Determination of the instantaneous shut in pressure from hydraulic fracturing data and its reliability as a measure of the minimum principal stress

1983 ◽  
Vol 20 (3) ◽  
pp. A94
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Minimum Principal Stress

Determination of In-Situ Stresses From Hydraulically Fractured Spherical Cavities

1983 ◽  
Vol 105 (2) ◽  
pp. 125-127 ◽  
Author(s):  
W. E. Warren
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Spherical Cavity ◽  
Hydraulic Fractures ◽  
Stress Measurements ◽  
In Situ Stresses ◽  
Spherical Cavities ◽  
Stress Directions

Several problems in analysis can arise in estimating in-situ stresses from standard hydraulic fracturing operations if the borehole is not aligned with one of the principal stress directions. In these nonaligned situations, the possibility of fracturing a spherical cavity for estimating the in-situ stresses is investigated. The theory utilizes all the advantages of direct stress measurements associated with hydraulic fracturing and eliminates the geometrical problems associated with the analysis of hydraulic fractures in cylindrical boreholes.

A Fast Calculation Method for Natural Fractures Activation Considering Stress Shadow and Study on the Law of Natural Fractures Activation State Changes

2021 ◽  
Author(s):  
Yan Qiao ◽  
Yang Zhang ◽  
Tianhong Jiang ◽  
Guobin Zhang ◽  
Qing Chen ◽  
...  
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Calculation Method ◽  
Maximum Principal Stress ◽  
Natural Fractures ◽  
Fast Calculation ◽  
Fracture Spacing ◽  
Stress Shadow ◽  
Minimum Principal Stress ◽  
Net Pressure

Abstract During hydraulic fracturing process of the Permian Basin in North America, the cluster spacing has been shortened to 3m, and stress shadow can no longer be ignored. Many scholars have studied the influence of stress shadows to optimize cluster spacing. For reservoirs with natural fractures, how to activate more natural fractures through hydraulic fracturing has become the purpose. However, few scholars have studied changes in the activation law of natural fractures under stress shadow conditions. This paper establishes stress change value around single fracture according to Sneddon formula, and calculates the maximum and minimum principal stress according to plane principal stress calculation formula. Considering attenuation of net pressure, stress field of multiple fractures is established, and influence of various factors on stress re-orientation is studied. Finally, considering attenuation of net pressure with distance, according to discriminant formulas of tension & shear activation, the proportion of natural fractures that are easily activated is calculated. By designing orthogonal experiments, the influence of different factors on the proportion of activated natural fractures was studied. The stress increase in the direction of the minimum principal stress is much greater than the increase in the direction of the maximum principal stress. The stress increases in the direction of the maximum principal stress at the tip of the hydraulic fracture. The tip position between hydraulic fractures is "neutralized" due to the superposition of shear stress. Stress-fracture angle and the in-situ stress difference are the common main influencing factors for both tensile and shear activation, but the net pressure has little effect on the tensile activation of natural fracture. The fracture spacing has little effect on the activation of natural fractures. When formulating the fracturing scheme, we should pay more attention to the net pressure rather than the fracture spacing. This article provides a fast calculation method for the activation state of natural fractures considering the stress shadow, which provides a reference index for activating more natural fractures and increasing the production of a single well.

scholarly journals A Calculation Model of the Net Pressure for Forming Map Cracking in Coalbed with Cleats During Hydraulic Fracturing Process

2015 ◽  
Vol 8 (1) ◽  
pp. 193-197
Author(s):  
Li Yuwei ◽  
Ai Chi ◽  
Liu Yazhen
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Coalbed Methane ◽  
Maximum Principal Stress ◽  
Calculation Model ◽  
Coal Bed ◽  
Minimum Principal Stress ◽  
Fracturing Process ◽  
The Face ◽  
Net Pressure

An important prerequisite for achieving efficient exploitation of coalbed methane wells is through forming map cracking by hydraulic fracturing. In order to analyze the mechanical mechanism for forming map cracking of the coal bed with cleats, the mechanical conditions for forming map cracking during hydraulic fracturing process of coal bed was proposed using extensional faulting in elastic mechanics and the shear damage criterion, and the minimum net pressure calculation model for forming map cracking was established when the butt cleat and face cleat in coal opened at the same time. It can be concluded through using the calculation model that the net pressure value that needed for forming map cracking first decreased and then increased with the increasing of the angle between the face cleat and the direction of horizontal minimum principal stress. The cleats and fissures developed along the horizontal maximum principal stress were easy to open and extend under the effect of hydraulic fracturing. The variation of the internal friction coefficient variation of the face cleat had little effect on the minimum net pressure that was needed for forming map fracturing after the angle between the direction of face cleat and horizontal minimum principal stress is determined.

Characterizing Hydraulic Fracturing With a Tendency-for-Shear-Stimulation Test

2014 ◽  
Vol 17 (02) ◽  
pp. 233-243 ◽  
Author(s):  
Mark McClure ◽  
Roland Horne
Keyword(s):  
Hydraulic Fracturing ◽  
Principal Stress ◽  
Fluid Pressure ◽  
Test Fluid ◽  
Enhanced Geothermal Systems ◽  
Geothermal Systems ◽  
Natural Fractures ◽  
Permeability Enhancement ◽  
Minimum Principal Stress ◽  
Tensile Fracturing

Summary The classical concept of hydraulic fracturing is that a single, planar, opening mode fracture propagates through the formation. In recent years, there has been a growing consensus that natural fractures play an important role during stimulation in many settings. There is not universal agreement on the mechanisms by which natural fractures affect stimulation, and these mechanisms may vary depending on formation properties. One potentially important mechanism is shear stimulation, in which increased fluid pressure induces slip and permeability enhancement on pre-existing fractures. We propose a tendency-for-shear-stimulation (TSS) test as a direct, relatively unambiguous method for determining the degree to which shear stimulation contributes to stimulation in a formation. In a TSS test, fluid injection is performed while maintaining the bottomhole fluid pressure slightly less than the minimum principal stress. Under these conditions, shear stimulation is the only possible mechanism for permeability enhancement (except, perhaps, thermally induced tensile fracturing). A TSS test is different from a conventional procedure because injection is performed at a specified pressure (rather than a specified rate). With injection at a specified rate, fluid pressure may exceed the minimum principal stress, and it may cause tensile fractures to propagate through the formation. If this occurs, it will be ambiguous whether stimulation was because of shear stimulation or tensile fracturing. Maintaining pressure less than the minimum principal stress ensures that the effect of shear stimulation can be isolated. Low-rate injectivity tests could be performed before and after the TSS test to estimate formation permeability. An increase in formation permeability would indicate that shear stimulation has occurred. The flow-rate transient during injection may also be interpreted to identify shear stimulation. Numerical simulations of shear stimulation were performed with a discrete-fracture-network (DFN) simulator that couples fluid flow with the stresses induced by fracture deformation. These simulations were used to qualitatively investigate how shear stimulation and fracture connectivity affect the results of a TSS test. Two specific field projects are discussed as examples of a TSS test, the Enhanced Geothermal Systems (EGS) projects at Desert Peak, Nevada, and Soultz-sous-Forêts, France.

Study on Hydraulic Fracturing Affected by Horizontal Principal Stress

2013 ◽  
Vol 423-426 ◽  
pp. 1467-1470
Author(s):  
Bo Huang ◽  
Tian Hui Ma ◽  
Ai Shan Li ◽  
Jian Qiu Sun ◽  
Liao Yuan Zhang
Keyword(s):  
Elastic Modulus ◽  
Hydraulic Fracturing ◽  
Crack Propagation ◽  
Weibull Distribution ◽  
Principal Stress ◽  
Poisson Ratio ◽  
Propagation Direction ◽  
Wing Crack ◽  
Crack Propagation Direction ◽  
Minimum Principal Stress

Adopted with the actual value of statistic geo-stress, using RFPA software to simulate the hydraulic fracturing of underground. The sample is treated as elastomers and simplified into plane problem, submit strength, elastic modulus, poisson ratio to weibull distribution. It could be found in figures that the size, length, extending direction of two crack is not identical. The cracks` forms grow into symmetry horizontal double-wing crack from the final result, besides, crack propagation direction is perpendicular to the direction of the minimum principal stress.

scholarly journals Numerical simulation on the simultaneous stress interference of parallel multiple hydraulic fractures

2021 ◽  
pp. 014459872110019
Author(s):  
Weiyong Lu ◽  
Changchun He
Keyword(s):  
Principal Stress ◽  
Hydraulic Fracture ◽  
Stress Ratio ◽  
Fracture Network ◽  
Hydraulic Fractures ◽  
Fracture Spacing ◽  
Induced Stress ◽  
Minimum Principal Stress ◽  
Fracturing Process ◽  
Stress Ratios

During horizontal well staged fracturing, there is stress interference between multiple transverse fractures in the same perforation cluster. Theoretical analysis and numerical calculation methods are applied in this study. We analysed the mechanism of induced stress interference in a single fracture under different fracture spacings and principal stress ratios. We also investigated the hydraulic fracture morphology and synchronous expansion process under different fracture spacings and principal stress ratios. The results show that the essence of induced stress is the stress increment in the area around the hydraulic fracture. Induced stress had a dual role in the fracturing process. It created favourable ground stress conditions for the diversion of hydraulic fractures and the formation of complex fracture network systems, inhibited fracture expansion in local areas, stopped hydraulic fractures, and prevented the formation of effective fractures. The curves of the maximum principal stress, minimum principal stress, and induced principal stress difference with distance under different fracture lengths, different fracture spacings, and different principal stress ratios were consistent overall. With a small fracture spacing and a small principal stress ratio, intermediate hydraulic fractures were difficult to initiate or arrest soon after initiation, fractures did not expand easily, and the expansion speed of lateral hydraulic fractures was fast. Moreover, with a smaller fracture spacing and a smaller principal stress ratio, hydraulic fractures were more prone to steering, and even new fractures were produced in the minimum principal stress direction, which was beneficial to the fracture network communication in the reservoir. When the local stress and fracture spacing were appropriate, the intermediate fracture could expand normally, which could effectively increase the reservoir permeability.

Sign in / Sign up

Export Citation Format

Share Document