ExxonMobil

About: ExxonMobil is a company organization based out in Irving, Texas, United States. It is known for research contribution in the topics: Catalysis & Polymer. The organization has 16969 authors who have published 23758 publications receiving 535713 citations. The organization is also known as: Exxon Mobil Corporation & Exxon Mobil Corp..

Carbonate Cementation in a Sequence-Stratigraphic Framework: Upper Cretaceous Sandstones, Book Cliffs, Utah-Colorado

Abstract: Three macroscopic diagenetic features can be recognized in the sandstones of the Upper Cretaceous Desert Member of the Blackhawk Formation and Castlegate Sandstone of the Mesaverde Group exposed in the Book Cliffs, Utah, each of which have distinctive form, geometry, and stratigraphic distribution. Diagenetic alterations are: (1) leached zones ("whitecaps"), up to 10 m thick, beneath coal beds; (2) large (up to 8 m) concretionary carbonate-cemented bodies in amalgamated shoreface and thin fluvial sandstones; and (3) thin (up to 2 m), laterally extensive carbonate-cemented horizons beneath major marine flooding surfaces. Each feature has distinct petrographic and geochemical signatures, and formed through discrete diagenetic processes. Large isolated carbonate-cemented bodies are composed of ferroan dolomite, most of which precipitated during early diagenesis. Field and petrographic data, coupled with stable-isotope data (early cements, 13C = -2.5 to +3.4o/oo VPDB; 18O = -7.8 to -12.0o/oo VPDB; 87Sr/86Sr = 0.7078; later cements, 13C = -3.1 to -5.7o/oo VPDB; 18O = -12.0 to -15.1o/oo VPDB; 87Sr/86Sr = 0.7093) suggest precipitation from meteoric fluids, input into sediments during times of relative sea-level fall. The source of carbonate for the dolomite cement was dissolution of detrital dolomite from beneath coals by organic acids and subsequent mobilization by meteoric fluids. Carbonate precipitation in laterally extensive cement horizons appears to have started as a result of hiatus in sediment accumulation during marine flooding events (relative sea-level rise). Cement precipitation in these horizons continued through sediment burial as a result of organic-matter oxidation reactions in overlying organic-rich mudstones. The results of this study show a link between sedimentation (related to changes in relative sea level) and diagenesis, leading to the potential for the development of process-based, predictive models of early diagenesis in depositional successions.

Physical Structure of Asphaltenes

Abstract: While colloidal models of asphaltenes were extremely beneficial in the early stages of understanding asphaltene behavior, these analogies are often overused. The evidence often cited showing asphaltenes to be particles several nanometers in size is small-angle neutron and X-ray scattering (SANS and SAXS) results. Data from other techniques are often interpreted with the assumption that the asphaltenes form colloids or micelles. Asphaltenes are molecules which can undergo a thermodynamic liquid−liquid phase separation from solution. The asphaltene-rich phase is often below its glass transition and therefore appears solid, exhibiting a fractal-like morphology only because of the kinetic inability for the “droplets” to coalesce. Its colloidal appearance at micrometer to millimeter lengths should not be confused with or be used to imply such colloidal structure for solvated asphaltenes at nanometer length scales. From SAXS and SANS we show that the scattering often attributed to asphaltene colloidal aggregate...

Pathways toward Electric Field Induced Alignment of Block Copolymers

Abstract: Using in situ small-angle X-ray scattering, the electric field induced orientation in a block copolymer having a cylindrical microdomain morphology was investigated. Studies were performed with the copolymer in different initial states. Beginning with a disordered copolymer, composition fluctuations are oriented by the electric field. Following cooling across the disorder-to-order-transition, microdomains are oriented parallel to the applied field. Beginning with a microphase-separated copolymer where the microdomains are oriented normal to the field, the domain orientation becomes unstable at high field strengths, and the microdomains reorient in a piecewise manner.

Gas Condensate Reservoir Behaviour: Productivity and Recovery Reduction Due to Condensation

Abstract: The depletion of gas condensate reservoirs to pressures below the dew point has been studied by reservoir engineers for many years. Pressure decline below the dew point pressure causes condensation to occur which creates a hydrocarbon liquid saturation in the reservoir. This process reduces liquid recovery and may reduce gas productivity and gas recovery. Exxon experience, particularly in low-productivity, high-yield gas condensate fields, suggests that liquid condensate formation can result in severe loss of well deliverability and therefore of gas recovery. This study was undertaken to evaluate the historical frequency and severity of productivity impairment due to near-wellbore condensate buildup and to identify reservoir parameters associated with severe productivity and recovery reduction. This study of gas condensate reservoirs included a survey of Exxon and published industry experience, a review of published laboratory data, and simulations with single well flow models. Data from 17 fields are included in this paper to demonstrate that severe loss of gas recovery occurs primarily in low productivity reservoirs. Production data from two wells were history matched with simple radial models to evaluate the potential range of the critical condensate saturation (the minimum mobile condensate saturation) and its impact on gas recovery. Published laboratory data for gas-condensate relative permeability were used as a starting point for these simulations. The primary conclusion from this study is that productivity impairment results in reductions in gas recovery for wells with a permeability-thickness below 1000 md-ft. The history matched simulations support a range of critical condensate saturations from 10% to 30%, in good agreement with published laboratory values.

Suppression of Rupture in Thin, Nonwetting Liquid Films

Abstract: Stabilization against the rupture and breakup of thin, nonwetting liquid films spread on surfaces is generally sought by modification of equilibrium interfacial properties. A mechanism for suppressing rupture in such films that uses surface-attached polymers togetherwithfree chains in the bulk of the film is reported. Films of an oligostyrene liquid, which rupture within several minutes when spread on a silicon wafer, may be stabilized for many months by a polystyrene brush attached to the substrate, together with some free polystyrene in the liquid. The effect may arise from entanglements of the free chains with the immobilized brush.