predicting hydraulic tensile fracture spacing in strata bound systems a model is presented which predicts the spacing of tensile fractures due to fluid pressure increase in a multilayered sedimentary sequence comprising different typical sedimentary deposits such as mudstones siltstones and sandstones during normal burial and tectonic conditions strata will undergo both extensional forces and an increase in fluid pressures this model addresses the effects of the diffuse fluid pressure increase and is useful for engineered applications such as the injection of fluid into a reservoir that may cause an increase of fluid pressure beneath a caprock and for sedimentary sequences during normal digenetic processes of burial and fault activation analytical and numerical elastic stress strain solutions are compared to provide a robust normalised standard relationship for predicting the spacing of fractures key parameters are the local minimum horizontal stress variability of the tensile strengths of the layers of a sedimentary sequence and the thickness of the beds permeability and storage are also shown to affect the fracture spacing the model predicts many of the field observations made regarding strata bound fracture systems and should also prove useful in consideration of the impact of raised reservoir fluid pressures on caprock integrity

development of efficiently coupled thermo hydro mechanical model to predict hydraulic fracture morphology in heavy oil reservoirs the aim of the study involves examining the effect of heavy oil viscosity on fracture geometry in detail by establishing a heavy oil fracturing model and conventional fracturing model based on thermal hydraulic mechanical thm coupled theory walther viscosity model and k d r temperature model we consider viscosity and density within the heavy oil fracturing model as functions of pressure and temperature while that as constants within the conventional fracturing model a heavy oil production well is set as an example to analyze the differences between the two models to account for the thermo poro elastic effect the results show that temperature exhibits the most significant influence on the heavy oil viscosity while the influence of pressure is the least in addition a cooling area with a width of 0 1 m and varied length is generated near the fracture the heavy oil viscosity increases sharply in this area thereby indicating an area of viscosity increment the heavy oil viscosity increases faster and is closer to wellbore and a high viscosity increment reduces the mobility of the heavy oil and prevents the fracturing fluid from entering into the reservoir the special viscosity distribution results in significant differences in pore pressure oil saturation and changing trends between these two models in the heavy oil reservoir fracturing model the thermal effect completely exceeds the influence of pore elasticity and the values of the fracture length width and static pressure exceed those calculated in the conventional fracturing model thus a comparison of the measured values indicates that the results obtained by considering viscosity as a function of temperature and pressure are more accurate therefore the results of this study are expected to provide good guidelines for the design of heavy oil fracturing

theoretical investigation of the oceanic inverted barometer response dynamic tidal theory is generalized in order to predict the oceanic response to atmospheric pressure variations the oceans are found to exhibit distinct dynamic behavior when forced at periods less than 1 week depending on the harmonic type of forcing the amplitude of the response can differ by 20 or more from the static response even at roughly 2 months the traditional inverted barometer may not be sufficiently accurate for applications in which detection of long term sea level trends or vertical crustal motion is the goal for forcing at periods of order 1 year the oceanic response differs by at most a few percent from the static not the inverted barometer response thus calculations of meteorological excitation of the annual and chandler wobbles can employ the static approximation without reservation

resolving mass flux at high spatial and temporal resolution using grace intersatellite measurements 1 the grace mission is designed to monitor mass flux on the earth s surface at one month and high spatial resolution through the estimation of monthly gravity fields although this approach has been largely successful information at submonthly time scales can be lost or even aliased through the estimation of static monthly parameters through an analysis of the grace data residuals we show that the fundamental temporal and spatial resolution of the grace data is 10 days and 400 km we present an approach similar in concept to altimetric methods that recovers submonthly mass flux at a high spatial resolution using 4 4 blocks at 10 day intervals we estimate the mass of surplus or deficit water over a 52 60 grid centered on the amazon basin for july 2003 we demonstrate that the recovered signals are coherent and correlate well with the expected hydrological signal

the effects of lateral property variations on fault zone reactivation by fluid pressurization application to co2 pressurization effects within major and undetected fault zones in this study we performed in situ multidisciplinary analyses of two different fault zones in carbonate formations one is a seismically active fault zone several kilometers long the roccasseira fault zone the other is a small fault zone a few hundred meters long the gas fault zone the smaller immature fault zone displays a discontinuous damage zone because tectonic deformations have been accommodated differently according to the initial properties of the host rock the larger mature fault zone displays a continuous damage zone caused by the presence of secondary fault cores embedded in a heavily fractured area inside the damage zone these markedly different fault zone architectures were reflected in two hydraulic and geomechanical fault models both generated from a coupled fluid flow and geomechanical simulator to examine the impact of hydromechanical property distribution on fault stability when the faults are reactivated by co2 injection in the smaller fault zone marked differences in hydromechanical properties young s modulus and permeability favor fluid accumulation inducing high pressurization in parts of the damage zone potentially resulting in small seismic events on the other hand in the mature fault zone fluid flows more easily and thus fluid induced earthquakes may not readily occur because the fault zone pressurization is much lower insufficient for triggering a seismic event

3 d reconstruction method for complex pore structures of rocks using a small number of 2 d x ray computed tomography images underground hydrocarbon reservoir rocks comprise numerous multiscale irregular pores that significantly affect the mechanical and fluid transport properties of the rock it is considerably challenging for in situ geological monitoring and laboratory tests to accurately characterize the changes in the interior structure and the corresponding mechanical properties of the rock mass during dynamic excavation processes the 3 d numerical reconstruction models that are based on the statistical information extracted from x ray computed tomography xct images provide a feasible method to obtain and characterize the interior pore structures and their effects on the physical responses of reservoir rocks however obtaining sufficient high resolution 2 d xct images is economically expensive by the traditional fan beam ct scan system reconstructing 3 d porous structures by computational methods using statistical information extracted from xct images usually has low efficiency therefore in this paper we introduce a novel method to numerically reconstruct natural sandstone rock using a small number of 2 d xct images the bayesian information criterion was used to determine the minimum number of 2 d xct images required to ensure the expected reconstruction accuracy a multithread parallel reconstruction scheme was employed to improve the efficiency the accuracy of the proposed method was verified by comparing the statistical correlation functions geometrical and topological characteristics and mechanical properties of pore structures between the reconstructed model and a sandstone prototype this paper provides a method to achieve fast economic and accurate 3 d reconstruction of porous rock

equatorial mid tropospheric easterly jet over the eastern pacific comparison from the ecmwf and ncep ncar reanalyses 1 the upper air data set of the european centre for medium range weather forecasts ecm 1979 93 reanalysis is evaluated in comparison to the national centers for environmental prediction national center for atmospheric research ncp reanalysis for the same period attention is focused on the equatorial mid tropospheric easterly jet emtej over the eastern pacific first noted from a short series of rawin soundings at galapagos and then corroborated in its broad spatial context from the ncp 40 year reanalysis the present follow up study contributes a comparison of evidence from the two sources with different model assimilations the major characteristics of the emtej are confirmed although the winds from ecm are overall slower and those from ncp faster than the measurements over galapagos in both ecm and ncp the easterly speed maximum along the equator is over the eastern pacific located around 600 700 mb and further westward at progressively lower elevations divergence prevails in the realm of the speed maximum and is primarily fed by subsidence from aloft the ecm evidence differs from ncp by a more westward location of the easterly speed maximum and overall weaker flow

numerical modeling of the tensile fracture reactivation under the effects of rock geomechanical properties and heterogeneity during co2 storage the injection of co2 into aquifers increases fluid pressure and induces a change of the geomechanical state this is expected to be a cause of fracture reactivation which is an important issue for the safety of co2 storage using the geomechanics module fracture reactivation which was induced by tensile failure was considered for the investigation of a potential co2 leakage numerical simulations were conducted to analyze the effects of the rock geomechanical properties on the fracture reactivation in a two dimensional system and then the properties of fracture propagation were extended to the different rock types hard shale and weak shale in a three dimensional system changes of the stress state rock deformation and the pressure build up induced by co2 injection were examined when a rock has a high young s modulus effective stress decreases rapidly leading to an earlier fracture reactivation the total reduction of effective stress in the rock with a low poisson s ratio was less than that of the rock with a high poisson s ratio the magnitude of pressure build up is lower in the high permeability rock so that the fracture propagates more slowly hard shale s caprock is more favorable than that of weak shale for co2 storage because fractures are opened later retarding the co2 leakage the injected co2 flows through a preferable region with reactivated fractures in the heterogeneous caprock this study broadens our perception of the mechanical behavior that is induced by co2 injection and it could be helpful for the precise safety assessment of co2 storage projects

off axis sonar beam pattern of free ranging finless porpoises measured by a stereo pulse event data logger the off axis sonar beam patterns of eight free ranging finless porpoises were measured using attached data logger systems the transmitted sound pressure level at each beam angle was calculated from the animal s body angle the water surface echo level and the swimming depth the beam pattern of the off axis signals between 45 degrees and 115 degrees where 0 degrees corresponds to the on axis direction was nearly constant the sound pressure level of the off axis signals reached 162 db re 1 micropa peak to peak the surface echo level received at the animal was over 140 db much higher than the auditory threshold level of small odontocetes finless porpoises are estimated to be able to receive the surface echoes of off axis signals even at 50 m depth shallow water systems less than 50 m depth are the dominant habitat of both oceanic and freshwater populations of this species surface echoes may provide porpoises not only with diving depth information but also with information about surface direction and location of obstacles including prey items outside the on axis sector of the sonar beam

grace measurements of mass variability in the earth system monthly gravity field estimates made by the twin gravity recovery and climate experiment grace satellites have a geoid height accuracy of 2 to 3 millimeters at a spatial resolution as small as 400 kilometers the annual cycle in the geoid variations up to 10 millimeters in some regions peaked predominantly in the spring and fall seasons geoid variations observed over south america that can be largely attributed to surface water and groundwater changes show a clear separation between the large amazon watershed and the smaller watersheds to the north such observations will help hydrologists to connect processes at traditional length scales tens of kilometers or less to those at regional and global scales

impact of co2 injection through horizontal and vertical wells on the caprock mechanical stability abstract subsurface injection of carbon dioxide co2 may induce large overpressures that may put caprock integrity at risk this overpressure may induce microseismic events if the rock yields yielding of the caprock could open up a leakage path for co2 rock mechanical integrity is strongly related to fluid pressure evolution which is significantly different for vertical and horizontal wells while co2 pressure builds up sharply at the beginning of injection but afterwards drops when injecting a constant co2 mass flow rate through a vertical well a horizontal well leads to a continuous co2 pressure increase thus for a vertical well the less stable situation in the saline aquifer occurs at the beginning of injection however the changes induced in the effective stress field are small so unstable conditions are unlikely both in a normal faulting and a reverse faulting stress regimes in extensive saline aquifers such as the one considered in this study by contrast fluid pressure becomes larger than that of a vertical well for a common length of horizontal wells around 2 km which causes a significant increase in horizontal total stresses that improves the reservoir and caprock mechanical stability in a nf stress regime but worsens it in a rf stress regime though in general the caprock integrity is unlikely to be compromised fluid pressure evolution should be always monitored and mitigation measures should be carried out if it deviates from its expected evolution

experimental evaluation of mixed fluid reactions between supercritical carbon dioxide and nacl brine relevance to the integrity of a geologic carbon repository abstract the reactive behavior of a mixed fluid supercritical co2 and brine under physical chemical conditions relevant to geologic storage and sequestration in a carbon repository is largely unknown experiments were conducted in a flexible cell hydrothermal apparatus to evaluate fluid rock aquifer plus aquitard reactions that may adversely impact the integrity of the repository a 5 5 molal nacl brine rock system was held at 200 c and 200 bars 20 mpa for 32 days 772 h to approach steady state then injected with co2 and allowed to react for an additional 45 days 1079 h in a separate experiment at 200 c and 200 bars the system was allowed to react for 77 days 1845 h without injection of co2 corroded magnesite and euhedral siderite crystallized in a paragenetic sequence after co2 injection nucleation and growth of siderite on shale suggests the aquitard is a reactive component in the system changes in elemental abundances in the brine following addition of co2 include ph decrease and depletion of sodium due to accelerated growth of analcime a ph increase follows pressure and temperature decrease and loss of saturated co2 from acidic brine silica concentrations and dissolution rates are enhanced and silica precipitation inhibited in the acidic brine geochemical reactions in a carbon repository extend beyond ph decrease and carbonate mineral precipitation rock dominated reaction systems yield to acid dominated and related reactions controlled by mixed fluid equilibria i e a fluid dominated system escape of co2 or migration of brine from the repository into overlying aquifers may cause silica super saturation and increased alkalinity due to mixed fluid phase equilibria these geochemical changes could be monitored in aquifers as indicators of repository integrity return of silica super saturated brine to a rock dominated reaction system buffered to neutral ph conditions may enhance precipitation of quartz chalcedony or amorphous silica in addition to the potential effects beneficial or deleterious that silica super saturation and precipitation may hold for repository performance an understanding of the effects of multi phase equilibrium relationships between supercritical co2 and dissolved silica in aquifer brine systems also raises new questions for a variety of geologic systems multi phase fluid equilibria may for example account for quartz cements in some sedimentary basin sandstones and quartz vein mineralization in some ore districts

wellbore cement fracture evolution at the cement basalt caprock interface during geologic carbon sequestration abstract composite portland cement basalt caprock cores with fractures as well as neat portland cement columns were prepared to understand the geochemical and geomechanical effects on the integrity of wellbores with defects during geologic carbon sequestration the samples were reacted with co 2 saturated groundwater at 50 c and 10 mpa for 3 months under static conditions while one cement basalt core was subjected to mechanical stress at 2 7 mpa before the co 2 reaction micro xrd and sem eds data collected along the cement basalt interface after 3 month reaction with co 2 saturated groundwater indicate that carbonation of cement matrix was extensive with the precipitation of calcite aragonite and vaterite whereas the alteration of basalt caprock was minor x ray microtomography xmt provided three dimensional 3 d visualization of the opening and interconnection of cement fractures due to mechanical stress computational fluid dynamics cfd modeling further revealed that this stress led to the increase in fluid flow and hence permeability after the co 2 reaction xmt images displayed that calcium carbonate precipitation occurred extensively within the fractures in the cement matrix but only partially along the fracture located at the cement basalt interface the 3 d visualization and cfd modeling also showed that the precipitation of calcium carbonate within the cement fractures after the co 2 reaction resulted in the disconnection of cement fractures and permeability decrease the permeability calculated based on cfd modeling was in agreement with the experimentally determined permeability this study demonstrates that xmt imaging coupled with cfd modeling represent a powerful tool to visualize and quantify fracture evolution and permeability change in geologic materials and to predict their behavior during geologic carbon sequestration or hydraulic fracturing for shale gas production and enhanced geothermal systems

investigation of geomechanical responses of reservoirs induced by carbon dioxide storage assessment of the suitability of potential sub surface storage sites for co2 storage cuts across several issues a dominant part being the sustainability in terms of the retention capacity of prospective reservoirs questions often raised but not properly investigated border on the stability of underground reservoirs during the injection process and the protracted effect after injection is fully completed a review of studies on co2 sequestration reveals several uncovered areas with one significant aspect being the geo mechanical effect of co2 injection and storage within the underground formation a computational framework has been built as part of a series of ongoing investigations to ascertain the susceptibility of underground formations during and after co2 is introduced this is made possible by adopting a discrete element modelling methodology as a first step in the sequence of a designed procedure by applying this technique the formation materials are idealised as an assembly of discrete particles interacting in a manner which allows for specific descriptions of the morphology and fracturing events computational tests conducted on several types of models representative of reservoir formations reveal reservoir geo mechanical responses highly dependent on factors such as material property of rocks pressure build up and injection pressure an example of this is observed in the mode of fracturing events which is significantly influenced by the rate of fluid injection the outcome of this study forms a strong basis towards a better understanding of the behaviour of reservoir formations subjected to co2 injection and storage in addition information from these studies could serve as a reference for enhanced oil recovery processes and enhanced coal bed methane productions

a study of caprock hydromechanical changes associated with co2 injection into a brine formation a numerical study of hydromechanical changes during a deep underground injection of supercritical co2 in a hypothetical brine aquifer caprock system is conducted the injection process is simulated using a newly developed computer model for multi phase analysis of co2 and brine water flow coupled with heat transfer and rock deformations in this modeling co2 is injected at a constant rate over a 10 year period at a depth of 1 300 1 500 m the injection zone is overlain by a 100 m thick caprock located at 1 200 1 300 m which in one of the studied cases is intersected by a vertical fault the hydraulic mechanical as well as hydromechanical responses caused by the injection are studied this includes the spread of the co2 plume effective stress changes ground surface uplift stress induced permeability changes and mechanical failure analysis the analysis shows that most hydromechanical changes are induced in the lower part of the caprock near its contact with the injection zone whereas the sealing mechanism of the upper part may remain intact despite an injection pressure close to the lithostratic stress value

a quadruple porosity model for transient production analysis of multiple fractured horizontal wells in shale gas reservoirs multiple types of pores are present in shale gas reservoirs including organic pores of nano scale non organic pores natural and hydraulic fractures gas flow in different types of pores is controlled by different mechanisms and darcy s law is not able to describe all these processes adequately this paper presents a quadruple porosity model and corresponding analytical solutions to describe the different permeable media and simulate transient production behavior of multiple fractured horizontal wells in shale gas reservoirs dimensionless transient production decline curves are plotted and characteristic bilinear flow and linear flow periods are identified based on the analysis of type curves sensitivity analysis of transient production dynamics suggests that desorption of absorbed gas knudsen diffusive flow gas slippage and parameters related to hydraulic fractures have significant influence on the production dynamics of a multiple fractured horizontal well in shale gas reservoirs the model provides insights into multiple shale gas flow mechanisms and production prediction of shale gas reservoirs

investigations on fluid transport properties in the north german rotliegend tight gas sandstones and applications tight gas reservoirs are an important part of the world gas resources such reservoirs have very low permeability usually below 0 1 md and show a strong stress sensitivity to fluid transport properties and a considerable productivity decline during the production process due to increasing effective stress in an experimental study several measurement series were performed on plugs from the north german rotliegend tight gas reservoirs to improve knowledge and understanding of the effects of changing stress and pore pressure conditions on reservoir rocks during gas production in addition to the experimental study an interactive rock data catalog irdc has been developed which contains a database coupled with a correlation module the database contains metadata of the fields and wellbores included in the irdc the corresponding log data and petrophysical data the correlation module contains correlations derived both from the study measurements and from literature the results of this study will enable reservoir engineers to select specific data from the database and process it in the correlation module to generate secondary sets of data which can then be used for modeling and simulation of tight gas reservoirs

earth s variable rotation recent improvements in geodetic data and practical meteorology have advanced research on fluctuations in the earth9s rotation theinterpretation of these fluctuations is inextricably linked with studies of the dynamics of the earth moon system and dynamical processes in the liquid metallic core of the earth where the geomagnetic field originates other parts of the earth9s interior and the hydrosphere and atmosphere fluctuations in the length of the day occurring on decadal time scales have implications for the topography of the core mantle boundary and the electrical magnetic and other properties of the core and lower mantle investigations of more rapid fluctuations bear on meteorological studies of interannual seasonal and intraseasonal variations in the general circulation of the atmosphere and the response of the oceans to such variations

localization and tracking of phonating finless porpoises using towed stereo acoustic data loggers cetaceans produce sound signals frequently usually acoustic localization of cetaceans was made by cable hydrophone arrays and multichannel recording systems in this study a simple and relatively inexpensive towed acoustic system consisting of two miniature stereo acoustic data loggers is described for localization and tracking of finless porpoises in a mobile survey among 204 porpoises detected acoustically 34 individuals similar to 17 were localized and 4 of the 34 localized individuals were tracked the accuracy of the localization is considered to be fairly high as the upper bounds of relative distance errors were less than 41 within 173 m with the location information source levels of finless porpoise clicks were estimated to range from 180 to 209 db re 1 mu pa pp at 1 m with an average of 197 db n 34 which is over 20 db higher than that estimated previously from animals in enclosed waters for the four tracked porpoises two dimensional swimming trajectories relative to the moving survey boat absolute swimming speed and absolute heading direction are deduced by assuming the animal movements are straight and at constant speed in the segment between two consecutive locations

evaluating the impact of caprock and reservoir properties on potential risk of co2 leakage after injection numerical models are essential tools in fully understanding the fate of injected co2 for commercial scale sequestration projects and should be included in the life cycle of a project common practice involves modeling the behavior of co2 during and after injection using site specific reservoir and caprock properties little has been done to systematically evaluate and compare the effects of a broad but realistic range of reservoir and caprock properties on potential co2 leakage through caprocks this effort requires sampling the physically measurable range of caprock and reservoir properties and performing numerical simulations of co2 migration and leakage in this study factors affecting co2 leakage through intact caprocks are identified their physical ranges are determined from the literature from various field sites a quasi monte carlo sampling approach is used such that the full range of caprock and reservoir properties can be evaluated without bias and redundant simulations for each set of sampled properties the migration of injected co2 is simulated for up to 200 years using the water salt co2 operational mode of the stomp simulator preliminary results show that critical factors determining co2 leakage rate through caprocks are in decreasing order of significance the caprock thickness caprock permeability reservoir permeability caprock porosity and reservoir porosity this study provides a function for prediction of potential co2 leakage risk due to permeation of intact caprock and identifies a range of acceptable seal thicknesses and permeability for sequestration projects the study includes an evaluation of the dependence of co2 injectivity on reservoir properties

mineral carbon sequestration and induced seismicity 1 the seismic safety of current technologies for co2 sequestration has been questioned in several recent publications and whitepapers while there is a definite risk from unbalanced subsurface fluid injection because of hydraulic fracturing we propose a simple model to demonstrate that mineral carbonation in mafic rocks can mitigate seismic risk in particular mineral precipitation will increase the solid grain grain contact area which reduces the effective fluid pressure distributes the deviatoric stress load and increases frictional contact thus mineral sequestration can potentially reduce seismic risk provided fluid pumping rates do not exceed a critical value

modelling carbon dioxide accumulation at sleipner implications for underground carbon storage an analytical solution to the equations describing the flow of a buoyant fluid released into a porous medium below a horizontal impermeable boundary is used to model the growth of co2 accumulations beneath thin mudstone beds in the utsira sand reservoir at sleipner in the north sea here supercritical co2 has been injected at a rate of 1 mt yr since 1996 and imaged by time lapse seismic data in 1999 2001 and 2002 the co2 rises as a narrow plume and is partially trapped by a number of thin mudstones before reaching the caprock to the reservoir the radii of the individual layers of trapped co2 increase as the square root of time since initiation as predicted by the modelling for constant input flux however apparent negative initiation times for horizons low in the reservoir suggests that net input fluxes for these layers have decreased with time most probably as the spreading layers have increased their leakage rates accumulation of co2 in the layers higher in the reservoir was initiated up to 3 yr after injection started modelling of the thickness profiles across three of the higher layers suggests that their net input fluxes have increased with time the observation that the central thicknesses of the deeper layers have remained approximately constant or have slightly decreased since first imaged in 1999 is consistent with the model predictions that the central thickness is directly proportional to net input flux however estimates of the permeability of the reservoir from the rate of increase of the radii of the co2 accumulations are an order of magnitude less than measured permeabilities on the reservoir sandstone permeabilities estimated from the modelling of layer thickness changes scatter in the same range these discrepancies may arise from 1 approximations in the model not being valid 2 the measured permeabilities not being representative of the permeability for two phase flow on the scale of the reservoir or considered less likely 3 that much less co2 is being stored in the imaged co2 accumulations than estimated from the seismic reflection profiles the most probable cause of the discrepancy is that the relative permeability for the co2 phase is significantly reduced at lower co2 saturations

numerical study on hydraulic fracturing in different types of georeservoirs with consideration of h2m coupled leak off effects with the increase in the world s energy consumption and the change in climate unconventional energy resources become more and more popular since geological formations of low or ultra low permeability are usually involved hydraulic fracturing is one of the most important tools for their exploitation the objective of this paper is to investigate hydraulic fracturing and its hydro mechanical influences on different types of georeservoirs including tight gas oil and geothermal reservoirs based on the previous work of hydraulic fracturing simulation with flac3dplus the multi phase multi component flow simulator tough2mp is coupled for the numerical study a new coupling approach is designed with special consideration of the h2m coupled process in different types of georeservoirs for the simulation a generic 3d model 200 300 200 m consisting of 50 m caprock 100 m reservoir formation and 50 m base rock is adopted the simulations are run under comparable reservoir and operative conditions the results show that fracture propagation and proppant concentration are comparable with a short period of slurry injection 80 min 6 m3 min the fracturing fluid does not penetrate deep into the formation due to the high compressibility of gas the induced pore pressure is much lower than that in oil and geothermal reservoirs although the final leak off ratio is comparable the hydraulic fracturing causes stress reorientation in georeservoirs according to the criterion of 5 stress reorientation the minimum fracture spacing for a multiple fracture system in the assumed geothermal reservoir is 73 m while that in an oil and gas reservoir is 66 and 60 m respectively this work expands on the numerical simulator as well as the understanding of hydraulic fracturing in unconventional georeservoirs the results of this study can be used further to optimize the fracture spacing in a multiple hydraulic fracture system in different reservoir types

acoustic capture recapture method for towed acoustic surveys of echolocating porpoises passive acoustic monitoring for cetaceans mainly employ fixed location methods or point transect samplings an acoustic survey from a moving platform to conduct line transects is less common in this study acoustic capture recapture by combining a double observer method with line transect sampling was performed to observe yangtze finless porpoises two acoustic devices were towed with the distance between them varying 0 5 to 89 5 m the conditional probabilities that both devices would detect the porpoises within the same time window were calculated in a 1 s time window it became smaller as the distance between the devices increased approaching zero when the distance between them was more than 50 m it was considered that the devices with less than 50m distance detected the same signals from the same animals which means the identical detection when the distance between them is too great the recapture rate is reduced and the incidence of false matching may increase thus a separation distance of around 50m between two devices in acoustic capture recapture of yangtze finless porpoises was recommended note that the performance of the double detections can change depending on the particular device used and on animal behaviors such as vocalizing interval ship avoidance c 2014 acoustical society of america

coupled reservoir geomechanical analysis of the potential for tensile and shear failure associated with co2 injection in multilayered reservoir caprock systems coupled reservoir geomechanical simulations were conductedto study the potential for tensile and shear failure e g tensilefracturing and shear slip along pre existing fractures associated withunderground co2 injection in a multilayered geological system thisfailure analysis aimed to study factors affecting the potential forbreaching a geological co2 storage system and to study methods forestimating the maximum co2 injection pressure that could be sustainedwithout causing such a breach we pay special attention to geomechanicalstress changes resulting from upward migration of the co2 and how theinitial stress regime affects the potential for inducing failure weconclude that it is essential to have an accurate estimate of thethree dimensional in situ stress field to support the design andperformance assessment of a geological co2 injection operation moreover we also conclude that it is important to consider mechanical stresschanges that might occur outside the region of increased reservoir fluidpressure e g in the overburden rock between the co2 injectionreservoir and the ground surface

numerical modeling of percolating flow path in a caprock formation during aquifer pressurization and its implication for co2 sequestration spatial distribution of sand bodies in caprock is important to its sealing potential in the evaluation of a potential waste disposal site a numerical investigation was conducted to investigate the roles of sand bodies in caprock integrity and a new leaking mechanism associated with the embedded sand bodies has been identified for the first time this numerical model is characterized by a low proportion of sand bodies in caprock formation and stochastic permeability assignments to the shale facies with a consideration of stress sensitive permeability the research revealed that sand bodies in caprock even initially unconnected due to their low concentration represent the foundation for creating a percolating flow path if certain conditions are met these conditions include a relatively high pore pressure gradient across the caprock which may occur during fluid injection and a favorable geometric configuration of these sand bodies sand bodies of different shapes play different roles in forming a percolating flow path sand bars dykes can lead pore pressure front to cover a considerable vertical thickness quickly while thin sand sheets tend to transfer the pore pressure front across a large horizontal range and thus increase the possibility of involving other local sand bodies in the evolution of percolating flow paths on the other hand the presence of percolating flow path in caprock can limit the pore pressure increase in the aquifer formation during fluid injection the more active the flow paths the less increase the pore pressure that occurs in the aquifer stress dependent permeability can facilitate the formation of percolating flow path but evaluating how much impact it may have remains a question for future research the modeling results indicate that the underlying geologically based discrete structure of permeable domains even when masked by a low permeable rock matrix exerts a significant influence on the location and magnitude of fluid flow within the system during fluid injection

monitoring pacific ocean seismicity from an autonomous hydrophone array since may 1996 an array of autonomous hydrophone moorings has been continuously deployed in the eastern equatorial pacific to provide long term monitoring of seismic activity including low level volcanic signals along the east pacific rise between 20 n and 20 s and the galapagos ridge the instruments and moorings were designed to continuously record low frequency acoustic energy in the sofar channel for extended periods and produce results comparable to those previously derived by using the u s navy sound surveillance system sosus in the northeast pacific the technology and methodology developed for this experiment including instrument design mooring configuration analysis software location algorithms with an analysis of errors and a predicted error field are described in detail volcanic activity is observed throughout the pacific along with seismicity along transform faults subduction zones and intraplate regions comparison data sets indicate detection thresholds and accuracy better than the land networks for open ocean areas and results comparable to or better than sosus volcanic seismicity along the fast spreading east pacific rise appears similar to documented examples in the northeast pacific but with much shorter durations one example from the intermediate spreading galapagos ridge is comparable to northeast pacific examples and several episodes of activity were observed in the wilkes transform fault zone a site of continuing off axis seismicity is located near 18 s and 116 w isolated intraplate earthquakes are observed throughout the study area earthquake information from this experiment and future observations will be provided through the world wide web and earthquake data centers

hydrological and oceanic excitations to polar motion andlength of day variation summary water mass redistributions in the global hydrosphere including continental water storage change and non steric sea level change introduce variations in the hydrological angular momentum ham and the oceanic angular momentum oam under the conservation of angular momentum ham and oam variations are signi cant excitation sources of the earth rotational variations at a wide range of timescales in this paper we estimate ham and oam variations and their excitations to polar motion and length of day variation using soil moisture and snow estimates and non steric sea level change determined by topex poseidon satellite radar altimeter observations and a simpli ed steric sea level change model the results are compared with the variations of polar motion and lod that are not accounted for by the atmosphere this study indicates that seasonal continental water storage change provides signi cant contributions to both polar motion and lod variation especially to polar motion x and the non steric sea level change is responsible for a major part of the remaining excitations at both seasonal scale and high frequencies particularly in polar motion y and lod the good correlation between oam contributions and the remaining excitations shows that large scale non tidal mass variation exists in the oceans and can be detected by topex poseidon altimeter observations

estimation of the detection probability for yangtze finless porpoises neophocaena phocaenoides asiaeorientalis with a passive acoustic method yangtze finless porpoises were surveyed by using simultaneous visual and acoustical methods from 6 november to 13 december 2006 two research vessels towed stereo acoustic data loggers which were used to store the intensity and sound source direction of the high frequency sonar signals produced by finless porpoises at detection ranges up to 300 m on each side of the vessel simple stereo beam forming allowed the separation of distinct biosonar sound source which enabled us to count the number of vocalizing porpoises acoustically 204 porpoises were detected from one vessel and 199 from the other vessel in the same section of the yangtze river visually 163 and 162 porpoises were detected from two vessels within 300 m of the vessel track the calculated detection probability using acoustic method was approximately twice that for visual detection for each vessel the difference in detection probabilities between the two methods was caused by the large number of single individuals that were missed by visual observers however the sizes of large groups were underestimated by using the acoustic methods acoustic and visual observations complemented each other in the accurate detection of porpoises the use of simple relatively inexpensive acoustic monitoring systems should enhance population surveys of free ranging echolocating odontocetes

thermo hydro mechanical modeling of carbon dioxide injection for enhanced gas recovery co2 egr a benchmarking study for code comparison the objective of this paper was to investigate the thm coupled responses of the storage formation and caprock induced by gas production co2 egr enhanced gas recovery and co2 storage a generic 3d planer model 20 000 3 000 100 m consisting of 1 200 m overburden 100 m caprock 200 m gas reservoir and 1 500 m base rock is adopted for the simulation process using the integrated code tough2 eos7c flac3d and the multi purpose simulator opengeosys both simulators agree that the co2 egr phase under a balanced injection rate 31 500 tons year will cause almost no change in the reservoir pressure the gas recovery rate increases 1 4 in the 5 year co2 egr phase and a better egr effect could be achieved by increasing the distance between injection and production wells e g 5 83 for 5 km distance instead of 1 2 km in this study under the considered conditions there is no evidence of plastic deformation and both reservoir and caprock behave elastically at all operation stages the stress path could be predicted analytically and the results show that the isotropic and extensional stress regime will switch to the compressional stress regime when the pore pressure rises to a specific level both simulators agree regarding modification of the reservoir stress state with further co2 injection tension failure in reservoir could occur but shear failure will never happen under these conditions using tough flac a scenario case is also analyzed with the assumption that the reservoir is naturally fractured the specific analysis shows that the maximal storage pressure is 13 6 mpa which is determined by the penetration criterion of the caprock

an international model comparison study of controlled fault activation experiments in argillaceous claystone at the mont terri laboratory abstract we present results from an international model comparison study involving a series of controlled fault activation experiments in opalinus clay at the mont terri laboratory switzerland the fault activation experiments were conducted in situ by water injection at variable pressure from boreholes targeting different parts of the main fault crossing several tunnels and galleries of the mont terri laboratory the model simulations focused on 1 an experiment activating a discontinuity fracture or minor fault within the damage zone of the main fault and 2 an experiment activating discontinuities close to the core of the main fault the experimental data consist of coupled hydraulic and mechanical responses monitored at an injection borehole and a monitoring borehole located a few meters away after overcoming several modeling issues along with necessary model developments a reasonably good agreement was achieved between the modeling results and the field observations the fault activation experiments displayed an abrupt flow rate increase associated with a sudden fracture opening and rupture propagation after the injection pressure reached above the estimated normal stress on the fracture this was followed by an abrupt flow rate decrease indicating hydraulic closing once the injection pressure decreases to an estimated 1 2 mpa below the stress normal to the opened fracture the models were able to capture this abrupt hydromechanical behavior including an observed dominant opening behavior along with the rupture propagation while the spatial extent of the shear rupture and the quantity of peak injection flow were the most challenging to predict

uncertainty analysis of impact indicators for the integrity of combined caprock during co2 geosequestration abstract co2 capture and geologic sequestration represent one of the most promising options for reducing atmospheric emissions of co2 operator choices and subsurface uncertainties each have significant effects on avoiding the risk of triggering fault failure or intact rock failure that could lead to co2 leakage with the application of response surface methodology a box behnken design of experiments was utilized to evaluate the statistical significance of impact indicators and uncertainty analysis was performed using a robust model to forecast the optimal combination of impact indicators for maintaining caprock integrity during co2 injection in saline aquifers of the ordos basin china the coulomb failure stress and vertical deformation of 130 statistically designed combinations were experimentally determined using numerical simulation then according to the analysis of variance conducted for the response surface quadratic model the burying depth friction angle young s modulus poisson s ratio and stress field as well as quadratic terms such as burying depth friction angle and poisson s ratio poisson s ratio were found to be highly significant with respect to the level of coulomb failure stress among the variables only burying depth was highly significant with respect to the level of vertical deformation furthermore the results were analyzed and an optimal combination of impact indicators for coulomb failure stress was determined according to the minimum coulomb failure stress the optimum combination had a desirability value of 1 000 which demonstrated the fitness of the selected statistical model in analyzing the experimental data

a coupled hydro mechanical model for simulation of gas migration in host sedimentary rocks for nuclear waste repositories abstract in a deep geological repository dgr for nuclear wastes several mechanisms such as waste form degradation and corrosion could lead to gas generation the produced gas can potentially overpressurize the repository alter the hydraulic and mechanical properties of the host rock and affect the long term containment function of the natural host rock and engineered barriers thus the understanding of the gas migration within the host rock and engineered barriers and the associated potential impacts on their integrity is important for the safety assessment of a dgr in this paper a coupled hydro mechanical model for predicting and simulating the gas migration in sedimentary host rock is presented a detailed formulation coupling moisture liquid water and water vapor and gas transfer in a deformable porous medium is given the model takes into account the damage controlled fluid gas water flow as well as the coupling of hydraulic and mechanical processes e g stress deformation the model also considers the coupling of the diffusion coefficient with mechanical deformation as well as considers the modification of capillary pressure due to the variation of permeability and porosity the prediction capability of the developed model is tested against laboratory scale and in situ experiments conducted on potential host sedimentary rocks for nuclear waste disposal the model predictions are in good agreement with the experimental results the numerical simulations of the laboratory and field gas injection tests provide a better understanding of the mechanisms of gas migration and the potential effects of excessive gas pressure on the host sedimentary rocks this research work has allowed us to identify key features related to gas generation and migration that are considered important in the long term safety assessment of a dgr in sedimentary host formations

effect of oxygen co injected with carbon dioxide on gothic shale caprock co2 brine interaction during geologic carbon sequestration abstract co injection of oxygen a significant component in co 2 streams produced by the oxyfuel combustion process can cause a significant alteration of the redox state in deep geologic formations during geologic carbon sequestration the potential impact of co injected oxygen on the interaction between synthetic co 2 brine 0 1 m nacl and shale caprock gothic shale from the aneth unit in utah and mobilization of trace metals was investigated at 10 mpa and 75 c a range of relative volume percentages of o 2 to co 2 0 1 4 and 8 were used in these experiments to address the effect of oxygen on shale co 2 brine interaction under various conditions major mineral phases in gothic shale are quartz calcite dolomite montmorillonite and pyrite during gothic shale co 2 brine interaction in the presence of oxygen pyrite oxidation occurred extensively and caused enhanced dissolution of calcite and dolomite pyrite oxidation and calcite dissolution subsequently resulted in the precipitation of fe iii oxides and gypsum caso 4 2h 2 o in the presence of oxygen dissolved mn and ni were elevated because of oxidative dissolution of pyrite the mobility of dissolved ba was controlled by barite baso 4 precipitation in the presence of oxygen dissolved u in the experimental brines increased to 8 14 g l with concentrations being slightly higher in the absence of oxygen than in the presence of oxygen experimental and modeling results indicate the interaction between shale caprock and oxygen co injected with co 2 during geologic carbon sequestration can exert significant impacts on brine ph solubility of carbonate minerals stability of sulfide minerals and mobility of trace metals the major impact of oxygen is most likely to occur in the zone near co 2 injection wells where impurity gases can accumulate oxygen in co 2 brine migrating away from the injection well will be continually consumed through the reactions with sulfide minerals in deep geologic formations

atmospheric and oceanic excitation of the earth s wobbles during 1980 2000 1 because of the action of various geophysical excitation mechanisms the earth does not rotate about its figure axis so it wobbles as it rotates here the effectiveness of atmospheric and oceanic processes in exciting the earth s wobbles during 1980 2000 is evaluated using estimates of atmospheric angular momentum from the national centers for environmental prediction national center for atmospheric research ncep ncar reanalysis project and estimates of oceanic angular momentum from the estimating the circulation and climate of the ocean ecco consortium s simulation of the general circulation of the oceans on intraseasonal timescales atmospheric surface pressure changes are found to be the single most effective process exciting the earth s wobbles explaining about twice as much of the observed variance as do either atmospheric wind or ocean bottom pressure changes and nearly 4 times as much of the observed variance as do oceanic currents however on interannual timescales ocean bottom pressure changes are found to be the single most effective process exciting the earth s wobbles explaining more than 5 times as much of the observed variance as do atmospheric wind and pressure changes combined and more than twice as much of the observed variance as do oceanic currents within the chandler band it is found that during 1980 2000 atmospheric and oceanic processes have enough power to excite the chandler wobble and are significantly coherent with it the single most important mechanism exciting the chandler wobble is found to be ocean bottom pressure variations atmospheric and oceanic processes do not appear to have enough power to excite the earth s wobbles to their observed levels on pentadal and longer timescales although series longer than the 21 yearlong series used here need to be studied in order to obtain greater statistical significance of this result

thermohydromechanics of partially saturated geological media governing equations and formulation of four finite element models this paper presents the general governing equations for coupled thermohydromechanical thm processes in saturated and unsaturated geologic formations and reviews four finite element codes for modeling of such system three of the codes are developed for the special purpose of analyzing coupled thm processes in unsaturated porous and fractured geological media and the fourth is a commercial code that has been used in its standard version with a few adaptations for this specialized problem the basic assumptions and fundamental equations for coupled thm processes in unsaturated porous fractured rock are presented and formulations of the four finite element models are compared

interaction analysis for co2 geological storage and underground coal mining in ordos basin china abstract the co 2 geological storage in ordos basin and coal mining activities occurring simultaneously at the same location is a highly challenging coupled thermo hydro mechano chemical thmc problem to address this problem an in house program named aeea coupler was developed by linking two commercial software packages simulia abaqus and schlumberger eclipse both of which are widely used and highly recognized in their respective fields the applicability and accuracy of the developed coupler were tested by benchmark studies a coupled multi physics analysis was conducted based on real formation data of the ordos and shenhua ccs demonstration project with an injection rate of 0 1 mtpa million tonnes per annum a larger injection rate of 1 0 mtpa was also investigated to explore the potential for the commercialization of large scale ccs projects in the area the primary conclusions that were obtained from the numerical simulations are as follows a the pore pressure and displacement at the top of the reservoir increase with co 2 injection and the displacement continues to increase even after the termination of the co 2 injection due to the coal mining activity b the displacement of the wellbore peaks at the coal seam floor where the axial strain of the well soars abruptly our work suggests that the distance between coal pillars should be at least 90 m to ensure that the mises stress of the casing is below the designed safe value c the tensile stress and shearing stress increase significantly in the caprock as a result of the coupling of the two engineering activities therefore damages in the caprock occur more easily d after co 2 injection only the strata with a depth of less than 769 m are affected by the coal mining activity e the combined activities achieve a surface subsidence reduction comparable to that of only coal mining finally several recommendations are given regarding the actual engineering implementation of the combined activities

discrete element modeling of indentation tests to investigate mechanisms of co2 related chemomechanical rock alteration during co2 injection into geological formations petrophysical and geomechanical properties of host formations can be altered due to mineral dissolution and precipitation field and laboratory results have shown that sandstone and siltstone can be altered by co2 water mixtures but few quantitative studies have been performed to fully investigate underlying mechanisms based on the hypothesis that co2 water mixtures alter the integrity of rock structure by attacking cements rather than grains we attempt to explain the degradation of cementation due to long term contact with co2 and water and mechanisms for changes in rock mechanical properties many sandstones including calcite cemented quartzitic sandstone chlorite cemented quartzitic sandstone and hematite cemented quartzitic sandstone contain interparticle cements that are more readily affected by co2 water mixtures than grains a model that couples the discrete element method dem and the bonded particle model bpm is used to perform simulations of indentation tests on synthetic rocks with crystal and random packings the model is verified against the analytical cavity expansion model cem and validated against laboratory indentation tests on entrada sandstone with and without co2 alteration sensitivity analysis is performed for cementation microscopic parameters including stiffness size axial and shear strength the simulation results indicate that the co2 related degradation of mechanical properties in bleached entrada sandstone can be attributed to the reduction of cement size rather than cement strength our study indicates that it is possible to describe the co2 related rock alteration through particle scale mechanisms

geological co2 sequestration in multi compartment reservoirs geomechanical challenges 1 sequestration of large amounts of co2 within deep underground reservoirs has been proposed as a potential approach for reducing atmospheric emissions of greenhouse gases a co2 sequestration project should address the associated environmental and safety issues and in this respect the importance of geomechanics has recently been widely recognized geomechanics is even more important when fluid injection is planned in faulted reservoirs how much co2 can be safely injected into multi compartment reservoirs are geomechanical constraints more restrictive than flow dynamic constraints these and other questions are addressed in the present study using a three dimensional finite element interface element geomechanical model we simulate the possible mechanical failure in both the injected formation and the caprock the fault thrust reactivation and the ground surface displacement in a faulted reservoir of the offshore northern italy where seismic surveys provided an accurate characterization of the faulted geological structure based on reliable petrophysical geomechanical properties from well logs and pore overpressure as predicted by a fluid dynamic model the results show that the injection of 1 106 ton a of co2 may be performed over a few years only thereafter part of the injected formation fails by shear stress a number of parametric scenarios are investigated to address the major uncertainties on the geomechanical response to co2 injection the modeling outcome suggests that shear failure and faults thrusts reactivation can occur much before attaining the hydraulic fracturing pressure hence representing two major constraints for a safe and permanent containment

wind field differences between three meteorological reanalysis data sets detected by evaluating atmospheric excitation of earth rotation 1 we compared atmospheric excitations of the varying earth rotation calculated from three different meteorological reanalysis data sets ncep ncar ncep doe and era 40 over 23 years from 1979 to 2001 atmospheric excitations are evaluated by atmospheric angular momentum aam functions we found that differences in aam functions are primarily caused by differences in the wind data especially the northward wind data between the three reanalysis data sets differences between the ncep doe and era 40 aam functions are larger than those between the ncep ncar and ncep doe ones the northward wind differences that have a large effect on the equatorial aam functions originate from the upper troposphere at the tropics and midlatitudes in the southern hemisphere especially in three regions east pacific off latin america africa and the indian ocean the eastward wind differences are seen at midlatitudes in the southern hemisphere these differences are not confined to a single frequency the difference spectra show a reddish frequency dependence with some peaks in seasonal bands and tidal diurnal bands since the eastward and northward winds over the tropics can most efficiently change the earth s spin rate and polar motion respectively the wind accuracy over the tropics directly determines the accuracy in evaluations of the atmospheric excitations

on the physics based processes behind production induced seismicity in natural gas fields author s zbinden d rinaldi ap urpi l wiemer s abstract 2017 american geophysical union all rights reserved induced seismicity due to natural gas production is observed at different sites worldwide common understanding states that the pressure drop caused by gas production leads to compaction which affects the stress field in the reservoir and the surrounding rock formations and hence reactivates preexisting faults and induces earthquakes in this study we show that the multiphase fluid flow involved in natural gas extraction activities should be included we use a fully coupled fluid flow and geomechanics simulator which accounts for stress dependent permeability and linear poroelasticity to better determine the conditions leading to fault reactivation in our model setup gas is produced from a porous reservoir divided into two compartments that are offset by a normal fault results show that fluid flow plays a major role in pore pressure and stress evolution within the fault fault strength is significantly reduced due to fluid flow into the fault zone from the neighboring reservoir compartment and other formations we also analyze scenarios for minimizing seismicity after a period of production such as i well shut in and ii gas reinjection in the case of well shut in a highly stressed fault zone can still be reactivated several decades after production has ceased although on average the shut in results in a reduction in seismicity in the case of gas reinjection fault reactivation can be avoided if gas is injected directly into the compartment under depletion however gas reinjection into a neighboring compartment does not stop the fault from being reactivated

hydraulic fracturing in unconventional gas reservoirs risks in the geological system part 2 hydraulic fracturing is a method used for the production of unconventional gas resources huge amounts of so called fracturing fluid 10 000 20 000 m3 are injected into a gas reservoir to create fractures in solid rock formations upon which mobilised methane fills the pore space and the fracturing fluid is withdrawn hydraulic fracturing may pose a threat to groundwater resources if fracturing fluid or brine can migrate through fault zones into shallow aquifers diffuse methane emissions from the gas reservoir may not only contaminate shallow groundwater aquifers but also escape into the atmosphere where methane acts as a greenhouse gas the working group risks in the geological system as part of exxonmobil s hydrofracking dialogue and information dissemination processes was tasked with the assessment of possible hazards posed by migrating fluids as a result of hydraulic fracturing activities in this work several flow paths for fracturing fluid brine and methane are identified and scenarios are set up to qualitatively estimate under what circumstances these fluids would leak into shallower layers the parametrisation for potential hydraulic fracturing sites in north rhine westphalia and lower saxony both in germany is derived from literature using upper and lower bounds of hydraulic parameters the results show that a significant fluid migration is only possible if a combination of several conservative assumptions is met by a scenario

on co2 fluid flow and heat transfer behavior in the subsurface following leakage from a geologic storage reservoir geologic storage of co2 is expected to produce plumes of large areal extent and some leakage may occur along fractures fault zones or improperly plugged pre existing wellbores a review of physical and chemical processes accompanying leakage suggests a potential for self enhancement the numerical simulations presented here confirm this expectation but reveal self limiting features as well it seems unlikely that co2 leakage could trigger a high energy run away discharge a so called pneumatic eruption but present understanding is insufficient to rule out this possibility the most promising avenue for increasing understanding of co2 leakage behavior is the study of natural analogues

three dimensional beam pattern of regular sperm whale clicks confirms bent horn hypothesis the three dimensional beam pattern of a sperm whale physeter macrocephalus tagged in the ligurian sea was derived using data on regular clicks from the tag and from hydrophones towed behind a ship circling the tagged whale the tag defined the orientation of the whale while sightings and beamformer data were used to locate the whale with respect to the ship the existence of a narrow forward directed p1 beam with source levels exceeding 210 db peak re 1 pa at 1 m is confirmed a modeled forward beam pattern that matches clicks 20 off axis predicts a directivity index of 26 7 db and source levels of up to 229 db peak re 1 pa at 1 m a broader backward directed beam is produced by the p0 pulse with source levels near 200 db peak re 1 pa at 1 m and a directivity index of 7 4 db a low frequency component with source levels near 190 db peak re 1 pa at 1 m is generated at the onset of the p0 pulse by air resonance the results support the bent horn model of sound production in sperm whales while the sperm whale nose appears primarily adapted to produce an intense forward directed sonar signal less directional click components convey information to conspecifics and give rise to echoes from the seafloor and the surface which may be useful for orientation during dives

sound source localization technique using a seismic streamer and its extension for whale localization during seismic surveys marine seismic surveys are under increasing scrutiny because of concern that they may disturb or otherwise harm marine mammals and impede their communications most of the energy from seismic surveys is low frequency so concerns are particularly focused on baleen whales extensive mitigation efforts accompany seismic surveys including visual and acoustic monitoring but the possibility remains that not all animals in an area can be observed and located one potential way to improve mitigation efforts is to utilize the seismic hydrophone streamer to detect and locate calling baleen whales this study describes a method to localize low frequency sound sources with data recoded by a streamer beamforming is used to estimate the angle of arriving energy relative to sub arrays of the streamer which constrains the horizontal propagation velocity to each sub array for a given trial location a grid search method is then used to minimize the time residual for relative arrival times along the streamer estimated by cross correlation results from both simulation and experiment are shown and data from the marine mammal observers and the passive acoustic monitoring conducted simultaneously with the seismic survey are used to verify the analysis