character and distribution of borehole breakouts and their relationship to in situ stresses in deep columbia river basalts the character and distribution of borehole breakouts in deeply buried basalts at the hanford site in south central washington state are examined in light of stress indicator data and hydraulic fracturing stress data by means of acoustic televiewer and acoustic waveform logging systems a series of boreholes penetrating the grande ronde basalt of the columbia river basalt group were logged to examine the extent of breakouts at depths near 1000 m breakouts occur discontinuously throughout the interiors of most flows in some boreholes the distribution of borehole wall breakouts closely correlates with the incidence of core disking differences in the distribution of breakouts and disking are attributed to differences in failure mechanisms a thin interval of breakout free basalt occurs near the upper and lower limits of flow interiors with many intervals of breakouts terminating at the intersection of oblique fractures with the borehole hydraulic fracturing stress measurement results obtained from four deep boreholes indicate anisotropic horizontal principal stresses with maximum principal stress along an approximate north trending axis consistent with the east trending orientation of breakouts acoustic waveform logs indicate that there is no measurable difference between the seismic properties of breakout free flow tops and flow interiors the highly coherent waveforms obtained in almost all flow interiors indicate that damage to the borehole wall associated with breakout formation remains confined to the thin annulus of stress concentration

well bore breakouts and in situ stress the detailed cross sectional shape of stress induced well bore breakouts has been studied using specially processed ultrasonic borehole televiewer data we show breakout shapes for a variety of rock types and introduce a simple elastic failure model which explains many features of the observations both the observations and calculations indicate that the breakouts define relatively broad and flat curvilinear surfaces which enlarge the borehole in the direction of minimum horizontal compression this work supports the hypothesis that breakouts result from shear failure of the rock where the compressive stress concentration around the well bore is greatest and that breakouts can be used to determine the orientation of the horizontal principal stresses in situ

orientation of the stress field from breakouts in a crystalline well in a seismic active area abstract the orientation of the regional stress field in the swabian jura was determined from borehole breakouts caused by stress accumulation at the borehole wall the analysis is based on caliper data recorded in the urach 3 geothermal well within an intervall of about 1450 m the azimuths of the breakouts are consistent with depth and indicate a stress direction which is in good agreement with the interpretation of fault plane solutions of nearby earthquakes

mantle upflow under north america and plate dynamics in the development of plate dynamics there are two fundamental questions first do the plates slide over a passive asthenosphere or are they driven by a convecting upper mantle second are all ocean ridges passive pull apart plate margins or do some lie above upcurrents in the mantle and in that sense become active margins the combination of stress orientations in the crust of north america with other geophysical and geological information favours an active mantle interpretation both for the north american plate and for the mantle upflow which lay beneath the east pacific rise in tertiary times and which now lies beneath the western united states

stress orientations from oil well fractures in alberta and texas many oil wells in alberta exhibit spalling of the walls known as breakouts which elongates the holes with the longer axis aligned northwest southeast this alignment is observed over an area in excess of 4 105 km2 in siltstones sandstones carbonate sediments and one shale formation through the stratigraphic column from devonian to cretaceous it is unrelated to dip of the beds we have elsewhere suggested that these breakouts are produced through stress concentration near the hole walls in a stress field having large unequal horizontal principal stresses and with the larger compression oriented northeast southwest it is probable that this northeast southwest principal stress is 1 this paper adds new data from oil wells in alberta and northern british columbia and shows that the breakouts and by inference the stress orientations are consistent through much of the western canadian sedimentary basin it also uses evidence from hydraulic fracturing in west central alberta and from steam injec

subsurface in situ stress magnitudes from oil well drilling records an example from the venture area offshore eastern canada this report describes a method of obtaining information on in situ stress magnitudes at depth in sedimentary basins by using information gathered while drilling oil wells if we assume that one of the principal stresses is vertical at a well site principal stress magnitudes can be estimated in the following manner sv is equated with overburden load which is obtained by integrating density log records shmin is equated with leak off test pressures measured over short open hole intervals and also from selected initial feed rate pressures shmax is derived from the equation shmax 2p1 p0 where p1 is the leak off pressure or the initial feed rate pressure and p0 is the fluid pressure over a specified depth interval this relationship is a simplified approximation of hubbert and willis well known equation pb t 3shmin shmax p0 describing hydraulic fracturing around a borehole using this approach stress magnitudes were estimated for 44 depth intervals in four wells drilled over the venture str

stress orientations from well bore breakouts in the coalinga region borehole breakouts are caused by unequal stress concentrations around a borehole resulting in shear failure of the borehole wall and creating hole elongation perpendicular to the maximum horizontal in situ stress breakouts in tertiary sedimentary rocks were identified in 10 holes in the west coalinga cantua creek and west haven oil fields in the western san joaquin valley the deeper and more reliable 1 5 to 3 7 km breakouts were oriented northwest indicating northeast compressive stress perpendicular to the major fold axes in the san joaquin valley and at a 70 90 angle to the major strike slip faults in the coast ranges this stress direction is consistent with a reverse slip component on northwest trending faults in the region and with the focal mechanisms reported for the may 1983 coalinga earthquake the existing literature on stress measurements in central and southern california indicates that on a regional scale the stress regime is transitional between thrust and strike slip faulting a hydraulic fracture test in the kettleman hills oil field at 3 km depth indicates that this stress regime exists in the upper crust near coalinga as well

incompatible stress regimes from geological and geomechanical datasets can they be reconciled an example from the carnarvon basin western australia abstract knowledge of the in situ stress field is essential in petroleum basins as it exerts a prime control over seal integrity fracture stimulation wellbore stability and fluid flow previous geomechanical analysis of australia s carnarvon basin the continent s premier hydrocarbon region highlights a normal to strike slip fault stress regime however neotectonic evidence and contemporary seismicity suggest the possibility of a strike slip to reverse fault stress regime we attempt to reconcile these conflicting datasets through new analysis of the in situ stresses principal stress magnitudes and orientations were defined with data from 76 previously unanalysed petroleum wells wellbore image logs yield a maximum horizontal stress orientation of 113 n consistent with modelling of the stress field throughout the indo australian plate vertical stress magnitudes are estimated to range from 20 mpa km 1 to 22 4 mpa km 1 leak off tests lot from 42 wells are analysed using two methodologies one assuming tensile failure as traditionally accepted the other assuming shear failure as outlined by couzens schultz and chan 2010 and result in two different sets of horizontal stress magnitude estimates traditional interpretation of lots results in a minimum horizontal stress gradient of 16 8 mpa km 1 and a maximum horizontal stress gradient of 21 8 mpa km 1 the new method for lot interpretation results in a minimum horizontal stress gradient of 18 1 mpa km 1 and a maximum horizontal stress gradient of 25 4 mpa km 1 inclined natural fractures observed at lot depths supports application of the new method of lot interpretation traditional interpretation of stress magnitudes implies a normal to strike slip fault stress regime while the new method implies a strike slip fault stress regime this latter interpretation is favoured by the authors as it allows for a reconciliation of the geological and geomechanical datasets the assessment undertaken herein allows for reinterpretation of stress magnitudes in seismically active basins hosting differing geomechanical and neotectonic regimes potentially altering existing understanding of seal integrity fracture stimulation wellbore stability and fluid flow

stress induced borehole elongation a comparison between the four arm dipmeter and the borehole televiewer in the auburn geothermal well the nature and origin of borehole elongation recorded by the four arm dipmeter calipers is studied utilizing information obtained from hydraulic fracturing stress measurements and borehole televiewer data taken in a well located in auburn new york a preferred orientation n10 w s10 e 10 and a less prominant e w orientation of borehole elongation was observed on two runs of the dipmeter comparisons of borehole geometry determined using the televiewer and the dipmeter show that both tools give the same orientation of borehole elongtion provided that the zone of elongation is longer than 30 cm comparisons of dipmeter caliper data with orientation of in situ stress and natural fractures obtained from hydrofracturing tests and televiewer data show that the n10 w s10 e borehole elongations 1 are axisymmetric 2 are aligned with the minimum horizontal stress sh and 3 are not associated with natural fractures intersecting the well these elongations are interpreted as stress induced well bore breakouts the e w elongation direction is characterized by an asymmetric borehole cross section in thinly bedded rocks and is not caused by breakouts this asymmetric geometry can be discriminated from breakouts using the oriented electric measurements provided by the dipmeter this study demonstrates that the dipmeter can be used to determine the orientation of sh by mapping breakouts confirming the results of earlier less detailed studies and provides a firm basis for mapping regional stress patterns using existing dipmeter data

orientation of in situ stresses in the oceanic crust two in situ measurements of principal stress directions have been made in dsdp holes 504b south of the costa rica rift on the nazca plate and 597c west of the east pacific rise on the pacific plate in both cases the orientations of in situ principal stresses determined from borehole breakouts are consistent with the stress directions inferred from intraplate earthquakes located near the sites

holographic in situ stress measurements a new instrument for measuring the in situ level of stress in boreholes has been developed the instrument operates on the principle of locally relieving the stresses acting on a rock mass by drilling a small hole into the borehole surface and recording the resultant displacement field by holographic interferometry because the recording technique is optical the entire displacement field due to stress relief is obtained a description of the stressmeter theory of the interferometric technique data reduction methodology and results of laboratory stress relief calibration tests are presented in addition we present results from a field deployment of the instrument in an underground shale mine in garfield county colorado using a test borehole within a support pillar sufficient data were obtained to constrain five of six stress components at a shallow level of the test borehole thereby demonstrating the viability of the holographic technique the holographic stress relief data yield an approximate ew maximum horizontal stress direction by comparison with previous hydrofracture measurements of bredehoeft et al our results indicate substantial stress relief near the pillar face thus masking any relicts of the far field tectonic stress

intraplate stresses a new tectonic mechanism for fluctuations of relative sea level stress variations in the lithosphere of a few hundred bars can explain the major part of the seismostratigraphic record at passive margins and intracratonic basins however to induce apparent sea level fluctuations with magnitudes greater than 50 m changes in stress level of more than 1 kbar are required these must be related to major reorganizations at convergent plate boundaries fragmentation of plates or collision processes specific rapid falls in the vail et al curves can be associated quantitatively with particular plate tectonic reorganizations of lithospheric stress fields the seismostratigraphic record may provide a new source of information on paleo stress fields to be correlated with results of independent numerical modeling of intraplate stresses

in situ stress from breakouts in the danish sector of the north sea abstract borehole breakouts from 26 wells situated in the danish central graben and one well situated in the northwestern section of the ringkobing fyn high have been studied the data provide information on the orientation of the contemporary principal horizontal stresses down to depths of 4 7 km statistics were used to obtain a mean azimuth of breakouts for each well and each individual breakout was weighted by its length data quality of breakouts is assigned according to the world stress map quality ranking scheme the breakout data reveal that s h orientations in the danish central graben are extremely scattered no regional trend in mean s h orientation can be identified as a result of the large standard deviation 77 similar scatterings of s h orientations have been reported from adjacent regions of the north sea the results indicate that the state of stress in the sedimentary cover of the danish central graben is influenced by a local stress generating mechanism rather than platewide stress transmissions mechanisms three units with different states of stress have been identified and found to correspond somewhat with the lithostratigraphic divisions of the post chalk group chalk group and pre chalk group

stress orientations from borehole wall fractures with examples from colorado east texas and northern canada azimuthally aligned breakouts in oil wells are explained as shear fractures in the zone of amplified stress difference near the borehole in a stress field having unequal horizontal principal stres

stress near the surface of the earth over most of the earth s surface earthquake hypocenters are concentrated in the depth range 0 15 km that is in the upper half of the crust chen molnar 1983 the exception is the subduction zones where cold litho sphere is underthrust to greater depths as a first approximation the top 10 15 km of the crust can be regarded as a region of nearly elastic response to stress with brittle fracture under sufficient stress difference this is the depth range discussed in this review the lower crust appears to be characterized by some form of ductile response to stress in large areas of the upper crust the stress field is related to large scale tectonic processes and represents the tractions acting on the plate concerned however some decoupled crustal blocks are known and are noted herein caution is necessary in generalizing the stress in a region to the plate that contains it recent reviews of crustal stress are given by ranalli chandler 1975 wyss 1977 mcgarr gay 1978 and gay 1980 in the upper crust one principal stress is generally within 20 of the vertical except beneath very rough topography and this vertical principal stress jz is usually within 10 of the lithostatic pressure j pg dz due to overlying rock mcgarr gay 1978 the horizontal principal stresses generally increase with depth and may be less or greater than the vertical pressure within a few hundred meters of the surface the rock mass is divided into blocks by numerous fractures including large and small faults on which shear displacements can be identified and joints on which no shear movement can be seen if the ambient stress is comparable to the strengths of these

breakouts in alberta and stress in the north american plate the paper reports a detailed statistical study of breakout azimuths in 48 oil wells widely distributed in the alberta sedimentary basin bringing the number of oil wells contributing azimuths to 94 for the western canadian basin the azimuths show significant regional variation between the northern central and southern parts of the basin twenty one wells in which breakouts cover depth ranges greater than 600 m were used to investigate regression of breakout azimuths on depth ten wells give positive regression coefficients 11 are negative and no coefficient is significant at 95 confidence level if the dominant northwest southeast orientation of the long axes of breakouts gives the orientation of the lesser horizontal principal stress sh following the hypothesis of bell and gough the inferred stress orientations indicate that throughout the whole basin the direction of the maximum horizontal stress sh is northeast southwest stress measurements by strain relief techniques in a mine and from hyd

present day stress orientation in the molasse basin abstract the present day state of stress in western europe is considered to be controlled by forces acting at the plate boundaries it is assumed that the alpine orogen only influence the regional pattern of present day stress in western europe within the alps themselves we examine the present day maximum horizontal stress orientation in the molasse basin in the alpine foreland in order to investigate the possible influence of the alps on the far field stress pattern of western europe four arm caliper and image logs were analysed in 137 wells in which a total of 1348 borehole breakouts and 59 drilling induced fractures were observed in 98 wells in the german molasse basin the borehole breakouts and drilling induced fractures reveal that stress orientations are highly consistent within the molasse basin and that the present day maximum horizontal stress orientation rotates from n s in southeast germany 002 n 19 to approximately nnw sse in southwest germany and the swiss molasse basin 150 n 24 the present day maximum horizontal stress orientation in the molasse basin is broadly perpendicular to the strike of the alpine front indicating that the stress pattern is probably controlled by gravitational potential energy of alpine topography rather than by plate boundary forces the present day maximum horizontal stress orientations determined herein have important implications for the production of hydrocarbons and geothermal energy in the german molasse basin in particular that hydraulically induced fractures are likely to propagate n s and that wells deviated to the north or south may have reduced wellbore instability problems

relationship between geomorphic settings and unsaturated flow in an arid setting because geomorphology can readily be mapped our ability to characterize unsaturated flow over large areas would be greatly enhanced if relationships between geomorphic settings and unsaturated flow could be identified the purpose of this study was to evaluate relationships between geomorphic settings and spatial and temporal variability in unsaturated flow at a field site in the chihuahuan desert of texas this study differs from most previous studies in the variety of geomorphic settings studied including drainage areas blanca draw and grayton lake playa and interdrainage areas basin fill deposits eolian sheets alluvial fans and a fissure density of data 50 sampled boreholes 3 31 m deep and variety of techniques physical chemical and electromagnetic used to quantify unsaturated flow spatial variability in unsaturated flow parameters is related to geomorphic settings the various geomorphic settings form distinct groups on a plot of chloride versus water potential interdrainage areas have low water potentials and high chloride concentrations indicating low water fluxes mean water fluxes estimated from chloride data ranged from 0 02 to 0 05 mm yr 1 in contrast localized topographic depressions fissure gully and borrow pit have high water potentials and low chloride concentrations which indicate high mean water flux 100 mm yr 1 these topographic depressions occupy 1 of the basin area drainage areas have low water potentials which indicate low water fluxes and low to moderate chloride concentrations which indicate higher water fluxes in the past 40 mm yr 1 short term variability in response to precipitation events was only monitored in topographic depressions the age of the pore water in the interdrainage areas spanned paleoclimatic variations 136 000 years at 25 m depth however most interdrainage profiles show negligible response to past climate fluctuations some profiles in eolian sheets showed increased water flux in response to pleistocene climate change the findings from this study indicate that geomorphology can provide valuable information on unsaturated flow and underscore the importance of localized topographic depressions for focusing unsaturated flow