, the theory of large deformation and fracture mechanics theory, hydraulic fracturing of soft coal seam is divided into three phases, namely, coal bed compaction, fracture initiation and crack propagation from the view of the deformation mechanism, the occurring and developing mechanism. The initiation pressure of soft seams considered strain softening character after plastic deformation is obtained on the basis of above. The result shows that the initiation pressure is related to elastic modulus, Poisson's ratio, the angle of internal friction and residual strength. Elastic modulus is inversely proportional to the initiation pressure, the greater its value, the smaller the initiation pressure; but Poisson's ratio, the angle of internal friction and the residual strength and fracture initiation pressure is directly proportional relationship, the greater its value, since the smaller the crack pressure.

scholarly journals Experimental Investigation on Hydraulic Fracture Propagation of Carbonate Rocks under Different Fracturing Fluids

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3502 ◽  
Author(s):  
Yintong Guo ◽  
Peng Deng ◽  
Chunhe Yang ◽  
Xin Chang ◽  
Lei Wang ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Flow Rate ◽  
Radial Strain ◽  
Fracture Initiation ◽  
Fracture Morphology ◽  
Fracturing Fluid ◽  
Breakdown Pressure ◽  
Pump Flow ◽  
Fracturing Fluids ◽  
Pump Flow Rate

Deep carbonate reservoirs are rich in oil and gas resources. However, due to poor pore connectivity and low permeability, it is necessary to adopt hydraulic fracturing technology for their development. The mechanism of hydraulic fracturing for fracture initiation and propagation in carbonate rocks remains unclear, especially with regard to selection of the type of fracturing fluid and the fracturing parameters. In this article, an experimental study focusing on the mechanisms of hydraulic fracturing fracture initiation and propagation is discussed. Several factors were studied, including the type of injecting fracturing fluids, pump flow rate, fracturing pressure curve characteristics, and fracture morphology. The results showed the following: (1) The viscosity of fracturing fluid had a significant effect on fracturing breakdown pressure. Under the same pump flow rate, the fracturing breakdown pressure of slick water was the lowest. Fracturing fluids with low viscosity could easily activate weakly natural fractures or filled fractures, leading to open microcracks, and could effectively reduce the fracturing breakdown pressure. (2) The fluctuations in fracturing pump pressure corresponded with the acoustic emission hits and changes in radial strain; for every drop of fracturing pressure, acoustic emission hits and changes in radial strain were mutated. (3) Under the same fracturing fluid, the pump flow rate mainly affected fracturing breakdown pressure and had little effect on fracture morphology. (4) The width of the main fracture was affected by the viscosity and pump flow rate. Maximum changes in radial strain at the fracturing breakdown pressure point occurred when the fracturing fluid was guar gum. (5) With gelled acid and cross-linked acid fracturing, the main fractures were observed on the surface. The extension of the fracturing crack was mainly focused near the crack initiation parts. The crack expanded asymmetrically; the wormhole was dissolved to break through to the surface of the specimen. (6) The dissolution of gelled acid solution could increase the width of the fracturing crack and improve the conductivity of carbonate reservoirs.

scholarly journals Laboratory Testing of Fracture Conductivity Damage by Foam-Based Fracturing Fluids in Low Permeability Tight Gas Formations

Energies ◽  
2021 ◽  
Vol 14 (6) ◽  
pp. 1783
Author(s):  
Klaudia Wilk-Zajdel ◽  
Piotr Kasza ◽  
Mateusz Masłowski
Keyword(s):  
Hydraulic Fracturing ◽  
Guar Gum ◽  
Polymer Concentration ◽  
Laboratory Research ◽  
Damage Effect ◽  
Tight Gas ◽  
Fracturing Fluid ◽  
Fracture Conductivity ◽  
Fracturing Fluids ◽  
Sandstone Rock

In the case of fracturing of the reservoirs using fracturing fluids, the size of damage to the proppant conductivity caused by treatment fluids is significant, which greatly influence the effective execution of hydraulic fracturing operations. The fracturing fluid should be characterized by the minimum damage to the conductivity of a fracture filled with proppant. A laboratory research procedure has been developed to study the damage effect caused by foamed and non-foamed fracturing fluids in the fractures filled with proppant material. The paper discusses the results for high quality foamed guar-based linear gels, which is an innovative aspect of the work compared to the non-foamed frac described in most of the studies and simulations. The tests were performed for the fracturing fluid based on a linear polymer (HPG—hydroxypropyl guar, in liquid and powder form). The rheology of nitrogen foamed-based fracturing fluids (FF) with a quality of 70% was investigated. The quartz sand and ceramic light proppant LCP proppant was placed between two Ohio sandstone rock slabs and subjected to a given compressive stress of 4000–6000 psi, at a temperature of 60 °C for 5 h. A significant reduction in damage to the quartz proppant was observed for the foamed fluid compared to that damaged by the 7.5 L/m3 natural polymer-based non-foamed linear fluid. The damage was 72.3% for the non-foamed fluid and 31.5% for the 70% foamed fluid, which are superior to the guar gum non-foamed fracturing fluid system. For tests based on a polymer concentration of 4.88 g/L, the damage to the fracture conductivity by the non-foamed fluid was 64.8%, and 26.3% for the foamed fluid. These results lead to the conclusion that foamed fluids could damage the fracture filled with proppant much less during hydraulic fracturing treatment. At the same time, when using foamed fluids, the viscosity coefficient increases a few times compared to the use of non-foamed fluids, which is necessary for proppant carrying capacities and properly conducted stimulation treatment. The research results can be beneficial for optimizing the type and performance of fracturing fluid for hydraulic fracturing in tight gas formations.

scholarly journals Wind Farm Cable Connection Layout Optimization with Several Substations

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3615
Author(s):  
Adelaide Cerveira ◽  
Eduardo J. Solteiro Pires ◽  
José Baptista
Keyword(s):  
Energy Production ◽  
Wind Farm ◽  
Programming Model ◽  
Optimal Solution ◽  
Wind Farms ◽  
Green Energy ◽  
Fossil Energy ◽  
Proposed Model ◽  
Short Time ◽  
Cable Connection

Green energy has become a media issue due to climate changes, and consequently, the population has become more aware of pollution. Wind farms are an essential energy production alternative to fossil energy. The incentive to produce wind energy was a government policy some decades ago to decrease carbon emissions. In recent decades, wind farms were formed by a substation and a couple of turbines. Nowadays, wind farms are designed with hundreds of turbines requiring more than one substation. This paper formulates an integer linear programming model to design wind farms’ cable layout with several turbines. The proposed model obtains the optimal solution considering different cable types, infrastructure costs, and energy losses. An additional constraint was considered to limit the number of cables that cross a walkway, i.e., the number of connections between a set of wind turbines and the remaining wind farm. Furthermore, considering a discrete set of possible turbine locations, the model allows identifying those that should be present in the optimal solution, thereby addressing the optimal location of the substation(s) in the wind farm. The paper illustrates solutions and the associated costs of two wind farms, with up to 102 turbines and three substations in the optimal solution, selected among sixteen possible places. The optimal solutions are obtained in a short time.

scholarly journals Fracture Initiation Model of Shale Fracturing Based on Effective Stress Theory of Porous Media

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Yuwei Li ◽  
Dan Jia
Keyword(s):  
Porous Media ◽  
Mechanical Characteristics ◽  
Oil And Gas ◽  
Elastic Anisotropy ◽  
Special Kind ◽  
Fracture Initiation ◽  
Propagation Mechanism ◽  
Stress Theory ◽  
Unconventional Oil And Gas ◽  
Initiation Pressure

Unconventional oil and gas are important resources of future energy supply, and shale gas is the focus of the development of unconventional resources. Shale is a special kind rock of porous medium, and an orderly structure of beddings aligned in the horizontal direction where causing the strong elastic anisotropy of shale is easy. A new model has been established to calculate the fracture initiation pressure with the consideration of mechanical characteristics of shale and the anisotropic tensile strength when judging rock failure. The fracture initiation model established in this paper accurately reflects the stress anisotropy and matches well with the actual situation in porous media. Through the sensitivity analysis, the results show that σv/σH, Ev/EH, υv/υH, m/s, and A/B have a certain impact on the tangential stress when the circumferential angle changes, and there is a positive relationship between the initiation pressure and the above sensitive factors except for A/B. The results can provide a valuable and effective guidance for the prediction of fracture initiation pressure and fracture propagation mechanism under special stratum conditions of shale.

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