scholarly journals Cyclic Injection to Enhance Hydraulic Fracturing Efficiency: Insights from Laboratory Experiments

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Hao Kang ◽  
Jincai Zhang ◽  
Xin Fan ◽  
Zhiwen Huang
Keyword(s):  
Hydraulic Fracturing ◽  
Injection Pressure ◽  
Pressure Amplitude ◽  
Pressure Reduction ◽  
Breakdown Pressure ◽  
Injection Method ◽  
Number Of Cycles ◽  
Fracturing Experiments ◽  
Cyclic Injection

In hydraulic fracturing applications, there is substantial interest to reduce the formation breakdown pressure. Previous research results show that the cyclic injection method can be used to reduce that pressure. In this study, we conducted laboratory hydraulic fracturing experiments to apply cyclic injection to reduce the breakdown pressures of very tight and strong sandstones. Experimental results show that using cyclic injection the average breakdown pressure was reduced by 18.9% in very tight sandstones and by 7.18% in normal sandstones. This indicates that the effect of cyclic injection is more significant for stronger and tighter rocks. The experiments also reveal that the rock tensile strength plays a more important role in the formation breakdown pressure with a rock strength factor of 2.85. This suggests that the breakdown pressure is higher than expected. In addition, we empirically related the breakdown pressure reduction and the injection pressure amplitude to the number of injection cycles. The curve fitting results imply that the effect of cyclic injection is more important if the number of cycles or the injection pressure amplitude is increased. Based on the results of this research, the in-situ formation breakdown pressure can be reduced by applying the cyclic injection method, and the breakdown pressure reduction is more significant as the number of cycles increases.

The effect of stress on the primary permeability of rock cores—a facet of hydraulic fracturing

1981 ◽  
Vol 18 (2) ◽  
pp. 195-204 ◽  
Author(s):  
R. Heystee ◽  
J.-C. Roegiers
Keyword(s):  
Rock Mass ◽  
Hydraulic Fracturing ◽  
The State ◽  
Stress Conditions ◽  
Breakdown Pressure ◽  
Rock Types ◽  
State Of Stress ◽  
Pressurization Rate ◽  
Fluid Penetration ◽  
Fracturing Experiments

Recent laboratory hydraulic fracturing experiments have shown that fluid penetration into the rock mass adjacent to the borehole being pressurized has a significant influence on the magnitude of the breakdown pressure. One factor affecting the degree of penetration of the pressurizing fluid is the permeability of the rock mass, which in turn is a function of the state of stress present in the rock mass. To study this permeability–stress relationship, a radial permeameter was constructed and three rock types tested. Derived expressions show that during radially divergent and convergent flow in the permeameter, the state of stress in the rock specimen is tensile and compressive respectively. The radial permeameter test results show that the permeability of rock increases significantly under tensile stress conditions and reduces under compressive stress conditions. The results from this study were used to develop a conceptual model which explains the dependency of breakdown pressure levels on the pressurization rate.

scholarly journals Numerical Investigation of the Impacts of Borehole Breakouts on Breakdown Pressure

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 888 ◽  
Author(s):  
Hua Zhang ◽  
Shunde Yin ◽  
Bernt Aadnoy
Keyword(s):  
Hydraulic Fracturing ◽  
Shear Failure ◽  
In Situ Stress ◽  
Test Results ◽  
Breakdown Pressure ◽  
Borehole Breakout ◽  
Borehole Breakouts ◽  
The Difference ◽  
Mud Pressure

Borehole breakouts appear in drilling and production operations when rock subjected to in situ stress experiences shear failure. However, if a borehole breakout occurs, the boundary of the borehole is no longer circular and the stress distribution around it is different. So, the interpretation of the hydraulic fracturing test results based on the Kirsch solution may not be valid. Therefore, it is important to investigate the factors that may affect the correct interpretation of the breakdown pressure in a hydraulic fracturing test for a borehole that had breakouts. In this paper, two steps are taken to implement this investigation. First, sets of finite element modeling provide sets of data on borehole breakout measures. Second, for a given measure of borehole breakouts, according to the linear relation between the mud pressure and the stress on the borehole wall, the breakdown pressure considering the borehole breakouts is acquired by applying different mud pressure in the model. Results show the difference between the breakdown pressure of a circular borehole and that of borehole that had breakouts could be as large as 82% in some situations.

A Data-Driven Approach to Predict the Breakdown Pressure of the Tight and Unconventional Formation

2021 ◽  
Author(s):  
Zeeshan Tariq ◽  
Murtada Saleh Aljawad ◽  
Mobeen Murtaza ◽  
Mohamed Mahmoud ◽  
Dhafer Al-Shehri ◽  
...  
Keyword(s):  
Neural Network ◽  
Hydraulic Fracturing ◽  
Rock Properties ◽  
Breakdown Pressure ◽  
Rock Samples ◽  
In Situ Stresses ◽  
Fracturing Fluids ◽  
The Neural Network ◽  
Different Types

Abstract Unconventional reservoirs are characterized by their extremely low permeabilities surrounded by huge in-situ stresses. Hydraulic fracturing is a most commonly used stimulation technique to produce from such reservoirs. Due to high in situ stresses, breakdown pressure of the rock can be too difficult to achieve despite of reaching maximum pumping capacity. In this study, a new model is proposed to predict the breakdown pressures of the rock. An extensive experimental study was carried out on different cylindrical specimens and the hydraulic fracturing stimulation was performed with different fracturing fluids. Stimulation was carried out to record the rock breakdown pressure. Different types of fracturing fluids such as slick water, linear gel, cross-linked gels, guar gum, and heavy oil were tested. The experiments were carried out on different types of rock samples such as shales, sandstone, and tight carbonates. An extensive rock mechanical study was conducted to measure the elastic and failure parameters of the rock samples tested. An artificial neural network was used to correlate the breakdown pressure of the rock as a function of fracturing fluids, experimental conditions, and rock properties. Fracturing fluid properties included injection rate and fluid viscosity. Rock properties included were tensile strength, unconfined compressive strength, Young's Modulus, Poisson's ratio, porosity, permeability, and bulk density. In the process of data training, we analyzed and optimized the parameters of the neural network, including activation function, number of hidden layers, number of neurons in each layer, training times, data set division, and obtained the optimal model suitable for prediction of breakdown pressure. With the optimal setting of the neural network, we were successfully able to predict the breakdown pressure of the unconventional formation with an accuracy of 95%. The proposed method can greatly reduce the prediction cost of rock breakdown pressure before the fracturing operation of new wells and provides an optional method for the evaluation of tight oil reservoirs.

Field Experiments on Hydraulic Fracturing

1972 ◽  
Vol 12 (01) ◽  
pp. 69-77 ◽  
Author(s):  
Hilmar von Schonfeldt ◽  
C. Fairhurst
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Compressive Stress ◽  
Rupture Strength ◽  
Breakdown Pressure ◽  
Near Surface ◽  
Fracturing Process ◽  
Fluid Penetration ◽  
Regional Stresses

Abstract Hydraulic fracturing experiments at two underground and one near-surface location in igneous and shale formations were described. The tests were designed to study the feasibility of hydraulic fracturing as a method of determining in-situ stresses. The tests were carried out in open holes of 2-3/8-in. diameter. Fracturing tests on two 5-ft diameter cores were also reported. The test results revealed an increase in the magnitude of the stress as the face of an opening was approached from inside a rock mass. Horizontal fractures also were observed in areas of reportedly high lateral stress, providing some evidence for the validity of the providing some evidence for the validity of the principle of least resistance. The results also principle of least resistance. The results also indicate that caution must be used in using the shut-in pressure as a measure of the least compressive stress. Introduction Hydraulic fracturing is best known as a well stimulation method. There are other important applications, however, for which the process shows great potential. One of these is in the area of in-situ stress determination as suggested by Scheidegger Kehle and Fairhurst. The mechanics of the fracturing process is the same in any application, and improvement of the method may therefore be expected through a mutual exchange of experience in each of these areas. The theory of the hydraulic fracturing technique relates measurable quantities such as the breakdown pressure and the instantaneous shut-in pressure to pressure and the instantaneous shut-in pressure to the tectonic stresses and certain physical rock properties. properties. Assuming negligible pore pressure and fluid penetration, the break-down pressure (pC) at the penetration, the break-down pressure (pC) at the instant of fracture initiation is given by the following expressions....................(1) when the fracture extends in a "radial" direction (in a plane parallel to the axis of the borehole). And...................(2) when the fracture extends in a direction normal to the borehole axis. Corresponding expressions that include the effect of pore pressure and fluid penetration are given in the literature Because our work was done in dry and impermeable formations, Eqs. 1 and 2 are considered adequate. These formulae are based on the assumption that the borehole is drilled parallel to 3 and that the rock behaves as a linearly elastic isotropic material; it also assumes that the fracture is initiated in a direction perpendicular to the least compressive stress, i.e., 2 or 3, respectively, in accordance with the principle of least resistance. The terms "radial" and "normal" fractures are introduced in place of the commonly used terms "vertical" and "horizontal" fractures in order to avoid possible confusion in the event a borehole is drilled in a direction other than the vertical. Eqs. 1 and 2 establish a simple relation between the breakdown pressure and the regional (far-field) stresses. It also has been suggested that the instantaneous shut-in pressure is a measure for the least compressive stress because a fracture will propagate in a direction normal to it. Therefore, propagate in a direction normal to it. Therefore, or ..........................(3) Thus Eqs. 1 and 3 may serve to estimate the regional stresses 1, and 2 provided it is known that a radial fracture was generated, and it is possible to determine the rupture strength (K ). possible to determine the rupture strength (K ). Similarly Eqs. 2 or 3 will give an estimate of the stress 3. Scheidegger and Kehle determined regional stresses through a similar analysis of hydraulic fracturing data. SPEJ P. 69

Chemically-Induced Pressure Pulse: Fracturing Competent Reservoirs

2021 ◽  
Author(s):  
Ayman R. Al-Nakhli ◽  
Zeeshan Tariq ◽  
Mohamed Mahmoud ◽  
Abdulazeez Abdulraheem
Keyword(s):  
Hydraulic Fracturing ◽  
Rock Fracture ◽  
Applied Pressure ◽  
Hydraulic Fractures ◽  
Breakdown Pressure ◽  
Hydrocarbon Production ◽  
Fracture Pressure ◽  
Micro Cracks ◽  
Chemically Induced ◽  
Fracturing Experiments

Abstract Commercial volumes of hydrocarbon production from tight unconventional reservoirs need massive hydraulic fracturing operations. Tight unconventional formations are typically located inside deep and over-pressured formations where the rock fracture pressure with slickwater becomes so high because of huge in situ stresses. Therefore, several lost potentials and failures were recorded because of high pumping pressure requirements and reservoir tightness. In this study, thermochemical fluids are introduced as a replacement for slickwater. These thermochemical fluids are capable of reducing the rock fracture pressure by generating micro-cracks and tiny fractures along with the main hydraulic fractures. Thermochemical upon reaction can generate heat and pressure simultaneously. In this study, several hydraulic fracturing experiments in the laboratory on different synthetic cement samples blocks were carried out. Cement blocks were made up of several combinations of cement and sand ratios to simulate real rock scenarios. Results showed that fracturing with thermochemical fluids can reduce the breakdown pressure of the cement blocks by 30%, while applied pressure was reduced up to 88%, when using thermochemical fluid, compared to slickwater. In basins with excessive tectonic stresses, the current invention can become an enabler to fracture and stimulate well stages which otherwise left untreated. A new methodology is developed to lower the breakdown pressure of such reservoirs, and enable fracturing. Keywords: Unconventional formation; breakdown pressure; thermochemicals; micro fractures.

Productivity Enhancement in Multilayered Unconventional Rocks Using Thermochemicals

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Zeeshan Tariq ◽  
Mohamed Mahmoud ◽  
Olalekan Alade ◽  
Abdulazeez Abdulraheem ◽  
Ayyaz Mustafa ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Elastic Moduli ◽  
Cost Effective ◽  
The Novel ◽  
Productivity Analysis ◽  
Breakdown Pressure ◽  
Linear Elastic ◽  
Layered Formation ◽  
Fracture Height ◽  
Fracturing Experiments

Abstract Elastic moduli contrast between the adjacent layers in a layered formation can lead to various problems in a conventional hydraulic fracturing job such as improper fracture height growth, limited penetration in a weaker layer only, and nonconductive fractures. In this study, the results of thermochemical fracturing experiment are presented. The hydraulic fracturing experiments presented in this study were carried out on four-layered very tight cement block samples. The results revealed that the novel fracturing technique can reduce the required breakdown pressure in a layered rock by 26%, from 1495 psi (reference breakdown pressure recorded in the conventional hydraulic fracturing technique) to 1107 psi (breakdown pressure recorded in the thermochemical fracturing). The posttreatment experimental analysis showed that the thermochemical fracturing approach resulted in deep and long fractures, passing through majority of the layers, while conventional hydraulic fracturing resulted in a thin fracture that affected only the top layer. A productivity analysis was also carried out which suggested that the fracturing with thermochemical fluids can raise the oil flowrate up to 76% when compared to a conventional hydraulic fracturing technique. Thermochemical fluids injection caused the creation of microfractures and reduces the linear elastic parameters of the rocks. The new technique is cost effective, nontoxic, and sustainable in terms of no environmental hazards.

Hydraulic fracturing experiment at the University of Regina Campus

1986 ◽  
Vol 23 (4) ◽  
pp. 548-555 ◽  
Author(s):  
J. D. McLennan ◽  
H. S. Hasegawa ◽  
J -C Roegiers ◽  
Alan M. Jessop
Keyword(s):  
Hydraulic Fracturing ◽  
Stress Component ◽  
Horizontal Stress ◽  
Depth Range ◽  
Precambrian Basement ◽  
Breakdown Pressure ◽  
Overburden Pressure ◽  
Minimum Horizontal Stress ◽  
The University

A hydraulic fracturing stress determination was carried out during May and June, 1979, in a water well intended for the Geothermal Feasibility Project on the campus of the University of Regina, Saskatchewan. Four intervals between depths of 2062 and 2215 m were fractured successfully, one in the Winnipeg Formation (2034–2083 m), two in the Deadwood Formation (2083–2209 m), and one under the Phanerozoic sequence near the top of the Precambrian basement (2209–2215 m).Over the depth range (2062–2215 m) covered by this hydrofracture experiment, the results and inferences are as follow. Downhole breakdown pressure ranges from 42 to 45 MPa, and downhole shut-in pressure from 35 to 42 MPa. The minimum horizontal stress component, σhmin, is taken as being equal to the corresponding shut-in pressure. The vertical stress component, σv, is assumed to be essentially equal to the overburden pressure and varies from 51 to 56 MPa. Whereas σv and σhmin apparently vary smoothly across the Deadwood Formation, the maximum horizontal component, σhmax, appears to undergo a discontinuity in the upper part of the Deadwood Formation, as σHMAX varies from 40 MPa in the Winnipeg Formation to 53 MPa in the upper part of the Precambrian basement. In so far as seismotectonics is concerned, the physical implications of these measurements are that normal faulting should prevail in the Winnipeg (and overlying) formations whereas strike-slip faulting could occur in the Precambrian basement; however, the latter inference has not been firmly established. Breakdown pressure is a useful guide (upper limit) for the potential geothermal demonstration project. Key words: hydraulic fracture, fracture mechanics, faulting, stresses, in situ, breakdown, shut-in pressure, seismotectonics.

Simulation of Multiple Hydraulic Fracturing in Non-Uniform Pore Pressure Field

2005 ◽  
Vol 9 ◽  
pp. 163-172 ◽  
Author(s):  
Lian Chong Li ◽  
Chun An Tang ◽  
Leslie George Tham ◽  
Tian Hong Yang ◽  
Shao Hong Wang
Keyword(s):  
Hydraulic Fracturing ◽  
Pore Pressure ◽  
Process Analysis ◽  
Failure Process ◽  
Fracture Initiation ◽  
Global Scale ◽  
Breakdown Pressure ◽  
Failure Evolution ◽  
Rock Failure Process ◽  
Fracturing Experiments

A series of numerical simulations of hydraulic fracturing were performed to study the initiation, propagation and breakdown of fluid driven fractures. The simulations are conducted with a flow-coupled Rock Failure Process Analysis code (RFPA2D). Both heterogeneity and permeability of the rocks are taken into account in the studies. The simulated results reflect macroscopic failure evolution process induced by microscopic fracture subjected to porosity pressure, which are well agreeable to the character of multiple hydraulic fracturing experiments. Based on the modeling results, it is pointed out that fracture is influenced not only by pore pressure magnitude on a local scale around the fracture tip but also by the orientation and the distribution of pore pressure gradients on a global scale. The fracture initiation, the orientation of crack path, the breakdown pressure and the stress field evolution around the fracture tip are influenced considerably by the orientation of the pore pressure. The research provides valuable guidance to the designers of hydraulic fracturing engineering.

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