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| 1 | Spontaneous Imbibition of Water and Determination of Effective Contact Angles in the Eagle Ford Shale Formation Using Neutron Imaging显示文摘Understanding of fundamental processes and prediction of optimal parameters during the horizontal drilling and hydraulic fracturing process results in economically effective improvement of oil and natural gas extraction. Although modern analytical and computational models can capture fracture growth, there is a lack of experimental data on spontaneous imbibition and wettability in oil and gas reservoirs for the validation of further model development. In this work, we used neutron imaging to measure the spontaneous imbibition of water into fractures of Eagle Ford shale with known geometries and fracture orientations. An analytical solution for a set of nonlinear second-order differential equations was applied to the measured imbibition data to determine effective contact angles. The analytical solution fit the measured imbibition data reasonably well and determined effective contact angles that were slightly higher than static contact angles due to effects of in-situ changes in velocity, surface roughness, and heterogeneity of mineral surfaces on the fracture surface. Additionally, small fracture widths may have retarded imbibition and affected model fits, which suggests that average fracture widths are not satisfactory for modeling imbibition in natural systems. | Victoria H.DiStefano Michael C.Cheshire Joanna McFarlane Lindsay M.Kolbus Richard E.Hale Edmund Perfect Hassina Z.Bilheux Louis J.Santodonato Daniel S.Hussey David L.Jacobson Jacob M.LaManna Philip R.Bingham Vitaliy Starchenko Lawrence M.Anovitz | 2017 | Journal of Earth Science2017，28，5： | 1 |
| 2 | Maser radiation from collisionless shocks: application to astrophysical jets显示文摘This paper describes a model of electron energization and cyclotron-maser emission applicable to astrophysical magnetized collisionless shocks. It is motivated by the work of Begelman, Ergun and Rees [Astrophys. J. 625, 51(2005)] who argued that the cyclotron-maser instability occurs in localized magnetized collisionless shocks such as those expected in blazar jets. We report on recent research carried out to investigate electron acceleration at collisionless shocks and maser radiation associated with the accelerated electrons. We describe how electrons accelerated by lower-hybrid waves at collisionless shocks generate cyclotron-maser radiation when the accelerated electrons move into regions of stronger magnetic fields. The electrons are accelerated along the magnetic field and magnetically compressed leading to the formation of an electron velocity distribution having a horseshoe shape due to conservation of the electron magnetic moment. Under certain conditions the horseshoe electron velocity distribution function is unstable to the cyclotron-maser instability [Bingham and Cairns, Phys. Plasmas 7, 3089(2000); Melrose, Rev. Mod. Plasma Phys. 1, 5(2017)]. | D.C.Speirs K.Ronald A.D.R.Phelps M.E.Koepke R.A.Cairns A.Rigby F.Cruz R.M.G.M.Trines R.Bamford B.J.Kellett B.Albertazzi J.E.Cross F.Fraschetti P.Graham P.M.Kozlowski Y.Kuramitsu F.Miniati T.Morita M.Oliver B.Reville Y.Sakawa S.Sarkar C.Spindloe M.Koenig L.O.Silva D.Q.Lamb P.Tzeferacos S.Lebedev G.Gregori R.Bingham | 2019 | High Power Laser Science and Engineering2019，7，1： | 0 |
| 3 | Insensitivity of a turbulent laser-plasma dynamo to initial conditions显示文摘It has recently been demonstrated experimentally that a turbulent plasma created by the collision of two inhomogeneous,asymmetric,weakly magnetized,laser-produced plasma jets can generate strong stochastic magnetic fields via the small-scale turbulent dynamo mechanism,provided the magnetic Reynolds number of the plasma is sufficiently large.In this paper,we compare such a plasma with one arising from two pre-magnetized plasma jets whose creation is identical save for the addition of a strong external magnetic field imposed by a pulsed magnetic field generator.We investigate the differences between the two turbulent systems using a Thomson-scattering diagnostic,x-ray selfemission imaging,and proton radiography.The Thomson-scattering spectra and x-ray images suggest that the external magnetic field has a limited effect on the plasma dynamics in the experiment.Although the external magnetic field induces collimation of the flows in the colliding plasma jets and although the initial strengths of the magnetic fields arising from the interaction between the colliding jets are significantly larger as a result of the external field,the energies and morphologies of the stochastic magnetic fields post-amplification are indistinguishable.We conclude that,for turbulent laser-plasmas with supercritical magnetic Reynolds numbers,the dynamo-amplified magnetic fields are determined by the turbulent dynamics rather than the seed fields or modest changes in the initial flow dynamics of the plasma,a finding consistent with theoretical expectations and simulations of turbulent dynamos. | A.F.A.Bott L.Chen P.Tzeferacos C.A.J.Palmer A.R.Bell R.Bingham A.Birkel D.H.Froula J.Katz M.W.Kunz C.-K.Li H-S.Park R.Petrasso J.S.Ross B.Reville D.Ryu F.H.Séguin T.G.White A.A.Schekochihin D.Q.Lamb G.Gregori | 2022 | Matter and Radiation at Extremes2022，7，4： | 0 |
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