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George J. Hirasaki

Other affiliations: Mobil, Royal Dutch Shell, University of Texas at Austin  ...read more
Bio: George J. Hirasaki is an academic researcher from Rice University. The author has contributed to research in topics: Pulmonary surfactant & Enhanced oil recovery. The author has an hindex of 65, co-authored 278 publications receiving 14164 citations. Previous affiliations of George J. Hirasaki include Mobil & Royal Dutch Shell.


Papers
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Journal ArticleDOI
TL;DR: In this paper, anionic surfactant solutions are evaluated for enhancing oil recovery by spontaneous imbibition from oil-wet carbonate rocks, and the ease of wettability alteration is a function of the aging time and temperature and the surfactants formulation.
Abstract: Oil recovery by waterflooding in fractured formations is often dependent on spontaneous imbibition. However, spontaneous imbibition is often insignificant in oil-wet, carbonate rocks. Sodium carbonate and anionic surfactant solutions are evaluated for enhancing oil recovery by spontaneous imbibition from oil-wet carbonate rocks. Crude-oil samples must be free of surface-active contaminants to be representative of the reservoir. Calcite, which is normally positively charged, can be made negative with sodium carbonate. The ease of wettability alteration is a function of the aging time and temperature and the surfactant formulation.

520 citations

Journal ArticleDOI
TL;DR: In this paper, the apparent viscosity of foam flowing through smooth capillaries was measured experimentally and a mathematical model was developed to determine whether the foam exists as bulk foam or as a chain of bubbles where each pair of bubbles is separated by individual lamella, the number of lamellae per unit length of the capillary, and the radius of curvature of the gas-liquid interface.
Abstract: The apparent viscosity of foam flowing through smooth capillaries was measured experimentally and a mathematical model was developed. Foam texture (a measure of bubble volume) is a key parameter in determining the following properties of foam flowing through a capillary: whether the foam exists as bulk foam or as a chain of bubbles where each pair of bubbles is separated by an individual lamella, the number of lamellae per unit length of the capillary, and the radius of curvature of the gas-liquid interface. The apparent viscosity is the sum of three contributions: that from slugs of liquid between bubbles, the resistance to deformation of the interface of a bubble passing through a capillary, and the surface tension gradient that results when surface active material is swept from the front of a bubble and accumulates at the back of it. The sensitivity of both measured and calculated apparent viscosity is presented as a function of bubble size, capillary radius, ratio of bubble radius to capillary radius, velocity, quality, and surface tension gradient.

512 citations

Journal ArticleDOI
TL;DR: In this paper, the surface forces are expressed as a disjoining pressure isotherm, and its integral is the specific interaction potential isotherms, which can be used to determine the stable and metastable film-thickness profiles at the three-phase contact region for a given capillary pressure and/or curvature of the substrate.
Abstract: The wetting of mineral surfaces by water and oil is described by models of surface forces that become important when two surfaces approach each other. Force components are electrostatic, van der Waals, and structural. The electrostatic forces depends on brine pH and salinity, crude oil composition, and the mineral. The surface forces are expressed as a disjoining pressure isotherm, and its integral is the specific interaction potential isotherm. The specific interaction potential isotherm can be used to determine the stable and metastable film-thickness profiles at the three-phase contact region for a given capillary pressure and/or curvature of the substrate. This paper gives the contact angle.

461 citations

Journal ArticleDOI
TL;DR: The mechanisms and theories suggested in the literature to explain the impact of oil on foam stability in the bulk and porous media are reviewed and various ideas on an improvement of foam stability and longevity in the presence of oil are presented.

453 citations


Cited by
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01 May 1993
TL;DR: Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems.
Abstract: Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

29,323 citations

Book
01 Jan 1979

2,451 citations

Journal ArticleDOI
TL;DR: The structural features of cationic compounds are evaluated and the relationship of toxicity and structure is summarized and available suggestions are provided to provide available suggestions on the development of these cATIONic compounds.

1,910 citations

Journal ArticleDOI
Dan Luo1, Saltzman Wm1
TL;DR: The ability to safely and efficiently transfer foreign DNA into cells is a fundamental goal in biotechnology and rapid advances have recently been made in understanding of mechanisms for DNA stability and transport within cells.
Abstract: The ability to safely and efficiently transfer foreign DNA into cells is a fundamental goal in biotechnology. Toward this end, rapid advances have recently been made in our understanding of mechanisms for DNA stability and transport within cells. Current synthetic DNA delivery systems are versatile and safe, but substantially less efficient than viruses. Indeed, most current systems address only one of the obstacles to DNA delivery by enhancing DNA uptake. In fact, the effectiveness of gene expression is also dependent on several additional factors, including the release of intracellular DNA, stability of DNA in the cytoplasm, unpackaging of the DNA-vector complex, and the targeting of DNA to the nucleus. Delivery systems of the future must fully accommodate all these processes to effectively shepherd DNA across the plasma membrane, through the hostile intracellular environment, and into the nucleus.

1,768 citations