Showing papers by "Mobil published in 1996"

New direct observations of asphalts and asphalt binders by scanning electron microscopy and atomic force microscopy

Abstract: Observations made using AFM and SEM have been combined in order to study the structure of asphalts. Fluorescence microscopy was used to aid in understanding the structural changes occurring when polymer is added to the asphalts. With the atomic force microscope we are able to study the structure of the asphalts without any pre-preparation. Despite very low resolution, our study reveal ed a network of asphaltene molecules with regard to asphalt gel. The same result is obtained by SEM observation but with a much better resolution. SEM observation, however, needs an adequate preparation method. In the presence of polymer we observed a rearrangement of the initial asphaltene association which leads to the assumption that polymer can aggregate the asphaltene phase.

High-density turbidity currents; are they sandy debris flows?

Abstract: Conventionally, turbidity currents are considered as fluidal flows in which sediment is supported by fluid turbulence, whereas debris flows are plastic flows in which sediment is supported by matrix strength, dispersive pressure, and buoyant lift. The concept of high-density turbidity current refers to high-concentration, commonly nonturbulent, flows of fluids in which sediment is supported mainly by matrix strength, dispersive pressure, and buoyant lift. The conventional wisdom that traction carpets with entrained turbulent clouds on top represent high-density turbidity currents is a misnomer because traction carpets are neither fluidal nor turbulent. Debris flows may also have entrained turbulent clouds on top. The traction carpet/debris flow and the overriding turbulent clouds are two separate entities in terms of flow rheology and sediment-support mechanism. In experimental and theoretical studies, which has linked massive sands and floating clasts to high-density turbidity currents, the term "high-density turbidity current" has actually been used for laminar flows. In alleviating this conceptual problem, sandy debris flow is suggested as a substitute for high-density turbidity current. Sandy debris flows represent a continuous spectrum of processes between cohesive and cohesionless debris flows. Commonly they are rheologically plastic. They may occur with or without entrained turbulent clouds on top. Their sediment-support mechanisms include matrix strength, dispersive pressure, and buoyant lift. They are characterized by laminar flow conditions, a moderate to high grain concentration, and a low to moderate mud content. Although flows evolve and transform during the course of transport in density-stratified flows, the preserved features in a deposit are useful to decipher only the final stages of deposition. At present, there are no established criteria to decipher transport mechanisms from the depositional record.

Chemostratigraphic reconstruction of biofacies: Molecular evidence linking cyst-forming dinoflagellates with pre-Triassic ancestors

Abstract: New data from numerous detailed mass-spectrometric studies have detected triaromatic dinosteroids in Precambrian to Cenozoic rock samples. Triaromatic dinosteroids are organic geochemicals derived from dinosterols, compounds known in modern organisms to be the nearly exclusive widely occurring products of dinoflagellates. We observed the ubiquitous occurrence of these dinosteroids in 49 Late Triassic through Cretaceous marine source rocks and the absence of them in 13 Permian-Carboniferous source rocks synergistic with the dinoflagellate cyst record. However, finding dinosteroids in lower Paleozoic and Precambrian strata presents challenging results for molecular paleontologists, evolutionary biologists, palynologists, and especially for those concerned with the food web at various times of biological crisis. Other than the few species known as parasites and symbionts, many other dinoflagellate species are important as primary producers. The presence of Precambrian to Devonian triaromatic dinosteroids gives chemostratigraphic evidence of dinoflagellates (or other organisms with similar chemosynthetic capabilities) in rocks significantly older than the oldest undisputed dinoflagellate fossils (dinoflagellate cysts from the Middle Triassic, ∼ 240 Ma), and older than the putative Silurian ∼ 420 Ma) dinocyst, Arpylorus antiquus (Calandra) Sargent, from Tunisia. This systematic chemostratigraphic approach can shed light not only on lineages of dinoflagellates and their precursors, but potentially on many other lineages, especially bacteria, algae, plants, and possibly some metazoans.

Portable point-of sale terminal with device for inputting security code access key

Abstract: A point-of-sale (POS) processing system includes a host and a plurality of portable POS terminals. A local controller may be provided intermediate the host and the POS terminals, so that the POS terminals communicate with the host via the local controller. Each POS terminal includes a main portion and an extension portion. The main portion may be supported by a harness for strapping the main portion to a dealer's body. The extension portion may be small in size and light in weight so that it can be easily held with one hand. The main portion includes a two-way communication subsystem, a processor, and at least one data interface. The extension portion includes a reading device (e.g., a magnetic strip reader) for reading financial account data from an account authorization device (e.g., a credit card, debit card or prepay card). It further includes an input device (e.g., a keypad) for inputting a security code access key (e.g., a PIN), and a device for generating encrypted data representative of the security code access key. The main portion may also include a printer for printing receipts generated as a result of a sale transaction.

Dealumination of zeolite {beta} via dicarboxylic acid treatment

Abstract: It is demonstrated that zeolite {beta} and zeolite {beta} containing catalysts can be dealuminated to very low acidity levels using a novel oxalic acid treatment without reducing zeolite integrity. The effect of the oxalic acid treatment has been studied over a wide range of treatment conditions for both silica-bound and unbound zeolite {beta} catalysts. Greater than 90% dealumination is observed with a concomitant reduction in n-hexane-cracking activity as measured by the alpha ({alpha}) test. Removal of framework aluminum occurs via a two-step hyrolysis/chelation mechanism, with the oxalic acid acting both as an acid and as a chelating agent. Framework aluminum removal is accompanied by the formation of internal silanol groups. Water soluble aluminum oxalates are present in the extracted solutions. Silanol groups are annealed with extended oxalic acid treatment. Oxalic acid treatment results in a unique contraction of the zeolite {beta} lattice structure not observed for mineral acid treated or steamed zeolite {beta} catalysts. 15 refs., 11 figs., 5 tabs.

The southern Whidbey Island fault: An active structure in the Puget Lowland, Washington

Abstract: Information from seismic-reflection profiles, outcrops, boreholes, and potential field surveys is used to interpret the structure and history of the southern Whidbey Island fault in the Puget Lowland of western Washington. This northwest-trending fault comprises a broad (as wide as 6–11 km), steep, northeast-dipping zone that includes several splays with inferred strike-slip, reverse, and thrust displacement. Transpressional deformation along the southern Whidbey Island fault is indicated by along-strike variations in structural style and geometry, positive flower structure, local unconformities, out-of-plane displacements, and juxtaposition of correlative sedimentary units with different histories. The southern Whidbey Island fault represents a segment of a boundary between two major crustal blocks. The Cascade block to the northeast is floored by diverse assemblages of pre-Tertiary rocks; the Coast Range block to the southwest is floored by lower Eocene marine basaltic rocks of the Crescent Formation. The fault probably originated during the early Eocene as a dextral strike-slip fault along the eastern side of a continental-margin rift. Bending of the fault and transpressional deformation began during the late middle Eocene and continues to the present. Oblique convergence and clockwise rotation along the continental margin are the inferred driving forces for ongoing deformation. Evidence for Quaternary movement on the southern Whidbey Island fault includes (1) offset and disrupted upper Quaternary strata imaged on seismic-reflection profiles; (2) borehole data that suggests as much as 420 m of structural relief on the Tertiary-Quaternary boundary in the fault zone; (3) several meters of displacement along exposed faults in upper Quaternary sediments; (4) late Quaternary folds with limb dips of as much as ≈9°; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. The southern Whidbey Island fault should be considered capable of generating large earthquakes (M s ≥7) and represents a potential seismic hazard to residents of the Puget Lowland.

Leukemia mortality by cell type in petroleum workers with potential exposure to benzene.

Abstract: Workers in the petroleum industry are potentially exposed to a variety of petrochemicals, including benzene or benzene-containing liquids. Although a large number of studies of petroleum workers have been conducted to examine leukemia and other cancer risks, few existing studies have investigated cell-type-specific leukemias. One of the major reasons for the lack of cell-type-specific analysis was the small number of deaths by cell type in individual studies. In the present investigation, all cohort studies of petroleum workers in the United States and the United Kingdom were combined into a single database for cell-type-specific leukemia analysis. The majority of these workers were petroleum refinery employees, but production, pipeline, and distribution workers in the petroleum industry were also included. The combined cohort consisted of more than 208,000 petroleum workers, who contributed more than 4.6 million person-years of observation. Based on a meta-analysis of the combined data, cell-type-specific leukemia risks were expressed in terms of standardized mortality ratios (meta-SMRs). The meta-SMR for acute myeloid leukemia was 0.96. The lack of an increase of acute myeloid leukemia was attributed to the low levels of benzene exposure in the petroleum industry, particularly in comparison to benzene exposure levels in some previous studies of workers in other industries, who had been found to experience an increased risk of acute myeloid leukemia. Similarly, no increase in chronic myeloid, acute lymphocytic, or chronic lymphocytic leukemias was found in petroleum workers (meta-SMRs of 0.89, 1.16, and 0.84, respectively). Stratified meta-analyses restricted to refinery studies or to studies with at least 15 years of follow-up yielded similar results. The findings of the present investigation are consistent with those from several recent case-control studies of cell-type-specific leukemia. Patterns and levels of benzene exposure in the petroleum industry are reviewed. The results of the present epidemiologic investigation are discussed in conjunction with recent advances in leukemogenesis from other scientific disciplines.

Lubricant compositions of polyalphaolefin and alkylated aromatic fluids

Abstract: The inclusion of alkylated aromatic base fluids, such as alkylated naphthalene, blending stocks with polyalphaolefin base fluids provides significant performance improvements in oxidation stability, solubility, elastomer compatibility and hydrolytic stability.

High fidelity vibratory source seismic method

Abstract: A method for recording and pre-processing high fidelity vibratory seismic data includes measuring the motion of the vibrator (36) which is related to the vibrator applied force times a transfer function of minimum phase, causal, linar system relating the actual vibrator output with the measured vibrator motion, determining a ratio (52) by dividing the vibratory seismic data by the measured motion of the vibrator to remove the unknown applied force leaving the earcj reflectivity times a time derivative divided by a minimum phase function, minimum phase band pass filtering the resulting ratio and performing mimimum phase deconvolution to remove the time derivative divided by the transfer function of mimimum phase. The method may also include the steps of receiver ensemble deconvolution (56), statics correction (58), F-K filtering for noise (60), zero phase spiking deconvolution (64) and model dephasing (66). The actual signal that the vibrator (36) is sending into the ground is used in pre-processing.

Process for treating a gas stream to selectively separate acid gases therefrom

Abstract: A treatment method for removing acid gases by contacting a sour gas stream with a solvent (e.g., an organic amine) which absorbs H2S in preference to CO2 and hydrocarbons. The rich solvent is then regenerated by selectively separating the absorbed hydrocarbons in a first flash tank, a large portion of the CO2 in a high-temperature, low-pressure second flash tank, and substantially all of the remaining acid gases in a high-temperature, low-pressure stripper. The regenerated solvent is recycled and the recovered acid gases; are processed to recover sulphur from the H2S. The CO2 recovered from the second tank is contacted with a second solvent to provide high-quality CO2.

Single reactor bimodal hmw-hdpe film resin with improved bubble stability

Abstract: Single reactor bimodal MWD high molecular weight polyethylene film resin has improved bubble stability. The bimodal molecular weight distribution resin has low resin elasticity. Preferably the resin is made catalytically in one reactor. The preferred catalyst appears to control the properties of bubble stability and elasticity.

Integrated hydroprocessing scheme with segregated recycle

Abstract: Petroleum products are refined in an integrated hydroprocessing scheme involving a hydrocracking stage (1) and subsequent dewaxing stage (16). Materials boiling in the middle distillate or lube oil range may be dewaxed. The bottoms streams (12, 34) and optionally other streams from each stage are maintained separately from one another during processing. Dewaxing may occur using either hydroisomerization catalysts or shape-selective catalysts or both in series. One embodiment employs a baffle (14) in the flash zone of a fractionator (13) to separate bottoms streams from each other. Alternatively, the effluent (4) from the hydrocracking stage may be processed separately from the effluent (18) from the dewaxing stage. The bottoms fraction from the dewaxing stage may be recycled back to the hydrocracking stage for futher processing or used as lube base stock.

Multi-layer hermetically sealable film and method of making same

Abstract: The present invention is a multi-layer film which has an improved composite structure for providing hermetic seals to packages manufactured in high speed packaging apparatus. The structure of the multi-layer film of the present invention includes a main substrate and a sealant layer. The sealant layer, in turn, includes two components, an intermediate layer which has the primary function of compliance during sealing, and a sealing layer which has the primary function of providing adhesivity to the completed seal. As a result of this invention, high strength hermetic seals can be provided to multi-layer films effectively and efficiently, and hermetic seals are provided with the ability to be peeled open without destruction of several layers of the film.

Method for separation of a plurality of vibratory seismic energy source signals

Abstract: A method and apparatus for separating and pre-processing vibratory source data includes varying the phase of vibratory sources according to two patterns. A first pattern is used for odd numbered sources while a second pattern is used for even numbered sources. Each pattern begins with a zero phase shift, the zero phase shift occurring at the sweep number corresponding to the position number of the source. The first pattern is one of zero phase shift, ninety degree phase shift, ninety degree phase shift and one hundred eighty degree phase shift. The second pattern is one of zero phase shift, one hundred eighty degree phase shift, ninety degree phase shift and ninety degree phase shift. The patterns are alternated for each source, the beginning of the pattern corresponds to the position of the source in a line. The first source begins with the first pattern. The second source begins with the second pattern, with zero starting at the second sweep. The third source begins with the first pattern, with zero occurring at the third sweep. The fourth source follows the second pattern, with zero being at the fourth sweep.

Silicate-Based Drilling Fluids: Competent, Cost-effective and Benign Solutions to Wellbore Stability Problems

Abstract: New and improved water-based drilling fluids based on soluble silicates have been developed and applied in the field in a unique collaboration between BW Mud, Mobil NSL, BP Exploration and Shell Research. Silicate-based muds are introduced as superior fluids for drilling troublesome formations like intact and (micro-)fractured shales and chalks. In addition, these inorganic systems are environmentally friendly and inexpensive. Details are presented on the wellbore stabilisation mechanism of silicate-based muds and their drilling fluid engineering. In addition, field trial results are presented which demonstrate the excellent cuttings- and wellbore-stabilising capacity of these exciting new mud systems.

Analysis of the pre-Tertiary rifting history of the Rockall Trough

Abstract: The Rockall Trough is a large, lightly explored, deep water basin offshore West of Britain. Only the 132/15-1 well has penetrated Mesozoic section within the Rockall Trough encountering a syn-rift section, interpreted on seismic reflection data, of early Cretaceous age (Hauterivian-Cenomanian) lying directly on crystalline basement. Older rift events have been proposed in the Rockall Trough to explain the extensive crustal thinning (Beta = 3 to 5) and because of the presence of older rifts on adjacent basins. Although the evidence is not conclusive, analysis of seismic reflection data within the Rockall Trough and of rift system trends on an early Cretaceous plate reconstruction do not require or suggest older than Cretaceous rifts in the Rockall Trough but also do not preclude them. Structurally, the Cretaceous rifting is highly assymetric being dominated by faults downthrowing to the southeast. A model of a reactivated Caledonian foreland thrust belt is proposed similar to that reported on the adjacent Hebridean shelf.

Method for hydrotreating and upgrading heavy crude oil during production

Abstract: Heavy crude oil containing at least 1% by weight water is hydrotreated and upgraded while being produced downhole in a production well. During production the heavy crude oil containing water is subjected to sonic energy at a low frequency of 400 Hz to 10 kHz downhole in the presence of a metal hydrogenation catalyst that causes the water in the crude oil to react and form hydrogen which then hydrotreats and upgrades the heavy crude oil during production. In another embodiment, if the heavy crude oil does not contain water, the hydrogen may be formed in-situ by contacting the heavy crude oil downhole with a chemical compound comprising ammonia, hydrazine and formic acid that in the presence of a metal hydrogenation catalyst and sonic energy causes the chemical compound to react and form hydrogen which then hydrotreats the heavy crude oil during production. Suitable catalysts include nickel on zinc dust, platinum on carbon and palladium on carbon, preferably nickel on zinc dust. The hydrotreated and upgraded heavy crude oil has improved properties making it easier to refine and transport by pipeline. The upgrading includes reducing the amount of asphaltenes and resins in the heavy crude oil and increasing the amount of aromatics and saturates.

Method of monitoring fluids entering a wellbore

Abstract: In a borehole logging tool, a hot wire anemometer measures fluid flow entering or exiting the borehole (16) at the wall of the borehole. The logging tool has open aperture sensing pads (14, 15) mounted onto arms (12, 13) placed in mechanical contact with the wall that place the sensor pads at the wall surface. The sensor pads have an open aperture across their central area to permit fluid flow therethrough in such a manner that provides minimum disruption of flow between the borehole and the surrounding earth formations about the borehole being logged. Other sensors mounted on the sensor pad measure parameters such as fluid type, flowrate or fluid flow direction, as well as fluid properties including capacitance, dielectric constant and temperature of the passing fluid; or contain a shield attached at the end of the sensor pad upstream of the fluid flowing in the borehole center so as to minimize effects from fluids flowing in the center of the borehole.

Method for extracting bitumen from tar sands

Abstract: A method for extracting bitumen from crushed mined tar sands comprising contacting the mined tar sands with a solvent in the presence of sonic energy in the frequency range of 0.5 to 2.0 kHz. Specifically, a solvent is first mixed with crushed mined tar sands and the mixture is then formed into a slurry of tar sand suspended in the solvent. Thereafter the tar sand slurry is injected into the top of a vertically disposed, substantially rectangular shaped, hollow acoustic chamber of uniform cross-section. Fresh solvent is injected into the bottom of the acoustic chamber and flows upwardly through the cell. The fresh solvent is injected into the bottom of the acoustic chamber at a rate low enough whereby the tar sand particles in the slurry fall by gravity through the upwardly flowing solvent. The tar sand particles and solvent in the acoustic chamber are subjected to acoustic energy in the frequency range of 0.5 to 2.0 kHz whereby the bitumen is separated from the tar sand and dissolved by the upwardly flowing solvent without cavitation of the solvent. The bitumen dissolved in the solvent is recovered from the top of the acoustic chamber and transferred by pipeline to an off-site refinery. The bitumen-extracted sand particles recovered from the bottom of the acoustic chamber may be recycled to the top of the acoustic chamber to recover additional bitumen after injection of the slurry has been discontinued.

Developments in Synchrotron X-Ray Microtomography with Applications to Flow in Porous Media

Abstract: High resolution computed microtomography (CMT) using synchrotron X-ray sources provides the ability to obtain three-dimensional images of specimens with a spatial resolution on the order of micrometers. Microimaging capabilities at Brookhaven National Laboratory`s National Synchrotron Light Source have been enhanced to provide larger and higher resolution 3-D renderings of pore networks in reservoir rocks at a fraction of the time required in previous first generation scanning methods. Such data are used to model single and multiphase flow properties in digital images of real porous media. Pore networks are analyzed for tortuosity and connectivity measures, which have been elusive parameters in transport property models. We present examples of porosimetry simulation via network modeling to produce initial water saturation and residual oil distributions in a water-wet pore system. Furthermore, pore networks can provide the boundary condition framework for more rigorous simulations of displacement, such as in the lattice Boltzmann simulated waterflood example provided. Direct comparison between simulation and experiment is also possible. CMT images of a 6 mm subsection of a one inch diameter reservoir core sample were obtained prior and subsequent to flooding to residual oil. The fluid distributions from CMT, lattice Boltzmann waterflood simulation, and percolation-based network modeling were foundmore » to be highly correlated. Advances in 3-D visualization, implemented in Brookhaven National Laboratory`s 3-D theater, will allow even greater digestion and interpretation of phenomena dependent upon pore interconnectivity and multipore interactions.« less

Method for fracturing and gravel-packing a well

Abstract: A method for gravel-packing an interval within a cased wellbore wherein perforations in the well casing are cleaned of any plugging materials before placement of the gravel (e.g. sand). A screen having alternate flowpaths thereon is lowered adjacent the perforated casing and a clear fluid (e.g. clear fracturing gel) is pumped through the perforations into the formation. The gel cleans the perforation of any plugging material and fractures the formation. A gravel (e.g. sand) slurry is then pumped into the annulus and through the perforations to deposit sand in the fracture, the perforations, and the annulus around the screen. If a sand bridge(s) forms in the annulus, the alternate flowpaths will deliver the slurry to all levels within the annulus insuring good distribution of sand across the interval.

Cold sealable cohesive polymers

Abstract: An adhesive coating which is pressure sealable to itself and non-blocking to a dissimilar coating is described. The coating comprises a blend of (a) a soft polymer having a measured glass transition temperature below room temperature; and (b) a hard polymer having a measured glass transition temperature which is above the measured glass transition temperature of the soft polymer (a). The soft polymer and the hard polymer are combined in a low blocking, pressure sealable coating formable proportion. A method of making the adhesive coating comprising the step of blending the soft polymer and the hard polymer and coated substrates formed from the adhesive coating are also described.

Drilling Liner Technology for Depleted Reservoir

Abstract: The Drilling Liner System makes use of the liner/casing as a drill string that would normally be set at the casing point. As a drilling tool, it can be set when the string becomes stuck due to formation collapse or severe differential pressure sticking. Background cases for developing this system were wellbores in the North Sumatra (Indonesia) Arun field. This field has highly pressured shales and salt water sand layers overlying a depleted, highly permeable reservoir. Conventional drilling techniques became impossible since a total loss of circulation occurred as soon as the bit drilled through the highly pressured cap rock into the severely depleted reservoir. The resulting drop of hydrostatic pressure usually causes the shale to collapse and stick the drillstring. The reduced hydrostatic head also induces flow from the shallower salt water sands. With the Drilling Liner System, the liner will be set simultaneously when drilling into the low pressure formation. Although the mud losses still occur, the liner is then already in place and protects the borehole. After releasing the running tool, cementing and changing the mud, drilling operations may in the low pressure formation using conventional drilling techniques. Several successful runs have been performed in the Arun gas field where formation pressure drops from 8,000 psi in the overlying shale to less than 2,000 psi in the permeable Arun limestone. Prior to application of the drilling liner system, drilling through the described formation had been difficult and costly. Salt water kicks, borehole collapse and stuck pipe were common problems. The system described has allowed repair of 2 of 3 failed wells with full productivity at a cost much less than for a new well. But the system is not fully perfected yet. In the third well, the drilling liner did not completely isolate the shale. A workover to install a scab liner will be required to allow shale-free production.

Coating for printable plastic films

Abstract: The invention provides a lithographic printable plastic film. A plastic film is coated with a coating formulation which allows lithographic printing on plastic films. The coating composition comprises an acrylic binder, specifically a blend of acrylic polymer and ethylene-acrylic acid copolymer, at least one particulate filler, specifically silica, calcium carbonate, clay, talc, titanium dioxide and mixtures thereof, a surfactant and, optionally, an ultraviolet stabilizer. The coating composition is applied to a plastic film for lithographic printing.

Oriented hdpe films with metallized skin layer

Abstract: A metallizable multilayer film structure of enhanced bond strength comprises a) a flame or corona discharge treated upper skin layer (a) consisting essentially of ethylene-propylene-butylene terpolymer and low density polyethylene; b) a base layer comprising high density polyethylene, and c) a lower skin layer (c) comprising ethylene-propylene-butylene terpolymer and an antiblock component selected from the group consisting of silicone oil and silicone particulate.

Method for preparing a modified solid oxide

Abstract: There is provided a method for preparing an acidic solid comprising a Group IVB metal oxide modified with an oxyanion of a Group VIB metal. An example of this acidic solid is zirconia, modified with tungstate. This modified solid oxide may be used as a catalyst, for example, to isomerize C4 to C8 paraffins. The modified solid oxide is prepared by co-precipitating the Group IVB metal oxide along with the oxyanion of the Group VIB metal.

Finite-difference depth migration of exploration-scale 3-D seismic data

Abstract: Most migration methods are based on a variety of one-way approximations of the wave equation, one noticeable exception being the finite-difference, reverse-time, depth migration algorithm. Since this method requires enormous computer resources as compared to all other migration algorithms, its applications have been restricted primarily to 2-D synthetic data. Consequently, its potential for migrating poststack real data and imaging complex 3-D structures by constructive interference of wavefronts has not been exploited. Finite-difference depth migration is subject to the same conditions for avoiding grid dispersion and numerical instability as are forward modeling techniques. For field data, this can necessitate interpolation both in space and time. One can, however, exploit the fact that in forward modeling one tries to generate accurate reflection signals; whereas in migration, the primary objective is to accomplish imaging from the prerecorded signals, which may be attainable under less stringent conditions. Indeed our investigations indicate that accurate imaging can be clone without making rigid provisions for grid dispersion in the lateral direction, which reduces or eliminates the use of interpolated traces. In the case of 3-D data, the elimination of an interpolation step reduces the computational task by a factor of 50 or more, with similar reductions in memory requirements. Further efficiency can be achieved by using a nonuniform grid in the vertical direction that adapts to the expansion and contraction of the downward propagating wavelet in response to variations in velocity and frequency content of the input data. These steps reduce the time required to do high-resolution migration of large 3-D data volumes to several hours or less, depending on the machine and the size of the input data. Two applications on large, exploration-scale, 3-D field data carried out on a massively-parallel machine are presented. We compare our results with the results obtained by the Hale-McClellan algorithm.