scholarly journals Rupture Directivity in 3D Inferred From Acoustic Emissions Events in a Mine-Scale Hydraulic Fracturing Experiment

2021 ◽  
Vol 9 ◽  
Author(s):  
José Ángel López-Comino ◽  
Simone Cesca ◽  
Peter Niemz ◽  
Torsten Dahm ◽  
Arno Zang
Keyword(s):  
Hydraulic Fracturing ◽  
Acoustic Emissions ◽  
Local Stress ◽  
Horizontal Stress ◽  
Monitoring Networks ◽  
Rupture Directivity ◽  
Shallow Subsurface ◽  
Minimum Horizontal Stress ◽  
Directivity Effects ◽  
Full Waveforms

Rupture directivity, implying a predominant earthquake rupture propagation direction, is typically inferred upon the identification of 2D azimuthal patterns of seismic observations for weak to large earthquakes using surface-monitoring networks. However, the recent increase of 3D monitoring networks deployed in the shallow subsurface and underground laboratories toward the monitoring of microseismicity allows to extend the directivity analysis to 3D modeling, beyond the usual range of magnitudes. The high-quality full waveforms recorded for the largest, decimeter-scale acoustic emission (AE) events during a meter-scale hydraulic fracturing experiment in granites at ∼410 m depth allow us to resolve the apparent durations observed at each AE sensor to analyze 3D-directivity effects. Unilateral and (asymmetric) bilateral ruptures are then characterized by the introduction of a parameter κ, representing the angle between the directivity vector and the station vector. While the cloud of AE activity indicates the planes of the hydrofractures, the resolved directivity vectors show off-plane orientations, indicating that rupture planes of microfractures on a scale of centimeters have different geometries. Our results reveal a general alignment of the rupture directivity with the orientation of the minimum horizontal stress, implying that not only the slip direction but also the fracture growth produced by the fluid injections is controlled by the local stress conditions.

A homogenization approach for modeling a propagating hydraulic fracture in a layered material

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. MR153-MR162 ◽  
Author(s):  
Egor V. Dontsov
Keyword(s):  
Elastic Properties ◽  
Hydraulic Fracture ◽  
Local Stress ◽  
Transversely Isotropic ◽  
Horizontal Stress ◽  
Layered Material ◽  
Elastic Response ◽  
Effective Parameters ◽  
Fine Mesh ◽  
Minimum Horizontal Stress

Shales are known to have a finely layered structure, which greatly influences the overall material’s response. Incorporating the effect of all these layers explicitly in a hydraulic fracture simulator would require a prohibitively fine mesh. To avoid such a scenario, a suitable homogenization, which would represent the effect of multiple layers in an average sense, should be performed. We consider a sample variation of elastic properties and minimum horizontal stress versus depth that has more than a hundred layers. We evaluate methodologies to homogenize the stress and the elastic properties. The elastic response of a layered material is found to be equivalent to that of a transversely isotropic material, and the explicit relations for the effective parameters are obtained. To illustrate the relevance of the homogenization procedure for hydraulic fracturing, the propagation of a plane strain hydraulic fracture in a finely layered shale is studied. To reduce the complexity of the numerical model, elastic layering is neglected and only the effect of the stress layers is analyzed. The results demonstrate the ability of the homogenized stress model to accurately capture the hydraulic fracture behavior using a relatively coarse mesh. This result is obtained by using a special asymptotic solution at the tip element that accounts for the local stress variation near the tip, which effectively treats the material at the tip element as nonhomogenized.

Valuation of hydraulic fracturing potentials of organic-rich shales from the Anambra basin using rock mechanical properties from wireline logs

2021 ◽  
Vol 19 (3) ◽  
pp. 45-44
Author(s):  
Homa Viola Akaha-Tse ◽  
Michael Oti ◽  
Selegha Abrakasa ◽  
Charles Ugwu Ugwueze
Keyword(s):  
Mechanical Properties ◽  
Hydraulic Fracturing ◽  
Horizontal Stress ◽  
Shale Formations ◽  
In Situ Stresses ◽  
Anambra Basin ◽  
Wireline Logs ◽  
Rock Mechanical Properties ◽  
Minimum Horizontal Stress

This study was carried out to determine the rock mechanical properties relevant for hydrocarbon exploration and production by hydraulic  fracturing of organic rich shale formations in Anambra basin. Shale samples and wireline logs were analysed to determine the petrophysical, elastic, strength and in-situ properties necessary for the design of a hydraulic fracturing programme for the exploitation of the shales. The results obtained indicated shale failure in shear and barreling under triaxial test conditions. The average effective porosity of 0.06 and permeability of the order of 10-1 to 101 millidarcies showed the imperative for induced fracturing to assure fluid flow. Average Young’s modulus and Poisson’s ratio of about 2.06 and 0.20 respectively imply that the rocks are favourable for the formation and propagation of fractures during hydraulic fracking. The minimum horizontal stress, which determines the direction of formation and growth of artificially induced hydraulic fractures varies from wellto-well, averaging between 6802.62 to 32790.58 psi. The order of variation of the in-situ stresses is maximum horizontal stress>vertical stress>minimum horizontal stress which implies a reverse fault fracture regime. The study predicts that the sweet spots for the exploration and development of the shale-gas are those sections of the shale formations that exhibit high Young’s modulus, low Poisson’s ratio, and high brittleness. The in-situ stresses required for artificially induced fractures which provide pore space for shale gas accumulation and expulsion are adequate. The shales possess suitable mechanical properties to fracture during hydraulic fracturing. Application of these results will enhance the potentials of the onshore Anambra basin as a reliable component in increasing Nigeria’s gas reserves, for the improvement of the nation’s economy and energy security. Key Words: Hydraulic Fracturing, Organic-rich Shales, Rock Mechanical Properties, Petrophysical Properties, Anambra Basin

Lithology-controlled stress variations and pad-scale faults: A case study of hydraulic fracturing in the Woodford Shale, Oklahoma

Geophysics ◽  
2017 ◽  
Vol 82 (6) ◽  
pp. ID35-ID44 ◽  
Author(s):  
Xiaodong Ma ◽  
Mark D. Zoback
Keyword(s):  
Hydraulic Fracturing ◽  
Horizontal Wells ◽  
Horizontal Stress ◽  
Strike Slip ◽  
Woodford Shale ◽  
Stress Regime ◽  
Component Content ◽  
Microseismic Events ◽  
Minimum Horizontal Stress ◽  
Stress Variations

We have conducted an integrated study to investigate the petrophysical and geomechanical factors controlling the effectiveness of hydraulic fracturing (HF) in four subparallel horizontal wells in the Mississippi Limestone-Woodford Shale (MSSP-WDFD) play in Oklahoma. In two MSSP wells, the minimum horizontal stress [Formula: see text] indicated by the instantaneous shut-in pressures of the HF stages are significantly less than the vertical stress [Formula: see text]. This, combined with observations of drilling-induced tensile fractures in the MSSP in a vertical well at the site, indicates that this formation is in a normal/strike-slip faulting stress regime, consistent with earthquake focal mechanisms and other stress indicators in the area. However, the [Formula: see text] values are systematically higher and vary significantly from stage to stage in two WDFD wells. The stages associated with the abnormally high [Formula: see text] values (close to [Formula: see text]) were associated with little to no proppant placement and a limited number of microseismic events. We used compositional logs to determine the content of compliant components (clay and kerogen). Due to small variations in the trajectories of the horizontal wells, they penetrated three thin, but compositionally distinct WDFD lithofacies. We found that [Formula: see text] along the WDFD horizontals increases when the stage occurred in a zone with high clay and kerogen content. These variations of [Formula: see text] can be explained by various degrees of viscous stress relaxation, which results in the increase in [Formula: see text] (less stress anisotropy), as the compliant component content increases. The distribution of microseismic events was also affected by normal and strike-slip faults cutting across the wells. The locations of these faults were consistent with unusual lineations of microseismic events and were confirmed by 3D seismic data. Thus, the overall effectiveness of HF stimulation in the WDFD wells at this site was strongly affected the abnormally high HF gradients in clay-rich lithofacies and the presence of preexisting, pad-scale faults.

Attribute analyses of acoustic emissions in hydraulic fracturing

2021 ◽  
pp. 1-43
Author(s):  
Juan Camilo Acosta ◽  
Son T. Dang ◽  
Carl H. Sondergeld ◽  
Chandra S. Rai
Keyword(s):  
Hydraulic Fracturing ◽  
Acoustic Waves ◽  
Failure Modes ◽  
Acoustic Emissions ◽  
Fracture Initiation ◽  
Horizontal Stress ◽  
Cylindrical Sample ◽  
Variable Rate ◽  
Horizontal Drilling ◽  
Injection Test

Hydraulic fracturing (HF) and horizontal drilling are essential to the development of shale gas and oil. Production depends on the stimulation success. During fracture initiation, propagation, and closure, cracks emit acoustic waves; these can be monitored in real time as microseismics in the field and as acoustic emissions (AEs) in the laboratory. AEs are the laboratory equivalent of field-scale microseismics and contain detailed information about HF fracture mechanics. The number of acoustic events correlates with the number of induced fractures and hence the stimulation volume. Three HF protocols under dry conditions were carried out on Tennessee sandstone: (1) a constant injection rate, (2) a precyclic injection, and (3) a variable-rate injection test. All three tests were performed under the same principal stress conditions: vertical stress of 10.3 MPa (1500 psi), minimum horizontal stress of 3.5 MPa (500 psi), and maximum horizontal stress of 20.7 MPa (3000 psi). In total, 16 piezoelectric transducers were mounted around a cylindrical sample to record the AEs. We have performed postsignal processing to extract AE event attributes, including the amplitudes, signal-to-noise ratio, arrival time, event location (with the velocity-anisotropy input), and frequency analyses. The AE events associated with the constant-rate injection test possessed the lowest frequencies (150–270 kHz). The variable-rate test AE events possessed higher frequencies (160–310 kHz), whereas the precyclic injection had events with the highest frequencies, peaking at 330 kHz. Acoustic events before failure had lower amplitudes, but higher frequency compared to those recorded postbreakdown, suggesting different failure modes. Precyclic injection induced the greatest number of locatable events before and after failure.

scholarly journals Hydraulic Fracture Propagation in Layered Rock: Experimental Studies of Fracture Containment

1984 ◽  
Vol 24 (01) ◽  
pp. 19-32 ◽  
Author(s):  
Lawrence W. Teufel ◽  
James A. Clark
Keyword(s):  
Hydraulic Fracturing ◽  
Hydraulic Fracture ◽  
Horizontal Stress ◽  
Hydraulic Fractures ◽  
Low Permeability ◽  
Fracture Treatment ◽  
Gas Recovery ◽  
Layered Rock ◽  
Fracture Fluid ◽  
Minimum Horizontal Stress

Abstract Fracture geometry is an important concern in the design of a massive hydraulic fracture for improved natural gas recovery from low-permeability reservoirs. Determination of the extent of vertical fracture growth and containment in layered rock, a priori, requires an improved understanding of the parameters that may control fracture growth across layer interfaces. We have conducted laboratory hydraulic fracture experiments and elastic finite element studies that show that at least two distinct geologic conditions can inhibit or contain the vertical growth of hydraulic fractures in layered rock:a weak interfacial shear strength of the layers andan increase in the minimum horizontal compressive stress in the bounding layers. The second condition is more important and more likely to occur at depth. Differences in elastic properties within a layered rock mass may be important-not as a containment barrier perse, but in the manner in which variations in elastic properties affect the vertical distribution of the minimum horizontal stress magnitude. These results suggest that improved fracture treatment designs and an assessment of the potential success of stimulations in low-permeability reservoirs can be made by determining the in-situ stress st ate in the producing interval and bounding formations before stimulation. If the bounding formations have a higher minimum horizontal stress, then one can optimize the fracture treatment and maximize the ratio of productive formation fracture area to volume of fluid pumped by limiting bottomhole pressures to that of the bounding formation. Introduction In 1949, Clark introduced the concept of hydraulic fracturing to the petroleum industry. Since then, hydraulic fracture treatment to enhance oil and gas recovery in tight reservoir rocks has become standard practice. More recently, as a result of an increased need for better recovery techniques, massive hydraulic fracturing (MHF) has been used in low-permeability, gas-bearing sandstones in the Rock Mountain region and in Devonian shales of the Appalachian region, where it is uneconomical to retrieve gas in the conventional manner. Massive hydraulic fractures are designed to extend as much as 1000 m (3,281 ft) radially from the wellbore and generally require up to 1000 m3 (6,293 bbl) of fracture fluid. MHF has been developed by trial and error, and the results are uncertain in many situations. Some of these large-scale stimulation efforts have been successful, but others have been extremely disappointing failures. The reasons for these failures are not clear, but it seems likely that improved understanding of the fundamental mechanisms of hydraulic fracturing should suggest ways of improving the efficiency and reliability of the MHF stimulation technique or at least indicate where this technique can be applied successfully. Among the many technological problems encountered in MHF, one of the most important questions that must be answered properly to design a hydraulic fracture treatment for optimal gas recovery concerns the shape and overall geometry of the fracture. The question of fracture height and whether the hydraulic fracture will propagate into formations lying above and below the producing zone. When a fracture treatment is designed, the height of the fracture is the parameter about which the least is known, yet this influences all aspects of the design. A hydraulic fracture usually grows outward in a vertical plane and propagates above and below the packers as well as laterally away from the wellbore. Vertical propagation is undesirable whenever the fracturing is to be contained within a single stratigraphic interval. If the hydraulic fracture is not contained within the producing formation and propagates in both the vertical and lateral directions (an elliptical fracture), failure of the treatment can occur because the fracture fails to contact a sufficiently large area of the reservoir. Moreover, there is an effective loss of the expensive fracture fluid and proppant used to fracture the unproductive formations. An extreme example where the containment of a hydraulic fracture is essential is the case of developing a fracture in a gas-producing sandstone without fracturing through the underlying shale into another sandstone that is water-bearing. Therefore, it is of great economic importance to the gas industry to understand the parameters that can restrict the vertical propagation of massive hydraulic fractures. There are several parameters that are considered to have some effect on the vertical growth and possible containment of hydraulic fractures. SPEJ P. 19^

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.

Tunnel Ground Stress Test and Rock Burst Prediction Based on Hydraulic Fracturing Method

2013 ◽  
Vol 368-370 ◽  
pp. 1830-1837
Author(s):  
Xin Zhe Li ◽  
Geng Feng Wang ◽  
Jun Mei Li
Keyword(s):  
Hydraulic Fracturing ◽  
Rock Burst ◽  
Stress Test ◽  
Large Angle ◽  
Horizontal Stress ◽  
Stress Direction ◽  
Ground Stress ◽  
The Stability ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

The hydraulic fracturing method is a common method to measure the ground stress. This article describes the principles of the hydraulic fracturing method, studies the distribution and the value of the ground stress in a tunnel area with the hydraulic fracturing method, and predicts rock burst by using the Russenes discriminance and the Turchaninov discriminance. The results show that the maximum horizontal stress is between 4.7MPa and 11.1MPa, and the minimum horizontal stress is between 4.0MPa and 8.0MPa. The maximum horizontal stress direction of the drilling is between N63 °W and N72 °W, and it is not conducive to the stability of the tunnel surrounding rocks because the large angle intersection of the tunnel axis direction and the maximum horizontal stress direction.

Geomechanics Without Sonic In Tight Gas Reservoirs In The North Of Oman

2015 ◽  
Author(s):  
Rinat Lukmanov ◽  
Mohammed Aamri
Keyword(s):  
Hydraulic Fracturing ◽  
Gamma Ray ◽  
Total Porosity ◽  
Horizontal Stress ◽  
Tight Gas ◽  
Gas Reservoirs ◽  
The North ◽  
Minimum Horizontal Stress ◽  
Stress Contrast ◽  
Clastic Reservoirs

Abstract Barik and Miqrat are the main two deep tight gas clastic reservoirs in several fields of Oman. In the area of the current Study, these reservoirs are encountered at depth 4500-5200 m and contain rich gas/condensate. Average permeability for different units ranges from 0.02 to 4 mD, porosity up to 14% with averages values within the range 5-10%. In order to produce economically, hydraulic fracturing is applied in these reservoirs. Geomechanics calculations are essential for the fracturing design. One of the particular challenges is fracture containment within the gas zone because in view of low stress contrast between different lithologies. Sonic data are normally used for these calculations. However, based on the analysis of the Sonic data available, a simple workflow was developed for Geomechanics calculations which don't require Sonic. A good restoration of compressional Sonic was achieved using the total porosity and the rock volumetrics as the input data. The analysis reveals good correlation between the complex rock constituents and the Poisson's ratio. These findings resulted in good Shear Sonic restoration and fir for purpose calculations of Geomechanics parameters. The Minimum horizontal stress data obtained based on actual Sonic data matches very well with the Minimum horizontal stress derived without Sonic resulting in practically the same hydraulic fracturing design. The normalization of Gamma Ray and Neutron and rigorous multimineral analysis was a key to success for this methodology. A fit for purpose methodology was developed which enabled to perform identification of 3 key rock constituents even from the basic Triple Combo. The methodology for Geomechanics without Sonic was used for frac design in several wells. The proposed model is found to be very robust.

Calculation Method of Earth Stress in Zhenjing Oil Fileld in China

2014 ◽  
Vol 548-549 ◽  
pp. 1885-1892
Author(s):  
Li Min Ran ◽  
He Ping Pan ◽  
Yong Gang Zhao
Keyword(s):  
Spatial Distribution ◽  
Hydraulic Fracturing ◽  
Test Data ◽  
Calculation Method ◽  
Continuous Distribution ◽  
Horizontal Stress ◽  
Vertical Stress ◽  
Magnitude Distribution ◽  
Minimum Horizontal Stress ◽  
Maximum Horizontal Stress

The magnitude, distribution of earth stress are important parameters. In this paper, based on the hydraulic fracturing test data and logging data, the model of earth stress has been established. The vertical stress (Sv),the maximum horizontal stress (SH), the minimum horizontal stress (Sh) can be calculated by logging data with this model. The profiles of earth stress along the depth with continuous distribution can be determined, and stress spatial distribution has been described.

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