In Situ Stresses in Borehole Blanche-1/South Australia Derived from Breakouts, Core Discing and Hydraulic Fracturing to 2 km Depth

Abstract In-situ stress state plays an important role in controlling fracture growth and containment in hydraulic fracturing managements. It is evident that the mechanical properties, existing stress regime and the natural fracture network of its reservoir rocks and the surrounding formations mainly control the geometry, size and containments of produced hydraulic fractures. Furthermore, the three principal in situ stresses' axes swap directions and magnitudes at different depths giving rise to identifying different mechanical bedrocks with corresponding stress regimes at different depths. Hence predicting the hydro-fractures can be theoretically achieved once all the above data are available. This is particularly difficult in unconventional and tight carbonate reservoirs, where heterogeneity and highly stress variation, in terms of magnitude and orientation, are expected. To optimize the field development plan (FDP) of a tight carbonate gas reservoir in Abu Dhabi, 1D Mechanical Earth Models (MEMs), involving generating the three principal in-situ stresses' profiles and mechanical property characterization with depth, have been constructed for four vertical wells. The results reveal the swap of stress magnitudes at different mechanical layers, which controls the dimension and orientation of the produced hydro-fractures. Predicted containment of the Hydro-fractures within the specific zones is likely with inevitable high uncertainty when the stress contrast between Sv, SHmax with Shmin respectively as well as Young's modulus and Poisson's Ratio variations cannot be estimated accurately. The uncertainty associated with this analysis is mainly related to the lacking of the calibration of the stress profiles of the 1D MEMs with minifrac and/or XLOT data, and both mechanical and elastic properties with rock mechanic testing results. This study investigates the uncertainty in predicting hydraulic fracture containment due to lacking such calibration, which highlights that a complete suite of data, including calibration of 1D MEMs, is crucial in hydraulic fracture treatment.

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Determination of in-situ stresses around underground excavations by means of hydraulic fracturing.-Final technical report

International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts ◽

10.1016/0148-9062(74)92093-2 ◽

1974 ◽

Vol 11 (12) ◽

pp. 246 ◽

Cited By ~ 2

Author(s):

B.C. Haimson

Keyword(s):

Hydraulic Fracturing ◽

Underground Excavations ◽

In Situ Stresses ◽

Technical Report

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Mechanism of core discing in the relaxation zone around an underground opening under high in situ stresses

Bulletin of Engineering Geology and the Environment ◽

10.1007/s10064-017-1168-3 ◽

2017 ◽

Vol 77 (3) ◽

pp. 1179-1189 ◽

Cited By ~ 4

Author(s):

Long An ◽

Changyu Jin ◽

Dong Liu ◽

Chenggong Ding ◽

Xinghang Dai

Keyword(s):

Underground Opening ◽

Relaxation Zone ◽

In Situ Stresses ◽

Core Discing

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Determination of In-Situ Stresses From Hydraulically Fractured Spherical Cavities

Journal of Energy Resources Technology ◽

10.1115/1.3230890 ◽

1983 ◽

Vol 105 (2) ◽

pp. 125-127 ◽

Cited By ~ 2

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.

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

Scientia Africana ◽

10.4314/sa.v19i3.3 ◽

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

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

10.2118/206136-ms ◽

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.

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Integrated Application of Three In Situ Stress Measurement Techniques

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.301-303.949 ◽

2011 ◽

Vol 301-303 ◽

pp. 949-953

Author(s):

Yuan Li ◽

Lan Qiao ◽

Zhi Li Sui

Keyword(s):

Acoustic Emission ◽

Hydraulic Fracturing ◽

Stress Measurement ◽

Stress Relief ◽

In Situ Stress ◽

In Situ Stresses ◽

In Situ Stress Measurement ◽

Iron Mine ◽

Acoustic Emission Test

The CSIRO overcoring stress relief and hydraulic fracturing methods are the most popular methods used for the measurement of in-situ stress at depth. One major advantage of the CSIRO overcoring stress relief method is that the three dimensional state of stress can be obtained, but the measurement must be done in an excavated tunnel[1]. Hydraulic fracturing method can be carried out on the ground surface, but it assumed that one of the principal stresses direction is vertical[2,3]. In terms of the disadvantages of the two methods, the techniques based on core orientation and acoustic emission behavior of rocks are incorporated in the in-situ stress measurement in order to obtain the in-situ stress conditions at depth in Shuichang Iron Mine. According to the comparison of the measurement data obtained from the acoustic emission test in the laboratory and CSIRO overcoring stress relief measurement in the field, effectiveness of the acoustic emission test is confirmed. In addition, the relationships between in-situ stresses and tectonic settings are analyzed. Finally, the distribution of in-situ stresses in Shuichang Iron Mine is given, which provides a meaningful guideline for the following mining and design.

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