Effects of Normal Stress and Clay Content on the Frictional Properties of Reservoir Rocks Under Fully Saturated Conditions

2018 ◽  
pp. 220-231
Author(s):  
Mengke An ◽  
Fengshou Zhang ◽  
Lianyang Zhang ◽  
Yi Fang
Keyword(s):  
Normal Stress ◽  
Clay Content ◽  
Reservoir Rocks ◽  
Frictional Properties

Residual Strength: Does BS 5930 Help or Hinder?

1986 ◽  
Vol 2 (1) ◽  
pp. 279-282 ◽  
Author(s):  
A. B. Hawkins ◽  
K. D. Privett
Keyword(s):  
Stability Analysis ◽  
Normal Stress ◽  
Residual Strength ◽  
Clay Content ◽  
Failure Envelope ◽  
Strength Parameters ◽  
Effective Normal Stress ◽  
Ring Shear ◽  
Stress Dependent ◽  
Shear Box

AbstractBS 5930 offers little assistance to engineers wishing to use residual strength parameters in slope stability analysis. It wrongly suggests the ring shear gives lower parameters than the shear box.BS 5930 does not mention the fact that the residual strength is stress dependent, hence the failure envelope is curved and the parameters must be assessed using an appropriate effective normal stress. For this reason the correlation charts relating ϕ′R to plasticity index or clay content need replacing with a series of charts in which these properties are plotted against ϕ′R values obtained at a number of effective normal stress loadings. Even then such correlations should be treated with caution.

scholarly journals Frictional properties between geocells filled with granular material

2021 ◽  
Vol 20 (2) ◽  
pp. 332-345
Author(s):  
Gökhan Altay ◽  
◽  
Cafer Kayadelen ◽  
Taha Taskiran ◽  
Baki Bagriacik ◽  
...  
Keyword(s):  
Granular Material ◽  
Normal Stress ◽  
Granular Materials ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Frictional Properties ◽  
Geotechnical Structures ◽  
Series Of Experiments ◽  
Restricted Volume

The parameters concerning the interaction between geocell and granular materials is required for the design of many geotechnical structures. With this in mind, a series of experiments using simple direct shear tests are conducted in order to understand the frictional properties between geocells filled with granular materials. The 54 test samples are prepared by filling the geocell with granular materials having three different gradations. These samples are tested at three different relative densities under three different normal stress levels. As a result, it was observed that interface resistance between the geocells filled with granular material is found to be generally greater than in the samples without geocells. Additionally, these samples with geocells are found to be stiffer; this is due to the fact that the samples with geocell gained more cohesion because geocells confined the grains within a restricted volume.

The slip behavior of velocity-weakening fault barriers

2021 ◽  
Author(s):  
Diego Molina ◽  
Jean-Paul Ampuero ◽  
Andres Tassara
Keyword(s):  
Fracture Energy ◽  
Normal Stress ◽  
Seismic Hazard Assessment ◽  
Large Earthquake ◽  
Earthquake Scenarios ◽  
Structural Controls ◽  
Frictional Properties ◽  
Geological Features ◽  
Rate And State Friction ◽  
Multiple Behaviors

<p>Subduction earthquakes are among the most devastating natural hazards across the planet and yet the factors controlling their size remain poorly understood. It is thus important to investigate the mechanisms controlling rupture arrest and runaway, in particular the nature of rupture barriers (areas where earthquakes tend to stop). Geodetic and seismic observations along several faults suggest that barriers are mostly creeping (low seismic coupling). It is often interpreted that creeping barriers are governed by velocity-strengthening friction (VS), which is a sufficient condition for stable slip. However, some barriers have been observed to host intermediate magnitude earthquakes or to be completely ruptured by a large earthquake. Therefore, the frictional properties of seismic barriers may not be restricted to VS. In particular, the possibility of velocity-weakening (VW) areas behaving as barriers needs to be further explored.</p><p>In this work, we characterize the multiple behaviors of seismic barriers on faults governed by velocity-weakening (VW) rate-and-state friction, using earthquake cycle simulations. We consider a 2D model, where a central VW area has a larger critical slip distance (Dc) or higher normal stress (σ) than the surrounding VW areas. We found that the central areas can behave as permanent or temporal barriers to earthquake propagation if their Dc or σ are large enough. On permanent barriers, creep occurs steadily. However, on temporary barriers, the locking degree changes throughout the cycle, despite frictional properties remaining constant.</p><p>To understand the efficiency of VW barriers (that is, to determine under what conditions they can stop ruptures), we use fracture mechanics theory. We found that barrier efficiency depends mainly on the ratio between the fracture energy of the barrier, which is proportional to Dc and normal stress, and the energy release rate of the neighboring seismic segment, which is proportional to its stress drop squared and length. If geological features of the overriding and subducting plates affect Dc and σ on the megathrust, our results support the idea of structural controls on the seismic behavior of megathrusts. Thus, understanding how geological features are linked to fracture energy may contribute to seismic hazard assessment by constraining rupture arrest and multi-segment ruptures in earthquake scenarios.</p>

scholarly journals The role of effective normal stress, frictional properties, and convergence rates in characteristics of simulated slow slip events

2015 ◽  
Vol 42 (4) ◽  
pp. 1061-1067 ◽  
Author(s):  
W. David Watkins ◽  
Harmony V. Colella ◽  
Michael R. Brudzinski ◽  
Keith B. Richards-Dinger ◽  
James H. Dieterich
Keyword(s):  
Normal Stress ◽  
Convergence Rates ◽  
Slow Slip ◽  
Slow Slip Events ◽  
Frictional Properties ◽  
Effective Normal Stress

Interpretation of wireline log and core data from a mid-Jurassic sand/shale sequence

Clay Minerals ◽  
1984 ◽  
Vol 19 (3) ◽  
pp. 483-505 ◽  
Author(s):  
R. C. A. Peveraro ◽  
K. J. Russell
Keyword(s):  
Bulk Density ◽  
Mineral Composition ◽  
Cross Section ◽  
Atomic Number ◽  
Clay Content ◽  
Single Factor ◽  
Reservoir Rocks ◽  
Wireline Logs ◽  
Photoelectric Cross Section ◽  
Source Of Information

AbstractInterpretation of downhole wireline logs is generally a major source of information used to build up a picture of the quality and distribution of reservoir rocks. Logging tools respond to a number of variables and comparison of a suite of different logs is usually required to isolate and identify the response due to a single factor, e.g. porosity or clay content. A new tool, the litho-density tool (LDT), has been used along with conventional logging tools in a mid-Jurassic sand/shale sequence. The LDT simultaneously measures Pe (effective photoelectric cross-section) and ρa (apparent bulk density). Pe is a function of atomic number which in turn reflects lithology or mineral composition. By using cross-plots derived from the LDT and other logs, patterns of mineral abundance are indicated.

scholarly journals Frictional slip weakening and shear-enhanced crystallinity in simulated coal fault gouges at subseismic slip rates

2020 ◽  
Author(s):  
Caiyuan Fan ◽  
Jinfeng Liu ◽  
Luuk B. Hunfeld ◽  
Christopher J. Spiers
Keyword(s):  
Steady State ◽  
Normal Stress ◽  
Hold Time ◽  
Shear Bands ◽  
Fluid Pressure ◽  
Organic Content ◽  
Local Conditions ◽  
Frictional Properties ◽  
Effective Normal Stress ◽  
Fault Gouges

Abstract. Previous studies show that organic-rich fault patches may play an important role in promoting unstable fault slip. However, the frictional properties of rock materials with near 100 % organic content, e.g. coal, and the controlling microscale mechanisms, remain unclear. Here, we report seven velocity stepping (VS) and one slide-hold-slide (SHS) friction experiments performed on simulated fault gouges prepared from bituminous coal, collected from the upper Silesian Basin of Poland. These experiments were performed at 25–45 MPa effective normal stress and 100 °C, employing sliding velocities of 0.1–100 μm s−1, using a conventional triaxial apparatus plus direct shear assembly. All samples showed marked slip weakening behaviour at shear displacements beyond ~ 1–2 mm, from a peak friction coefficient approaching ~ 0.5 to (near) steady state values of ~ 0.3, regardless of effective normal stress or whether vacuum dry flooded with distilled (DI) water at 15 MPa pore fluid pressure. Analysis of both unsheared and sheared samples by means of microstructural observation, micro-area X-ray diffraction (XRD) and Raman spectroscopy suggests that the marked slip weakening behaviour can be attributed to the development of R-, B- and Y- shear bands, with internal shear-enhanced coal crystallinity development. The SHS experiment performed showed a transient peak healing (restrengthening) effect that increased with the logarithm of hold time at a linearized rate of ~ 0.006. We also determined the rate-dependence of steady state friction for all VS samples using a full rate and state friction approach. This showed a transition from velocity strengthening to velocity weakening at slip velocities > 1 μm s−1 in the coal sample under vacuum dry conditions, but at > 10 μm s−1 in coal samples exposed to DI water at 15 MPa pore pressure. This may be controlled by competition between dilatant granular flow and compaction enhanced by presence of water. Together with our previous work on frictional properties of coal-shale mixtures, our results imply that the presence of a weak, coal-dominated patch on faults that cut or smear-out coal seams may promote unstable, seismogenic slip behaviour, though the importance of this in enhancing either induced or natural seismicity depends on local conditions.

The accuracy of estimating Q from seismic data

Geophysics ◽  
1992 ◽  
Vol 57 (11) ◽  
pp. 1508-1511 ◽  
Author(s):  
R. E. White
Keyword(s):  
Seismic Data ◽  
Poisson’S Ratio ◽  
Seismic Velocity ◽  
Clay Content ◽  
Seismic Interpretation ◽  
Poisson's Ratio ◽  
Petrophysical Properties ◽  
Complementary Information ◽  
Seismic Parameters ◽  
Reservoir Rocks

A major aim of seismic interpretation is the inference of petrophysical properties of reservoir rocks. Because the inversion from seismic to petrophysical characteristics is far from unique, this task requires a range of seismic parameters, prominent among which are seismic velocity, impedance, and Poisson’s ratio. The inclusion of seismic absorption in this list could add desirable complementary information. For example, absorption may be more sensitive to clay content than seismic velocity (Klimento and McCann, 1990). However seismic absorption is difficult to measure, particularly over depth intervals as short as most reservoir intervals.

scholarly journals Effect of normal stress on the friction of brucite: Application to slow earthquake in the mantle wedge

2020 ◽  
Author(s):  
Hanaya Okuda ◽  
Ikuo Katayama ◽  
Hiroshi Sakuma ◽  
Kenji Kawai
Keyword(s):  
Normal Stress ◽  
Small Volume ◽  
Mantle Wedge ◽  
Normal Stresses ◽  
Localized Deformation ◽  
Low Friction ◽  
Frictional Properties ◽  
Slow Earthquakes ◽  
Dry Conditions ◽  
Water Saturated

Abstract. We report the results of friction experiments on brucite under both dry and water-saturated (wet) conditions under various normal stresses (10–60 MPa). The steady-state friction coefficients of brucite were determined to be 0.40 and 0.26 for the dry and wet cases, respectively, independent of the normal stress. Under dry conditions, velocity-weakening behavior was observed in all experiments at various normal stresses. Under wet conditions, velocity weakening was observed at low normal stress (10 and 20 MPa), whereas velocity strengthening was determined at a higher applied normal stress. The microstructural observations on recovered experimental samples indicate localized deformation within the narrow shear band, implying that a small volume of brucite can control the bulk strength in an ultramafic setting and significantly change the frictional properties. Brucite is found to be the only mineral that has a low friction coefficient and exhibits unstable frictional behavior under hydrated mantle wedge conditions, explaining the occurrence of slow earthquakes in the mantle wedge.

Geological and Field Feasibility Study of Field Development Management Using Marker-Based Production Profiling Surveillance in Horizontal Wells: The Case Study of the Yuzhno-Vyintoiskoye Field

2021 ◽  
Author(s):  
Marat Rafailevich Dulkarnaev ◽  
Yuri Alexeyevich Kotenev ◽  
Shamil Khanifovich Sultanov ◽  
Alexander Viacheslavovich Chibisov ◽  
Daria Yurievna Chudinova ◽  
...  
Keyword(s):  
Oil Recovery ◽  
Oil And Gas ◽  
Water Saturation ◽  
Clay Content ◽  
Horizontal Wells ◽  
Integrated Approach ◽  
Geological Structure ◽  
Gas Field ◽  
Field Development ◽  
Reservoir Rocks

In pursuit of efficient oil and gas field development, including hard-to-recover reserves, the key objective is to develop and provide the rationale for oil recovery improvement recommendations. This paper presents the results of the use of the workflow process for optimized field development at two field clusters of the Yuzhno-Vyintoiskoye field using geological and reservoir modelling and dynamic marker-based flow production surveillance in producing horizontal wells. The target reservoir of the Yuzhno-Vyntoiskoye deposit is represented by a series of wedge-shaped Neocomian sandstones. Sand bodies typically have a complex geological structure, lateral continuity and a complex distribution of reservoir rocks. Reservoir beds are characterised by low thickness and permeability. The pay zone of the section is a highly heterogeneous formation, which is manifested through vertical variability of the lithological type of reservoir rocks, lithological substitutions, and the high clay content of reservoirs. The target reservoir of the Yuzhno-Vyintoiskoye field is marked by an extensive water-oil zone with highly variable water saturation. According to paleogeographic data, the reservoir was formed in shallow marine settings. Sand deposits are represented by regressive cyclites that are typical for the progressing coastal shallow water (Dulkarnaev et al., 2020). Currently, the reservoir is in production increase cycle. That is why an integrated approach is used in this work to provide a further rationale and creation of the starting points of the reservoir pressure maintenance system impact at new drilling fields to improve oil recovery and secure sustainable oil production and the reserve development rate under high uncertainty.

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