In Situ Stress Prediction in Subsurface Rocks: An Overview and a New Method

Zhang, Yushuai; Yin, Shangxian; Zhang, Jincai

doi:10.1155/2021/6639793

Cited by 3 publications

(1 citation statement)

References 40 publications

(49 reference statements)

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“…Hence, some tests like LOT/XLOT or FIT are conducted for stress measurements [67][68][69][70]. Zhang et.al [71], reviewed the theoretical methods for evaluating in situ stresses and concluded XLOT results are acceptable in estimating horizontal principal stresses, especially in the normal or strike-slip faulting stress regime.…”

Section: Lot/xlot In Relation To Wellbore Stabilitymentioning

confidence: 99%

Review of the Leak-off Tests with a Focus on Automation and Digitalization

Bakhshi

Elahifar

Shahrabadi³

et al. 2022

Int. J. Petrol. Technol.

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The drilling and research communities are leading the way toward more digitally-controlled operations to ensure that the drilling process takes place as safely and gently as possible with the lowest possible carbon footprint. Today’s cutting-edge operations are run on large high-performance drilling installations where operations are largely run remotely from the driller’s operating station. Digitalization of the drilling process is the goal for performing drilling operations remotely from onshore. Leak-off test (LOT) or extended leak-off test (XLOT) plays a critical role in the petroleum industry. Therefore, recognizing all affecting parameters on LOT/XLOT and Formation integrity test (FIT) performance is vital. Because, in some cases, it is not possible to fully understand what happened during the test, having a deep insight into the LOT procedure is very important. One of the current study's main objectives is to thoroughly explain all stages of these tests and assemble all the significant parameters. Thus, many scientific papers on these tests were deeply reviewed and were classified into four main groups focusing on the application of LOT/XLOT (i) in stress estimation and geomechanical studies, (ii) concerning hydraulic fracturing, (iii) concerning wellbore stability, and (iv) numerical modeling, and then, the corresponding discussions were conducted. It was found that in-situ stress estimation is the most common application of the leak-off test. Moreover, considering the importance of LOT and the desire to digitize operations in the oil and gas industry, it was found that the automatic LOT/XLOT is a fully required approach. The primary purpose of this study, which is hence considered its main contribution, is to prepare a LOT flowchart that would set off the further code development tasks of the field. The fundamental code of the present study was written and checked using a real dataset in a Python environment. The results were satisfying and indicated a successful start, which lays a foundation for future automated LOT/XLOT tests.

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Section: Lot/xlot In Relation To Wellbore Stabilitymentioning

confidence: 99%

Review of the Leak-off Tests with a Focus on Automation and Digitalization

Bakhshi

Elahifar

Shahrabadi³

et al. 2022

Int. J. Petrol. Technol.

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Hydrostatic, strike-slip and normal stress true triaxial hydrofracturing testing of Blanco Mera Granite: breakdown pressure and tensile strength assessment

Muñoz‐Ibáñez

Herbón-Penabad

Martín

et al. 2023

Geomech. Geophys. Geo-energ. Geo-resour.

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We have designed and built a versatile testing device to perform hydraulic fracturing experiments under true triaxial conditions. The device, based on a stiff biaxial frame that can be installed in a servocontrolled press, can accommodate cube rock samples of up to 150 mm-edge. Using a low-permeability rock known as Blanco Mera granite, we have performed a series of tests across a range of confining pressures including hydrostatic, normal, and strike-slip regimes. We have verified the applicability of two simple fracture mechanics-based models for the interpretation of experimental results, and we have determined the value of tensile strength of the rock from the injection curves recorded. The orientation of the hydraulically-triggered fractures with respect to the applied stress has also been analyzed. Although the models proposed by Rummel and Abou-Sayed provided reasonably satisfactory results, especially for hydrostatic and strike-slip tests, the presence of heterogeneities and defects in the rock matrix may have a strong influence on the fracture behavior and, therefore, affect the interpretation of hydrofracturing tests.

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Estimation of in situ stresses from PP-wave azimuthal seismic data in fracture-induced anisotropic media

et al. 2022

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Horizontally transverse isotropy (HTI) induced by vertical or subvertical, aligned fractures is common for unconventional fractured porous shale oil or gas reservoirs. Compared with the unfractured rocks, the seismic response characteristics of PP-wave azimuthal amplitudes are usually disturbed by the fractures and the in-situ stresses. Knowledge of fracture properties, as well as in-situ stresses, is required to optimize horizontal well planning and hydraulic fracturing during production, and seismic inversion for in-situ stresses from the PP-wave azimuthal amplitude data in fracture-induced anisotropic media is an essential step. Using the linear-slip theory and the effective stress law, we derive the fluid-saturated effective elastic stiffness tensors parameterized by background elastic moduli, the effective stress coefficient of isotropic host rocks, fluid modulus, porosity, and fracture parameters based on the anisotropic Gassmanns fluid substitution equation. Combining the perturbations in saturated stiffness tensors and scattering theory, we formulate the reflection coefficient equation of PP-wave data as a function of background porosity-related stress parameter, and two (i.e., normal and shear) fracture weakness parameters. Following Bayes rule, we estimate the porosity-related stress parameter and fracture weaknesses using the inversion method of azimuthal Fourier coefficients. We finally compute the effective horizontal and vertical in-situ stresses using the estimated elastic moduli, porosity-related stress parameter and fracture weaknesses. Synthetic and real data sets demonstrate that our proposed inversion approach based on the derived reflection equation provides us another way to obtain reasonable estimates of in-situ stresses in a complex fractured porous shale reservoir.

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In Situ Stress Prediction in Subsurface Rocks: An Overview and a New Method

Cited by 3 publications

References 40 publications

Review of the Leak-off Tests with a Focus on Automation and Digitalization

Review of the Leak-off Tests with a Focus on Automation and Digitalization

Hydrostatic, strike-slip and normal stress true triaxial hydrofracturing testing of Blanco Mera Granite: breakdown pressure and tensile strength assessment

Estimation of in situ stresses from PP-wave azimuthal seismic data in fracture-induced anisotropic media

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