Experimental Study on Formation Slip under Injection-Production Interregional Pressure Difference Based on the Abnormal Similarity Theory

In oilfield development, the pore pressure difference between adjacent areas leads to cracks and slipping in the weak structural surface layer, which triggers the shear failure of the casing. The formation slip involves a large range of formation, and its amount is not proportional to the size of the slipping rock mass, which conventional physical models cannot simulate. In this study, based on the abnormal similarity theory, we derived the similarity coefficients of mechanical parameters with different horizontal and vertical proportions. Furthermore, an experimental device for simulating the formation crack and slip under interregional formation pressure difference was developed. Through the experiments, we obtained slip conditions under different pressure differences between adjacent areas and different oil layers and fault surface depths. The study shows that the pore pressure difference between adjacent areas is the driving force of the formation slips. The slip zone is located in the middle of two abnormal pressure zones, and the distance between the adjacent areas can affect the slip range. The deep burial of the oil layer and shallow depth of the weak structural surface can trigger a more significant formation slip. The experimental method proposed in this paper provides an experimental device and method for understanding the formation of cracks and slips on weak structural surfaces. The experimental results provide a theoretical basis for the prevention of shear-type casing damage caused by formation slip.

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Evaluation of Induced Thermal Pressurization in Clearwater Shale Caprock in Electromagnetic Steam-Assisted Gravity-Drainage Projects

SPE Journal ◽

10.2118/156876-pa ◽

2013 ◽

Vol 19 (03) ◽

pp. 443-462 ◽

Cited By ~ 4

Author(s):

Sahar Ghannadi ◽

Mazda Irani ◽

Rick Chalaturnyk

Keyword(s):

Pore Pressure ◽

Analytical Solutions ◽

Oil Sands ◽

Shear Failure ◽

Gravity Drainage ◽

Hydraulic Fractures ◽

Low Permeability ◽

Steam Assisted Gravity Drainage ◽

Thermal Pressurization ◽

Shale Formation

Summary Inductive methods, such as electromagnetic steam-assisted gravity drainage (EM-SAGD), have been identified as technically and economically feasible recovery methods for shallow oil-sands reservoirs with overburdens of more than 30 m (Koolman et al. 2008). However, in EM-SAGD projects, the caprock overlying oil-sands reservoirs is also electromagnetically heated along with the bitumen reservoir. Because permeability is low in Alberta thermal-project caprock formations (i.e., the Clearwater shale formation in the Athabasca deposit and the Colorado shale formation in the Cold Lake deposit), the pore pressure resulting from the thermal expansion of pore fluids may not be balanced with the fluid loss caused by flow and the fluid-volume changes resulting from pore dilation. In extreme cases, the water boils, and the pore pressure increases dramatically as a result of the phase change in the water, which causes profound effective-stress reduction. After this condition is established, pore pressure increases can lead to shear failure of the caprock, the creation of microcracks and hydraulic fractures, and subsequent caprock integrity failure. It is typically believed that low-permeability caprocks impede the transmission of pore pressure from the reservoir, making them more resistant to shear failure (Collins 2005, 2007). In cases of induced thermal pressurization, low-permeability caprocks are not always more resistant. In this study, analytical solutions are obtained for temperature and pore-pressure rises caused by the constant EM heating rate of the caprock. These analytical solutions show that pore-pressure increases from EM heating depend on the permeability and compressibility of the caprock formation. For stiff or low-compressibility media, thermal pressurization can cause fluid pressures to approach hydrostatic pressure, and shear strength to approach zero for low-cohesive-strength units of the caprock (units of the caprock with high silt and sand percentage) and sections of the caprock with pre-existing fractures with no cohesion.

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Centrifuge-model test study of key hazard factors of deep toppling deformation and disaster pattern of anti-dip layered-rock slope under gravity

10.5194/egusphere-egu2020-1474 ◽

2020 ◽

Author(s):

Da Zheng ◽

Hua Zhao

Keyword(s):

Model Test ◽

Rock Slope ◽

Shear Failure ◽

Similarity Theory ◽

Distinct Element ◽

Centrifuge Model Test ◽

Centrifuge Model ◽

Layered Rock ◽

External Conditions ◽

Toppling Deformation

<p>To study the toppling deformed body before construction of the dam at the Gushui hydropower station, we developed here a physical model of the slope on the basis of known local geology and of similarity theory. We simulated valley trenching by a method using prior produced block modules and three levels of excavation, and we studied key hazard factors of deep toppling deformation and the disaster pattern related to anti-dip, layered-rock slope under gravity by a five-stage centrifuge-model test and Universal Distinct Element Code numerical-simulation analysis. The results show the following: (1) The occurrence, development and destruction of deep toppling deformation of anti-dip layered rock slopes must have gone through a long geological history; the accumulation of energy and deformation is a very long process, and accelerated-deformation is closely related to changes in external conditions (such as excavation, earthquake, etc.); (2) lithologic conditions (relatively weak rock mass), structural conditions (appropriate layer thickness and dip angle), and external conditions (valley trenching or excavation of slopes) are key factors for deep toppling deformation, while the free-surface condition is the key hazard factor; (3) deep toppling deformation can lead to multilevel bending zones at different depths inside the slope after the several stages of valley trenching (multilevel excavation); the bending zone is gradually connected from the foot of the slope all the way to the top, which eventually becomes the failure boundary; and the development and connection of the bending zone may result in the overall shear failure of the slope along the bending zone; (4) for deep toppling deformation, we propose a qualitative-judgment index and quantitative-judgment indicators of the degree of toppling deformation. We derived quantitative-judgment formulas for the degree of toppling deformation and the calculation formulas were used for the maximum depth of toppling deformation, and we established a system for discrimination of destruction patterns for deep toppling deformation of anti-dip slope.</p>

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Understanding the Thermo-Hydromechanical Pressurization in Two-Phase (Steam/Water) Flow and Its Application in Low-Permeability Caprock Formations in Steam-Assisted-Gravity-Drainage Projects

SPE Journal ◽

10.2118/165544-pa ◽

2014 ◽

Vol 19 (06) ◽

pp. 1126-1150 ◽

Cited By ~ 1

Author(s):

Sahar Ghannadi ◽

Mazda Irani ◽

Rick Chalaturnyk

Keyword(s):

Pore Pressure ◽

Shear Failure ◽

Thermal Recovery ◽

Subcritical State ◽

Gravity Drainage ◽

Low Permeability ◽

Steam Chamber ◽

Steam Assisted Gravity Drainage ◽

Caprock Integrity ◽

Casing Failure

Summary Steam-assisted gravity drainage (SAGD) is one successful thermal-recovery technique applied in Alberta oil-sand reservoirs. When considering in-situ production from bitumen reservoirs, one must reduce viscosity for the bitumen to flow toward the production well. Steam injection is currently the most promising thermal-recovery method. Although steamflooding has proved to be a commercially viable way to extract bitumen from bitumen reservoirs, caprock integrity and the risk of losing steam containment can be challenging operational problems. Because permeability is low in Albertan thermal-project caprock formations, heating greatly increases the pressure on any water trapped in pores as a result of water thermal expansion. This water also sees a great increase in volume as it flashes to steam, causing a large effective-stress reduction. After this condition is established, pore-pressure increases can lead to caprock shear failure or tensile fracturing, and to subsequent caprock-integrity failure or potential casing failure. It is typically believed that low-permeability caprocks impede the transmission of pore pressure from reservoirs, making them more resistant to shear failure (Collins 2005, 2007). In considering the “thermo-hydromechanical pressurization” physics, low-permeability caprocks are not always more resistant. As the steam chamber rises into the caprock, the heated pore fluids may flash to steam. Consequently, there is a vapor region between the steam-chamber interface penetrated into the caprock and the water region within the caprock which is still at a subcritical state. This study develops equations for fluid-mass and thermal-energy conservation, evaluating the thermo-hydromechanical pressurization in low-permeability caprocks and the flow of steam and water after steam starts to be injected as part of the SAGD process. Calculations are made for both short-term and long-term responses, and evaluated thermal pressurization is compared for caprocks with different stiffness states and with different permeabilities. One can conclude that the stiffer and less permeable the caprock, the greater the thermo-hydromechanical pressurization; and that the application of SAGD can lead to high pore pressure and potentially to caprock shear, and to subsequent steam release to the surface or potential casing failure.

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Measuring uncertainty assessment of an experimental device used to determine the thermo-optico-physical properties of translucent construction materials

Measurement Science and Technology ◽

10.1088/1361-6501/ac407b ◽

2021 ◽

Author(s):

Mélanie Delort ◽

Damien Ali Hamada FAKRA ◽

Bruno Mallet-Damour ◽

Jean Claude Gatina

Keyword(s):

Measurement Uncertainty ◽

Construction Materials ◽

Optical Transmittance ◽

Uncertainty Assessment ◽

Physical Models ◽

Experimental Device ◽

Optical Absorbance ◽

New Device ◽

Uncertainty Estimates ◽

Experimental Apparatus

Abstract Studying thermo-optical (i.e., thermal conductivity, optical re ectance, optical transmittance, and optical absorbance) properties of construction materials is essential for improving human comfort within a building. Typically, these properties are measured independently using specific equipment. The emerging of new innovative construction structures, such as translucent materials, makes the experimental characterization of these properties more challenging to observe. Recently, a new device, called MultiCoefMeter (McM), which rapidly and simultaneously measures all these properties, has been created. The study described in this article covers the calculation technique for estimating measurement uncertainties linked to morphology, the component parts, and the physical formula of the experimental apparatus. The measurement uncertainty estimates are obtained from knowledge of the color of the system's walls, placement, and form of the McM components, placement of measurement sensors, and the application of measurement collection equipment. Therefore, a thorough calculation analysis was performed on the sub-systems. Calculations are divided between two categories: those based on mathematical tools and information given by the makers, and those based on experimental observations obtained during reliability testing. These uncertainties originate from statistical tools, geometric tolerance of the system, comparison with standards, and the error propagation laws of the physical models link with the device. All these uncertainties were summed up and given a global value, no more than 5%, conforming to the ASTM standard (E1225). Finally, a general method to quantify measurement uncertainty value of any experimental device was proposed.

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Instability Process of Crack Propagation and Tunnel Failure Affected by Cross-Sectional Geometry of an Underground Tunnel

Advances in Civil Engineering ◽

10.1155/2019/3439543 ◽

2019 ◽

Vol 2019 ◽

pp. 1-17 ◽

Cited By ~ 2

Author(s):

Xianjie Hao ◽

Shaohua Wang ◽

Duoxiang Jin ◽

Bo Ren ◽

Xiangyang Zhang ◽

...

Keyword(s):

Crack Propagation ◽

Large Scale ◽

Shear Failure ◽

Side Wall ◽

Surrounding Rock ◽

Physical Models ◽

Tensile Failure ◽

Circular Tunnel ◽

Cross Sectional ◽

Underground Tunnel

The process of crack propagation and tunnel failure is affected by the cross-sectional geometry of an underground tunnel. In order to quantify the effect of section shape on the process of crack propagation in deep tunnels under high ground stress conditions, a total of four physical models with two cross-sectional shapes and twelve stress levels were designed and several large-scale physical model tests were conducted. The results indicated that, when the vertical stress is 4.94 MPa, the length and depth of the cracks generated in the rock surrounding the horseshoe tunnel are about eight times that around a circular tunnel. The position where the circumferential displacement of the horseshoe tunnel begins to be stable is about two, to two and a half, times that around a circular tunnel. After the deep chamber was excavated, continuous spalling was found to occur at the foot of the horseshoe tunnel and microcracks in the surrounding rock were initially generated from the foot of the side wall and then developed upwards to form a conjugate sliding shape to the foot of the arch roof, where the cracks finally coalesced. Discontinuous spalling occurred at the midheight of the side wall of the circular tunnel after excavation, and microcracks in the surrounding rock were initially generated from the midheight of the side wall and then extended concentrically to greater depth in the rock mass surrounding the tunnel. Tensile failure mainly occurred on the surface of the side wall: shear failure mainly appeared in the surrounding rock.

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Deep Learning a Poro-Elastic Rock Physics Model for Pressure and Saturation Discrimination

Geophysics ◽

10.1190/geo2020-0049.1 ◽

2020 ◽

pp. 1-55

Author(s):

Wolfgang Weinzierl ◽

Bernd Wiese

Keyword(s):

Pore Pressure ◽

Co2 Storage ◽

Rock Physics ◽

Seismic Attenuation ◽

Physical Models ◽

Physical Parameters ◽

High Porosity ◽

Hydrocarbon Production ◽

Physical Attributes ◽

Physics Model

Determining saturation and pore pressure is relevant for hydrocarbon production as well as natural gas and CO2 storage. In this context seismic methods provide spatially distributed data used to determine gas and fluid migration. A method is developed that allows to determine saturation and reservoir pressure from seismic data, more precisely from rock physical attributes that are velocity, attenuation and density. Two rock physical models based on Hertz-Mindlin-Gassmann and Biot-Gassmann are developed. Both generate poroelastic attributes from pore pressure, gas saturation and other rock-physical parameters. The rock physical models are inverted with deep neural networks to derive e.g. saturation, pore pressure and porosity from rock physical attributes. The method is demonstrated with a 65 m deep unconsolidated high porosity reservoir at the Svelvik ridge, Norway. Tests for the most suitable structure of the neural network are carried out. Saturation and pressure can be meaningfully determined under condition of a gas-free baseline with known pressure and data from an accurate seismic campaign, preferably cross-well seismic. Including seismic attenuation increases the accuracy. The training requires hours, predictions just a few seconds, allowing for rapid interpretation of seismic results.

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CEOHYDRAULIC INVESTIGATIONS OF RUBBLE MOUND BREAKWATERS

Coastal Engineering Proceedings ◽

10.9753/icce.v21.166 ◽

1988 ◽

Vol 1 (21) ◽

pp. 166 ◽

Cited By ~ 3

Author(s):

W. Burger ◽

H. Oumeraci ◽

H.W. Partenscky

Keyword(s):

Pore Pressure ◽

Scale Effects ◽

Numerical Models ◽

Model Tests ◽

Physical Models ◽

Core Material ◽

Scale Model ◽

Small Scale ◽

Rubble Mound ◽

Rubble Mound Breakwaters

Due to the increase of ship sizes in recent decades a number of harbours and terminals have been built in deeper waters. Accordingly, the structures which have to provide protection against wave action become higher, too. In most cases, these protective structures are of the rubble mound type. Under such conditions the flow induced by waves within the breakwater and the related geotechnical behaviour of the rubble mound fill become more significant fcr the overall stability and should be considered in the design. In addition, it is known that the scales usually adopted in hydraulic models (1:30 to 1:60) for investigating the stability of large rubble mound breakwaters generally lead to scale effects with respect to the flow field inside the breakwater. This means that small-scale model tests are not appropriate for investigating the internal flow patterns or for evaluating the pore pressure field induced by the incident waves in,the core material. because of the uncontrolled conditions in the prototype, and since the actual permeability of the prototype rubble mound fill cannot be predicted (segregation, settlement, variation in grading, etc.), the use of large-scale physical models seems to be the most promising method for basic investigations of this kind. Moreover, the results of such largescale model tests may be used to validate the usual smaller scale models and to calibrate numerical models. Therefore, it is one of the objectives of our research programme on rubble mound breakwaters, which started in 1987, to concentrate on the evaluation of the wave-induced flow and pore pressure distribution within the breakwater.

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Experimental Study on the Mechanical Properties and Seepage Characteristics of Red Sandstone with a Single Persistent Joint under Triaxial Compression

Geofluids ◽

10.1155/2021/3884605 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Wei Wang ◽

Shifan Liu ◽

Chong Shi ◽

Shanxi Zheng ◽

Qizhi Zhu

Keyword(s):

Mechanical Properties ◽

Pore Pressure ◽

Failure Modes ◽

Shear Failure ◽

Triaxial Compression ◽

Confining Pressure ◽

Strengthening Effect ◽

Red Sandstone ◽

Inclination Angles ◽

Seepage Characteristics

In this research, the conventional triaxial compression experiments for intact red sandstone specimens and the specimens with a single persistent joint at different inclination angles, i.e., 0°, 30°, 45°, and 90°, were conducted at first. Based on the results of the conventional tests, the effects of the confining pressure and the joint inclination angle on the mechanical properties including deformation behavior and strength parameters were summarized and analyzed, respectively. We find that the strength and deformation of jointed red sandstone are enlarged due to the increment of confining pressure, and the mechanical parameters of specimens show a U-shaped development with the rise of the joint angle. Besides, to investigate the effects of the pore pressure on seepage characteristics of rocks with joint angles at 0°, 45°, and 90°, a series of triaxial compression drainage tests on the jointed red sandstone were performed. The results show that the pore pressure has a weakening effect on the strength of jointed specimens, which can reduce the strengthening effect induced by confining pressure. Meanwhile, the tested specimens mostly present shear failure modes. As a result, the mechanical responses, seepage characteristics, and cracking modes in red sandstone containing a single persistent joint under triaxial compression are revealed.

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Fluid mechanical valving of air flow in bird lungs

Journal of Experimental Biology ◽

10.1242/jeb.136.1.1 ◽

1988 ◽

Vol 136 (1) ◽

pp. 1-12 ◽

Cited By ~ 3

Author(s):

D. O. Kuethe

Keyword(s):

High Pressure ◽

Flow Rate ◽

Pressure Difference ◽

Air Flow ◽

Low Pressure ◽

Physical Models ◽

Unidirectional Flow ◽

Air Sacs ◽

Caudal Portion ◽

Flow Through

The unidirectional flow through the gas-exchanging bronchi of bird lungs is known to be effected by (1) the structure of the major bronchi and (2) a pressure difference between the cranial and caudal air sacs. To study the effects of bronchial structure, simple physical models of bird lungs were constructed. They suggested that, to achieve unidirectional flow, air in the caudal portion of the primary bronchus must be directed towards the orifices of the mediodorsal bronchi. To study the effect of air sac pressures, a controllable pressure difference was produced between the air sac orifices of fixed duck lungs. The cranial orifices had a higher pressure than the caudal ones during inhalation and vice versa during exhalation. There was a set of pressure differences for which the paleopulmo received the same flow rate during inhalation as during exhalation. High pressure differences caused more flow in the paleopulmo during exhalation than during inhalation; low pressure differences had the converse effect.

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Investigation of physical and mechanical properties of peat

International Journal of Engineering & Technology ◽

10.14419/ijet.v7i3.12999 ◽

2018 ◽

Vol 7 (3) ◽

pp. 1056 ◽

Cited By ~ 1

Author(s):

Aleksandr V. Kulikov ◽

Vyacheslav V. Vorontsov ◽

Anatolii N. Shuvaev

Keyword(s):

Pore Pressure ◽

Strain Gauge ◽

Laboratory Tests ◽

Load Transfer ◽

Physical And Mechanical Properties ◽

Experimental Device ◽

Sensor Element ◽

Lever System ◽

Strain Gauge Sensor ◽

Water Saturated

The article describes results of laboratory tests of weak water-saturated soils (remote from day surface) in stress-strain state under influence of compression with double-sided filtration of pore’s water. The experimental device with console-lever system of load transfer and potential of double-sided filtration was made for current research. The compression specification was controlled with the strain gauge sensor element of general pressure (i.e. the load cell).The deformation in sample were measured with the motion detecting transducer that based on indicating gage. The excessive pore pressure was measured with strain gauge sensor elements and digital manometer. Also the plots of compression deformation against pressure and changes of excessive pore pressure during the time on different load degrees were drawn. Although, authors made the new experimental device for research of the water saturated peat mechanics properties with excessive pore pressure.

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