calculated volumes of individual shield volcanoes at the young end of the hawaiian ridge abstract high resolution multibeam bathymetry and a digital elevation model of the hawaiian islands are used to calculate the volumes of individual shield volcanoes and island complexes niihau kauai oahu the maui nui complex and hawaii taking into account subsidence of the pacific plate under the load of the hawaiian ridge our calculated volume for the island of hawaii and its submarine extent 213 103 km3 is nearly twice the previous estimate 113 103 km3 due primarily to crustal subsidence that had not been accounted for in the earlier work the volcanoes that make up the island of hawaii mahukona kohala mauna kea hualalai mauna loa kilauea and loihi are generally considered to have been formed within the past million years and our revised volume for the island indicates that magma supply rates are greater than previously estimated 0 21 km3 yr as opposed to 0 1 km3 yr this result also shows that compared with rates calculated for the hawaiian islands 0 6 ma 0 095 km3 yr the hawaiian ridge 0 45 ma 0 017 km3 yr and the emperor seamounts 45 80 ma 0 010 km3 yr magma supply rates have increased dramatically to build the island of hawaii

geochemical variations among eastern saudi arabian paleozoic condensates related to different source kitchen areas abstract large reserves of gas and condensate are found in paleozoic reservoirs khuff unayzah and jauf in the ghawar area of eastern saudi arabia the source rock for these hydrocarbons is the basal organic rich hot shale of the qusaiba member of the silurian qalibah formation this is the same prolific source rock that generated the sweet light crude oil and condensate found in the unayzah reservoirs in central saudi arabia thermal maturity modeling of the source rock identifies two kitchen areas to the east and west of the ghawar structure the west kitchen was well into the oil window by 210 ma while the east kitchen was just entering the oil window large areas of both kitchens were in the wet gas window by 125 ma and by 90 ma most of the area north of ghawar was generating dry gas in eastern saudi arabia paleozoic oil and condensate are found in early formed structures carboniferous and early triassic growth whereas late cretaceous and tertiary structures contain only dry gas the geochemistry of the oils and condensates indicates two groups each generated from a different hydrocarbon kitchen suggesting that the two kitchens differ slightly in organic facies within each group variations among hydrocarbons are related to the thermal maturity of the source rock during generation within the khuff reservoir gas souring is caused by thermochemical sulfate reduction

postshield volcanism and catastrophic mass wasting of the waianae volcano oahu hawaii the 3 9 to 2 9 ma waianae volcano is the older of two volcanoes making up the island of oahu hawaii exposed on the volcanic edifice are tholeiitic shield lavas overlain by transitional and alkalic postshield lavas the postshield alkalic cap consists of aphyric hawaiite of the palehua member of the waianae volcanics overlain unconformably by a small volume of alkalic basalt of the kolekole volcanics kolekole volcanics mantle erosional topography including the uppermost slopes of the great lualualei valley on the lee side of the waianae range twenty new k ar dates combined with magnetic polarity data and geologic relationships constrain the ages of lavas of the palehua member to 3 06 2 98 ma and lavas of the kolekole volcanics to 2 97 2 90 ma the geochemical data and the nearly contemporaneous ages suggest that the kolekole volcanics do not represent a completely independent or separate volcanic event from earlier postshield activity thus the kolekole volcanics are reduced in rank becoming the kolekole member of the waianae volcanics magmas of the palehua and kolekole members have similar incompatible element ratios and both suites show evidence for early crystallization of clinopyroxene consistent with evolution at high pressures below the edifice however lavas of the kolekole member are less fractionated and appear to have evolved at greater depths than the earlier palehua hawaiites postshield primary magma compositions of the palehua and kolekole members are consistent with formation by partial melting of mantle material of less than 5 10 relative to waianae shield lavas within the section of palehua member lavas an increase with respect to time of highly incompatible to moderately incompatible element ratios is consistent with a further decrease in partial melting by approximately 1 2 this trend is reversed with the onset of eruption of kolekole member lavas where an increase in extent of partial melting is indicated the relatively short time interval between the eruption of palehua and kolekole member lavas appears to date the initial formation of lualualei valley which was accompanied by a marked change in magmatic conditions we speculate that the mass wasting event separating lavas of the palehua and kolekole members may be related to the formation of a large submarine landslide west and southwest of waianae volcano enhanced decompression melting associated with removal of the equivalent volume of this landslide deposit from the edifice is more than sufficient to produce the modeled increase of 1 2 in extent of melting between the youngest palehua magmas and the posterosional magmas of the kolekole member the association between magmatic change and a giant landsliding event suggests that there may be a general relationship between large mass wasting events and subsequent magmatism in hawaiian volcano evolution

early growth of kohala volcano and formation of long hawaiian rift zones transitional composition pillow basalts from the toe of the hilo ridge collected from outcrop by submersible have yielded the oldest ages known from the island of hawaii 1138 34 to 1159 33 ka hilo ridge has long been interpreted as a submarine rift zone of mauna kea but the new ages validate proposals that it is the distal east rift zone of kohala the oldest subaerial volcano on the island these ages constrain the inception of tholeiitic volcanism at kohala provide the first measured duration of tholeiitic shield building 870 k y for any hawaiian volcano and show that this 125 km long rift zone developed to near total length during early growth of kohala long eastern trending rift zones of hawaiian volcanoes may follow fractures in oceanic crust activated by arching of the hawaiian swell in front of the propagating hotspot

fracture apertures from electrical borehole scans three dimensional finite element modeling was performed to investigate the response to fractures of the formation microscanner mark of schlumberger which records high resolution electrical scans of the borehole wall it is found that the equation w carmbrx0l describes over two orders of magnitude of resistivity contrasts between borehole mud and the formation the relationship between fracture width w in mm formation sensitivity rx0 mud resistivity rm and the additional current flow a caused by the presence of the fracture a is the additional current which can be injected into the formation divided by the voltage integrated along a line perpendicular across the fracture trace coefficient c and exponent b are obtained numerically from forward modeling tool standoffs of up to 2 5 mm and fracture dips in the range from 0 to 40 were found to have an insignificant effect on the above relation a three step approach to detect trace and quantify fractures is used potential fractures in formation

active deformation within the zagros mountains deduced from gps measurements we present and interpret the results of global positioning system gps measurements at 35 stations in and beside the zagros mountain belt sw iran for three campaigns ending march 1998 december 1999 and june 2001 preliminary motion estimates show clearly the change in character along the strike of the belt stations to the se move at 13 22 3 mm a 1 towards n 7 5 e with respect to eurasia most of the shortening indicated by the gps velocities seems to occur in the se zagros along two major seismic zones and along the zagros front to the nw stations move oblique to the trend of the belt towards n 12 8 w at 14 19 3 mm a 1 most of the shortening in the nw zagros seems to occur along the mountain front fault with its major earthquakes as well as along the zagros front the change in direction and magnitude of the velocity vectors across the north south trending kazerun and karebas faults involves extension of up to 4 mm a 1 along the strike of the zagros belt

jurassic cretaceous boundary age and mid ocean ridge type mantle source for shatsky rise basalt sills cored in lowermost berriasian sediments on shatsky rise in the northwest pacific yield a mean 4 0 ar 3 9 ar incremental heating age of 144 6 0 8 ma providing a minimum estimate on the age of the jurassic cretaceous boundary the largest part of the rise was emplaced at rates similar to those of several continental flood basalts the rise formed at an oceanic triple junction and the sills as well as lavas from two dredge sites exhibit an ocean ridge type nd pb sr isotope signature this signature is provisionally consistent with either a perisphere or meteorite impact model but is not predicted by the plume head model of plateau formation however no model can yet be rejected given the very sparse sampling of shatsky rise

multi scale imaging and simulation of structure flow and reactive transport for co2 storage and eor in carbonate reservoirs as we continue to use fossil fuels for our energy supply the concentration of co2 in the earth s atmosphere is likely to continue to increase it has been shown that this is correlated with an increase in the temperature of the atmosphere and potential associated climate change to mitigate this problem carbon capture and storage ccs has been mooted over the past decade in this chapter we will focus on co2 storage in downhole rock formations rock formations suitable for storage include saline aquifers and depleted oil and gas reservoirs also coal bed methane cbm reservoirs may be suitable for storage but we will not consider these in the current chapter in the case of saline aquifers we consider only the storage of co2 in the case of depleted oil gas reservoirs the storage of co2 can be combined with enhanced oil recovery eor this may lead to a more favorable economic scenario and has recently been coined as ccus carbon capture and utilized storage in particular we will focus in this chapter on carbonate reservoirs sandstone reservoirs have been relatively well studied however much less is known about the storage properties of carbonate rocks which have very different petrophysical and flow properties moreover carbonate rocks constitute a significant fraction of existing depleted hydrocarbon reservoirs our aim is to study the pore scale properties of carbonates and upscale these to the core and field scales first carbonates have a very different structure from sandstones associated with their composition and diagenesis carbonates usually have a much broader pore size distribution psd than sandstones with extensive microporosity cantrell and hagerty 1999 in addition carbonates are often naturally fractured ameen et al 2010 this leads to a broad range of heterogeneity as a function of length scale in comparison

dating of the upper pleistocene holocene volcanic activity of la palma using the unspiked k ar technique abstract combined unspiked k ar dating and detailed mapping have established the eruptive chronology of the cumbre vieja volcano in the canary islands the cv volcano is a large polygenetic volcano subaerial area 220 km2 subaerial volume 125 km3 elevation above sea level 2000 m which rests on the southern flank of the older taburiente cumbre nueva volcano we defined two stratigraphic units by their relationship to the development of coastal cliffs developed around the cumbre vieja volcano a cliff forming series and a scree forming series which is draped over the cliffs and forms the coastal platforms at their bases k ar ages were measured from 20 samples from the two series there are no discrepancies between k ar ages and the stratigraphy the k ar ages of one flow compare well with 14 c determinations 14 c 3 2 0 1 ka k ar 4 2 ka the ages of the scree forming series range from 3 2 ka to 21 2 ka the cliff forming series ages range from 20 2 ka to 123 3 ka but as the base of the sequence is not exposed the growth of the cumbre vieja volcano must have begun substantially earlier the boundary between the two coincides with the low sea level stand in the last glacial maximum which we infer to have been a period of intense coastal erosion dated samples from the upper part of the taburiente cumbre nueva volcano range in age from 853 10 ka to 566 8 ka the age of the youngest taburiente cumbre nueva volcano sample provides an upper bound on the age of the subsequent cumbre nueva giant lateral collapse

a scale independent approach to fracture intensity and average spacing measurement fracture intensity the number of fractures per unit length along a sample line is an important attribute of fracture systems that can be problematic to establish in the subsurface lack of adequate constraints on fracture intensity may limit the economic exploitation of fractured reservoirs because intensity describes the abundance of fractures potentially available for fluid flow and the probability of encountering fractures in a borehole traditional methods of fracture intensity measurement are inadequate because they ignore the wide spectrum of fracture sizes found in many fracture systems and the consequent scale dependence of fracture intensity an alternative approach makes use of fracture size distributions which allow more meaningful comparisons between different locations and allow microfractures in subsurface samples to be used for fracture intensity measurement comparisons are more meaningful because sampling artifacts can be recognized and avoided and because common thresholds of fracture size can be enforced for counting in different locations additionally quantification of the fracture size distribution provides a mechanism for evaluation of uncertainties estimates of fracture intensity using this approach for two carbonate beds in the sierra madre oriental mexico illustrate how size cognizant measurements cast new light on widely accepted interpretation of geologic controls of fracture intensity

age of tilted reefs hawaii submerged carbonate reefs are preserved as a series of submarine terraces between molokai and hawaii along a 200 km span of the southeastern hawaiian ridge limestones from two of the terraces have been sampled from submersibles and dated radiometrically at 13 and 120 ka recognition that the terraces are tilted permits assignment of about a dozen terraces from 150 to 1300 m depth to eight general reef platforms these reefs were drowned by the combined effects of island subsidence and sea level rise at the end of successive glacial stages from 13 to 647 ka the platforms are tilted 5 m km southeast toward the locus of volcanic loading centered on the island of hawaii the end of the active period of volcanic shield building is represented on each nonactive volcano by a submerged change in slope dating of this slope change by reference to the dated reefs provides independent evidence that shield building ended at about the same time that the volcano changed from eruption of tholeiitic to alkalic basalt the variation in depth of the dated tilted reefs along the ridge indicates that the end of subsidence follows the end of shield building by about one half million years the present northwest margin of major subsidence probably crosses southeast maui during the last half million years the rate of southeast migration of the beginning of both subsidence and of tholeiitic volcanism does not appear to have increased however the rate of southeast migration of the end of both subsidence and of tholeiitic volcanism has apparently increased this shortening of the life history of the younger volcanoes implies an increase in eruption rates

dual porosity fractured miocene syn rift dolomite reservoir in the issaran field gulf of suez egypt a case history of the zonal isolation of highly fractured water carrier bed

comparison of the diagenetic and reservoir quality evolution between the anticline crest and flank of an upper jurassic carbonate gas reservoir abu dhabi united arab emirates abstract this petrographic stable isotopic and fluid inclusion microthermometric study of the upper jurassic limestones of an onshore field abu dhabi united arab emirates uae compares diagenesis in flanks and crest of the anticline the results revealed that the diagenetic and related reservoir quality evolution occurred during three phases including i eogenesis to mesogenesis 1 during which reservoir quality across the field was either deteriorated or preserved by calcite cementation presumably derived from marine or evolved marine pore waters improvement of reservoir quality was due to the formation of micropores by micritization of allochems and creation of moldic intragranular pores by dissolution of peloids and skeletal fragments ii obduction of oman ophiolites and formation of the anticline of the studied field was accompanied by cementation by saddle dolomite and blocky calcite high homogenization temperatures 125 175 c and high salinity 19 26 wt nacl eq of the fluid inclusions negative 18ovpdb values 7 7 to 2 9 saddle shape of dolomite and the presence of exotic cements i e fluorite and sphalerite suggest that these carbonates were formed by flux of hot basinal brines probably related to this tectonic compression event iii mesogenesis 2 during subsidence subsequent to the obduction event which resulted in extensive stylolitization and cementation by calcite this calcite cement occluded most of the remaining moldic and inter intragranular pores of the flank limestones water zone whereas porosity was preserved in the crest this study contributes to 1 our understanding of differences in the impact of diagenesis on reservoir quality evolution in flanks and crests of anticlines i e impact of hydrocarbon emplacement on diagenesis and 2 relating various diagenetic processes to burial history and tectonic events of foreland basins in the arabian gulf area and elsewhere

geomagnetic paleosecular variation at hawaii around 3 ma from a sequence of 107 lava flows at kaena point oahu abstract we have sampled a sequence of 107 lava flows in the waianae series on oahu hawaii in two separate stretches the first 51 flows at kaena point extends from sea level to an altitude of 190 m and the second 56 flows follows the satellite tracking station road from 218 m to 360 m above sea level thermal and af demagnetization yield very similar results and reveal only normal polarities k ar dating at five different horizons combined with the paleomagnetic results indicate that the sequence was emplaced entirely in the normal polarity interval between the upper mammoth and the lower kaena polarity transitions 3 22 3 11 ma some of the flows are serially correlated filtering does not however drastically affect the final results inclinations are shallower than those expected from a centered dipole field although large 13 the inclination anomaly is consistent with results from other sites at the same latitude the scatter of the vgps about the geographic pole is consistent with available data from other regions at similar latitudes the scatter of the directions is also consistent with the predictions of recent statistical models of paleosecular variation therefore these results do not support the hypothesis of a pacific dipole window

the paleozoic petroleum geology of central arabia exploratory drilling in central saudi arabia has established significant paleozoic petroleum potential in this region in recent discoveries the permian interval of the unayzah formation has been identified as the primary oil and gas reservoir the unayzah formation consists of alluvial and fluvial to shallow marine siliciclastic sandstones and siltstones that were deposited on a major pre unayzah unconformity saudi arabian paleozoic oil is a high gravity 43 53 degrees api crude with low sulfur content usually less than 0 07 that is classified as arabian super light oil gas with condensate has also been discovered in the unayzah formation the identified paleozoic traps are moderate relief fault generated structures with generally 30 100 m of closure unayzah structural traps developed primarily during the triassic to early jurassic however an earlier phase of significant pre unayzah structural development is also indicated between the devonian and late carboniferous and is related to a hercynian structural event post triassic structure in central arabia is mainly regional and results principally from late cretaceous to tertiary development of the central arabian arch the established source rock is the basal qusaiba shale a widespread organic rich shale that was deposited following regional deglaciation in the early silurian migration occurred regionally updip through unayzah formation reservoirs from the underlying qusaiba shale subcrop and or vertically along fault bounded zones on the flanks of structures from the underlying qusaiba shale interbedded upper permian shales and evaporites provide a top seal for the unayzah and form the basal sequence of the overlying transgressive khuff carbonate pre qusaiba reservoir targets include the cambrian ordovician saq sandstone the ordovician qasim formation and upper ordovician to lower silurian periglacial clastics of the zarqa and sarah formations high gravity low sulfur oil has also been discovered in this pre qusaiba clastic section the reservoirs of the pre qusaiba structures are fault bounded and sources laterally by the down faulted qusaiba shale

diverse fracture properties and their impact on performance in conventional and tight gas reservoirs saudi arabia the unayzah south haradh case study the upper permian carboniferous unayzah formation in south haradh saudi arabia includes two major mechanical and petrophysical layers that are separated by shale rich zones open tectonic fracture clusters are rare and not essential for fluid flow in the unayzah a zone which has high porosity and permeability however such fracture clusters are essential to and impact the production performance in the unayzah b c tight gas reservoir the occurrence of the tectonic fractures in the unayzah formation is linked to the rock mechanical properties which vary with porosity shale volume cement type and texture the b c unit is more fractured than the a unit but its layers vary in the degree of fracturing the variation in fracture development within the b c unit results in differences in fracture enhanced permeability based on production profiles where flow is restricted to preferentially fractured mechanical layers that lack effective vertical fluid communication with other layers we identify two tectonic fracture systems an older subordinate fully mineralized system and a younger primary mostly open system early extensional fractures including joints and faults developed parallel to the basement faults during the opening of the neotethys these are fully mineralized and have little or no function as fluid conduits the younger system includes open fracture clusters that are predominantly parallel or nearly parallel to the regional east northeast west southwest maximum horizontal stress of the zagros that has been active since the late cretaceous and is independent of local structures therefore these fractures are controlled by remote stresses instead of the basement rooted forced folds and faults in this article we demonstrate that in the unayzah b c natural fractures are essential to permeability and in some areas to porosity and thence to reservoir performance the results of this study are being implemented in well placement and completion design to optimize the intersection of open fracture clusters with positive preliminary results

gravity anomalies of the northern hawaiian islands implications on the shield evolutions of kauai and niihau 1 new land and marine gravity data reveal two positive residual gravity anomalies in the northern hawaiian islands one over kaua i the other between the islands of kaua i and ni ihau these gravitational highs are similar in size and magnitude to those of other hawaiian volcanoes indicating local zones of high density crust attributed to olivine cumulates in solidified magma reservoirs the residual gravity high over kaua i is located in the l hu e basin offset 8 12 km east of kaua i s geologically mapped caldera this offset suggests that the mapped caldera is a collapsed feature later filled in with lava and not the long term center of kaua i shield volcanism a second residual gravity high in the submarine channel between kaua i and ni ihau marks the volcanic center of the ni ihau shield volcano this second residual gravity anomaly implies that ni ihau s eastern boundary extended 20 km east of its present location through inversion the residual gravity anomalies were modeled as being produced by two solidified magma reservoirs with average densities of 3100 kg m3 and volumes between 2470 and 2540 km3 considering the locations and sizes of the residual gravity anomalies magma reservoirs the extent of the two islands paleoshorelines and potassium argon dating of shield stage lavas we conclude that the two islands were not connected subaerially during their respective shield stages and that ni ihau s topographic summit was removed by an eastern flank collapse between 4 3 and 5 6 ma continued constructional volcanism on western kaua i likely covered much of the submerged remains of eastern ni ihau

the function of fractures and in situ stresses in the khuff reservoir performance onshore fields saudi arabia the highly variable performance of the permian triassic khuff reservoir in onshore saudi arabia has been attributed to the presence of natural fractures similar preproduction pressure profile and hydrocarbons in the different reservoir units in some fields have been attributed to vertical communication through large faults to validate these assumptions we studied the static and dynamic data from the khuff reservoir in 19 major structural traps we identified two distinctive fracture domains based on fracture orientation and density fracture evolution is mainly controlled by the extensional and consequent compressional plate tectonics instead of local structures in situ stresses are dominated by the zagros plate tectonics and affect fracture aperture differently in the two fracture domains the fracture impact on the khuff reservoir performance is mostly subtle because of the nature and distribution of the fractures high fracture enhanced productivity occurs locally in some of the producing wells and it results from high density fracture clusters including mesoscopic faults with channel type apertures the following findings challenge the perceived major functions of fractures in the khuff reservoir performance in onshore fields 1 individual fractures are dominantly tensile and small mesoscopic and microscopic 2 individual faults are small and not readily resolvable at seismic scale 3 the depth and carbonate nature of the khuff reservoir make the fractures highly susceptible to fast healing unless preserved within the hydrocarbon column 4 initial vertical pressure gradient changes with production indicate a lack of present day communication across the anhydrite sealing layers between the different khuff reservoir units 5 horizontal well direction does not generally have an impact on productivity and 6 sustained and heavy losses of circulation are rarely encountered in the khuff reservoir wells mohammed s ameen received his ph d and diploma of imperial college in structural geology and geomechanics from imperial college london 1988 he has more than 20 years of academic and industrial experience and has patented a new method for the characterization of microfractured reservoirs he has published 25 articles on fractures and folds and has edited three special publications for the geological society london he conducted the first classic work on the fractures and folds across the taurus zagros range iraq covering 30 major fold traps the work is published in the aapg bulletin the geological magazine and the journal of petroleum geology he joined the reservoir characterization department at saudi aramco in 1998 since 2004 he has been leading the structural geology and rock mechanics group in the geological technical services division saudi aramco he is an active member of the aapg society of petroleum engineers european association of geoscientists and engineers and the geological society london ismail m buhidma is a petroleum engineering consultant in the gas reservoir management division of saudi aramco with 32 years of diverse industrial experience for the last 12 years he has been actively involved in aramco s nonassociated gas development program his areas of interest include reservoir management well performance analysis well test analysis phase behavior geomechanics reservoir simulation reservoir characterization and well stimulation prior to joining aramco ismail worked for exxon in libya schlumberger and atlantic richfield in the usa and qatar petroleum in qatar ismail holds b s and m s degrees in petroleum engineering from the university of tulsa he is a member of society of petroleum engineers spe and has published numerous spe appears zillur rahim is a petroleum engineering consultant with saudi aramco working in gas field development he received his b s degree from algerian petroleum institute and m s degree and ph d from texas a m university college station all in petroleum engineering he has 25 years of industry experience has published more than 50 technical papers and has taught numerous industry courses previously he worked with holditch and associates petroleum consultants and with schlumberger reservoir technology group his area of expertise includes reservoir engineering hydraulic and acid fracturing and reservoir management

fracture patterns and petrophysical properties of carbonates undergoing regional folding a case study from kurdistan n iraq abstract the zagros taurus fold and thrust belt hosts a prolific hydrocarbon system most hydrocarbon reserves are stored in naturally fractured reservoirs and such fracture systems can therefore have a significant impact on reservoir performance fractures are one of the most important paths for fluid flow in carbonate reservoirs and industrial geoscientists and engineers therefore need to understand and study fracture patterns in order to optimise hydrocarbon production the observed fracture patterns in outcrops may have implications on fluid flow and reservoir modelling in subsurface reservoirs and we have therefore undertaken a case study of fracturing associated with regional folding in iraqi kurdistan in this area some exploration wells currently target upper triassic dolostones kurra chine formation and or lower jurassic limestones and dolomitised limestones sehkaniyan formation in both units hydrocarbon production comes mainly from secondary porosity created by dolomitisation dissolution and fracturing both formations have undergone multiple phases of deformation associated with burial uplift folding and thrusting we investigate some fracture pattern characteristics and some petrophysical properties of these units using selected outcrops around the gara ora and ranya anticlines that form folds directly traceable for 25 70 km our outcrop data is compared with subsurface fracture and petrophysical datasets reported from wells in the nearby shaikhan and swara tika fields the 1 2 3d fracture attributes collected from outcrops are fracture orientation type spacing intensity length and cross cutting and abutting relationships fracture orientations show a clear relationship to the local fold axis in both the outcrop and subsurface although in some cases they appear to relate more to the present day in situ maximum horizontal stress direction or local strike slip faulting three stages of fracturing are proposed pre folding early folding and post folding fractures in addition we report petrophysical properties porosity permeability and acoustic velocity of both the kurra chine and sehkaniyan formations in relation to their structural position within folds and faults and stratigraphic level the highest porosities and permeabilities are recorded in the hinges and backlimbs of the gara anticline the best reservoir quality highest porosity and permeability is often found in areas associated with replacement dolomite i e solution vugs and intercrystalline porosity the kurra chine formation displays similar trends in velocity porosity data at both outcrop and the subsurface however the sehkaniyan formation displays lower acoustic velocity for a given porosity at outcrop compared to the subsurface

piggyback tectonics long term growth of kilauea on the south flank of mauna loa abstract compositional and age data from offshore pillow lavas and volcaniclastic sediments along with on land geologic seismic and deformation data provide broad perspectives on the early growth of kilauea volcano and the long term geometric evolution of its rift zones sulfur rich glass rinds on pillow lavas and volcaniclastic sediments derived from them document early underwater growth of a large compositionally diverse alkalic edifice the alkalic rocks yield 40ar 39ar ages as old as about 275 ka transitional composition lavas which mark beginning of the shield stage while most or all the edifice remained below sea level probably first erupted after about 150 ka and tholeiitic lavas of present day type are probably younger than 100 ka breccia clasts from papau seamount and along the lower southwest corner of the hilina bench are derived from subaerial mauna loa requiring that mauna loa s flank underlies western parts of kilauea at shallow depth the volume of the kilauea edifice is therefore smaller 10 000 km3 than previous estimates 15 40 000 km3 lava thickness accumulation rates appear to have remained nearly constant during edifice growth as effusion rates increased from 25 106 m3 yr at end of the alkalic stage to the present day tholeiite rate of 100 106 m3 yr seismic and gravity data show that the deep plumbing system for kilauea s magma supply extends nearly vertically through the oceanic crust at least to mantle depths of 30 35 km directly below its present day caldera proximity of kilauea s caldera to the surface boundary with mauna loa and the presence of mauna loa rocks at shallow depth beneath the south flank are difficult to reconcile with a submarine origin for early kilauea alkalic lavas unless geometric relations between the two volcanoes have changed substantially during growth of the kilauea shield seismic and ground deformation data suggest seaward spreading of the entire south flank of hawaii island independently of the boundary between kilauea and mauna loa along a landward dipping detachment fault system near the basal contact of the composite volcanic edifices with underlying oceanic crust current steady state horizontal displacements increase seaward at rates of 1 5 cm yr on the lower flank of mauna loa and reaching 5 8 cm yr at the kilauea coastline infrequent 100 yr large earthquakes generate similar geometries but 102 larger displacements per event present day kilauea is the more dynamic edifice but prior to inception of kilauea and during its early growth mauna loa is inferred to have undergone intense volcano spreading involving the kaoiki honuapo fault system considered a geometric analog of the hilina system on kilauea cumulative deformation of mauna loa s south flank during growth of kilauea since 200 300 ka is estimated to have involved 10 km of seaward spreading displacing the rift zones of k lauea while its deep plumbing system and summit magma reservoir remained nearly fixed in space kilauea s rift zones rather than migrating southward with time solely due to dike emplacement preferentially on the mobile seaward side alternatively are interpreted to have been transported passively southward piggyback style during shield stage growth of kilauea as a blister on the still mobile south flank of mauna loa such an evolution of kilauea accounts for the arcuate geometry of the present day rift zones proximity of the summit magma supply to the exposed flank of mauna loa initial submarine growth of the ancestral edifice and present day location of mauna loa rocks at shallow depth beneath the south flank of kilauea

a review on the applications of image logs in structural analysis and sedimentary characterization abstract image logs provide important information on lithology sedimentary textures paleoflow directions fractures and in situ stress analysis lacking of criteria used for establishing the image log facies limits the applications of image logs in sedimentary reservoir interpretation this paper provides a thoroughgoing review focusing on the recent applications of borehole image logs for sedimentological and structural description and interpretation and aims to establish image log facies which can provide guidelines in sedimentary reservoir interpretation this paper firstly summarizes the principles and basic characteristics of various imaging logging tools and then briefly introduces the pre processing workflow of the image log data then the generated images are used for depth and orientation shifts of cores by calibrating individual sedimentary and structural features descriptive and concise image log facies are established based on combinations of image textures including dip type dip pattern and color scheme and the characteristics as well as physical criteria for each individual image facies are summarized the established image log facies are then interpreted in terms of structural and sedimentological features such as lithology sedimentary structures vugs fractures and faults the image log facies and its stacking patterns are then used to interpret the lithofacies associations by calibrating with cores and conventional logs natural fractures and induced fractures are recognized by image logs and the principles of breakouts and drilling induced fractures for in situ stress analysis are reviewed then the applications of image logs in investigation of fracture attitudes and states as well as in computation of fracture parameters are summarized the procedures to evaluate fracture effectiveness through image logs are discussed at last the application of image logs for structural dip analysis is reviewed and image logs are used for recognizing faults fracture sets and attitudes of stratum through the dip patterns the basic procedures for paleocurrent reconstruction which includes dip picking of cross beddings structural dip determination and structural dip removal are reviewed then the paleocurrent directions of the lower cretaceous bashijiqike formation in the kuqa depression were reconstructed which could help further understanding of the depositional systems this review will help extend the utility of image logs in interpreting small to large scale sedimentary and structural features and bridges the gaps between well log analysis and sedimentary and structural interpretation

rejuvenated stage volcanism after 0 6 m y quiescence at west maui volcano hawaii new evidence from k ar ages and chemistry of lahaina volcanics abstract west maui s rejuvenated stage lahaina volcanics were erupted from four discrete sites new k ar ages indicate two pulses of volcanism the older about 0 6 ma and the younger about 0 4 ma compositionally the lava flows are entirely basanitic but each pulse is diverse the underlying postshield stage honolua volcanics were emplaced by about 1 2 ma on the basis of previously published ages therefore the duration of volcanic quiescence prior to rejuvenation is about 0 6 m y at west maui much longer than estimated previously

madagascar basalts tracking oceanic and continental sources extensive upper cretaceous volcanism in southern madagascar was fed in part by mantle sources resembling those expressed today in the indian ocean at marion and prince edward islands and on the central southwest indian ridge in addition very low end t to 17 4 high 87sr 86sr t to 0 72126 tholeiites in southwestern madagascar were variably but highly contaminated by ancient continental material broadly like that affecting the bushe and poladpur formations of the later deccan traps in india alkalic dikes in southwestern madagascar have a rough analogue in the mahabaleshwar formation of the deccan in that they document the influence of a low 206pb 204pb negative end relatively low 87sr 86sr reservoir a very similar reservoir is manifested at present in mid ocean ridge basalts on the central southwest indian ridge near 40 e the original location of this end member appears likely to have been in the madagascan lithospheric mantle a portion of which may have been removed in the middle cretaceous by the action of the marion hotspot or the rifting of indo madagascar an origin within the hotspot itself also may be possible however recent products of the hotspot appear to lack completely the necessary low 206pb 204pb low end signatures

contemporary tectonic stress pattern of the persian gulf basin iran abstract the contemporary crustal stress pattern is important to several aspects of earth sciences such as reservoir geomechanics neotectonic deformation and geodynamic modelling the persian gulf basin is a petroliferous region in southern iran that hosts hundreds of petroleum wells and hence the knowledge of the present day stress is critical for any exploration and production in this region in addition to geo resources this region has a great economic importance and the in situ stresses provide key insights on neotectonic and seismic hazard of the basin however there is limited in situ stress information in the persian gulf region in this study we analyse 8 km of borehole image logs in 20 wellbores in the persian gulf in order to provide a clear picture of the stress pattern in this region our wellbore stress analyses provide 35 quality ranked maximum horizontal stress orientations shmax data records in addition we compile 27 earthquake focal mechanisms in the study region from different seismic catalogues and published literature and present the first comprehensive quality ranked in situ stress map of the persian gulf basin with 62 data records which can be used as a valuable source of information for future exploration and seismic hazard assessment the resulting database suggests that the shmax azimuth in central and western persian gulf is ne sw parallel to the arabia eurasia tectonic plate convergence which demonstrate the key role of relative plate motion in the present day stress pattern of these areas however the shmax azimuth in the eastern part of the study area is nw se which is different from the central and western persian gulf the nw se shmax azimuth is consistent with other geological and geophysical observations that suggest an indentor model for musandam peninsula oman in the zagros makran syntaxis

crustal structure flexure and subsidence history of the hawaiian islands seismic reflection profile data have been used to estimate the long term 106 years mechanical properties of the oceanic lithosphere underlying the hawaiian islands the data show prominent reflectors associated with the top of the oceanic crust reflector 2 the m discontinuity and the base of the crust reflector 3 the two way travel time to the reflectors has been depth converted using velocity depth functions derived from seismic refraction expanding spread profile data and compared to calculated depths based on simple three dimensional elastic plate models a good fit to the reflector depths was obtained for a model with an effective elastic thickness of the lithosphere te of 40 km the main discrepancies with the refraction data occur beneath oahu and molokai where the predicted depth of the base of the flexed crust is too shallow and beneath the southeast flank of hawaii where it is too deep we attribute the thickened crust beneath oahu to ponding of magma at the base of the crust following the last phases of tholeiitic shield building and the thinned crust beneath the flanks of hawaii to crustal melting beneath the youngest part of the chain the effective te of 40 km is higher than expected for 80 m y oceanic lithosphere possibly due to the effects of subsurface loads that act at or near the base of the flexed crust according to free air gravity anomaly and bathymetry data te does not change significantly along the island chain retaining a similar value for hawaii as it does for oahu we have used this result to estimate the pattern of subsidence and uplift that would be expected along the hawaiian islands because of flexural loading of hawaii the observed depth of the haleakala wave cut terrace northeast of maui can be generally explained by the flexure model the main discrepancies between observed and the predicted depths occur northwest of hawaii where they suggest a somewhat higher value of te possibly due to incomplete adjustment of the lithosphere we suggest that the addition of loads to the end of a volcanic chain generated as a plate moves over a mantle hotspot is accommodated by progressive flexing downstream causing subsidence of preexisting volcanos that lie in the flexural moat and uplift of islands on the flanking bulge the progressive flexure model predicts a characteristic pattern of offlap and onlap in the regions flanking the hawaiian islands that is generally similar to stratigraphic relationships observed along previously published seismic profiles of the moat a progressive flexure model may also apply to the case of a continental plate moving over a mantle hotspot and could explain the observations of 1 a clinoform pattern of stratigraphy in some flood basalt provinces and 2 a seaward dipping reflector sequence at some passive continental margins

petrography and geochemistry of fault controlled hydrothermal dolomites in the riopar area prebetic zone se spain abstract the present paper reports the first detailed petrographical and geochemical studies of hydrothermal dolomites related to mvt zn fe pb deposits in the riopar area mesozoic prebetic basin se spain constraining the nature origin and evolution of dolomitizing and ore forming fluids mapping and stratigraphic studies revealed two stratabound dolostone geobodies connected by other patchy bodies which replace carbonate units of upper jurassic to lower cretaceous ages these dolostones are associated to the w e trending san jorge fault indicating a main tectonic control for fluid flow seven different dolomite types were identified i matrix replacive planar s red i ii matrix replacive planar e red ii iii planar e sucrosic cement sud iv non planar grey saddle dolomite cement sad i pre dating zn fe pb sulfides v non planar milky to pinkish saddle dolomite cement sad ii post dating zn fe pb ores vi ore replacive planar e porphyrotopic pod and vii planar s cloudy cement ced meteoric calcite types were also recognized the different dolomite types are isotopically characterized by i depleted 18 o from 25 1 to 27 6 v smow and 13 c from 2 3 to 0 9 v pdb values compared to upper jurassic to lower cretaceous limestone signature 18 o 27 6 to 30 9 v smow 13 c 0 5 to 3 2 v pdb and ii 87 sr 86 sr ratios for the main dolomitization phases red and sud 0 70736 0 70773 close to the jurassic and cretaceous carbonate values 0 70723 0 70731 whereas more radiogenic values 0 70741 0 70830 for saddle dolomites sad related to the zn fe pb sulfide mineralization prevailed after fluid interaction with rb bearing minerals microthermometrical studies on two phase liquid and vapor fluid inclusion populations in planar and non planar dolomites and sphalerite show homogenization temperatures between 150 and 250 c these data indicate that both planar and non planar dolomite textures formed at high temperatures under hydrothermal conditions in deep burial diagenetic environments the main dolomitizing phase red i red ii and sad i shows low to moderate fluid inclusions salinity 5 14 wt eq nacl whereas the dolomitization related to ore precipitation sphalerite and sad ii spreads to higher salinity values 5 25 wt eq nacl these data may respond to a mixing between a low salinity fluid fluid a less than 5 wt eq nacl and a more saline brine fluid b more than 25 wt eq nacl at different fluid proportions

possible forced folding in the taurus zagros belt of northern iraq the folds in the taurus zagros belt of northern iraq have generally been considered to be decollement buckle folds this implies the presence of a decollement horizon at or near the base of the sedimentary cover the infra cambrian hormuz salt and a passive role of the precambrian basement in the tectonic evolution of the folded belt structural stratigraphic geophysical and remote sensing evidence suggests that forced folding due to faulting in the basement has played a significant role in the development of many of the folds in this region this is clear from the substantial evidence of basement faulting the lack of any convincing evidence for the presence of an extensive and regional decollement horizon i e the hormuz salt between the basement and the cover rocks and the geometries of the folds and related mesostructures the study shows that in the taurus foothills zone the folds are short oval in plan shape and arranged in an en echelon pattern along two sets of dislocation zones in the basement however the folds in the zagros foothills zone are longer linear and arcuate in plan shape many of the studied folds show similar features to those observed in the rocky mountains u s a

comparison of carbonate reservoir fractures from core and modern electrical borehole images abstract several methods exist for collecting data about opening mode fractures hereinafter fractures in subsurface reservoir rocks the datasets with the exception of core data are indirect and subject to limited resolutions this paper includes new results on the detection of fractures in carbonate reservoirs by modern electrical borehole imagers barren fractures and calcite filled fractures calcite veins were described and compared from whole core and borehole images these datasets were obtained from directional drilling into the arab petroleum reservoirs in a low relief dome structure in eastern arabia the comparison of fracture abundance resulted in a significant mismatch because many reservoir fractures in the core could not be detected from corresponding borehole images most calcite veins were undetected because of their small widths below 2 mm exceptions include a few calcite veins of 0 5 mm that were detected because of the strong contrast between resistive veins and conductive host rock beds the barren fractures that are aligned sub parallel to the maximum horizontal principal stress shmax were detected more abundantly than other non aligned barren fractures the present day shmax is roughly trending between 60 and 100 azimuth in eastern arabia the aligned fractures have larger apertures in the borehole images than the non aligned fractures the apertures diminish in size as the fractures gradually deviate in orientation from the shmax most of the non aligned barren fractures were undetected except the fractures with rough and mismatching walls this indicates that the walls of the non aligned fractures are mechanically closed by the normal shmax and that the remaining apertures were dependent on the availability of roughness mismatches between the closed fracture walls electrical borehole images are biased in measuring fracture abundance but indispensable to detect and measure the orientations and apertures of fractures especially the large i e more conductive fractures in reservoir rocks

postshield stage transitional volcanism on mahukona volcano hawaii age spectra from 40ar 39ar incremental heating experiments yield ages of 298 25 ka and 310 31 ka for transitional composition lavas from two cones on submarine mahukona volcano hawaii these ages are younger than the inferred end of the tholeiitic shield stage and indicate that the volcano had entered the postshield alkalic stage before going extinct previously reported elevated helium isotopic ratios of lavas from one of these cones were incorrectly interpreted to indicate eruption during a preshield alkalic stage consequently high helium isotopic ratios are a poor indicator of eruptive stage as they occur in preshield shield and postshield stage lavas loihi seamount and kilauea are the only known hawaiian volcanoes where the volume of preshield alkalic stage lavas can be estimated

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

ages rare earth element enrichment and petrogenesis of tholeiitic and alkalic basalts from kahoolawe island hawaii kahoolawe island hawaii 18 11 km is a basaltic shield volcano with caldera filling lavas seven identified postshield vents and at least two occurrences of apparent rejuvenated stage eruptive we examined 42 samples that represent all stages of kahoolawe volcano stratigraphy for their petrography whole rock major and trace element contents mineral compositions and k ar ages the two oldest shield samples have an average age of 1 34 0 08 ma and four postshield samples 3 are alkalic average 1 15 0 03 ma ages of 1 08 and 0 99 ma for two additional tholeiitic samples probably are minimum ages whole rock major and trace element and mineral compositions of kahoolawe shield and caldera fill laves are generally similar to the lavas forming kilauea and mauna loa tholeiitic shields but in detail kahoolawe shield lavas have distinctive compositions an unusual aspect of many postshield ka hoolawe lavas is anomalously high ree and y abundances up to 200 ppm la and 175 ppm y and negative ce anomalies these enrichments reflect surficial processes where weathering and soil development promoted ree y transport at the weathering front major element abundances mgo 10 6 wt for shield and caldera fill basalts are consistent with fractionation of ol px pl in frequently replenished magma reservoirs in general tholeiitic basalts erupted from late vents are higher in sio2 than the shield lavas and temporal differences in parental magma compositions are the likely explanation alkalic basalts that erupted from vents are comparable in composition to those at other hawaiian volcanoes trace element abundance ratios indicate that alkalic basalts represent either relatively lower degrees of melting of the shield source or a distinct source apparent rejuvenated stage basalts i e emplaced after substantial kahoolawe erosion are tholeiitic unlike the rejuvenated stages at other hawaiian volcanoes alkalic kahoolawe like several other hawaiian volcanoes has intercalated tholeiitic and alkalic basalts in the postshield stage but it is the only volcano that appears to have produced tholeiitic rejuvenated stage lavas

a new technology for the characterization of microfractured reservoirs test case unayzah reservoir wudayhi field saudi arabia this article presents a test case of a new technology using artificially enhanced anisotropy of magnetic susceptibility referred to here as eams for the characterization of microfractured reservoirs these are reservoirs in which microfractures are essential to porosity and or permeability a conventional geological characterization is costly time consuming and difficult to quantify in terms of assessing fracture impact on porosity and permeability therefore an efficient and effective method is required to characterize these microfractures and to determine their contribution to porosity and permeability the eams technology which we developed and tested allows rapid analysis that bridges reservoir geology and engineering using petrography the margin of error to detect microfractures that impact porosity and or permeability is 43 however it requires three times the sampling rate of the new eams technology the lower part of the unayzah reservoir unayzah b c in the wudayhi field saudi arabia where fractures were studied and microfractures are known to impact reservoir performance is used to develop and verify the eams technology the results show that eams derived microfracture fabric strikes east northeast west southwest consistent with that obtained by geological means the effective porosity profile obtained from eams tests is similar to that of the conventionally acquired porosity open microfractures in tested samples increase mean values of reservoir effective porosity by 36 50 in unayzah b c the occurrence of connected microfractures is estimated to cause an increase in average permeability of 75 in unayzah b c this is in agreement with the fact that wells in microfractured unayzah b c have 4 5 14 times the productivity of wells as nonfractured sections of this reservoir a maximum permeability trend of northeast southwest permeability anisotropy is detected the implementation of the eams technology in other fields with microfractured reservoirs will directly impact operational and simulation effort

hawaiian submarine manganese iron oxide crusts a dating tool black manganese iron oxide crusts form on most exposed rock on the ocean floor such crusts are well developed on the steep lava slopes of the hawaiian ridge and have been sampled during dredging and submersible dives the crusts also occur on fragments detached from bedrock by mass wasting on submerged coral reefs and on poorly lithified sedimentary rocks the thickness of the crusts was measured on samples collected since 1965 on the hawaiian ridge from 140 dive or dredge localities fifty nine 42 of the sites were collected in 2001 by remotely operated vehicles rovs the thinner crusts on many samples apparently result from post depositional breakage landsliding and intermittent burial of outcrops by sediment the maximum crust thickness was selected from each dredge or dive site to best represent crusts on the original rock surface at that site the measurements show an irregular progressive thickening of the crusts toward the northwest i e progressive thickening toward the older volcanic features with increasing distance from the hawaiian hotspot comparison of the maximum crust thickness with radiometric ages of related subaerial features supports previous studies that indicate a crust growth rate of about 2 5 mm m y the thickness information not only allows a comparison of the relative exposure ages of two or more features offshore from different volcanoes but also provides specific age estimates of volcanic and landslide deposits the data indicate that some of the landslide blocks within the south kona landslide are the oldest exposed rock on mauna loa kilauea or loihi volcanoes crusts on the floors of submarine canyons off kohala and east molokai volcanoes indicate that these canyons are no longer serving as channelways for down slope sediment laden currents mahukona volcano was approximately synchronous with hilo ridge both being younger than hana ridge the nuuanu landslide is considerably older than the wailau landslide the waianae landslide southwest of oahu has yielded samples with the greatest manganese iron oxide crusts 9 5 mm thick and therefore apparently represents the oldest submarine material yet found in the study area the submarine volcanic field 100 km southwest of oahu is apparently younger than the waianae landslide

geology and petrology of mahukona volcano hawaii the submarine mahukona volcano west of the island of hawaii is located on the loa loci line between kahoolawe and hualalai volcanoes the west rift zone ridge of the volcano extends across a drowned coral reef at about 1150 m and a major slope break at about 1340 m both of which represent former shoreines the summit of the volcano apparently reached to about 250 m above sea level now at 1100 m depth did was surmounted by a roughly circular caldera a econd rift zone probably extended toward the east or sutheast but is completely covered by younger lavas from the adjacent subaerial volcanoes samples were vecovered from nine dredges and four submersible lives using subsidence rates and the compositions of flows which drape the dated shoreline terraces we infer that the voluminous phase of tholeiitic shield growth ended about 470 ka but tholeiitic eruptions continued until at least 435 ka basalt transitional between tholeiitic and alkalic basalt erupted at the end of tholeiitic volcanism but no postshield alkalic stage volcanism occurred the summit of the volcano apparently subcided below sea level between 435 and 365 ka the tholeiitic lavas recovered are compositionally diverse

intershield geochemical differences among hawaiian volcanoes implications for source compositions melting process and magma ascent paths as hawaiian volcanoes develop their lavas systematically change in composition and isotopic ratios of sr nd and pb these trends provide important constraints for understanding plume related volcanism as a volcano migrates away from the hotspot there are also geochemical differences between hawaiian shields in particular lavas from adjacent shields such as kilauea and mauna loa on hawaii and koolau and waianae on oahu have significant differences in abundances of some major and incompatible elements and isotopic ratios of sr nd and pb some incompatible element abundance ratios such as zr nb and sr nb are correlated with intershield differences in sr and nd isotope ratios but these isotopic ratios are not correlated with intershield differences in major element composition or even parent daughter abundance ratios such as rb sr and sm nd moreover at kilauea and mauna loa the intershield differences have apparently persisted for a relatively long time perhaps 100 ka these intershield geochemical differences provide important constraints on plume volcanism specifically i each volcano must have distinct magma ascent paths from the region of melt segregation ii the 25 50 km distance between adjacent but geochemically distinct shields requires that the sources vary on a similar scale and that the melt production region is similarly restricted the absence of correlations between lava compositions and radiogenic isotope ratios provides evidence for significant differences in melting process such as each shield forming by a different mean extent of melting with melt segregation at different mean pressures two types of models are consistent with the intershield geochemical differences i a relatively large radius ca 40 km plume conduit with a systematic spatial distribution of geochemical heterogeneities or ii a small radius less than 20 km plume conduit composed of geochemically distinct diapirs because relatively small radius diapirs of limited vertical extent are too small to create the large hawaiian shields a possible alternative is a continuous conduit containing solitary waves which transport geochemically distinct packets of material

fracture detection in oil based drilling mud using a combination of borehole image and sonic logs abstract the deeply buried 5 5 7 1 km lower cretaceous bashijiqike sandstones are important fractured reservoirs in the kuqa depression in these high temperature high pressure drilling environments oil based muds are used to limit drilling risks and improve efficiency making facture detection using resistivity based image logs difficult the maximum horizontal stress sh max trends close to north south 0 10 based on orientations of the drilling induced fractures and borehole breakouts core descriptions thin sections and image logs used to describe the fractures in the bashijiqike sandstone reservoirs show that opening mode natural fractures are common and the fractures range from fully open to sealed by calcite and clay minerals the open fractures are dominantly steeply dipping or vertical and primarily strike north south locally horizontal fractures or fractures with low angle dip are detected we compare fracture visibility on image logs acquired in the same ks 2 2 12 key well in oil based mud and water based mud fmi hd logs successfully detect large 0 1 mm aperture vertical fractures in oil based mud better than obmi image logs and the two imaging tools have a similar ability in detecting the high dip angle fractures since the ubi tool is not affected by oil based muds most of the fractures can be picked out on ubi images minor negative deviations of bulk density could be observed in fractured zones and the presence of fractures obviously causes an increase in sonic transit time full waveforms from dsi tools combined with electrical image logs detect fractured zones both the velocity and amplitude of the sonic waves are sensitive to fractures and the fractured zones could be identified according to the attenuation of stoneley waves the combination of cores image logs and full wave sonic logs offers comprehensive detection of fractures in oil based mud environments

new k ar ages of shield lavas from waianae volcano oahu hawaiian archipelago abstract a geochronological study utilized the unspiked potassium argon k ar technique to obtain ages from the two main volcanic members of the shield stage of the waianae volcano hi these new dates are further constrained using a combination of stratigraphic relationships magnetostratigraphy and major element geochemistry exposed shield lavas encompass 0 85 ma with reliably dated tholeiitic lavas from the main shield ranging from 3 93 0 08 to 3 54 0 04 ma and a later shield stage ranging in age from 3 57 0 04 to 3 08 0 04 ma these data suggest that the total extent of waianae shield activity was significantly more than 1 ma the age of faulting in two flank zones is constrained to be about 3 4 ma preliminary estimates of lava accumulation rates vary from about 0 3 to 2 0 mm a calculated rates show no systematic variation with location in the volcano or with time

impact of stylolitization on fluid flow and diagenesis in foreland basins evidence from an upper jurassic carbonate gas reservoir abu dhabi united arab emirates

koolau dike complex oahu intensity and origin of a sheeted dike complex high in a hawaiian volcanic edifice the dike complex in the eroded koolau tholeiitic shield volcano is unique among described dike swarms for its coherence high dike injection intensity relatively uniform and non gaussian 50 to 65 intensity level and lack of dike divergence parts are like a sheeted dike complex though high in an intraplate volcanic edifice a model is proposed in which highly mobile tholeiitic magma having considerable freedom to move through the strongly disjointed volcano seeks zones in which it is gravitationally most stable these zones are marginal parts of the dike complex separating lavas having a lower than magmatic bulk density from a 50 dike complex having a higher than magmatic bulk density this model also explains the strong propensity for the magma of kilauea volcano to remain underground in a gravitationally stable zone magma erupts only when it vesiculates sufficiently often when it has degassed some of it promptly plunges back toward the stable zone again

fluid rock interactions associated with regional tectonics and basin evolution an integrated approach consisting of fracture analysis petrography carbon oxygen and strontium isotope analyses as well as fluid inclusion micro thermometry led to a better understanding of the evolution of fluid rock interactions and diagenesis of the upper permian to upper triassic carbonates of the united arab emirates the deposited carbonates were first marked by extensive early dolomitization during progressive burial the carbonates were affected by dolomite recrystallization as well as precipitation of vug and fracture filling dolomite quartz and calcite cements after considerable burial during the middle cretaceous sub vertical north south oriented fractures f1 were cemented by dolomite derived from mesosaline to hypersaline fluids upon the late cretaceous maximum burial and ophiolite obduction sub vertical east west fractures f2 were cemented by dolomite dc2 and saddle dolomite ds derived from hot highly saline fluids then minor quartz cement has precipitated in fractures from hydrothermal brines fluid inclusion analyses of the various diagenetic phases imply the involvement of increasingly hot 200 degrees c saline brines 20 to 23 nacl eq through one dimensional burial history numerical modelling the maximum temperatures reached by the studied rocks are estimated to be in the range of 160 to 200 degrees c tectonically driven flux of hot fluids and associated diagenetic products are interpreted to have initiated during the late cretaceous maximum burial and lasted until the oligocene miocene compressional tectonics and related uplift the circulation of such hydrothermal brines led to partial dissolution of dolomites dc2 and ds and to precipitation of hydrothermal calcite c1 in new mainly oriented north south f3 and pre existing reactivated fractures the integration of the obtained data confirms that the diagenetic evolution was controlled primarily by the interplay of the burial thermal evolution of the basin and the regional tectonic history hence this contribution highlights the impacts of regional tectonics and basin history on diagenetic processes which may subsequently affect reservoir properties

fracture density in the deep subsurface techniques with application to point arguello oil field because monterey formation reservoirs rely on fractures joints for permeability quantitative information on fracture spacing is important to exploration strategies and for understanding reservoir behavior density of joints in cores of four wells from the point arguello reservoir has been determined with a new probability based method and these subsurface joint densities are compared with joint densities measured at nearby outcrops my measure of joint density is the fracture spacing index which is the slope of the trend of layer thickness to joint spacing a single set of extension joints that strike parallel to bedding dip predominates at outcrops likewise the cores contain a single set of extension joints perpendicular to the anticline axis and parallel to present day maximum horizontal compressive stress in core and at outcrop the only lithologic control on joint density is between nonjointed mudstone and harder more brittle jointed rocks within each well the fracture spacing index is the same for all hard rocks though it varies between wells in the reservoir joint density relates to structural position the most densely jointed strata fracture spacing index 0 45 are from the hinge of a minor anticline where its plunge steepens a less steeply plunging anticlinal nose has lower joint density fracture spacing index 0 30 the lowest joint density fracture spacing index 0 095 and 0 12 is in cores from gently dipping areas at outcrops in various structural settings the fracture spacing index is the same approximately 1 29 in chert dolostone and porcelanite and siliceous shale these rocks may be saturated with joints so that differences in brittle strain due to local structural variations have been overwhelmed as joints continued to form during unroofing of these strata chert looks more fractured than other lithologies because of thin bedding fracture spacing index is used to compute such parameters as fracture porosity and volume of fractures that directly contact the well bore these parameters may be important when trying to model the behavior of a petroleum reservoir or when trying to assess the feasibility of strongly deviating wells to improve the performance of a fracture reservoir

intrusive dike complexes cumulate cores and the extrusive growth of hawaiian volcanoes 1 the hawaiian islands are the most geologically studied hot spot islands in the world yet surprisingly the only large scale compilation of marine and land gravity data is more than 45 years old early surveys served as reconnaissance studies only and detailed analyses of the crustal density structure have been limited here we present a new chain wide gravity compilation that incorporates historical island surveys recently published work on the islands of hawai i kaua i and ni ihau and 122 000 km of newly compiled marine gravity data positive residual gravity anomalies reflect dense intrusive bodies allowing us to locate current and former volcanic centers major rift zones and a previously suggested volcano on ka ena ridge by inverting the residual gravity data we generate a 3 d view of the dense intrusive complexes and olivine rich cumulate cores within individual volcanoes and rift zones we find that the h na and ka ena ridges are underlain by particularly high density intrusive material 2 85 g cm3 not observed beneath other hawaiian rift zones contrary to previous estimates volcanoes along the chain are shown to be composed of a small proportion of intrusive material 30 by volume implying that the islands are predominately built extrusively

geochemical constraints on the role of oceanic lithosphere in intra volcano heterogeneity at west maui hawaii 87 sr 86 sr 206 pb 204 pb variation in the stratigraphically lowest lavas is orthogonal to the all hawaii variation indicating that it is not the result of mixing between components normally sampled by hawaiian shield stage magmas we compare our west maui data with observed compositions of pacific oceanic basaltic and gabbroic crust and predicted compositions for 2ga basaltic and gabbroic oceanic crust the observed fine scale compositional variability in the stratigraphically lowest west maui lavas is consistent with 10 15 mixing of small degree 2 partial melts of the pacific gabbroic oceanic crust with plume derived kea type magmas mass balance considerations indicate that this geochemical signal can be present in no more than 5 of the total volume of lavas erupted at west maui

posterosional volcanism in the cretaceous part of the hawaiian hotspot trail multibeam bathymetry and seismic reflection profiling shows the cretaceous products of the hawaiian hotspot to be a ridge of coalesced guyots that prolong the n nw trend of the more isolated paleocene emperor seamounts a 10 000 km2 plateau detroit plateau where the trail changes strike to nw and the obruchev rise hotspot ridge which extends to the kamchatka trench the northernmost guyots were submerged and tilted southeast by the load of new shield volcanoes added to the end of the chain then secondary volcanism built small cones on their summit platforms and in a gap between two guyots dredged rock samples and the distribution of the cones indicates that on one guyot these submarine eruptions were in the alkalic postshield stage of hawaiian volcanism and at another were probably in the alkalic rejuvenated stage seamount building eruptions at detroit plateau produced lavas nepheline melilitites that belong geochemically to the alkalic rejuvenated stage and are very similar to pleistocene lavas in the hawaiian islands however these eruptions postdated passage off the hotspot plume by a much longer time than the 0 5 2 5 m y observed in the hawaiian islands and were probably initiated by different tectonic processes

models of hawaiian volcano growth and plume structure implications of results from the hawaii scientific drilling project the shapes of typical hawaiian volcanoes are simply parameterized and a relationship is derived for the dependence of lava accumulation rates on volcano volume and volumetric growth rate the dependence of lava accumulation rate on time is derived by estimating the eruption rate of a volcano as it traverses the hawaiian plume with the eruption rate determined from a specified radial dependence of magma generation in the plume and assuming that a volcano captures melt from a circular area centered on the volcano summit the timescale of volcano growth is t 2 r plate where r is the radius of the melting zone of the circular plume and plate is the velocity of the pacific plate the growth progress of a volcano can be described by a dimensionless time t t plate 2r where t 0 is chosen to be the start of volcano growth and t 1 approximates the end of shield growth using a melt generation rate for the whole plume of 0 2 km 3 yr a plume diameter of 50 km and a plate velocity of 10 cm yr we calculate that the lifetime of a typical volcano is 1000 kyr for a volcano that traverses the axis of the plume the standard dimensions are a volume of 57 000 km 3 a summit thickness of 18 km a summit elevation of 3 6 km and a basal radius of 60 km the volcano first breaches the sea surface at t 0 22 when it has attained only 5 of its eventual volume 80 of the volume accumulates between t 0 3 and t 0 7 typical lava accumulation rates start out over 50 m kyr in the earliest stages of growth from the seafloor and level out at 35 m kyr from t 0 05 until t 0 4 from t 0 4 to t 0 9 the submarine lava accumulation rates decrease almost linearly from 35 m kyr to 0 subaerial accumulation rates are about 30 lower the lava accumulation rate is a good indicator of volcano age a volcano that passes over the plume at a distance 0 4r off to the side of the plume axis is predicted to have a volume of about 60 of the standard volcano a lifetime about 8 shorter and lava accumulation rates about 15 20 smaller the depth age data for mauna kea lavas cored by the hawaii scientific drilling project are a good fit to the model parameters used given that mauna kea appears to have crossed the plume about 15 20 km off axis the lifetime of mauna kea is estimated to be 920 kyr mauna loa is predicted to be at a stage corresponding to t 0 8 kilauea is at t 0 6 and loihi is at t 0 16 the model also allows the subsurface structure of the volcanoes the interfaces between lavas from different volcanoes to be modeled radial geochemical structure in the plume may be blurred in the lavas because the volcanoes capture magma from a sizeable cross sectional area of the plume this inference is qualitatively born out by available isotopic data the model predicts that new hawaiian volcanoes are typically initiated on the seafloor near the base of the next older volcano but generally off the older volcano s flank

dikes and the petrology of waianae volcano oahu we summarize the distribution orientation and composition of the dikes of waianae volcano and attempt to relate this summary to the evolution of the volcano dikes are located in the caldera in a well defined northwest rift zone and in less well defined south and northeast rift zones the active axis of the south rift zone may have shifted with time the dikes generally are parallel to their rift zones and are oriented in many directions in the caldera area they commonly dip about 70 to 80 and are generally less than a meter thick most are virtually identical in texture mineralogy and composition to nearby extrusive rocks a few have unusual low magnesium silicic compositions not yet observed in flows these may be classified as icelandites trends defined by the compositions of tholeiitic dikes are similar to but extend further than crystal fractionation trends of tholeiitic flows of waianae and other hawaiian volcanoes the basalts can be divided into a more silica saturated strongly tholeiitic subgroup and a less saturated mildly tholeiitic subgroup the icelandites lie on trend with the second group most of the analyzed rift zone dikes are strongly tholeiitic most of the analyzed caldera dikes are mildly tholeiitic all of the differentiated high silica low magnesium dikes found are inside the caldera near the eruptive center

utilization of observations of well bore failure to constrain the orientation and magnitude of crustal stresses application to continental deep sea drilling project and ocean drilling program boreholes

hawaiian xenolith populations magma supply rates and development of magma chambers hawaiian volcanoes pass through a sequence of four eruptive stages characterized by distinct lava types magma supply rates and xenolith populations magma supply rates are low in the earliest and two latest alkalic stages and high in the tholeiitic second stage magma storage reservoirs develop at shallow and intermediate depths as the magma supply rate increases during the earliest stage magma in these reservoirs solidifies as the supply rate declines during the alkalic third stage these magma storage reservoirs function as hydraulic filters and remove dense xenoliths that the ascending magma has entrained during the earliest and latest stages no magma storage zone exists and mantle xenoliths of lherzolite are carried to the surface in primitive alkalic lava during the tholeiitic second stage magma storage reservoirs develop and persist both at the base of the ocean crust and 3 7 km below the caldera only xenoliths of shallow origin are carried to the surface by differentiated lava during the alkalic third stage magma in the shallow subcaldera reservoir solidifies and crustal xenoliths including oceanic crustal rocks are carried to the surface in lava that fractionates in an intermediate depth reservoir worldwide xenolith populations in tholeiitic and alkalic lava may reflect the presence or absence of subvolcanic magma storage reservoirs

south arch volcanic field newly identified young lava flows on the sea floor south of the hawaiian ridge several young lava fields were imaged by gloria sidescan sonar along the hawaiian arch south of hawaii the largest 35 by 50 km across includes a central area characterized by high sonar backscatter and composed of several flow lobes radiating from a vent area reflection profiling and sea floor photography indicate that the central lobes are flat sheet flowsbounded by pillowed margins thin surface sediment and thin palagonite rinds on lava surfaces suggest ages of 1 10 ka vents are localized along the arch crest near bases of cretaceous seamounts two dredged flows are basanite and alkalic basalt broadly similar to rejuvenated stage and some pre shield alkalic lavas on the hawaiian ridge arch volcanism representsperipheral leakage of melt from the hawaiian hot spot over much larger areas than previously recognized

prodigious submarine landslides on the hawaiian ridge the extensive area covered by major submarine mass wasting deposits on or near the hawaiian ridge has been delimited by systematic mapping of the hawaiian exclusive economic zone using the side looking sonar system gloria these surveys show that slumps and debris avalanche deposits are exposed over about 100 000 km2 of the ridge and adjacent seafloor from kauai to hawaii covering an area more than 5 times the land area of the islands some of the individual debris avalanches are more than 200 km long and about 5000 km3 in volume ranking them among the largest on earth the slope failures that produce these deposits begin early in the history of individual volcanoes when they are small submarine seamounts culminate near the end of subaerial shield building and apparently continue long after dormancy consequently landslide debris is an important element in the internal structure of the volcanoes the dynamic behavior of the volcanoes can be modulated by slope failure and the structural features of the landslides are related to elements of the volcanoes including rift zones and fault systems the landslides are of two general types slumps and debris avalanches the slumps are slow moving wide up to 110 km and thick about 10 km with transverse blocky ridges and steep toes the debris avalanches are fast moving long up to 230 km compared to width and thinner 0 05 2 km they commonly have a well defined amphitheater at their head and hummocky terrain in the lower part oceanic disturbance caused by rapid emplacement of debris avalanches may have produced high level wave deposits such as the 365 m elevation hulopoe gravel on lanai that are found on several islands most present day submarine canyons were originally carved subaerially in the upper parts of debris avalanches subaerial canyon cutting was apparently promoted by the recently steepened and stripped slopes of the landslide amphitheaters

drift pumice at christmas island and hawaii evidence of oceanic dispersal patterns the use of pumice as a geological tracer for oceanic dispersal patterns was evaluated by comparing the elemental signatures of drift pumice collected from christmas island and hawaii in relation to prevailing oceanic currents and pumice source areas both sites lie in the middle of the pacific ocean far from sources of volcanic pumice hawaii lies in the persistent westward flowing north equatorial current christmas island in contrast is influenced by the highly variable westward flowing south equatorial current and the eastward flowing equatorial counter current pumice is very abundant at christmas island in the beach drift pumice from christmas island is derived from the western pacific ocean krakatau southwestern pacific ocean tonga trench east pacific ocean mexico south atlantic ridge and an unknown source in contrast pumice is rare in hawaii pumice from hawaii originates primarily from the south sandwich islands mexico isla san benedicto and krakatau the currents that control dispersal of pumice also control dispersal of larvae and rafted organisms christmas island has a higher coral diversity 31 genera 81 species than hawaii 17 genera 50 species hawaii receives only small amounts of pumice drift from a limited area to the east and has a more restricted coral diversity while christmas receives massive amounts of pumice and presumably larvae and rafted organisms from the area of high coral diversity to the west

fracture and in situ stress patterns and impact on performance in the khuff structural prospects eastern offshore saudi arabia abstract we characterized natural fractures and in situ stresses for exploration and prospect evaluation in nine periclinal structural traps in the eastern province of saudi arabia where several major gas discoveries were made in the deeply buried permian triassic khuff formation borehole image logs oriented cores seismic gravity magnetic data and dynamic observations were used in the study two fracture systems were identified a younger major system which enhances reservoir permeability and an older minor fully mineralized system the older system consists of subordinate northerly striking extensional mesofractures including joints and faults which are fully mineralized by anhydrite and calcite this mineralization occurred during an early diagenetic phase this system acted as paleo fluid conduits facilitating the occlusion of matrix porosity and deteriorating the reservoir quality in the immediate vicinity of the fractures the younger system is regionally dominant and includes mesofractures with persistent strike ranging from ne sw to ese wnw irrespective of local structure these younger fractures are nearly parallel to the present day maximum horizontal in situ stress and perpendicular to the minimum horizontal in situ stress which are dominated by the zagros plate tectonics the development of this system commenced during the convergence of the arabian and eurasian plates late cretaceous to cenozoic and culminated during the continental collision the fractures are predominantly extension joints and hybrid extensional shear fractures and were facilitated by increases in pore pressure due to the oil placement and the subsequent cracking of this oil into gas hydrocarbon migration into the khuff reservoirs was crucial in slowing down diagenesis and preserving both fracture apertures and matrix porosity therefore most of the fractures in this system tend to be partly mineralized mainly by carbonates and or coated with hydrocarbons these fractures show channel type apertures that enhance permeability and productivity of the khuff by up to two fold the channel apertures can endure operational changes in reservoir pressure with little or no reduction of their permeability critically stressed open fractures have no major role geomechanical analyses show that they are estimated to occur under the upper limits of differential stresses within the margin of error of stress estimates the static and dynamic observations show the permeability and productivity enhancement follows mechanical layering patterns production and pressure profiles in individual wells indicate lack of vertical communication seal breach across the different reservoir units similar pre production pressure and hydrocarbons across the khuff reservoir units is the result of normalization over geological time hydrocarbon migration across the anhydrite seals happened via episodic paleoseismic pumping along faults with no sufficient vertical offset to permanently breach the reservoir seals

ka ena volcano a precursor volcano of the island of o ahu hawai i ka ena and wai alu ridges form prominent submarine ridges nw of the island of o ahu hawai i we evaluate whether or not either one of these ridges represents a submarine extension of wai anae volcano on o ahu using new bottom observations geophysical surveys and geochemical data acquired on new samples from the region wai alu ridge has the morphology of a submarine rift zone but is too shallow for its distance from the o ahu shoreline ka ena ridge also is unusually shallow and is surmounted by two topographic shields ka ena and wai alu ridges have similar magmatic and volcanic evolutionary histories beginning ca 5 ma with a submarine shield phase of volcanism that produced high sio 2 low feo tholeiites with higher 208 pb 204 pb than in the adjacent wai anae volcano late shield volcanism included transitional and alkalic rock types with lower sio 2 and enrichment in incompatible elements especially p 2 o 5 nb zr ti and light rare earth elements the transition from shield to late shield stage occurred as the edifice was beginning to emerge from the sea geological observations and k ar ages indicate that ka ena emerged above sea level ca 3 5 ma reaching a maximum height of 4000 m above the abyssal ocean floor and 1000 m above sea level relatively weak gravity anomalies topographic lineaments and the orientation of dike complexes indicate a volcanic structure that is independent of wai anae volcano thus volcanic structure geochemistry and age all indicate a precursor volcano to the island of o ahu which we call ka ena volcano after emergence ka ena volcano tilted 2 to the south we estimate a total volume of 20 27 10 3 km 3 for ka ena volcano taking into account overlapping geometry of concurrently active volcanoes sample compositions from the ka ena landslide deposit are entirely consistent with derivation from ka ena whereas most samples from the wai anae slump are likely derived from wai anae volcano uniformly oriented dikes in the wai anae nw rift zone likely reflect buttressing by a preexisting ka ena volcano unusual isotopic compositions of some wai anae samples including unique hydrous silicic lavas probably reflect interaction with underlying ka ena crust a newly recognized lava flow field on the southern flank of ka ena ridge extends the previously known distribution of secondary volcanism in the kaua i channel putative submarine volcanic activity in the region in 1956 cannot have built a large edifice and is unlikely to have produced pumice that was found on o ahu shores this eruptive activity therefore remains unconfirmed