oil and gas developments in western canada in 1989 there were 5513 wells drilled in western canada during 1989 30 fewer than in 1988 total meterage drilled was 6 459 797 m for an average well depth of 1172 m exploratory drilling in 1989 dropped by 13 and development drilling by 40 from 1988 levels british columbia was the only area in western canada with increased activity the industry continued to acquire more acreage for less total bonus at provincial crown sales throughout western canada during 1989 3 564 827 ha were acquired for a total bonus of 484 872 000 footnote 5 although the total disposition of crown lands decreased only 4 the average bonus dropped to 136 ha down 26 from 1988 in alberta the most active exploration areas were the southern and eastern mesozoic gas play the western deep devonian gas play the oil plays on and adjacent to the peace river arch and the middle devonian carbonate oil plays in the northwest in british columbia the most active exploration areas were the mesozoic and paleozoic gas plays in the northeastern portion of the province for the first time in 5 years crown drilling rights were issued within the fraser valley in the southwest there was a focus on gas exploration in the province as pipeline reversal was implemented permitting access to canadian and california markets through the alberta transportation network in manitoba exploration and development activity continued to decline in northern canada exploratory drilling success offering of crown lands for exploration approval of gas exports and indications that many of the native lands claims may be approaching settlement all provided exploration encouragement for the next decade exploration activities occurred throughout the northwest territories from the offshore beaufort to the southern border in saskatchewan active exploration areas were shallow mesozoic gas plays in the western portions of the province and deep paleozoic oil plays in the south

elastic finite difference modeling of the 1971 san fernando california earthquake finite difference seismograms calculated for the 1971 san fernando earthquake show strong effects due to lateral variation in sediment thickness in the san fernando valley and the los angeles basin using basin structure derived mostly from well logs and teleseismically determined source parameters two dimensional sh and p sv finite difference calculations reproduce the amplitude and duration of the strong motion velocities recorded across the los angeles and san fernando basins for the period range of 2 to 10 sec the edges of basins nearest the seismic source show ground motion amplification up to a factor of 3 over the case without the basin and tend to convert direct shear waves into love and rayleigh waves that travel within the basins

modeling of wave propagation in northern los angeles basin abstract the los angeles basin is characterized by deep structural complexity and is the site of numerous earthquakes we analyze the amplitude and waveform data of earthquakes recorded in the los angeles basin in order to identify the structurally controlled path effects this has been done in order to determine which features of the structure affect the observations and to generate improved models in different parts of the basin increasing our capabilities of predicting seismic hazard several structural models of the l a basin that are based on regional subsurface studies exposed sections scattered oil wells and other limited geophysical data have recently become available in this study we have used seismic modeling techniques together with geologic models to attempt to explain site variations in some important data bases we have modeled waveforms of 1 the 19 january 1989 malibu earthquake data recorded in pasadena 2 an m 2 8 earthquake recorded by the usc downhole array in the baldwin hills southern california and 3 two aftershocks of the whittier narrows earthquake recorded at five stations along a profile the modeling of the malibu earthquake results in a layered one dimensional model representing 6 5 km of layered sediment underlain by a high velocity basement direct arrivals basin reflected phases and multiple reverberations are modeled fairly well by this one dimensional model the downhole array data in the baldwin hills show a significant near surface amplification that can be modeled by very low velocity near surface materials a series of aftershocks of the whittier narrows earthquake recorded at close distances at temporary recording sites shows a wide variation in peak accelerations due both to radiation pattern and propagation effects the effect of lateral heterogeneity is evident in the travel time where stations within the basin show later arrival times than those away from the basin for the same epicentral distance seismograms recorded at different sites show variation in waveforms due to multi pathing of rays we use such triplicated arrivals to constrain the structure of different interfaces using these criteria and the synthetic seismograms calculated by ray theory and finite difference methods we have been able to model the tangential seismograms due to two of these events recorded at five stations along a two dimensional profile all three modeling exercises helped us understand wave propagation in the basin environment a basin reflected phase was identified in the seismogram from the malibu earthquake which was used to derive an effective depth of the basement near surface amplification of the waves observed in the downhole data could be explained by constructive interference of the multiply reflected waves through the thin near surface low velocity layer similarly site dependent variation of waveform and travel time shown by the seismograms from the aftershocks of the whittier narrows california earthquake could be accounted for when a laterally varying structure was used

volume based curvature computations illuminate fracture orientations early to mid paleozoic central basin platform west texas volumetric curvature analysis is a simple but computationally intensive procedure that provides insight into fracture orientation and regional stresses until recently curvature analysis has been limited to computation along horizon surfaces that may be affected by unintentional bias and picking errors introduced during the interpretation process volumetric curvature is best estimated in a two step process in the first step we use a moving analysis subvolume to estimate volumetric reflector dip and azimuth for the best fit tangent plane for each sample in the full volume in the second step we calculate curvature from adjacent measures of dip and azimuth we use larger curvature analysis windows to estimate longer wavelength curvatures such a technique allows us to output full 3d volumes of curvature values for one or more scales of analysis we apply these techniques to a data set from the central basin platform of west texas and find lineaments not observable with other seismic attributes these lineaments indicate that in the lower paleozoic interval a left lateral shear couple oriented due east west controls the local stress regime such a model predicts that extension faulting and fractures will be oriented northeast southwest the example demonstrates the potential of this new technology to determine stress regimes and predict azimuths of open fractures

source complexity of the october 1 1987 whittier narrows earthquake long and short period body waveform data recorded at regional and teleseismic distances are modeled to obtain the source parameters of the whittier narrows earthquake of october 1 1987 although the long period data can be satisfied by a simple thrust earthquake on a plane striking 280 at a depth of 14 km we require a double source solution to satisfy both the long and short period teleseismic data the first subevent has a focal mechanism of strike 250 dip 30 n and a slip vector 90 the second is 280 40 n and 98 the second event occurred 1 0 s after the first was 5 times larger 1 2 1025 dyn cm for the second 0 23 1025 for the first in terms of seismic moment and was also shallower 12 km whereas the first subevent was at 15 km the two subevents probably occurred on a north dipping listric fault but may have occurred on two subparallel faults these features were determined by studying a variety of phases including teleseismic p and sh and regional pnl the whittier narrows earthquake was a high stress drop event but a single value for stress drop cannot be obtained because of the complex nature of the source if we define the fault area as the aftershock area we obtain a stress drop of about 750 bars

eliassen palm fluxes of the 2 day wave abstract high resolution doppler imager hrdi winds and temperatures are used to diagnose a 2 day wave event detected in the southern hemisphere during january 1994 a novel aspect of this study is the focus upon the wave fluxes throughout the 65 100 km range and their relationship to the background state a wave packet composed of zonal wavenumbers 2 3 and 4 propagates westward with a phase speed near 60 m s 1 the periods associated with zonal wavenumbers 2 3 and 4 are 3 5 2 1 and 1 7 days respectively the morphology of the 2 day temperature and wind fields is consistent with that of a developing baroclinic wave the divergence of the eliassen palm flux of zonal wavenumbers 2 4 is dominated by the vertical convergence of meridional heat flux the wave driving or eliassen palm flux divergence per unit mass is predominantly westward with magnitudes on the order of 5 m s 1 day 1 a steady state quasigeostrophic model of the mean meridionai circulation is used to estimate the mean wind respon

aquathermal pressuring and geopressure evaluation geologic notes evaluation of the aquathermal mechanism proposed by barker indicates that this process cannot produce geopressures in clays or sediments with even negligible permeabilities it is suggested that because the amount of fluid expansion is very small with temperature increase typical hydraulic conductivities of clay rocks can accommodate the removal of this excess fluid in the time span available thus it would appear that expansion of waters cannot contribute to the geopressure generating process lithologies of effectively zero permeabilities however may provide adequate sealing of contained pore fluids so that pressures increase with increasing temperature the subsequent rupturing of the matrix as pore pressures reach overburden pressures particularly rapidly at shallow depths produces fractures which may later provide routes for hydrocarbon migration as a pressure transition zone cannot exist due to the necessary isolation of pore fluids current geopressure evaluation techniques are limited in their application such that only flowline temperature interpretation may indicate subsequent penetration of an aquathermally generated geopressure if a transition zone does exist above a geopressured interval then some process other than aquathermal pressuring must have been instrumental

smectite dehydration its relation to structural development and hydrocarbon accumulation in northern gulf of mexico basin a comparison of clay diagenesis data obtained from a study of tertiary shales from the brazos colorado river system of texas the mississippi river system of louisiana and the niger river system of nigeria illustrates significant differences in temperature intervals over which smectite diagenesis occurs the threshold temperature required to initiate diagenesis ranges from about 160 f 71 c in mississippi river sediments to more than 300 f 150 c in the niger delta water expelled from smectite into the pore system of the host shale during the process of diagenesis may migrate out of the shale early or may be totally or partially trapped and released slowly through time in either situation the water can act as a vehicle for hydrocarbon migration p ovided hydrocarbons are present in a form and in sufficient quantities to be transported observations from the northern gulf of mexico basin indicate a close relation between buildup of high fluid pressure and the smectite illite transformation process abnormal pressures exert partial control on the type and quantity of hydrocarbons accumulated because pressure potential determines the direction of fluid flow and overpressuring partly controls the geometry of growth faults and related folds in basins where shale structures are the dominant type formed the depths to which growth faults can penetrate and the angle of dip that these faults assume at depth are largely dependent on fluid pressure in the sedimentary section at the time of faulting dips of some faults in texas have been observed to change abruptly within the interval of smectite diagenesis and some faults formed in the overpressured miocene and younger sections become beddingplane types at depths where the temperature is near that required for thermal generation of petroleum although these faults may be important for fluid redistribution in shallow sandstone shale sections they are a minor factor in moving hydrocarbons out of shale below the faults in much of the texas offshore area fluid movement upward through microfracture systems in the deeply buried overpressured section overlying and extending upward from fault trends in the sub tertiary section is proposed as a mechanism for flushing hydrocarbons from the deeper portion of the northern gulf of mexico basin this flushing process would be enhanced by smectite diagenesis because water derived from smectite that was trapped during basin subsidence would cause the flushing process to continue for longer periods of time and to extend to greater depths than could be attained if only remnants of original pore water were present shale tectonism is also the primary mechanism for structural development in the tertiary section of the niger delta however seismic data indicate that the rate of dip change of seaward dipping listric growth faults is commonly less than that observed in texas where dips as low as 10 15 can occur at depths as shallow as 10 000 15 000 ft 3 048 4 572 m syndepositional faults in nigeria are formed in sandstone shale sections where the clay composition of shale is primarily kaolinite and where little water of smectite diagenesis has been added to the pore system of the host sedimentary section subtle differences in structural styles in the tertiary sections of texas and nigeria are probably the result of differences in clay composition of the shaly sections being deformed

thirtyone formation permian basin texas structural and lithologic heterogeneity in a lower devonian chert reservoir chert and carbonate reservoirs of the early devonian thirtyone formation comprise a major regional reservoir in the permian basin with more than 700 mbbl production to date and roughly an equal amount of potentially producible reserves remaining most major pools in the thirtyone formation were discovered several decades ago and are now in relatively advanced stages of enhanced recovery with significant variation apparent in response to waterflooding among different fields as shown by comparison between dollarhide and three bar fields reservoirs display significant heterogeneity due to structure and to depositional diagenetic factors affecting porosity development most studies of these fields to date have tended to emphasize depositional and diagenetic factors as the reason for observed variation in enhanced recovery performance however structural factors may be of nearly equal importance enhanced recovery at dollarhide field for example has been extremely successful with waterflood recoveries more than double those under primary production and a tertiary co2 flood expected to do nearly as well this extraordinary level of success is understood as a result of a combination of reservoir character and compartmentalization with the latter especially related to division of the field into several fault block portions mapping of these fault blocks and their related structures has been greatly advanced by a recent 3 d three dimensional seismic survey ultimate recovery at dollarhide is projected at 62 of original oil in place in comparison production history at three bar field shows a lower level of overall recovery yet a very similar increase between primary and secondary production reservoir heterogeneity related to depositional diagenetic factors appears more pronounced at three bar field than at dollarhide field but faulting is also significant with respect to division of the field into separate blocks with distinct productive histories a 3 d seismic survey may provide important discriminating data useful for a future co2 flood or other tertiary recovery project at three bar field

geochemistry of formation waters from the wolfcamp and cline shales insights into brine origin reservoir connectivity and fluid flow in the permian basin usa abstract despite being one of the most important oil producing provinces in the united states information on basinal hydrogeology and fluid flow in the permian basin of texas and new mexico is lacking the source and geochemistry of brines from the basin were investigated ordovician to guadalupian age reservoirs by combining previously published data from conventional reservoirs with geochemical results for 39 new produced water samples with a focus on those from shales salinity of the ca cl type brines in the basin generally increases with depth reaching a maximum in devonian median 154 g l reservoirs followed by decreases in salinity in the silurian median 77 g l and ordovician median 70 g l reservoirs isotopic data for b o h and sr and ion chemistry indicate three major types of water lower salinity fluids 100 g l isotopically heavy o and h water in leonardian permian to pennsylvanian reservoirs 2 3 2 km depth is evaporated late permian seawater water from the permian wolfcamp and pennsylvanian cline shales which are isotopically similar but lower in salinity and enriched in alkalis appear to have developed their composition due to post illitization diffusion into the shales samples from the cline shale are further enriched with nh 4 br i and isotopically light b sourced from the breakdown of marine kerogen in the unit lower salinity waters 3 km depth which plot near the modern local meteoric water line are distinct from the water in overlying reservoirs we propose that these deep meteoric waters are part of a newly identified hydrogeologic unit the deep basin meteoric aquifer system chemical isotopic and pressure data suggest that despite over pressuring in the wolfcamp shale there is little potential for vertical fluid migration to the surface environment via natural conduits

simulation of strong ground motions recorded during the 1985 michoacan mexico and valparaiso chile earthquakes abstract the purpose of this study is to develop and test a procedure for simulating acceleration time histories of large subduction earthquakes the ground motions of the large event are obtained by summing contributions from fault elements to simulate the propagation of rupture over the fault surface the radiation from the fault elements is represented by empirical source functions derived from near source strong motion recordings of m w 7 aftershocks and gross aspects of wave propagation are modeled by calculated green9s functions the procedure has been tested against the recorded strong ground motions of the m w 8 0 michoacan mexico and valparaiso chile earthquakes of 1985 we find that models of heterogeneous slip in these events derived by other investigators from the analysis of teleseismic and near source velocity seismograms also explain the shorter period motions of the recorded accelerograms the response spectra of the simulated motions generally have little or no significant bias in the period range of 0 05 to 2 sec for both earthquakes also the peak accelerations durations and envelope shapes of the time histories are in good agreement with the recorded motions the uncertainty associated with the modeling procedure estimated from the misfit between recorded and simulated response spectra shows a dependence on period and site conditions this uncertainty estimate includes the uncertainty involved in using empirical source functions derived from one subduction zone to simulate strong ground motions in another subduction zone the procedure is applied in a companion paper cohee et al 1991 to estimate strong ground motion characteristics in the pacific northwest region of the united states from hypothesized m w 8 subduction earthquakes on the cascadia plate interface

foreland basement involved structures basement involved structures commonly occur as long irregular chains of uplifts in foreland basins these structures commonly contain significant hydrocarbon accumulations with most major fields located on the broad crests of these structures the search for complex traps in deeper targets and in subthrust structures requires an improved understanding of the geometry and evolution of these structures characteristic features of basement structures include deformation zones within the sedimentary cover that dissipate significant fault slip and gently dipping frontlimbs and backlimbs fault slip in the basement is usually accommodated in the cover by a triangular widening upward deformation zone on the forelimb with the nature of deformation controlled primarily by the mechanical stratigraphy if the cover contains interlayered competent and incompetent units the incompetent units are characterized by significant penetrative deformation whereas the competent units are faulted after a relatively small amount of penetrative deformation depending on the competency contrast between the basement and cover the nature of basement and the physical conditions of deformation the deformation zone may also propagate downward into the basement gently dipping backlimb and frontlimb panels are related to movement of the hanging wall over synclinal and anticlinal bends in the major fault respectively many basement faults are characterized by a number of synclinal fault bends within the basement which result in long and gently dipping backlimbs forelimb panels are related to anticlinal bends that typically occur at the basement cover interface as well as at one or more locations in the sedimentary cover case studies of well constrained examples of structures from the bighorn and uinta basins and the central basin platform demonstrate the development of these characteristic features and their strong dependence on the mechanical stratigraphy these models and case studies will be useful in interpreting foreland basement structures in areas with poor or limited data

reconciling physical properties with surface seismic data from a layered mafic intrusion abstract compositional layering of intrusive rocks is often cited as a source of seismic reflectivity in the crystalline crust direct evidence for this is based primarily on synthetic seismograms calculated from laboratory measurements of rock velocity and density or estimates of aggregate rock properties from measurements of mineral velocities and densities little is known about how in situ effects such as fracturing chemical alteration or anisotropy may change the reflectivity character of the surface seismic data an ideal dataset for examining the hazards of using physical properties data for estimating crustal reflectivity occurs at the nellie intrusion a middle proterozoic age layered mafic intrusion that lies beneath the permian basin of west texas due to a well that penetrated 4 5 km of the intrusion we have a dataset that spans the scale from compositional data on the intrusion derived from well cuttings to log data to surface reflection data sonic and density log data from the well measure velocities and densities 10 to 15 below the values calculated from modal mineralogy we attribute this difference primarily to pervasive post emplacement alteration and fracturing of the rock mass in situ thus this unique dataset provides a quantitative estimate of the magnitude of difference between observed and theoretical velocities that can be expected for crystalline rocks in the upper crust and its cause despite the difference analysis of synthetic seismograms shows that primary compositional variation of the intrusion is still responsible for sub horizontal layered reflectivity in both the log based and petrology based synthetic seismograms boundaries of intrusive cycles are characterized by large negative reflection coefficients due to the juxtaposition of mafic rich basal layers against plagioclase rich layer tops in detail only the log based synthetic provides a good match to the surface seismic reflection data this suggests that physical properties from modal mineralogy are useful in obtaining a generalized model for reflectivity but that differences in bulk physical properties of the rock mass preclude the possiblity of obtaining a one to one match with surface seismic data

polar mesosphere and lower thermosphere dynamics 1 mean wind and gravity wave climatologies 1 mean wind and gravity wave climatologies are presented for the polar mesosphere and lower thermosphere mlt the data were derived using mf radars at davis 69 s 78 e and syowa 69 s 40 e in the antarctic and poker flat 65 n 147 w and andenes 69 n 16 e in the arctic the dynamics of the antarctic mlt are found to be significantly different from the arctic mlt summer maxima in both the westward and equatorward winds occur closer to the solstice in the antarctic than in the arctic the greater symmetry around the solstice suggests radiative effects may play a greater role in controlling the state of the antarctic mlt than in the arctic where dynamical effects appear to be more important gravity wave observations also suggest that wave drag may be greater in the arctic than in the antarctic the equatorward flow near the mesopause persists later in summer in the arctic than in the antarctic as do observations of polar mesospheric clouds and polar mesospheric summer echoes all three phenomena begin at about the same time in each hemisphere but end later in the arctic than in the antarctic it is proposed that the magnitude of the meridional winds can be used as a proxy for gravity wave driving and the consequent adiabatic cooling in the mlt seasonal variations in gravity wave activity are predominately combinations of annual and semiannual components significant hemispheric differences are observed for both the timing and magnitude of these seasonal variations

geopressured shale and sealing effect of smectite to illite transition ten shale samples of frio and vicksburg tertiary overpressured shales from brazoria and hidalgo counties texas were examined by transmission electron microscopy tem techniques initially illite and smectite with some mixed layer component are present in subparallel domains with smectite packets dominating and providing abundant dislocations for ion transport supplying avenues that contribute to local permeability as the transition proceeds illite packets grow within a shrinking matrix of smectite dislocations decrease and pathways for ion transport are restricted we suggest this development of illite packets and diminished ion transport causes loss of local permeability and a rise in the fluid pressure gradient as illite packets coalesce local permeabil ty is increasingly lost hydraulic continuity with the surface is further restricted and a more efficient geopressure seal is formed in both hidalgo and brazoria counties the base of normal hydropressure 0 465 psi ft or 10 5 kpa m coincides with the depth of onset of the smectite to illite transition geopressure greater than 0 7 psi ft 15 8 kpa m occurs at depths corresponding to 50 illite packets in brazoria county and 70 in hidalgo county in both cases 0 7 psi ft 15 8 kpa m geopressure occurs prior to the depth at which the transition ceases these relationships suggest that if the smectite to illite transition begins and proceeds to completion the development of coalescing illite packets during diagenesis will lead to increasing geopressure with the actual values of illite proportion and corresponding fluid pressure gradient determined by the local geologic setting

structural evolution of shale diapirs from reactive rise to mud volcanism 3d seismic data from the baram delta offshore brunei darussalam two areas of shale diapirism in a deltaic setting were examined using 3d seismic data from offshore brunei to determine the origin evolution and geometry of shale diapirs the study areas cover parts of the egret and ampa fields within the baram delta province the ampa diapir consists of a small bulge of the mobile setap shale around which lies a zone of chaotically disrupted country rock reflections at the crest of this chaotic zone vertical cylindrical shale pipes arise that end in a wider head the diapir heads wear halos of high amplitude reflections probably due to the presence of methane gas the egret data show the same features except that the bulge of the source layer is not detected due to low reflectivity and chaotic reflections at the base of the overburden the bulging of the setap shale on the ampa data is interpreted as modified reactive diapirism in response to differential loading the initial reactive diapir shape was modified by lateral or oblique upward migration of fluidized shales into the hanging wall of the fault controlling the reactive diapir this probably occurred as a network of dykes and sills the presence of some preserved bedding is indicated by weak but coherent reflectivity from the area initially defined as chaotic shale the spreading of overpressure and the injection of shale into the overburden is thought to be a late phenomenon possibly late pliocene or early pleistocene and the mobility of the shale is attributed to overpressure increase due to gas generation within the setap shale and maybe the lower part of the overburden gas migration perhaps ahead of the diapir intrusion probably facilitated the mud injection the ampa and egret diapirs formed in two diapiric phases an early reactive diapirism and a later active diapirism but the phases have little in common they are seperated by about 9 million years of inactivity and differ in process and probably differ in degree of overpressure in overpressure generating mechanism and in properties of the diapiric mud

a conjugate study of mean winds and planetary waves employing enhanced meteor radars at rio grande argentina 53 8 s and juliusruh germany 54 6 n 1 two meteor radars with enhanced power and sensitivity and located at closely conjugate latitudes 54 6 n and 53 8 s are employed for interhemispheric comparisons of mean winds and planetary wave structures at periods of 8 to 20 days our study uses data from june 2008 through may 2010 during which both radars provided nearly continuous wind measurements from 80 to 100 km monthly mean winds at 53 8 s exhibit a stronger westward zonal jet in spring and early summer at lower altitudes and no westward winds at higher altitudes in contrast westward mean winds of 5 10 ms 1 at 54 6 n extend to above 96 km during late winter and early spring each year equatorward mean winds extend approximately from spring to fall equinox at both latitudes with amplitudes of 5 10 ms 1 meridional mean winds are more variable at both latitudes during fall and winter with both poleward and equatorward monthly means indicating longer period variability planetary waves seen in the 2 day mean data are episodic and variable at both sites exhibit dominant periodicities of 8 10 and 16 20 days and are more confined to late fall and winter at 54 6 n at both latitudes planetary waves in the two period bands coincide closely in time and exhibit similar horizontal velocity covariances that are positive negative at 54 6 n 53 8 s during peak planetary wave responses

contributions of compaction and aquathermal pressuring to geopressure and the influence of environmental conditions reply luo and vasseur 1992 presented a useful methodology of simplifying the complex equations that describe basin compaction and thereby directly assessing the contribution of aquathermal effects in the development of abnormal pressures their methodology leads to the conclusion that aquathermal pressuring plays only a small role in the development of overpressures in sedimentary basins although this conclusion follows from the cases studied it is possible to conclude otherwise using 1 a more general model of sediment compaction and 2 material properties that are more representative of conditions at depth the primary factor behind objection to the conclusion in luo and vasseur 1992 is that is fundamental equations which formed the basis for the simplifying methodology do not account fully for conditions in which a sediment s effective stresses are reduced we emphasize here that we do not claim that thermal effects are the dominant cause of overpressures rather our calculations suggest that they are not negligible in all cases there is a complex interplay of the various mechanisms that cause excess pore water pressures no one mechanism of overpressuring dominates all others for all situations because thermal effects not only cause higher excess pore pressures but also reduce effective stresses thermal effectsmore will be minimized by default in calculations that do not account for effective stress reduction the resulting reduced effective stresses also have important implications for geological questions such as acoustic velocities and fracture potential less

play analysis and leading edge oil reservoir development methods in the permian basin increased recovery through advanced technologies the permian basin of west texas and southeast new mexico remains an important oil producing province accounting for 17 of united states production 327 million bbl in 2002 with a resource base of such size increased understanding of reservoir geology and improved use of enhanced recovery practices in the basin can have a substantial impact on united states oil production thirty two oil plays covering both the texas and new mexico portions of the permian basin were defined on the basis of reservoir stratigraphy lithology depositional environment and structural and tectonic setting one thousand three hundred and thirty nine significant sized reservoirs cumulative production of 1 million bbl 1 59 105 m3 of oil through 2000 were assigned to a geologic play cumulative production from these reservoirs was 28 9 billion bbl 4 59 109 m3 or 95 of the basin s total examples of successful reservoir development practices are listed by play because methods demonstrated to work well in one reservoir should be applicable to other reservoirs in the play the permian basin is dominantly a carbonate province carbonate reservoirs account for 75 of total oil production clastics 14 mixed clastics and carbonates 8 and chert 3 the plays having the largest cumulative production are the northwest shelf san andres platform carbonate play 4 0 billion bbl 6 31 108 m3 the leonard restricted platform carbonate play 3 3 billion bbl 5 25 108 m3 the pennsylvanian and lower permian horseshoe atoll carbonate play 2 7 billion bbl 4 29 108 m3 and the san andres platform carbonate play 2 2 billion bbl 3 42 108 m3 the permian system dominates production accounting for 73 of cumulative production followed by the pennsylvanian 13 and the ordovician 6 the estimated remaining reserves from that component of the resource base that is already discovered and producing is 3 25 billion bbl 5 17 108 m3

influence of focal mechanism on peak accelerations of strong motions of the whittier narrows california earthquake and an aftershock focal mechanisms affect the pattern of the peak accelerations of the october 1 1987 whittier narrows earthquake and its october 4 aftershock the peak accelerations observed on 21 strong motion instrumentation program and 22 u s geological survey accelerograms correlate well with the ratio of shear wave amplitude computed from the thrust mechanism of the main shock and the strike slip mechanism of the aftershock this correlation means that seismic energy is radiated from the fault with close to the standard double couple radiation pattern at the frequencies 3 6 hz corresponding to the peak accelerations

geophysical and geochronological constraints on the extent and age of mafic intrusions in the basement of west texas and eastern new mexico a deep drill hole recently completed on the central basin platform of west texas provides a rare look at almost 5 km of basement rocks most of the crystalline rocks encountered were basic and ultrabasic in composition a variety of geophysical data is available from the bore hole and vicinity the petrographic and geophysical data suggest that a large layered basic intrusion was penetrated by the well geochronologic u pb data indicate an age of about 1 1 ga for this intrusion this date has significant tectonic implications because it indicates that commonly accepted analogies with the southern oklahoma aulacogen 550 ma rifting are not valid however it is interesting to note that this feature formed during another widespread period of rifting keweenawan

seismic characteristics and identification of negative flower structures positive flower structures and positive structural inversion negative and positive flower structures and positive inverted structures imply specific modes of formation and their distinctive characteristics make them important criteria for the identification of certain structural styles a negative flower structure from the andaman sea consists of a shallow synform bounded by upward spreading strands of a wrench fault that have mostly normal separations paralleling monoclines and oblique en echelon normal faults flank the divergent wrench fault a positive flower structure from the ardmore basin oklahoma consists of a shallow antiform displaced by the upward diverging strands of a wrench fault that have mostly reverse separations en echelon folds are present on either side of this convergent wrench fault flower structures may resemble extensional or contractional fault blocks on individual seismic profiles flower structures are identified by their unique internal fault and fold architecture by their association with a straight and throughgoing zone of deformation and by their lack of a consistent sense of separation or regional upthrown side positive structural inversion at the rambutan oil field south sumatra basin has formed a shallow anticlinorium and has partly uplifted the underlying graben deeper fault segments bounding the graben have retained their normal fault profiles but at shallow levels some of these faults have reverse separations similar changes of separation with depth may be produced by strike slip but sets of faults with listric profiles and nearby blocklike trend patterns identify the inversion as a dip slip event where correlation of reflections is uncertain or deep control is unobtainable positive inverted structures may also resemble contrational fault blocks detached normal fault assemblages and certain negative inverted structures

westward extension of the devils river uplift implications for the paleozoic evolution of the southern margin of north america the devils river uplift is inferred to continue westward into trans pecos texas both the known devils river uplift and the tascotal uplift are bounded on the north by east west fault zones chalk draw and carta valley fault zones separating them from late pennsylvanian clastic foredeep basins marfa and val verde basins the exposed much shortened marathon thrust belt may have been emplaced in the earliest permian by gravity gliding meager evidence suggests that the devils river block represents a cambrian or infracambrian rift and that the uplift is an aulacogen the early cambrian continental margin probably continued southwest into mexico but has been displaced by mesozoic left lateral movement

an angular unconformity in the permian section of east central california the final phase of permian continental margin tectonism in east central california produced a widespread unconformity that separates lower permian strata from upper permian to lower and middle triassic strata this unconformity has a maximum angular discordance of about 25 and locally truncates at least 1 km of lower permian strata leonardian and or early guadalupian deformation that resulted in development of this unconformity may have been coeval with early phases of the sonoma orogeny in nevada and with permian tectonism in the western mojave desert of california but the tectonic relations among these events are uncertain permian deformation in east central california took place along a southeast trending segment of the continental margin that may have been bounded by an active sinistral transform fault zone

the magnetic fabric of the wolfcamp shale midland basin west texas understanding petrofabric variability hydrocarbon associations and iron enrichment rock fabrics have long been recognized as a key variable influencing unconventional reservoir properties and yet petrofabric analysis is rarely incorporated in reservoir characterization in a quantitative and scalable manner this work introduces anisotropy of magnetic susceptibility ams coupled with handheld x ray fluorescence to define the origin of petrofabrics in the wolfcamp shale and examine their relationship with total organic carbon toc and oil saturation indices osi standard paleomagnetic plugs were drilled from three vertical cores spanning the entire wolfcamp shale in the midland basin west texas low temperature magnetic experiments suggest paramagnetic minerals contribute between 93 4 and 98 6 to the low field bulk magnetic susceptibility klf across all lithotypes scanning electron microscopy revealed frequent occurrences of paramagnetic minerals such as chlorite illite ferroan dolomite marcasite and pyrite the fe rich clays such as chlorite carry the ams signal in mudrocks with a minor contribution from ferroan dolomite conversely ferroan dolomite carries the ams signal in most carbonate facies with a minor influence from fe rich clays the degree of magnetic anisotropy pj and shape factor t in mudrocks are compositionally dependent and respond to changes in both clay and framework grain concentration for carbonate facies pj and t vary widely because of changes in depositional facies and the concentration of ferroan dolomite the toc correlates well with pj and strongly oblate magnetic fabrics this relationship likely stems from the adsorption of organic matter om to clays during deposition and may indicate that organoclay composites were responsible for delivering om to the midland basin elevated osi are fabric selective favoring low pj and t fabrics suggesting that such fabrics facilitate hydrocarbon migration more so than high pj and t fabrics fuzzy c means clustering provides a framework to describe ams and geochemical transitions at the core scale and could serve as a tool to map barriers and pathways to hydrocarbon migration finally ti nb and klf data point to a mafic provenance lithotype and suggest layered intrusive complexes in the central basin uplift were exposed and eroded during deposition of the wolfcamp shale mafic source rocks probably increased supply of micronutrients such as dissolved iron and may have enhanced productivity in the midland basin

modelling of near surface seismic structure beneath hawaii using reverberations summary the reverberation in near surface layers contains valuable information about the near surface velocity and density structure however previously the reverberation was often regarded as noise to be eliminated this paper presents an approach for modelling the shallow velocity structure with the reverberation in the near surface layers the method was applied to three component waveform data recorded by seismic arrays during a passive seismic experiment arrays for lithosphere observations in hawaii aloha the near surface multiple reflections were enhanced by stacking the seismograms of local upper mantle earthquakes with near vertical incidence angles by matching synthetics and observed p and s multiple reflections we have successfully modelled the impedance structure for the top 2 3km of the crust beneath seven stations of aloha arrays in southern hawaii reverberative site effects are similar for stations in an array but vary significantly from one array to another reflecting the lateral heterogeneity of the near surface structure two short profiles of near surface p wave velocity structure were constructed across the ainapo and south flank areas in southern hawaii based on interpretation of the multiple reflections recorded by two of the aloha arrays the profiles reveal the detailed and variable shallow structure near two active volcanoes kilauea and mauna loa and provide basic information about site effects for further investigations of seismic hazard assessment earthquake source properties and deeper structure

climatological effects of orography and land sea heating contrasts on the gravity wave driven circulation of the mesosphere abstract on the basis of permanent january simulations performed with an idealized general circulation model for the troposphere and middle atmosphere the sensibility of the general circulation to orographic and thermal forcing of large scale stationary waves is assessed gravity waves are parameterized following lindzen s saturation theory up to the stratopause present model results coincide with earlier estimates confirming that the boreal winter zonal mean climate does crucially depend on the combined action of orography and land sea heating contrasts since in turn the propagation and breakdown of internal gravity waves is strongly modulated by the background horizontal winds the mesospheric response to stationary wave forcing turns out be substantial as well it is found that in the climatological zonal mean a warmer polar night stratosphere is accompanied by lower temperatures in the mesosphere up to about 80 km the temperature signal induced by stationary wave forcing changes sign again in

facies variability within a mixed carbonate siliciclastic sea floor fan upper wolfcamp formation permian delaware basin new mexico sea floor fans containing both carbonate and siliciclastic detritus are rarely recognized in the rock record but are common within the permian upper wolfcamp formation in the delaware basin in southeast new mexico and west texas one such compositionally mixed fan has been studied in detail as part of an unconventional oil and gas exploration and development program in southeast new mexico three cores were collected through an approximately 100 m 350 ft thick interval that defines the structurally controlled fan cores collected represent the frontal to distal fringe off axis and lateral fringe parts of the fan unlike siliciclastic fans where axial facies are characterized more by turbidites the axis off axis and lateral fringe cores in the wolfcamp are dominated by carbonate debrites coarse carbonate deposition decreases toward the frontal fringe areas where core facies are composed of mixed carbonate siliciclastic mud rich hybrid event beds and background sedimentation the core through the lateral fringe differs from the off axis core in that the debrites in the lateral fringe are thinner and commonly rheologically stratified with finer grained debrites sitting directly on top of coarse grained debrites suggesting a genetic link in their formation the axial facies appear to be dominated by thick amalgamated debrites changes in carbonate content from axis to frontal fringe appear to be gradual but rapid from axis to lateral fringe over a 3 km 2 mi distance the carbonate rich part of the fan trends at least 55 km 34 mi in a northeast southwest direction and extends 18 km 11 mi northwest southeast across

a comparison of mean winds and gravity wave activity in the northern and southern polar mlt mean winds and waves observed in the mesosphere and lower thermosphere with mf radars located at davis 69os 78oe and poker flat 65on 147ow are compared measurements covering the pe riod from 1999 to mid 2000 show differences in the strength of the horizontal wind fields in the southern hemisphere the zonal and meridional winds reach their maximum values near the summer solstice but are de layed by 2 3 weeks in the northern hemisphere gravity wave variances also show significant differences as do the strength of vertical velocities

estimated ground motions in los angeles due to mw 7 earthquake on the elysian thrust fault abstract the elysian thrust fault has been identified as a blind thrust fault davis et al 1989 hauksson and jones 1989 representing a potentially serious seismic hazard to the metropolitan los angeles and its neighboring areas we have simulated time histories peak ground accelerations and their uncertainties using a semi empirical method for a m w 7 0 earthquake on the elysian thrust fault using a flat layered crustal structure the accelerograms from the 4 october 1987 whittier narrows aftershock 10h 50m m l 5 3 are used to represent the source functions of each subfault on the fault surface to account for the velocity variation in the surface sediments we compared simulated ground motions using two separate shearwave velocities 0 6 km sec and 0 9 km sec respectively in the top layer of the crustal model the use of such a simple crustal model is validated by modeling the accelerograms recorded during the 1 october 1987 whittier narrows mainshock m l 6 0 the duration and the relative frequency content observed on these accelerograms are successfully modeled at some stations the simulated peak accelerations agree well with the observed values however at some sites the simulated and observed values differ by a factor of 2 to 3 the variation is attributed to a laterally varying crustal structure that is significant for small earthquakes additional site specific study is needed for an improved prediction of the observed peak accelerations for large magnitude earthquakes the near source peak ground acceleration appears to be controlled by the source receiver geometry relative to the fault as well as the location of asperities on the fault surface this is validated by simulating the peak acceleration data of the 1989 loma prieta earthquake recorded within 30 km of the source for our simulations on the elysian thrust fault an additional component is added to the uncertainty by analyzing several asperity models finally an analytical representation is given to the simulated average peak horizontal ground accelerations y r which is expressed by ln y r 5 38 0 085 2 09 0 0268 ln r 8 0 0 343 in the range of 7 5 r 35 km r is the closest distance to the seismogenic rupture zone this functional form predicts a rapid fall off rate for the simulated ground motions compared with the fall off rate predicted by the other published empirical attenuation relations we use the finite difference method to investigate the effects of irregular structure on ground motions resulting from point sources on the elysian park fault the response computed at several depths beneath the basin suggests that the response is dominated by the initial direct arrivals for sources located interior to the basin when the receivers are located at one end of the basin and the seismic sources are located at the opposite edge the characteristic features on the seismograms are the long durations caused by the trapped energy within the basin the level of trapped energy decreases as the depth of the source increases thus the fault model becomes important in determining the level of peak ground motions and shaking duration

further evidence of hemispheric differences in the mlt mean wind climatology simultaneous mf radar observations at poker flat 65 n 147 w and davis 69 s 78 e 1 results of a comparative study of the wind fields in the mesosphere and lower thermosphere over poker flat 65 n 147 w and davis 69 s 78 e are presented the study utilized the mf radar wind data collected simultaneously during the period 1999 2000 mean winds during this period are examined to study the hemispheric features emphasis has been given to the climatological variations over these two high latitude stations the results suggest large hemispheric differences in the mean circulation further the observed mean wind characteristics are compared with results obtained from other high latitude stations

polar mesosphere summer echoes pmse at halley 76 s 27 w antarctica 1 polar mesosphere summer echoes pmse are a pointer to summer mesospheric conditions and have fuelled the debate over temperature differences between the antarctic and arctic mesopause regions however few pmse observations have ever been made in antarctica we present initial pmse observations from halley 76 s 27 w taken during january and february 2004 these are the first observations at such high southern latitude the first using a dynasonde for detection and the first at 28 mhz pmse are frequently observed and exhibit a double maximum in diurnal occurrence in contrast to published observations at similar arctic latitudes the pmse season ends slightly earlier relative to summer solstice than in the arctic the strength of the pmse appear similar to pmse observed in the northern hemisphere this is consistent with published falling sphere measurements showing similar summer mesopause temperatures in january in the antarctic as in july in the arctic

using petrophysics and cross section balancing to interpret complex structure in a limited quality 3 d seismic image a study was done to characterize deep prolific ellenburger gas reservoirs at lockridge waha west waha and worsham bayer fields in pecos ward and reeves counties in west texas a major effort of the study was to interpret a 176 mi2 3 d seismic data volume that spanned these fields well control defined the depth of the ellenburger the principal interpretation target to be 17 000 21 000 ft 5200 6400 m over the image area ellenburger reflection signals were weak because of these great target depths additionally the top of the ellenburger had a gentle ramp like increase in acoustic impedance that did not produce a robust reflection event a further negative influence on seismic data quality was the fact that a large portion of the 3 d seismic area was covered by a variable surface layer of low velocity tertiary fill that was in turn underlain by a varying thickness of high velocity salt anhydrite these complicated near surface conditions attenuated seismic reflection signals and made static c

delaware mountain group west texas a case of refound opportunity part 2 cherry canyon formation recent drilling activity in the war wink area of west texas has established a new play in submarine channel and levee overbank sandstones of the middle and lower cherry canyon formation delaware mountain group guadalupian previous exploration and development spanning the 1960s 1970s and early 1980s had focused on the upper part of the formation the new play located a few miles west of the central basin platform suggests the existence of multiple channel trends not yet explored in the delaware basin entrapment in the war wink area is related to both structural and stratigraphic factors lower cherry canyon reservoirs have porosities ranging from 18 to 24 and permeabilities ranging from 10 to 60 md and thus are higher in quality than reservoirs of the underlying brushy canyon formation core data indicate that permeabilities increase rapidly above a threshold porosity value of about 18 lower cherry canyon wells are completed by fracture stimulation in one or two main reservoir zones with several secondary zones commonly behind pipe wells usually flow at rates of 100 200 bbl oil per day for up to 1 yr before being put on pump main producing zones are capable of recoveries ranging from 50 000 to 120 000 bbl attempts at using horizontal drilling in place of fracture stimulation have proved highly successful in certain cases use of this approach for cherry canyon development guided by good geologic control may provide an excellent technique applicable to many portions of the delaware basin

a review of producing fields inferred to have upslope stratigraphically trapped turbidite reservoirs trapping styles pure and combined pinch out formation and depositional setting siliciclastic turbidite systems that pinch out updip toward their proximal margin are prime targets for hydrocarbon exploration especially in deep water basins such upslope stratigraphic traps potentially offer large volume discoveries but have significant geological risks notably because of ineffective closure or containment in the published literature at least 20 fields from 11 basins globally with 6 7 billion boe of cumulative discovered reserves have been inferred to be reliant on upslope pinchout traps these fields are reviewed in terms of their interpreted trapping styles pinch out formation process and depositional tectonic setting reservoirs display a range of upslope trapping styles including pure depositional and erosional stratigraphic pinch outs and combined stratigraphic structural traps in one third of cases faulting appears intimately linked to updip trapping either through offsetting slope feeder conduits or assisting pinch out development and in some cases faulting may be the most important updip trapping element sediment bypass and erosion in proximal areas is the most common inferred pinch out formation mechanism some reservoirs also demonstrate the ability of erosional truncation by mud prone channels and mass transport deposits to form viable stratigraphic traps and seals encouragingly for exploration robust pinchout traps occur in various tectonic settings on a variety of different slope types and positions along the slope profile most large volume discoveries to date however are restricted to the toe of slope environment in graded passive margins or out of grade rift and transform margin settings insights into the nature and occurrence of upslope stratigraphic traps are important for future exploration especially for evaluating new license areas and risking prospects

permian bone spring formation sandstone play in the delaware basin part i slope new exploration in the permian leonardian bone spring formation has indicated regional potential in several sandstone sections across portions of the northern delaware basin significant production has been established in the first second and third bone spring sandstones as well as in a new reservoir interval the avalon sandstone above the first bone spring sandstone these sandstones were deposited as submarine fan systems within the northern delaware basin during periods of lowered sea level the bone spring as a whole consists of alternating carbonate and siliciclastic intervals representing the downdip equivalents to thick abo yeso wichita clear fork carbonate buildups along the leonardian shelf margin hydrocarbon exploration in the bone spring has traditionally focused on debris flow carbonate deposits restricted to the paleoslope submarine fan systems in contrast extend a considerable distance basinward of these deposits and have been recently proven productive as much as 40 48 km south of the carbonate trend

heat flow in the utah wyoming thrust belt from analysis of bottom hole temperature data measured in oil and gas wells bottom hole temperature bht data from oil and gas wells represent a large albeit low quality data base for heat flow determinations a method for analyzing bht data sets that directly addresses the problem of noise in the data is presented and illustrated by application to 303 bhts from the anschutz ranch ar cave creek cc and anschutz ranch east are oil gas fields in the utah wyoming thrust belt located in the middle rocky mountain physiographic province of the western united states correction of raw bht data by means of a horner plot yields 81 corrected bhts an additional 90 bhts not suitable for a horner correction are corrected by means of a new bht correction which may be applied to any single bht for which a depth and time of measurement are known the average geothermal gradient at both ar cc and are is found to be 23 c km although an average gradient analysis fails to explain scatter in the data analysis of corrected bhts through inversion of a layered earth model yields estimates of formation thermal gradients and temperature fields at ar cc and are that are stable and unique with an average precision of 2 to 3 c thermal conductivity measurements were made on 360 drill cutting samples representing 14 thrust belt formations in situ conductivity is estimated using porosity from calibrated well logs heat flow is estimated by comparing temperature calculated by a two dimensional finite element model with temperature estimated from analysis of bht data analysis of bht data from the ar cc area yields an estimated regional heat flow of 60 mw m2 8 mw m2 a similar analysis at are results in an estimate of 58 mw m2 8 mw m2 these estimates are close to values determined for the wyoming basin and the central colorado plateau and imply that a thermal transition from the middle rocky mountains to elevated heat flow characteristic of the basin and range province 80 to 90 mw m2 must take place within 50 km

pressures and hydrogeology in petroleum basins abstract in most deep sedimentary basins in the world there is a layered arrangement of at least two superimposed hydrogeological systems the shallowest hydrogeological system can extend to great depths however in many basins it extends from the surface down to only about 10 000 ft greatest historical depth of burial the shallow hydrogeological systems generally are basin wide in extent and exhibit normal pressures the pore water apparently is free to migrate approximately in accordance with the theory of fluid migration proposed by munn 1909 and quantified by hubbert 1940 and 1953 the deeper hydrogeological systems usually are not basin wide in extent and exhibit abnormal pressures they generally consist of a layer of individual fluid compartments which are sealed off from each other and from the overlying system in some basins mainly in the onshore u s there is an even deeper near normally pressured noncompartmented section the compartmented layer in those basins generally is in the sequence of rocks which were deposited during the period of most rapid deposition the underlying noncompartmented layer where present usually is in prebasin shelf deposits and basement rock the uppermost noncompartmented layer usually is in rocks which were deposited during the last 10 000 ft in basin filling correlations of petroleum in reservoirs with the rocks from which the petroleum was generated has imposed a system of mainly upwards paths for the first several thousand feet of migration of petroleum from source rocks largely within the compartmented layer to pools generally in the shallow hydrogeological system the migration paths of petroleum and water may not be coincident

hydrocarbon generation as a mechanism for overpressuring in rocky mountain region overpressured reservoirs are present in the deeper parts of most basins in the rocky mountain region a variety of conditions can cause overpressuring however most high pressures in the region are caused by present day or recently active oil and gas generation or generation in the last few million years in low permeability rock successions that still contain organic matter capable of yielding thermally generated hydrocarbons rocks with above normal pressure range from devonian to tertiary and commonly are associated with low permeability tight reservoirs most of the overpressuring occurs in cretaceous and tertiary rocks overpressuring in rocks older than cretaceous is rare and where present only occurs in strata with very rich hydrocarbon source beds such as the d vonian mississippian bakken formation most organically lean pre cretaceous source beds are no longer capable of yielding enough hydrocarbons to maintain abnormal pressure nearly all overpressured reservoirs and source rocks have temperatures of approximately 200 f 93 c or higher in addition available data indicate that hydrocarbon related overpressuring does not generally occur if vitrinite reflectance ro values are less than 0 6 in oil prone strata or less than 0 7 in gas prone strata overpressured gas bearing strata generally have ro values of 0 8 or higher maximum reservoir pressures are about equal to the fracture gradient pressure in the reservoir rocks some vertical fractures in reservoir rocks are probably caused by rapid expulsion of hydrocarbons from the source beds high pressures in the rocky mountain region means that the rock succession is gas or oil saturated and discrete hydrocarbon water contacts are generally not present classical concepts of hydrodynamics do not appear to be applicable to these overpressured successions the optimum depths for exploration are generally the upper 1 000 2 000 ft 305 610 m of the overpressured succession

conceptual model for origin of abnormally pressured gas accumulations in low permeability reservoirs the largest gas fields in the rocky mountain region occur in abnormally pressured reservoirs these gas accumulations are different from more conventional gas accumulations in that they are commonly located in basin center positions they occur downdip from water bearing rocks and they are in overpressured or underpressured low permeability reservoirs we suggest that overpressured and underpressured gas accumulations of this type have a common origin in basins containing overpressured gas accumulations rates of thermogenic gas accumulation exceed gas loss causing fluid gas pressure to rise above the regional hydrostatic pressure within the overpressured gas generation zone free water in the larger pores is forced out of the gas generation zone into overlying and updip normally pressured water bearing rocks the remaining tightly bound water at irreducible saturation levels cannot remove dissolution products precluding significant permeability and porosity enhancement thus while other diagenetic processes continue a pore network with very low permeability develops as a result gas accumulates in these low permeability reservoirs at rates higher than it is lost in basins containing underpressured gas accumulations rates of gas generation and accumulation are less than gas loss these basins have typically experienced significant uplift and erosion and or temporal variations of paleotemperature despite these modifications the basin center gas accumulation persists but because of changes in the basin dynamics the overpressured accumulation evolves into an underpressured system

laramide basement deformation in an evolving stress field bighorn mountain front five springs area wyoming discussion new road cuts of u s route 14a along the western flank of the bighorn mountains of wyoming create nearly continuous outcrops through the edge of a laramide uplift exposed granitic basement in the range front area is divided into three large differentially rotated blocks separated by shattered poorly exposed zones within each of these rotated blocks are three populations of faults 1 an early set of dominantly strike slip faults at high angles to the front with either polish or smearing of hematite epidote and or chlorite 2 a slightly younger set of faults with mostly similar motion and mineralization but no smear or polish and 3 a young set composed mostly of thrust faults marked by gouge and pervasive shattering stress tensor analysis on these three fault populations shows that maximum compressive stress sigma 1 acted n25e s25w normal to the local range front but changed plunge with time in the early buckling stages sigma 1 plunged at about 30 degrees in both directions away from the future buckle subsequently sigma 1 assumed a relatively uniform 30 degrees plunge into the range presumably as a result of reduced resistance to buckling finally under extremely brittle conditions associated with regional uplift and erosion sigma 1 assumed a relatively flat plunge through the rotating blocks the exposures support models of basement folding by subhorizontally driven tectonic forces creating an early buckle zone that expanded into a small number of rotated blocks with subsequent bea bag like minor reshaping of the rotating blocks by many small faults

distribution and generation of the overpressure system eastern delaware basin western texas and southern new mexico three subsurface pressure systems have been identified in the delaware basin an upper normal pressure system a middle overpressure system and a lower normal pressure system the overpressure system occurs in the eastern delaware basin covering six texas and new mexico counties the depth of the overpressure system ranges from 3100 to 5400 m the normal fluid pressure gradient is 0 0103 mpa m in the eastern delaware basin the highest overpressure gradient however approaches 0 02 mpa m which is close to the lithostatic gradient of 0 0231 mpa m the overpressure system has a relatively flat top and a downwarped bottom the maximum thickness of the overpressure system reaches about 2300 m at the depocenter and pinches out toward the edges an area of excess pressure o curs within the system where the highest excess pressure reaches 60 mpa local underpressured areas due to production are found in the lower normal pressure system in the war wink field area overpressure in the eastern delaware basin is mainly associated with mississippian pennsylvanian and permian wolfcampian shale sequences which also are major source rocks in the basin initial sedimentation rates within the overpressure system range from 17 to 90 m m y corrected bottom hole temperature measurements indicate that the geothermal gradient within the overpressure zone is 25 1 c km which is higher than the basin s average geothermal gradient of 21 c km temperatures at the top and bottom of the overpressure system are about 80 and 115 c respectively this temperature range approximates the temperature of the average clay dehydration zone the oil window in the war wink field is coincident with the overpressure system which implies that hydrocarbon g neration and migration are active in the overpressure system a two stage overpressure model is proposed hydrocarbon maturation combined with mechanical compaction disequilibrium and clay dehydration are the initial causes for overpressure generation due to an abnormal increase of fluid volume and pore space subsequently the increase in temperature due to a decrease of thermal conductivity and fluid migration within the preexisting overpressure system would reinforce further overpressuring due to the fluid thermal expansion

paleohydrology of the delaware basin western texas overpressure development hydrocarbon migration and ore genesis this study integrates quantitative modeling techniques with field observations to establish a paleohydrologic framework of the delaware basin western texas the reconstructed paleohydrologic models allow for a better understanding of the development and maintenance of anomalous overpressures hydro carbon generation and migration and ore genesis in the basin results of numerical modeling show that disequilibrium compaction and oil generation might generate excess fluid pressures during the late permian in response to the rapid deposition of evaporite beds the preservation of this overpressure to the present however requires the presence of an extremely low permeability 10 11 d top seal most shaly sediments with permeability ranging from 10 4 to 10 8 d thus may be too permeable by several orders of magnitude to preserve overpressure for more than 250 m y the predicted present day gas window is located within the overpressure zone suggesting that the volume increase associated with the oil to gas conversion may be attributed to present overpressures the native sulfur deposits likely formed in a fluid mixing zone resulting from the laramide uplift of the western basin during the tertiary in our model meteoric water recharged along the basin s uplifted western margin and discharged basinward hydrocarbons migrated landward by pressure gradients and buoyancy and discharged upward along faults in the western basin where they mixed with meteoric water many oil and mineral reservoirs may have formed in the fluid mixing zone where extensive chemical reactions take place in the culberson sulfur ore district for example fluids including hydrocarbons and meteoric water migrated upward through faults from underlying carrier beds into the permian salado limestone there the mixture of fluid drives biochemical reactions that precipitate native sulfur

the 1987 whittier narrows earthquake sequence in los angeles southern california seismological and tectonic analysis the october 1 1987 whittier narrows earthquake m l 5 9 was located at 34 2 96 n 118 4 86 w at a depth of 14 6 0 5 km in the northeastern los angeles basin the focal mechanism of the mainshock derived from first motion polarities shows pure thrust motion on west striking nodal planes with dips of 25 5 and 65 5 respectively the aftershocks define an approximately circular surface that dips gently to the north centered at the hypocenter of the mainshock with a diameter of 4 6 km hence the spatial distribution of the mainshock and aftershocks as well as the focal mechanisms of the mainshock indicate that the causative fault was a 25 north dipping thrust fault striking west and is confined to depths from 10 to 16 km although most of the 59 aftershock focal mechanisms presented here document a complex sequence of faulting they are consistent with deformation of the hanging wall caused by the thrust faulting observed in the mainshock a cluster of reverse faulting events on north striking planes occurred within hours after the mainshock 2 km to the west of the mainshock the largest aftershock m l 5 3 occurred on october 4 and showed mostly right lateral faulting on the same north northwest striking plane within the hanging wall similarly several left lateral focal mechanisms are observed near the eastern edge of the mainshock rupture the earthquake and calibration blast arrival time data were inverted to obtain two refined crustal velocity models and a set of station delays when relocating the blast using the new models and delays the absolute hypocentral location bias is less than 0 5 km the mainshock was followed by nearly 500 locatable aftershocks which is a small number of aftershocks for this magnitude mainshock the decay rate of aftershock occurrences with time was fast while the b value was low 0 67 0 05 for a los angeles basin sequence

long term observations of the wind field in the antarctic and arctic mesosphere and lower thermosphere at conjugate latitudes 1 mean winds semidiurnal and diurnal tides and trends and long period oscillations spanning a solar cycle from early 1999 through june 2010 measured by medium frequency mf radars at conjugate antarctic and arctic latitudes syowa antarctica 69 s 39 6 e and andenes norway 69 3 n 16 e are described and compared zonal mean winds are stronger and more uniform from year to year over the antarctic with a stronger eastward winter jet spanning the range of altitudes presented 70 to 96 km the summer westward jet is also stronger and maximizes at higher altitudes over the antarctic than over the arctic the eastward winter jet over the arctic while generally weaker exhibits a localized maximum in late winter at 2 to 3 year intervals meridional mean winds likewise achieve somewhat stronger maxima at higher altitudes over the antarctic than over the arctic semidiurnal tide amplitudes are typically somewhat larger over the antarctic and similar in the two components with maxima at 85 km or above and narrow responses that tend to cluster from february to may and september to november over the antarctic and from december to february and june to september over the arctic zonal diurnal tide amplitudes are quite similar between the sites with maxima extending from 70 to 90 km and slightly stronger over the antarctic meridional diurnal amplitudes display more significant growth with altitude achieve stronger maxima at the highest altitudes presented and typically exhibit a single and narrow maximum during december to february over the antarctic and double maxima from may to september over the arctic also discussed are trends and long period oscillations over a solar cycle observed in these mean and tidal wind fields

a cross section of the los angeles area seismically active fold and thrust belt the 1987 whittier narrows earthquake and earthquake hazard retrodeformable cross sections across the los angeles area interpret the pliocene to quaternary deformation to be a developing basement involved fold and thrust belt the fold and thrust belt is seismically active as evidenced by the 1987 whittier narrows earthquake ml 5 9 and the 1971 san fernando earthquake mw 6 6 the structural geology of the los angeles area is dominated by three major compressional uplift trends 1 the palos verdes anticlinorium and western shelf 2 the santa monica mountains anticlinorium and 3 the verdugo mountains san rafael hills and the san gabriel mountains these trends result from major thrust ramps off a detachment s at 10 15 km depth thrusts of the verdugo mountains san rafael hills and the san gabriel mountains reach the surface the other two uplifts are associated with blind thrusts compressional seismicity is concentrated along these thrust ramps the 1987 whittier narrows earthquake probably occurred on the elysian park thrust which underlies the santa monica mountains anticlinorium the thrust interpretation accounts for the geometry of the anticlinorium the seismological characteristics of the earthquake and the geometry of coseismic uplift the earthquake and aftershocks occurred within a structurally complex narrow zone of miocene and pliocene northwest trending faults that cross the anticlinorium at a high angle these northwest trending faults are interpreted to be reactivated faults now behaving as tears in the elysian park thrust and not the result of active right lateral deformation extending into the whittier narrows area our analysis suggests the whittier narrows earthquake sequence occurred within a structurally weakened zone along the elysian park thrust we also suggest that the whittier fault is not an important quaternary structure and may not be seismogenic the regional cross section is a nonunique solution and other possible solutions are considered multiple solutions arise from the presence of two intersecting compressional belts in the los angeles area the transverse ranges and the northern peninsular ranges the belts may be due to one or more regional detachments and the northern peninsular ranges may be northeast or southwest vergent the deformed top of the crystalline basement along the regional cross section requires a minimum of 15 0 km of north south convergence between the palos verdes hills and the san andreas fault regardless of the structural solution restoration of our cross section solution requires 21 4 km of north south convergence on top of the crystalline basement including 6 4 km of slip continuing offshore to make structures of the continental borderland and 29 7 km of convergence on the basal detachment geologic relationships suggest major shortening started between early and late pliocene time 2 2 4 0 ma which yields a minimum convergence rate of 3 8 6 8 mm yr between the palos verdes hills and the san andreas fault convergence rates for our solution range from 5 4 to 13 5 mm yr between the edge of the continental borderland and the san andreas fault slip rate estimates for the elysian park thrust along the eastern portion of the santa monica mountains anticlinorium are 2 5 5 2 mm yr if the 1987 whittier narrows earthquake is the characteristic earthquake along the 170 km long anticlinorium then recurrence intervals are estimated to be 5 6 12 1 years this recurrence is higher than the historic seismic record along the santa monica mountains anticlinorium and suggests that 1 our slip rates are too high 2 some crustal shortening is taken up aseismically and or 3 earthquakes larger than the 1987 whittier narrows earthquake will occur along the anticlinorium but less frequently

variable crustal structure of strike slip fault zones as observed on deep seismic reflection profiles seismic reflection profiling across strike slip faults has revealed a distinct variation in deep crustal structure profiles across the san andreas great glen and bray faults depict a near vertical reflection free zone that appears to truncate and in some cases offset reflections interpreted to have originated from the base of the crust a near vertical crustal penetrating fault zone is suggested for these continental transform faults in contrast reflection profiles across intra plate strike slip fault systems such as the northern walker lane and garlock faults suggest that they are decoupled in the middle crust by subhorizontal detachments these detachments are inferred from reflections that are traceable below the surface faults without disruption such detachments in the middle crust may act to ease the rotation of upper crustal blocks adjacent to strike slip fault zones as observed in paleomagnetic studies furthermore moderately dipping reflections interpreted to be from the fault zone project to the surface traces of the northern walker lane faults and the frontal faults of the wichita uplift indicating that these strike slip faults with large components of dip slip displacement are not vertical but dip moderately into the mid crust although the available data sets are still few they suggest that there is a primary variation in fault geometry that is related to the different behavior of transform versus intra plate strike slip fault systems

paleozoic structure of the central basin uplift and adjacent delaware basin west texas 1 structural cross sections and a regional tectonic map show that the central basin uplift consists of upthrust blocks of alternating vergence the uplift is separated from the adjacent delaware basin by a major fault that changes throw and structural style along strike accompanying changes in block vergence found along the uplift the west facing basement blocks were thrust westward over the delaware basin whereas the adjacent blocks face eastward the distribution and style of structures suggest that small amounts of left lateral movement occurred along west trending and northwest trending faults that separated rising blocks of the uplift transfer of lateral movement from vertical west trending faults on the central basin uplift and the ozona arch to the west trending mid basin fault in the delaware basin rotated blocks of the uplift in a clockwise sense faults and folds within the study area have trends and slip directions that are generally similar to those within the reagan and washita valley fault zones in the arbuckle uplift adjacent to the anadarko basin the difference in the style of deformation between the two uplifts relates to varied angular relationships between preexisting structure and the direction of late paleozoic stress the identity of structural trends within these two uplifts suggests that other late paleozoic basins and uplifts of the ancestral rocky mountains may have formed in a similar stress field and that crustal rotation was pervasive along the southwestern margin of the continent during the late paleozoic ouachita maratho deformation

geomechanical restoration as a tool for fractured reservoir characterization application to the permian basin west texas we present a three dimensional 3 d geomechanical restoration method as a reservoir characterization tool in the permian basin west texas the oates sw field produces gas from the lower devonian thirtyone formation within structural traps the thirtyone is a brittle chert with characteristics of a fractured reservoir field development has experienced variable production trends for decades to assess the impact of deformation on reservoir properties we employ 3 d geomechanical restorations to model strain patterns associated with fault displacement and fold growth we correlate these model strains with independent measures of natural rock strain to assess the viability of the restoration results a semblance volume generated from 3 d seismic reflection data illuminates secondary faults and fracture zones that are not incorporated in the geomechanical restorations our analysis yields strong correlations between low semblance and elevated strain throughout the thirtyone reservoir these correlations indicate that restoration strains may be used to describe the distribution of secondary faults and fractures that are not represented in our models providing predictive capabilities for defining fractured reservoir properties we integrate strain and semblance with production data to evaluate these correlations at the borehole scale in the study area we describe how tectonic strain likely enhanced permeability directly impacting observed production trends our characterization of the thirtyone reservoir demonstrates the ability to accurately predict strain distributions with geomechanical restorations where structure has been a significant factor in the development of reservoir permeability we suggest that these methods show promise as a reservoir characterization tool for conventional and unconventional development operations

pennsylvanian paleodepositional evolution of the greater permian basin texas and new mexico depositional systems and hydrocarbon reservoir analysis the permian basin of west texas and new mexico is the largest petroleum producing basin in the united states in this area multiple episodes of paleozoic faulting uplift and erosion occurred including those events related to the marathon ouachita orogeny hercynian orogenic cycle 350 250 ma within paleozoic rocks in the permian basin the pennsylvanian succession is the second most oil productive system next to the permian this succession has been viewed historically as sedimentologically and stratigraphically complex because of the interplay of deposition coinciding with icehouse climatic conditions during a second order global transgression and presumed active tectonism new paleodepositional systems maps for the morrowan atokan desmoinesian missourian and virgilian stages of the greater permian basin are presented this study integrates varied data including outcrop drill core geophysical seismic and gravity wireline log biostratigraphic and reservoir quality systems maps depict the spatial and temporal distribution of sediment source areas shallow water to basinal carbonates alluvial to open marine siliciclastics shales and areas of uplift a pennsylvanian reservoir architecture and facies evolution diagram combines data on key reservoir facies and targets including their dimensions the relative location of the facies tracts within each depositional system the overall system architecture and each stage s potential for diagenetic modification a unified depositional system model provides continuity between the paleodepositional systems maps and summarizes the entire pennsylvanian facies proportion evolution within eight provinces of the permian basin the depositional systems information is referenced to second to fourth order eustasy curves and tectonic input the reservoir evolution diagram and paleodepositional maps used in conjunction with the unified systems model provide the reader with the most current and extensive integration of data on the pennsylvanian geologic history in the greater permian basin from a sedimentologic and petroleum reservoir systems perspective insights into facies distribution the overall development of the basin and its subbasins tectonic episodes identification of potential new play types and exploration targets and new depositional and sequence stratigraphic architectural models are presented in this article

experimental evidence of arctic summer mesospheric upwelling and its connection to cold summer mesopause common volume mesospheric meteor detections from two radar stations separated by about 130 km were used to retrieve horizontal wind fields between 82 and 96 km altitudes at high latitudes near 69 n the horizontal wind divergence was estimated from the gradients of the wind fields this determination is the first of its kind for the mesosphere twelve years of nearly continuous datasets reveal systematic summer signatures in the horizontal wind divergence field namely a transition from negative to positive with increasing altitude while moving across the mesopause there are indications that the reversal altitude is also anti correlated with the mesopause temperature in addition for a tendency for the altitude of the reversal to increase over the years we show that the reversal in the horizontal wind divergence at the mesosphere is consistent with upward winds peaking near the mesopause these winds indicate that adiabatic cooling was strongest at the region of the deep temperature minimum seen in the summer mesopause

sedimentology and genetic stratigraphy of dean and spraberry formations permian midland basin texas the spraberry trend of west texas once known as the world s largest uneconomic oil field will undoubtedly become an increasingly important objective for the development of enhanced oil recovery techniques in fine grained low permeability low pressure reservoirs as the trend expands facies and stratigraphic data should be integrated into exploration strategies the spraberry and dean formations may be divided into three genetic sequences each consisting of several hundred feet of interbedded shale and carbonate overlain by a roughly equal amount of sandstone and siltstone these sequences record episodes of shelf margin progradation deep water resedimentation of shelf derived carbonate debris followed by influxes of terrigenous clastics into the basin by way of feeder channels or submarine canyons and suspension settling of fine grained sediment from the water column four lithofacies comprise the terrigenous clastics of the spraberry and dean formations 1 cross laminated massive and parallel laminated sandstone 2 laminated siltstone 3 bioturbated siltstone and 4 black organic rich shale carbonate lithofacies occur mostly in the form of thin bedded turbidites slump and debris flow deposits terrigenous clastic rocks display facies sequences isopach patterns and sedimentary structures suggestive of deposition from turbidity currents and long lived saline density underflow and interflow currents clastic isopach patterns reflect an overall southward thinning of clastics in the midland basin channelized flow and suspension settling were responsible for the formation of elongate fan shaped accumulations of clastic sediments