Laboratory study of borehole breakouts in Cordova Cream: a case of shear failure mechanism

Haimson, Bezalel C.; Song, Insun

doi:10.1016/0148-9062(93)90070-t

Cited by 111 publications

(49 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This work predicts analytically the expected final lengths of compaction bands created around holes, with practical implications to breakouts spontaneously formed in the vicinity of boreholes [13][14][15]31]. In particular, two different defect types are studied, both created by localized compaction: the first defect type is a filled compaction band (CB), and the second is an emptied CB where circulating fluid removes the broken grains that initially formed the CB.…”

Section: Discussionmentioning

confidence: 99%

“…Since it was experimentally observed that CBs emanating from the hole in both Berea and Mansfield sandstones had uniform thickness [15,31], CB thickness variations are not studied in the current model and stresses are evaluated along the X axis only.…”

Section: Stress Induced By a Borehole Under Compressionmentioning

confidence: 99%

“…To date, numerous vertical boreholes (in particular oil-field wellbores) have been logged and their breakout orientations used to estimate regional principal in situ stress directions, rendering them a major contributor to the World Stress Map [29]. In addition, it has been shown that definite correlations exist between borehole breakout dimensions and in situ stress magnitudes in laboratory rock samples [15,33]. Vernik and Zoback [37], Brudy et al [3], and Haimson and Chang [11] successfully utilized logged breakout spans and known rock criteria of failure to estimate the maximum horizontal in situ stress, r 1 , in the deep scientific holes of Cajun Pass, California and KTB, Germany.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Compaction bands induced by borehole drilling

2009

View full text Add to dashboard Cite

Drilling experiments in rock blocks subjected to pre-existing true triaxial far-field stresses simulating real in situ conditions often result in localized failure around the created borehole, which brings about the formation of borehole breakouts. In weakly bonded quartz-rich porous sandstones breakouts take the form of narrow tabular (slotlike) openings extending along a plane perpendicular to the maximum applied-stress direction. Scanning electron microscopes images of failed boreholes strongly suggest that these breakouts are compaction bands that have been emptied to different extents. The bands form as a result of the stress concentration accompanying the creation of the borehole. The evacuation of the compaction bands is brought about by the circulating drilling fluid flushing out debonded and often fragmented grains from within these bands co-workers, 2003-2007). The objective of this paper is to predict the conditions under which compaction bands are formed around boreholes. To this end, a new analytical model is formulated that enables prediction of the stress field around emptied and filled compaction bands, the various factors affecting the breakouts lengths, and their final length. Good agreement of the developed analytical model with experimental results obtained by Haimson and co-workers (Haimson and Klaetsch in Rock physics and geomechanics in the study of reservoirs and repositories) is demonstrated. The presented study is of practical relevance: boreholes are often drilled deep into weak porous sandstone formations for the purpose of extracting oil and gas, and the question of borehole stability is crucial. In addition, borehole breakouts are often used to estimate the state of stress in the Earth's crust, and our new formulation will help improve these estimates.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Stress Induced By a Borehole Under Compressionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Compaction bands induced by borehole drilling

2009

View full text Add to dashboard Cite

show abstract

“…Colmenares and Zoback, 2002;Zimmerman, 2005, 2006;You, 2009;Kwaśniewski, 2012Kwaśniewski, , 2013 and applications of these criteria to problems such as the estimation of far-field stresses from the analysis of hydraulic fractures and borehole breakouts (e.g. Haimson and Song, 1993;Lee and Haimson, 1993;Zimmerman, 2005, 2006;Colmenares and Zoback, 2002). Failure criteria employed fall into those that are based on attainment of a critical value of a function of stress invariants versus wholly empirical criteria.…”

Section: Rock Failure Under Polyaxial Stressesmentioning

confidence: 99%

The Mohr–Coulomb criterion for intact rock strength and friction – a re-evaluation and consideration of failure under polyaxial stresses

Hackston

Rutter

2016

Solid Earth

View full text Add to dashboard Cite

Abstract. Darley Dale and Pennant sandstones were tested under conditions of both axisymmetric shortening and extension normal to bedding. These are the two extremes of loading under polyaxial stress conditions. Failure under generalized stress conditions can be predicted from the MohrCoulomb failure criterion under axisymmetric shortening conditions, provided the best form of polyaxial failure criterion is known. The sandstone data are best reconciled using the Mogi (1967) empirical criterion. Fault plane orientations produced vary greatly with respect to the maximum compressive stress direction in the two loading configurations. The normals to the Mohr-Coulomb failure envelopes do not predict the orientations of the fault planes eventually produced. Frictional sliding on variously inclined saw cuts and failure surfaces produced in intact rock samples was also investigated. Friction coefficient is not affected by fault plane orientation in a given loading configuration, but friction coefficients in extension were systematically lower than in compression for both rock types. Friction data for these and other porous sandstones accord well with the Byerlee (1978) generalization about rock friction being largely independent of rock type. For engineering and geodynamic modelling purposes, the stress-state-dependent friction coefficient should be used for sandstones, but it is not known to what extent this might apply to other rock types.

show abstract

“…In an idealized triaxial stress field, where the intermediate principal stress is oriented parallel to the hole axis, high tangential shear stresses are developed along the borehole sidewalls oriented parallel to the minor principal stress axis. Failure will either take the form of conjugate fracture zones which intersect at some distance from the borehole wall (Haimson and Song, 1993), or extensile fracturing sub-parallel to the borehole wall and parallel to the major compressive stress direction (Ewy and Cook, 1990;Lee and Haimson, 1993;Sellers and Klerck, 2000). The former results in wedge-shaped fallout bounded by shear fractures, and generally occurs in weak sedimentary rocks.…”

mentioning

confidence: 99%

Calibration of a numerical model for bore-and-fill mining

Roberts¹

2017

J. South. Afr. Inst. Min. Metall.

View full text Add to dashboard Cite

Tau Tona mine has historically experienced damaging seismicity during attempts to extract its high-grade, highly stressed shaft pillar (Murphy, 2012). In an attempt to reduce the potential for seismic events a new mining method that involves the boring of largediameter holes on-reef has been trialled. The rationale behind reef boring is that it reduces the effective stoping height, thus limiting the influence of the excavation on the surrounding rock mass. This is particularly important in the shaft pillar, as high deformation and closure are associated with increased seismic hazard.Optimization of the boring sequence and in-hole support enable the extraction of as much of the reef as possible, while minimizing waste rock mining. Support must be installed in such a way that workers are never required to enter the holes. Filling the holes with a stiff, strong material will achieve these goals. Concrete, for example, has low porosity, can be engineered to have high strength and stiffness, and is easily poured or pumped into the holes from service excavations.This paper describes how observations and measurements at a reef-boring pilot site were used to calibrate nonlinear numerical models. Initial models were calibrated based on observations of breakout and additional fracturing that was exposed when a raise was mined along the axis of an existing hole. A novel criterion for simulating breakout was developed, based on displacement into the hole and parallel to the minor stress axis. This criterion was used with the calibrated model to simulate the drilling and filling of a sequence of five holes. Some of these holes were instrumented with stress-change gauges and some were scanned and surveyed. The in situ data was compared with modelled outcomes.The feasibility of reef boring was considered by Jager, Westcott, and Cook (1975). They analysed various reefs in terms of deviation from planarity, presenting charts and tables to indicate optimal hole diameters in different mining areas. Adams (1978) describes stoping using a raiseboring machine on the Carbon Leader Reef (CLR) at West Driefontein mine. Holes were drilled adjacent to each other to create a continuous slot between reef drives. Pilot holes were bored and then used to guide a raisebore reamer from the upper reef drive. The completed slot is shown in Figure 1. Calibration of a numerical model for bore-and-fill mining by D. RobertsBore-and-fill mining was implemented at a pilot site in Tau Tona mine's shaft pillar on 97 level. Observations, scan data, and measurements from this site were used to calibrate an inelastic numerical model of bore-andfill mining within the Carbon Leader Reef (CLR).Borehole breakout was found to occur around holes at the site as they were bored. A strike-parallel exposure showed that fracturing within the Carbon Leader stratum extended far beyond the breakout (up to 1.2 m from the hole sidewall). This was confirmed by borehole camera observations in a hole drilled on-reef through a bored-and-filled hole.A Mohr-Coulomb strain-softeni...

show abstract

Laboratory study of borehole breakouts in Cordova Cream: a case of shear failure mechanism

Cited by 111 publications

References 14 publications

Compaction bands induced by borehole drilling

Compaction bands induced by borehole drilling

The Mohr–Coulomb criterion for intact rock strength and friction – a re-evaluation and consideration of failure under polyaxial stresses

Calibration of a numerical model for bore-and-fill mining

Contact Info

Product

Resources

About