geochemistry and petrogenesis of intrusive and extrusive ophiolitic plagiogranites central anatolian crystalline complex turkey plagiogranites associated with the sarikaraman ophiolite of the central anatolian crystalline complex turkey closely resemble other plagiogranites from supra subduction zone type ophiolites of neotethys the ophiolite is remarkable in displaying a higher proportion of the plagiogranite suite ca 10 by volume than is usually associated with such bodies the sarikaraman plagiogranites are represented by intrusive sheets and netvein trondhjemites largely developed at the top of the upper gabbros and as multiphase dykes within the sheeted dyke complex the plagiogranite dykes are considered to feed extrusive silicified rhyolites associated with the basaltic lavas in the volcanic section of the ophiolite field relations suggest that the trondhjemites were probably generated from the roof section of a dynamic and evolving gabbroic magma chamber both the deep seated trondhjemites and the volcanic rhyolites constitute the sarikaraman plagiogranite suite geochemically there is complete overlap between the intrusive trondhjemites and extrusive rhyolites which are characterised by morb normalized low hfs element contents with small negative nb ta anomalies and variably enhanced lil element abundances unlike other plagiogranites however the sarikaraman suite is not characterized by consistently low k2o contents a feature that reflects the variable mobilization of the lil elements under lower greenschist facies conditions the ree are uniformly enriched relative to the basic components of the complex but have similar normalized patterns exhibiting mild light ree depletion in terms of their origin the initial or most primitive plagiogranite melts could have been generated by either fractional crystallization 70 85 of clinopyroxene feldspar amphibole or partial melting 5 15 batch melting of a gabbroic source material although only the first process can produce most of the range of the plagiogranite compositions as a group the plagiogranites exhibit some degree of internal variation which can be generated by further fractionation largely dominated by feldspar with minor apatite and amphibole

viscosity and other rheological properties of bitumen from the upper devonian grosmont reservoir alberta canada viscosity is directly related to the mobility and quality of hydrocarbons in reservoirs and its distribution is commonly heterogeneous therefore viscosity has a great impact on the exploitation of heavy oil and bitumen reservoirs previous studies showed that viscosity measurements are problematic and are often inconsistent mainly because of the challenges of sample preparation and lack of a standard procedure for measuring viscosity in the oil and gas industry this study aims to improve the characterization of reservoir viscosity by understanding the rheological properties of bitumen using bitumen samples from the upper devonian grosmont reservoir alberta canada this study shows that grosmont bitumen is essentially a non newtonian fluid exhibiting a distinctive shear thinning behavior at low temperatures of less than 40c with increasing temperature however the bitumen changes from a non newtonian fluid to a newtonian fluid at low temperatures the viscosity variations can be divided into four stages a standard viscosity called zero shear viscosity is obtained from the viscosity variations and can be used throughout the reservoir as characteristic viscosity for grosmont bitumen the viscosity distribution in the grosmont reservoir is complex and appears to be stratigraphically related bitumen samples from formation boundaries tend to have higher viscosities suggesting more severe biodegradation at these locations possible causes for the observed patterns in the grosmont include 1 oil water contacts migrating up and down over time 2 oil migration and or biodegradation controlled by aquitards that divide the reservoir into hydrostratigraphically separated units and 3 differences in microbial activity that is aerobic versus anaerobic possibly controlled by the level of oxygenation over time

gassmann s fluid substitution and shear modulus variability in carbonates at laboratory seismic and ultrasonic frequencies carbonates have become important targets for rock property research in recent years because they represent many of themajoroilandgasreservoirsintheworld someareundergoing enhanced oil recovery most laboratory studies to understand fluid and pressure effects on reservoir rocks have been performed on sandstones but applying relations developed for sandstones to carbonates is problematic at best we measure in the laboratory nine carbonate samples from the same reservoir at seismic 3 3000 hz and ultrasonic 0 8 mhz frequencies samples are measured dry humidified and saturated with liquid butane and brine our carbonate samples showed typical changes in moduli as a function of porosity andfluid saturation however we explore the applicability of gassmann s theory on limestone and dolomite rocks in the context of shear and bulk modulus dispersion andgassmann stheoryassumptions forourcarbonatesetat high differential pressures and seismic frequencies the bulk modulus of rocks with high aspect ratio pores and dolomite mineralogy is predicted by gassmann s relation we also explore in detail some of the assumptions of gassmann s relation especiallyrock framesensitivitytofluidsaturation our carbonate samples show rock shear modulus change from dry to brine saturation conditions and we investigate several rock fluid mechanisms responsible for this change to our knowledge these are the first controlled laboratory experimentsoncarbonatesintheseismicfrequencyrange

high resolution crosswell imaging of a west texas carbonate reservoir part 1 project summary and interpretation a carbon dioxide flood pilot is being conducted in a section of chevron s mcelroy field in crane county west texas prior to co2 injection two high frequency crosswell seismic profiles were recorded to investigate the use of seismic profiling for high resolution reservoir delineation and co2 monitoring these preinjection profiles provide the baseline for time lapse monitoring profile 1 was recorded between an injector well and an offset observation well at a nominal well to well distance of 184 ft 56 m profile 2 was recorded between a producing well and the observation well at a nominal distance of 600 ft 183 m the combination of traveltime tomography and stacked cdp reflection amplitudes demonstrates how high frequency crosswell seismic data can be used to image both large and small scale heterogeneity between wells transmission traveltime tomography is used to image the large scale velocity variations cdp reflection imaging is then used to image smaller scale impedance heterogeneities the

thermal expansion and pore pressure generation in oil sands the prediction of stress changes and deformations arising from ground heating requires the coupled solution of the heat transfer and consolidation equations heat consolidation as a class of problems is distinct from other thermally induced consolidation problems involving processes such as frost heave and thaw consolidation in that it involves heating to elevated temperatures well above normal ground temperatures two of the important parameters required in analyses of heat consolidation problems are thermal expansion coefficients and a coefficient of thermal pore pressure generation relationships describing thermal expansion behaviour and thermal pore pressure generation in oil sands are presented both drained and undrained thermal expansion coefficients for athabasca oil sand were determined by means of heating experiments in the temperature range 20 300 c the thermal pore pressure generation coefficient was evaluated in undrained heating experiments under constant total confining stresses and under

plagiogranite from the andaman ophiolite belt bay of bengal india plagiogranites occur on the eastern margin of the southern part of south andaman in the outer sedimentary arc of the andaman nicobar islands a part of the sunda burmese double chain arc system in the bay of bengal they intrude gabbros that are associated with pillow basalt east coast volcanic rocks basalt basaltic andesite to acid differentiates radiolarian cherts conglomerate and grit the plagiogranite characterized by the occurrence of interstitial vermicular and micrographic intergrowths of quartz and plagioclase shows some geochemical similarities with ophiolitic plagiogranites but rb yb nb ta and y abundances in the andaman plagiogranite are characteristic of volcanic arc granites rather than the ocean ridge granites it is suggested that the andaman plagiogranite has been generated by low pressure crystal fractionation of a low k tholeiitic magma derived from a mantle source in a supra subduction zone tectonic setting further it is suggested that this plagiogranite intruded the gabbro of the andaman ophiolite probably during mid eocene times as the andaman ophiolitic rocks late cretaceous to early eocene are believed to have been obducted onto the leading edge of the eurasian continent during the mid eocene to late oligocene subduction event prior to the currently active andaman java subduction system that was initiated during the late miocene

temperature dependent propagation of p and s waves in cold lake oil sands comparison of theory and experiment the measured dependence of ultrasonic velocity in cold lake oil sands on temperature is compared to theoretical model predictions for seismic wave propagation in porous media the experiments indicated that change in fluid properties with temperature most greatly affect observed velocities the theoretical model was constructed to account for temperature dependent fluid properties using correlations independent of the ultrasonic experiments theoretical and experimental p wave velocities agree within 5 percent for temperatures between 22 c to 125 c and effective stresses of 1 mpa and 8 mpa the modeling indicates that the change in fluid bulk modulus with temperature dominates the observed 15 percent p wave velocity decrease between 22 c to 125 c over the same temperature range the model predicts the s wave velocity remains almost constant 1 percent increase

seismic velocity models for heat zones in athabasca tar sands recent laboratory and field studies indicate that the p wave velocity in athabasca tar sands decreases when temperature increases during steam injection in this paper we derive time variant velocity models from seismic traveltime inversions of both reflection and borehole data prior to steam injection three dimensional 3 d reflector velocity depth models are established using image ray conversions of traveltimes to depth the changes in velocity due to steam injection are modeled by inverting traveltime data from seismic monitor surveys after steam injection and comparing these results to velocities computed prior to steam injection velocity models are essentially determined by traveltimes from the 3 d seismic reflection survey the surface to wellbore data traveltimes show the expected delay caused by steam injection but do not significantly alter the velocity model produced by reflection traveltimes for seismic monitor surveys low velocity zones show a very good correlation with zones of temperature increase at injector well positions the results indicate that velocity models obtained from seismic traveltimes may prove useful in detecting steam fronts in tar sands

controls on sonic velocity in carbonates compressional and shear wave velocities v p and v s of 210 minicores of carbonates from different areas and ages were measured under variable confining and pore fluid pressures the lithologies of the samples range from unconsolidated carbonate mud to completely lithified limestones the velocity measurements enable us to relate velocity variations in carbonates to factors such as mineralogy porosity pore types and density and to quantify the velocity effects of compaction and other diagenetic alterations

pressure and temperature dependence of acoustic wave speeds in bitumen saturated carbonates implications for seismic monitoring of the grosmont formation abstractrecent time lapse seismic observations in carbonate reservoirs subject to steam assisted enhanced oil recovery display substantial changes in seismic reflectivity due to the combined effects of saturation pressure and temperature understanding these field seismic observations requires knowledge of the effects on the seismic wave speeds in bitumen saturated carbonates we have conducted ultrasonic measurements of p and s wave velocities in bitumen saturated dolomite taken from the grosmont formation in northern alberta wave speeds are measured under a variety of conditions of constant pore pressure constant effective pressure and with varying temperature to map the various controlling factors the temperature dependent declines of 12 and 9 for the p and s wave speeds respectively with temperatures from 10 c to 102 c are most notable unlike oil sands at times the dolomite retains its structure upon removal of the bitumen allowing for measurement of the dry and water saturated frame pr

an overview of laboratory apparatuses to measure seismic attenuation in reservoir rocks intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability fluid properties and saturation however in order to use attenuation as an attribute to extract information on rock fluid properties from seismic data experimental studies on attenuation are necessary for a better understanding of physical mechanisms that are dominant at those frequencies an appropriate laboratory methodology to measure attenuation at seismic frequencies is the forced oscillation method but technical challenges kept this technique from being widely used there is a need for the standardization of devices employing this method and a comparison of existing setups is a step towards it here we summarize the apparatuses based on the forced oscillation method that were built in the last 30 years and were used to measure frequency dependent attenuation in fluid saturated and or dry reservoir rocks under small strains 10 8 10 5 we list and discuss important technical aspects to be taken into account when working with these devices or in the course of designing a new one we also present a summary of the attenuation measurements in reservoir rock samples performed with these apparatuses so far

seismic monitoring of steam based recovery of bitumen since 1985 imperial oil has been using a recovery process cyclic steam stimulation css to commercially produce bitumen from the clearwater formation near cold lake alberta canada figure 1 the clearwater reservoir an unconsolidated sand with a porosity of 32 percent and a permeability of 1 darcy is saturated with an extremely viscous bitumen viscosity about 150 000 cp the css oil recovery process involves injection of steam at high temperatures and pressures 310 c and 10 mpa followed by the production of bitumen from the same well twenty wells are directionally drilled from a single surface location or pad more than 2000 wells are spaced on a regular 1 6 hectares grid producing 100 000 b d

high resolution crosswell imaging of a west texas carbonate reservoir using crosswell data collected at a depth of about 3000 ft 900 m in west texas carbonates one of the first well to well reflection images of an oil reservoir was produced the p and s brute stack reflection images created after wavefield separation tied the sonic logs and exhibited a vertical resolution that was comparable to well log resolution both brute stacks demonstrated continuity of several reflectors known to be continuous from log control and also imaged an angular unconformity that was not detected in log correlations or in surface seismic profiling the brute stacks particularly the s wave reflection image also exhibited imaging artifacts we found that multichannel wavefield separation filters that attenuated interfering wavemodes were a critical component in producing high resolution reflection images in this study the most important elements for an effective wavefield separation were the time alignment of seismic arrivals prior to filter application and the implementation of wavefield separation filters in multiple domains particularly in common offset domain the effectiveness of the multichannel filtering was enhanced through the use of extremely fine wellbore sampling intervals in this study 2 5 ft 0 76 m vertical sampling intervals for both source and receiver were used whereas most previous crosswell data sets were collected with much coarser sampling intervals resulting in spatial aliasing and limiting the utility of the data for reflection processing the wavefield separation techniques employed in this study used data volumes and associated filtering operations that were several orders of magnitude larger than those encountered in conventional vsp data analysis

laboratory measurements of the effect of fluid saturation on elastic properties of carbonates at seismic frequencies abstract a significant portion of the world s hydrocarbon reserves are found in carbonate reservoirs yet analysis of the petrophysical properties of these reservoirs is associated with a number of challenges some of these challenges stem from physical and chemical interactions between the carbonate rock matrix and pore fluids which can affect elastic properties of the rock hence the study of the pore fluid effects on the elastic properties of carbonates is important for understanding a change of the field performance properties of carbonate reservoir caused by fluid movements during hydrocarbon extraction in producing fields in this laboratory study we investigate the applicability of gassmann s model for predictions of the elastic moduli of water and hydrocarbon saturated savonnieres limestone and the influence of partial water saturation on elastic and anelastic properties of the rock we present the results of two sets of laboratory experiments on the savonnieres oolitic limestone where we i evaluate the effect of full water and n decane saturation on elastic moduli and attenuation at seismic 0 1 hz 120 hz and ultrasonic 0 5 mhz frequencies and ii quantify the dependence of elastic moduli and extensional attenuation on water saturation at two seismic frequencies of 1 hz and 10 hz we demonstrate that the change in the bulk modulus of limestone fully saturated either with n decane or water is in agreement with gassmann s fluid substitution theory whereas the shear modulus is noticeably reduced the measurements with partial saturation show that the bulk modulus decreases with increasing water saturation to a lesser extent than the young s and shear moduli our results show that extensional attenuation in the samples with closed boundaries is insignificant under dry and fully saturated conditions but is influenced greatly by the liquid content when saturation is between 0 and 20 or 95 and 100

acoustic properties of young carbonate rocks odp leg 166 and boreholes clino and unda western great bahama bank acoustic properties determined from logs and discrete measurements along a borehole transect across the slope of the western great bahama bank margin odp leg 166 show a distinct relationship with primary sediment composition and noncarbonate content dominant sediment types are alternating cemented and uncompacted calciturbidites with shallow water derived grains and poorly to uncemented and compacted periplatform ooze of globigerinid dominated wackestone to packstone comparison of the velocity porosity variation from logs and discrete measurements reveals that both tend to follow the trend of generally accepted velocity transforms primary control on the acoustic velocity is exerted by total porosity whereas the remaining variation in velocity is explained by differential diagenesis the less cemented to uncemented and compacted background sediments have velocities that at a given porosity fall below the time average equation for calcite the cemented turbidites however have velocities that are higher than those predicted by the time average equation although it is unclear whether the original volume of aragonite or presence of organic matter controlled this difference it is suggested that the acoustic properties reflect an input signal the presence of noncarbonate material some of which is clay increases basinward and further reduces the acoustic velocities in the background sediment in contrast earlier work on the more proximal slope and nearly pure carbonate intervals in clino and unda cores documents diagenetic differentiation in compositionally similar sediment resulting in alternating acoustically fast and slow layers marginal and nearly pure limestones have a more complex acoustic behavior and hence are difficult to predict though both velocity logs and discrete velocity measurements show comparable general trends logging data show a considerably larger variation at a given porosity value up to 3 5 km s than discrete data which ranges between 1 0 and 2 5 km s to improve the quality of velocity logs it is suggested to groundtruth these data with other logging data general velocity transforms and ideally discrete measurements on core plugs

glacier acceleration and thinning after ice shelf collapse in the larsen b embayment antarctica 1 ice velocities derived from five landsat 7 images acquired between january 2000 and february 2003 show a two to six fold increase in centerline speed of four glaciers flowing into the now collapsed section of the larsen b ice shelf satellite laser altimetry from icesat indicates the surface of hektoria glacier lowered by up to 38 6 m in a six month period beginning one year after the break up in march 2002 smaller elevation losses are observed for crane and jorum glaciers over a later 5 month period two glaciers south of the collapse area flask and leppard show little change in speed or elevation seasonal variations in speed preceding the large post collapse velocity increases suggest that both summer melt percolation and changes in the stress field due to shelf removal play a major role in glacier dynamics

laboratory measurements of the acoustic and transport properties of carbonate rocks and their link with the amount of microcrystalline matrix laboratory data and computer tomography ct scan image analysis of carbonate rocks were combined demonstrating a quantitative link between acoustic and transport properties the fraction of microcrystalline calcite micrite in the matrix and the grain to micrite matrix ratio samples from the monte acuto formation gargano italy a transgressive system tract tst whose microstructure ranges from basal pelagic mudstones to coarse calciturbidites were analyzed results indicate that high micrite rocks with low grain to micrite matrix ratios typical of low energy depositional settings are relatively stiffer and more impermeable in contrast lower amounts of micrite due to high energy depositional settings or its removal from intergranular macropores by progressive leaching of the matrix leads to high grain to micrite matrix ratios this process will increase porosity and reduce rock stiffness both of which reduce velocity decreasing micrite content correlates well with increasing macroporosity

fluid substitution in rocks saturated with viscoelastic fluids heavyoilshavehighdensitiesandextremelyhighviscosities and they exhibit viscoelastic behavior traditional rock physics based on gassmann theory does not apply to materials saturated with viscoelastic fluids we use an effective medium approach known as coherent potential approximation cpa as an alternativefluid substitutionschemeforrockssaturatedwithviscoelasticfluids suchrocksaremodeledassolidswithellipticalfluidinclusions when fluid concentration is small and as suspensions of solid particles in the fluid when the solid concentration is small thisapproachisconsistentwithconceptsofpercolationandcritical porosity and it allows one to model sandstones and unconsolidated sands we model the viscoelastic properties of a heavyoil saturated rock sample using cpaand a measured frequencydependent complex shear modulus of the heavy oil comparison of modeled results with measured properties of the heavy oil rock reveals a large discrepancy over a range of frequencies and temperatures we modify the cpascheme to account for the effect of binary pore structure by introducing a compliant porosity term this dramatically improves the predictions the predicted values of the effective shear modulus of the rock are in good agreement with laboratory data for the range of frequencies and temperatures this confirms that our scheme realistically estimates the frequency and temperature dependent properties of heavy oil rocks and can be used as an approximate fluid substitutionapproachforrockssaturatedwithviscoelasticfluids

constraints on the tectonic setting of the andaman ophiolites bay of bengal india from shrimp u pb zircon geochronology of plagiogranite abstract the andaman ophiolites are well exposed in the andaman group of islands which is part of the sunda burmese double chain arc system in the bay of bengal india plagiogranites occurring on the eastern margin of the southern part of south andaman island appear as interstitial vermicular and micrographic intergrowths of quartz and plagioclase they are tonalitic to trondhjemitic in composition and their rb yb ta and y abundances are characteristic of a volcanic arc affinity sensitive high resolution ion microprobe u pb dating of zircons from a plagiogranite within the andaman ophiolite has yielded a weighted mean 206pb 238u age of ma interpreted as the age of its crystallization the subduction related plagiogranite has intruded a gabbro unit of the andaman ophiolites as well as extrusives of the east coast volcanics at this time since the andaman ophiolitic rocks predate the plagiogranite they cannot have been generated in the currently active late miocene andaman java subduction zone and

chemical characters of volcanic rocks from andaman ophiolite india two parallel belts of late mesozoic ophiolitic rocks occur along the outer arc ridge and inner volcanic line of the indonesian arc system the northernmost occurrence along the outer arc ridge is in the andaman group of islands where ophiolitic rocks occur as dismembered slices emplaced over eocene to oligocene turbidites volcanic members of the ophiolitic suite occur in two thrust slices one consisting only of pillow basalts while the other is made up of basalts basaltic andesites and acid differentiates certain chemical characters of the basaltic components are comparable to mar basalts at 45 n on the basis of comparable ree patterns and the presence of appreciable volumes of acid differentiates they are further suggested to represent marginal basin crust variable la ce n and la sm n ratios in these basalts are interpreted in terms of a heterogeneous source the basaltic melts have undergone extensive fractional crystallization of clinopyroxene olivine and plagioclase to produce basaltic andesite and acid volcanic rocks between the parent and the differentiates there is no appreciable change in ce yb n ratio or hree abundance level suggesting low pressure fractionation in a shallow magma chamber possibly beneath a slow spreading centre

accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf acceleration exceeds 27 km 3 per year and ice is thinning at rates of tens of meters per year we attribute this abrupt evolution of the glaciers to the removal of the buttressing ice shelf the magnitude of the glacier changes illustrates the importance of ice shelves on ice sheet mass balance and contribution to sea level change index terms 1827 hydrology glaciology 1863 1863 hydrology snow and ice 1827 3349 meteorology and atmospheric dynamics polar meteorology 6924 radio science interferometry 9310 information related to geographic region antarctica citation rignot e g casassa p gogineni w krabill a rivera and r thomas 2004 accelerated ice discharge from the antarctic peninsula following the collapse of larsen b ice shelf geophys res lett 31 l18401 doi 10 1029 2004gl020697

changes in dynamic shear moduli of carbonate rocks with fluid substitution to assess saturation effects on acoustic properties in carbonates we measure ultrasonic velocity on 38 limestone samples whose porosity ranges from 5 to 30 under dry and water saturated conditions complete saturation of the pore space with water causes an increase and decrease in compressional and shear wave velocity as well as significant changes in the shear moduli compressional velocities of most water saturated samples are up to 500 m s higher than the velocities of the dry samples some show no change and a few even show a decrease in velocity shear wave velocity vs generally decreases but nine samples show an increase of up to 230 m s water saturation decreases the shear modulus by up to 2 gpa in some samples and increases it by up to 3 gpa in others the average increase in the shear modulus with water saturation is 1 23 gpa the average decrease is 0 75gpa the vp vs ratio shows an overall increase with water saturation in particular rocks displaying shear weakening have disti

a case history of time lapse 3d seismic surveys at cold lake alberta canada time lapse 3d seismic surveys were acquired across a bitumen field at cold lake alberta canada during a production cycle 1990 and a steam injection cycle 1992 of a thermal enhanced oil recovery eor program we observed changes in interval traveltime and amplitude distributions between the processed surveys we interpret the increased traveltimes observed over most of the injection survey to be a result of lowered interval velocities in the reservoir caused primarily by higher temperature and lower effective pressure reflection strength variations within the reservoir are present in each data set and change spatially between the surveys in general we interpret the amplitude anomalies seen only on the production survey to be caused by local free gas and the amplitude anomalies seen only on the injection survey which are close to the perforation depths to be caused by thin vertically restricted steamed zones

seismic rock physics of steam injection in bituminous oil reservoirs this case study explores rock physics properties of heavy oil reservoirs subject to the steam assisted gravity drainage sagd thermal enhanced recovery process butler 1998 butler and stephens 1981 previous measurements e g wang et al 1990 and eastwood 1993 of the temperature dependant properties of heavy oil saturated sands are extended by fluid substitution modeling and wireline data to assess the effects of pore fluid composition and pressure and temperature changes on the seismic velocities of unconsolidated sands rock physics modeling is applied to a typical shallow mcmurray formation reservoir depth of 135 160 m within the bituminous athabasca oil sands deposit in western canada to construct a rock physics based velocity model of the sagd process although the injected steam pressure and temperature control the fluid bulk moduli within the pore space the effective stress dependant elastic frame moduli are the most poorly known yet most important factors governing the changes of

rock physics models for heavy oil and organic solid substitution rock physics models are often needed to interpret fluid signatures from subsurface seismic data over the last decade or so generalized fluid and solid substitution equations have been derived for estimating the exact change in seismic velocity or rock moduli upon changes in properties of quasisolids e g heavy oil bitumen kerogen ice and salt for the specified model conditions however these exact and mathematically elegant substitution equations fundamentally require details of rock microstructure which are seldom known still for problems involving solid or fluid substitution in rocks with heterogeneous pores a rigorous solution range can be predicted using recently derived substitution bounds these bounds only require total rock porosity which can be inferred easily from geophysical data in fact gassmann s equations are one of the lower bounds on the change in rock moduli upon fluid substitution but for solid substitution gassmann s predictions can be outside the bounds thus for

anisotropic elastic moduli of carbonates and evaporites from the weyburn midale reservoir and seal rocks assuming vertical transverse isotropy vti symmetry the elastic anisotropy as a function of confining pressure of four carbonates and one evaporite from the williston sedimentary basin in saskatchewan canada is investigated using the ultrasonic pulse transmission method ultrasonic p and s wave velocities are obtained from cylindrical plugs cut from a main sample along horizontal vertical and 45 orientations with respect to the sample s presumed vertical axis of symmetry the elastic constants were then calculated from the measured velocities and densities anisotropy was quantified by estimating thomsen parameters thomsen 1986 from elastic constants the results show that the samples are at the best weakly anisotropic the presence of microcracks and pores as well as the heterogeneity of the samples play an important role in defining the p and s wave velocities the weak anisotropy found in these samples suggests that intrinsic properties of these rocks negligibly contribute to the anisotropy observed at the seismic scale

viscoelasticity of ells river bitumen sand and 4d monitoring of thermal enhanced oil recovery processes abstractsamples of ells river bitumen sand from alberta canada were measured at low frequencies 0 2 205 hz to determine the temperature and frequency dependence of velocities and attenuations the samples were first measured as received where the pore space is mostly filled with bitumen but also contains small amounts of air and water with residual air in the pores at 5 c there is strong dispersion in the p wave modulus and a peak in attenuation at seismic frequencies the frequency dependent moduli and attenuations shift by three orders of magnitude in frequency as temperature is increased from 5 c to 48 c consistent with the bitumen viscosity samples were then saturated so any empty pore space is filled with water after saturation at 1 hz increasing temperature from 5 c to 49 c causes a 30 reduction in the saturated p wave modulus a 34 reduction in the saturated bulk modulus and a 6 reduction in the shear modulus this behavior can only be explained by the temperature dependent bulk mo

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

acoustic properties of carbonates effects of rock texture and implications for fluid substitution more than 250 plugs from outcrops and three nearby boreholes in an undisturbed reef of miocene tortonian age were quantitatively analyzed for texture mineralogy and acoustic properties we measured the p and s waves of carbonate rocks under dry humidified and brine saturated conditions at 10 mpa effective pressure with an ultrasonic pulse transmission technique 1 mhz the data set was compared with an extensive database of petrophysical measurements of a variety of rock types encountered in carbonate sedimentary sequences two major textural groups were distinguished on the basis of trends in plots of compressional wave velocity versus poisson s ratio a specific ratio of p wave over s wave velocity in granular rocks the framework of depositional grains is the main medium for acoustic wave propagation in crystalline rocks this medium is provided by a framework of interlocking crystals formed during diagenesis rock textures are connected to primary depositionalparameters and a diagenetic ov

detailed topography of the devonian grosmont formation surface from legacy high resolution seismic profiles northeast alberta abstractthe devonian grosmont formation in northeastern alberta canada is the world s largest accumulation of heavy oil in carbonate rock with estimated bitumen in place of 64 5 109 m3 much of the reservoir unconformably subcrops beneath cretaceous sediments this is an eroded surface modified by kartstification known as the sub mannville unconformity smu we studied the reanalysis and integration of legacy seismic data sets obtained in the mid 1980s to investigate the structure of this surface standard data processing was carried out supplemented by some more modern approaches to noise reduction the interpretation of these reprocessed data resulted in some key structural maps above and below the smu these seismic maps revealed substantially more detail than those constructed solely on the basis of well log data in fact the use of only well log information would likely result in erroneous interpretations although features smaller than about 40 m in radius cannot be easily discerned at the smu

elastic property changes in a bitumen reservoir during steam injection the hangingstone steam assisted gravity drainage sagd operation of japan canada oil sands limited jacos is approximately 50 km south southwest of fort mcmurray in northern alberta canada jacos started the operation in 1997 and has produced bitumen since 1999 the oil sands reservoirs in hangingstone occur in the lower cretaceous mcmurray formation and are about 300 m in depth the sedimentary environments are fluvial to upper estuarine channel fill and the oil sands reservoirs correspond to vertically stacked incised valley fill with very complex vertical and horizontal distribution

seismic attributes for monitoring of a shallow heated heavy oil reservoir a case study in production geophysics detecting the zones of production or constraining the in situ conditions within a reservoir are often of greater importance than obtaining highly resolved seismic structural images standard seismic data processing distorts the signal and limits the potential for extracting additional information especially for shallow targets an alternative shift stack procedure is applied in the processing of a shallow 12 fold 1 m common midpoint cmp spacing reflection profile acquired over a heated athabasca heavy oil sand reservoir the shift stack involves summing of cmp traces which have been flattened to an appropriate reference event simple modeling confirms that the prestack waveforms are better preserved by this process amplitude and frequency attributes are extracted from the reflection profile amplitudes of a continuous reservoir event vary by 600 over 35 m intervals along the profile bright spots correlate with heated regions apparent frequencies as measured by the instantaneous frequency and by short time window power spectral estimates of the subreservoir event are 20 30 hz lower in these same regions these diminished apparent frequencies most probably result from interference of the subreservoir reflection with events related to structural changes within the reservoir a complete interpretation of the results has not been attempted as knowledge of the in situ conditions is incomplete however changes in the seismic response at the well locations suggest that these attributes are useful in detection and mapping of heated zones the shiftstack procedure may also be useful in environmental and geotechnical applications

a comparison of bitumen sands and bitumen carbonates measured data abstractbitumen is a very important hydrocarbon resource which exists in enormous amounts all over the world bitumen sands and bitumen carbonates have large percentages of bitumen content however the differences in lithology porosity and bitumen content cause them to have distinct properties which can further lead to different production methods therefore it is significant to study the different properties between bitumen sands and bitumen carbonates so as to further analyze the factors causing the differences and to provide guidance for production to study the basic properties of the bitumen rocks we have developed a method to measure the rock samples true porosity which can estimate the porosity even for as is samples the method involves injecting water and can provide relatively accurate estimation of the porosity then we compared the porosities and bitumen content of the bitumen sands and bitumen carbonates from the same area due to different rock formation mechanisms mineral comp

seismic properties of heavy oils measured data seismic techniques hold great potential for characterization and recovery monitoring of heavy oil reservoirs however to be more effective we must understand the seismic properties of the heavy oils and the heavy oil sands because this knowledge of in situ properties is key to linking the seismic response to reservoir properties and changes in this article we examine the seismic properties of heavy oils in detail

heavy oils their shear story heavy oils are important unconventional hydrocarbon resources with huge reserves and are usually exploited through thermal recovery processes these thermal recovery processes can be monitored using seismic techniques shear wave properties inparticular areexpectedtobemostsensitivetothechanges in the heavy oil reservoir because heavy oils change from being solid like at low temperatures to fluid like at higher temperatures to understand their behavior we measure the complex shearmodulusandthusalsotheattenuationofaheavy oil saturated rock and the oil extracted from it within the seismic frequency band in the laboratory the modulus and quality factor qoftheheavy oil saturatedrockshowamoderatedependence on frequency but are strongly influenced by temperature the shear wave velocity dispersion in these rocks is significant at steam flooding temperatures as the oil inside the reservoir loses viscosity atroomtemperatures theextractedheavyoilsupports a shear wave but with increasing temperature its shear modulus decreases rapidly which translates to a rapid drop in the shear modulus of the heavy oil saturated rock as well at these low to intermediate temperatures 30 c 100 c an attenuation peak corresponding to the viscous relaxation of the heavy oil is encountered also resulting in significant shear wave velocity dispersion well described by the cole cole model thus shearwaveattenuationinheavy oilrockscanbesignificantlylargeand iscausedbyboththemeltingandviscousrelaxationoftheheavy oil at yet higher temperatures the lighter components of the heavy oil are lost making the oil stiffer and less attenuative the dramaticchangesinshearvelocitiesandattenuationinheavyoils should be clearly visible in multicomponent seismic data and suggestthatthesemeasurementscanbequalitativelyandquantitatively used in seismic monitoring of thermal recovery processes

fluid effects on velocity and attenuation in sandstones measurements of ultrasonic velocity and attenuation in sandstones with a variety of saturating fluids are compared with the predictions of biot s theory of porous media acoustics the data show systematic deviations from biot theory as a function of pore fluid viscosity two non biot attenuation mechanisms are needed to explain the data local flow in microcracks and enhanced attenuation from pore wall roughness a model calculation of attenuation with pore wall roughness shows that attenuation in rocks can be many times larger than biot predictions this attenuation enhancement explains the inability to detect a biot slow wave in fluid saturated rocks and the observed correlation between ultrasonic attenuation and clay content in sandstones the non biot attenuation mechanisms are negligible when extrapolated to the lower frequencies of geophysical field measurements so ultrasonic attenuation in rocks provides no information about attenuation at the field scale

three dimensional seismic monitoring of an enhanced oil recovery process seismic reflection data were used to monitor the progress of an in situ combustion enhanced oil recovery process three sets of three dimensional 3 d data were collected during a one year period in order to map the extent and directions of propagation in time acquisition and processing parameters were identical for each survey so that direct one to one comparison of traces could be made seismic attributes were calculated for each common depth point data set and in a unique application of seismic reflection data the preburn attributes were subtracted from the midburn and postburn attributes the resulting difference volumes of 3 d seismic data showed anomalies which were the basis for the interpretation shown in this case study profiles and horizon slices from the data sets clearly show the initiation and development of a bright spot in the reflection from the top of the reservoir and a dim spot in the reflection from a limestone below it interpretation of these anomalies is supported by informa

effect of fluids and frequencies on poisson s ratio of sandstone samples abstractpoisson s ratio is an important parameter when interpreting measured geophysical and seismic data for an isotropic medium it directly relates to the ratio of p and s wave velocities we have measured as a function of pressure and frequency in fluid saturated sandstones the method of measuring was first tested as a function of pressure and frequency using standard samples the phase shift between radial and axial strains was also measured for all standard samples such as the linear viscoelastic plexiglas the data indicated that tan correlated with and related to a dissipation on then and tan were measured as a function of pressure and frequency for two dry and fluid saturated fontainebleau sandstone samples under dry conditions no frequency dependence and very small pressure dependence were observed unusual behaviors were observed under fluid saturated conditions in particular of one sample indicated a frequency dependent bell shaped dispersion under water and gl

deep structure and tectonics of the burmese arc constraints from earthquake and gravity data abstract active subduction of the indian plate is currently occurring beneath the burmese arc along an east dipping benioff zone which extends to a depth of about 180 km the overriding burma plate has an appearance of an inland seismic slab that is deflected downwards in the vicinity of the benioff zone a crustal seismic zone some 60 80 km east of the benioff zone correlates to backarc activity a triangular aseismic wedge in the top part of the crust outlines the central belt molasse basin east of the burmese foldbdt fault plane solutions show that the burmese benioff zone is characterized by shallow angle thrusting at its upper edge whereas down tip tensional events dominate its lower edge most of the backarc seismicity is accounted for by the sagaing transform or by the activity of the shan scarp normal fault zone at the margin of the asian plate a gravity anomaly pair with amplitude of 175 mgal coincides with the 1100 km long burmese arc lying in a north south direction the gravity anomalies along a profile in central burma and in adjacent areas of the bengal basin are interpreted in terms of plate subduction as well as near surface mass anomalies this suggests that sediments below the central belt may have an average thickness of the order of 10 km but may be as thick as 15 km at the subduction zone the oceanic crust underlying deeper parts of the bengal basin experiences phase transition at about 30 km depth in a benioff zone environment east of the burmese foldbelt several thrust planes are present within the folded and deformed cretaceous tertiary sediments of the fold belt these are often associated with ophiolites and basic to ultrabasic rocks a low density zone at least 60 km wide underlies the andesitic volcanic axis in the overriding plate

wave velocities in hydrocarbon saturated rocks experimental results this paper contains laboratory measurements of the temperature dependence of velocities determined by ultrasonic pulse transmission methods in hydrocarbon liquids and rock samples saturated by the liquids the samples discussed include 26 hydrocarbons of varying molecular weight nine mixtures of these hydrocarbons four heavy oils tar three saturated sandstones and a saturated sand the data provide encouragement that high frequency high resolution seismic techniques may infer formation temperature changes thereby detecting the progress of thermal enhanced oil recovery processes

fluid mobility and frequency dependent seismic velocity direct measurements the influence of fluid mobility on seismic velocity dispersion is directly observed in laboratory measurements from seismic to ultrasonic frequencies a forceddeformation system is used in conjunction with pulse transmission to obtain elastic properties at seismic strain amplitude 10 7 from 5 hz to 800 khz varying fluid types and saturations document the influence of pore fluids the ratio of rock permeability to fluid viscosity defines mobility which largely controls pore fluid motion and pore pressure in a porous medium high fluid mobility permits pore pressure equilibrium either between pores or between heterogeneous regions resulting in a low frequency domain where gassmann s equations are valid in contrast low fluid mobility can produce strong dispersion even within the seismic band here the low frequency assumption fails since most rocks in the general sedimentary section have very low permeability and fluid mobility shales siltstones tight limestones etc most rocks are not in the lowfrequency domain even at seismic frequencies only those rocks with high permeability porous sands and carbonates will remain in the low frequency domain in the seismic or sonic band

effect of oil composition on fluid substitution in heavy oil reservoirs unlike light oils heavy oils do not have a well established scheme for modelling elastic moduli from dynamic reservoir properties one of the main challenges in the fluid substitution of heavy oils is their viscoelastic nature which is controlled by temperature pressure and fluid composition here we develop a framework for fluid substitution modelling that is reliable yet practical for a wide range of cold and thermal recovery scenarios in producing heavy oils and that takes into account the reservoir fluid composition grounded on the effective medium theories for estimating elastic moduli of an oil rock system we investigate the effect of fluid composition variations on oil rock elastic moduliwith temperature changes the fluid compositional behaviour is determined by flash calculations elastic moduli are then determined using the double porosity coherent potential approximation method and the calculated viscosity based on the fluid composition an increase in temperature imposes two opposing mechanisms on the viscosity behaviour of a heavy oil sample gas liberation which tends to increase the viscosity and melting which decreases the viscosity we demonstrate that melting dominates gas liberation and as a result the viscosity and consequently the shear modulus of the heavy oils always decrease with increasing temperature furthermore it turns out that one can disregard the effects of gas in the solution when modelling the elastic moduli of heavy oils here we compare oil rock elastic moduli when the rock is saturated with fluids that have different viscosity levels the objective is to characterize a unique relation between the temperature the frequency and the elastic moduli of an oil rock system we have proposed an approach that takes advantage of this relation to find the temperature and consequently the viscosity in different regions of the reservoir