scholarly journals Can Heating Induce Borehole Closure?

2020 ◽  
Vol 53 (12) ◽  
pp. 5715-5744
Author(s):  
Xiyang Xie ◽  
Andreas Bauer ◽  
Jørn F. Stenebråten ◽  
Sigurd Bakheim ◽  
Alexandre Lavrov ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Pore Pressure ◽  
Rock Failure ◽  
Field Scale ◽  
Thermally Induced ◽  
Pierre Shale ◽  
Lab Experiments ◽  
Post Test ◽  
Operation Cost ◽  
Cased Borehole

AbstractThe current study shows that heating a cased borehole in low-permeability shale rock can induce plastic deformation, leading to the closure of the casing annulus and decreasing annulus connectivity. The thermally induced borehole closure is interesting for the field operation of plug and abandonment (P&A), as it potentially saves operation cost and time by avoiding cutting casing and cementing. Lab experiments and numerical simulations are implemented to investigate the thermally induced borehole closure. Pierre shale and a field shale are tested. The lab experiments are performed by heating the borehole wall in a 10-cm-OD hollow cylinder specimen. Here, a novel experimental setup is applied, allowing for measuring temperature and pore pressure at different radii inside the specimen. Both the experimental data and the post-test CT images of the rock samples indicate the rock failure by borehole heating, and under certain conditions, heating results in an annulus closure. The decrease of hydraulic conductivity through the casing annulus is observed, but this decrease is not enough to form the hydraulic-sealed annulus barrier, based on the results obtained so far. Lab-scale finite-element simulations aim to match the lab results to obtain poro-elastoplastic parameters. Then the field-scale simulations assess the formation of shale barriers by heating in field scenarios. Overall, (i) the lab experiments show that heating a borehole can increase the pore pressure in shale and hence induce rock failure; (ii) the numerical simulations match the experimental results reasonably well and indicate that the heating-induced borehole closure can sufficiently seal the casing annulus in the field-scale simulation.

Numerical Studies of the Influence of Heterogeneity on Rock Failure and Induced Earthquake Precursors

2005 ◽  
Vol 297-300 ◽  
pp. 2648-2653
Author(s):  
Ming Ruo Jiao ◽  
Chun An Tang ◽  
W.F. Sun ◽  
Shu Hong Wang
Keyword(s):  
Numerical Simulations ◽  
Rock Failure ◽  
Earthquake Precursors ◽  
Numerical Results ◽  
Mechanical Heterogeneity ◽  
Induced Earthquake ◽  
Numerical Studies ◽  
Good Agreement

A series of numerical simulations were performed to investigate the effects of geometric and mechanical heterogeneity of pre-existing faults of rocks on their failure and induced earthquake precursors. The numerical results revealed that rock failures with the different heterogeneity produce the different earthquake precursors, which are in a good agreement with those of observations in nature.

Force-Deflection Characteristics of SMA-Based Belleville Springs

2012 ◽  
Author(s):  
Franco Furgiuele ◽  
Carmine Maletta ◽  
Emanuele Sgambitterra
Keyword(s):  
Numerical Simulations ◽  
Mechanical Response ◽  
Nickel Titanium ◽  
Thermally Induced ◽  
Niti Alloys ◽  
Strain Behavior ◽  
Finite Element Software ◽  
Transition Mechanism ◽  
Functional Features ◽  
Software Code

The thermo-mechanical properties of Nickel-Titanium based Belleville washers have been analyzed by numerical simulations. In fact, these components exhibit unique mechanical and functional features due to the reversible stress-induced and/or thermally-induced phase transition mechanism of NiTi alloys. The numerical simulations have been carried out by using a commercial finite element software code and a special constitutive model for SMAs. The effects of the geometrical configuration of the washers as well as of the operating temperature, under fully austenitic conditions, have been analyzed. The results highlighted a marked hysteretic response, in terms of force-deflection curve, due to the hysteresis in the stress-strain behavior of NiTi alloys. In addition, a marked influence of the geometry, as well as of the temperature, has been observed on the thermo-mechanical response of the washer, i.e. in terms of both mechanical and functional properties.

Compaction front controls soil liquefaction dynamics of drained saturated grain layers, as evident by theory, numerical simulations and lab experiments

2020 ◽  
Author(s):  
Shahar Ben-Zeev ◽  
Einat Aharonov ◽  
Liran Goren ◽  
Renaud Toussaint ◽  
Stanislav Parez
Keyword(s):  
Pressure Gradient ◽  
Pore Pressure ◽  
Interstitial Fluid ◽  
Stress Gradient ◽  
Soil Layer ◽  
Soil Liquefaction ◽  
Fluid System ◽  
Cyclic Shear ◽  
Lab Experiments ◽  
Pore Pressure Gradient

<p>Soil liquefaction is one of the most impactful secondary hazards of earthquakes. For example, it played a crucial role in driving the devastating landslides following the 2018 Palu earthquake, Indonesia. While traditionally, the initiation of liquefaction is treated as an undrained phenomenon, evidence shows that a well-drained end-member exists.</p><p>We develop a theory for the coupled grains - pore fluid system, and conduct numerical discrete element – fluid dynamics simulations and lab experiments under well-drained conditions. Here, a well-drained layer means that the interstitial fluid can flow out of the layer faster than a single earthquake shaking period. Theory, simulations, and experiments, all suggest that a saturated granular layer, although well-drained, can liquefy when subjected to horizontal cyclic shear. The liquefaction event, evident by high pore pressure, loss of shear strength, and dissipation of shear waves is spatially and temporally controlled by a compaction front that swipes upward through the layer. The compaction front separates the grain-fluid system into two sub-layers: The bottom sub-layer, below the front, is fully-compacted, and the pore pressure gradient across it is hydrostatic. The top sub-layer, above the front, is actively subsiding, and its pore pressure gradient reaches the total solid stress gradient. I.e., the fluid fully supports the granular skeleton. The velocity of the compaction front depends on the permeability of the soil layer and the viscosity of the interstitial fluid. Analytic considerations of the propagation rate of the compaction front allows us to evaluate the duration of a liquefaction event, the magnitude of soil subsidence, and the timing of water seepage at the surface level, which are all independent of the time scales related to the earthquake shaking. Our approach, when combined with field stratigraphy and groundwater level data, could explain and predict the occurrence and duration of soil liquefaction when the soil layer is effectively drained.</p>

Single-Blow Bit-Tooth Impact Tests on Saturated Rocks Under Confining Pressure: II. Elevated Pore Pressure

1967 ◽  
Vol 7 (04) ◽  
pp. 389-408 ◽  
Author(s):  
J.H. Yang ◽  
K.E. Gray
Keyword(s):  
Pore Pressure ◽  
Effective Stress ◽  
Confining Pressure ◽  
Rock Failure ◽  
Crater Formation ◽  
Depth Of Penetration ◽  
Impact Tests ◽  
Crater Volume ◽  
Confining Pressures ◽  
Stress States

Abstract Results of single-blow bit-tooth impact tests on saturated rocks under elevated confining pressures and zero pore pressure were reported in a previous publication. This paper presents an extension of the earlier work to include a study of crater formation during tooth impact on both gas- and liquid-saturated Berea and Bandera sandstones at elevated confining and pore pressures. The basic data obtained were force-time, displacement-time, velocity-time and force-displacement curves during crater formation. Crater volume was also measured and the mode of crater formation determined. Bit tooth geometry, depth of penetration and velocity of impact were held constant. Results indicate that, with pore fluid present in the rock, failure trends from brittle to ductile as pore pressure is increased at constant confining pressure (pore pressure and borehole pressure were equals For a given rock type, the mode of crater formation was dependent not only upon the nominal effective stress, but also upon the fluid which saturated the rock pore space. When confining pressure and pore pressure were equal (zero nominal effective stress), bit-tooth impact resulted in brittle failure for nitrogen-saturated Berea, and brittle to transitional failure for nitrogen-saturated Bandera; when saturated with liquid both rocks failed in a ductile manner at zero nominal effective stress. Introduction Dynamic wedge penetration tests have been conducted by investigators in several fields, but the failure mechanism of rock under dynamic stresses is not understood completely. The complex action of drilling bits, even considering the action of a single tooth, may be considered as a combination of drag bit and rolling cutter action. Thus, as a first step in understanding rock breakage in oil well drilling, single chisel impact and rock planing are of fundamental importance. For example, Gray and Crisp studied drag bit cutting action at brittle stress states. Simon and Hartman studied the reaction of rocks to vertical impact by means of drop tests. The depth of penetration, crater volume and force-vs-time curves during crater formation were observed. The significance of indexing single-bit impacts has been noted. Garner et al, reported impact tests on impermeable Leuders limestone at atmospheric and elevated confining pressures. In all cases the tests were accomplished on dry rock and pore pressure was considered to be zero. The importance of both confining pressure and pore pressure on the failure characteristics of rock was described. It was found that the yield strength and ductility of porous rock depend on the state of stress under which the sample is tested. The importance of pore pressure on drilling rate in microbit experiments was noted by Cunningham and Eenink, Robinson also pointed out that in drilling the most important parameter in rock failure is the effective stress, where effective stress is defined as confining pressure Pc minus pore pressure Pp. The effect of pore pressure and confining pressure on rock strength was also noted by Serdengecti and Boozer in strain rate tests, and by Gardner, Wyllie and Droschack in elastic wave studies. Until recently all reported wedge impact studies under simulated wellbore stress states have been conducted on dry rock. Maurer reported impact tests on samples saturated with deaerated water. Borehole and formation fluid pressures were equal in these tests except when mud was used in the borehole. With mud in the borehole and a high borehole-to-formation fluid pressure differential, Maurer observed "pseudoplastic" crater formation. Podio and Gray reported impact tests on Berea and Bandera sandstone saturated with pore fluids having wide ranges in viscosities. In Podio and Gray's tests, confining pressure was elevated, but pore pressure and borehole pressure were held fixed at atmospheric pressure. SPEJ P. 389ˆ

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