This paper presents the theory and application to modify the conventional simulator to describe the effects of gas adsorption and gas slippage flow in shale gas. Because of the local desorption of gas and the assumptions of gas desorption instantaneously with the decrease in pore pressure, we define one fictitious immobile “pseudo” oil with dissolved gas. The dissolved gas–oil ratio is calculated from the Langmuir adsorption isotherm constants and shale gas properties. Additional modifications required in the input data are the porosity and relative permeability curves to account for the existence of “pseudo” oil. The input rock table considers the changes of rock permeability versus pressure to describe the gas slippage flow effects. In addition, dual-porosity dual-permeability models coupled with local grid refinement method are used to distinguish the impacts of natural fractures and hydraulic fractures on shale gas production with the comparison of vertical well, fractured vertical well, horizontal well, and multistage fractured horizontal well production. This proposed simulation approach shows enough accuracy and outstanding time efficiency. Results show that ignoring gas desorption and slippage flow effects would bring significant error in shale gas simulation The existence of natural fractures also imposes great effects on the productivity of shale gas.
This paper examines an integrated approach to study the permeability alteration resulting from nanofluid flow through porous media. Hydrophilic nanostructure particles (NSPs) are dispersed in the brine stream at 0.05, 0.2, and 0.5 wt % concentrations and injected into several oil-wet Berea sandstones. The pressure drops across the cores and the effluent nanoparticle concentrations are monitored. To quantify the nanoparticle adsorption/detachment and straining behavior and associated effects on formation permeability, analytical mechanistic models are derived using the method of characteristics. The interplay between nanoparticles and rocks is described by the classical particle filtration theory coupled with the maximum adsorption concentration model. All of the necessary parameters, e.g., the maximum adsorption concentrations, reversible or detachment adsorption concentrations, nanoparticle adsorption and straining rates, and corresponding formation damage coefficients, are characterized. The experimental results indicate that nanoparticle adsorption and straining (i.e., the maximum adsorption concentration and nanoparticle adsorption straining rates) are enhanced along with the increase of the nanoparticle injection concentration. As a result, the breakthrough of injected nanoparticles is delayed, the steady-state effluent concentration decreases, and the pressure drop increases more rapidly. The nanoparticle adsorption consists of reversible and irreversible adsorption. During post-flush, the reversible nanoparticle concentrations are enhanced by the increase of nanoparticle concentrations. In practice, this paper contributes to the following applications: (1) Lab experiments are applied to highlight the effects of nanoparticle adsorption, straining, and detachment behaviors on the formation damage. (2) The analytical mechanistic model provides physical insights to quantify nanofluid flow performance and can be extended to optimize the treatment of nanofluid application (e.g., injection concentrations) while considering both the loss of nanoparticles and their induced formation damage.
We present a theoretical investigation of the simultaneous generation of two orthogonally polarized terahertz (THz) waves by stimulated polariton scattering (SPS) with a periodically poled LiNbO3 (PPLN) crystal. The two orthogonally polarized THz waves are generated from SPS with A1 and E symmetric transverse optical (TO) modes in a LiNbO3 crystal, respectively. The parallel polarized THz wave is generated from A1 symmetric TO modes with type-0 phase-matching of e = e + e, and the perpendicular polarized THz wave is generated from E symmetric TO modes with type-I phase-matching of e = o + o. The two types of phase-matching of e = e + e and e = o + o can be almost satisfied simultaneously by accurately selecting the poling period of the PPLN crystal. We calculate the photon flux density of the two orthogonally polarized THz waves by solving the coupled wave equations. The calculation results indicate that the two orthogonally polarized THz waves can be efficiently generated, and the relative intensities between the two orthogonally polarized THz waves can be modulated.
We hereby show that root systems adapt to a spatially discontinuous pattern of water availability even when the gradients of water potential across them are vanishingly small. A paper microfluidic approach allowed us to expose the entire root system of Brassica rapa plants to a square array of water sources, separated by dry areas. Gradients in the concentration of water vapor across the root system were as small as 10-4⋅mM⋅m-1 (∼4 orders of magnitude smaller than in conventional hydrotropism assays). Despite such minuscule gradients (which greatly limit the possible influence of the well-understood gradient-driven hydrotropic response), our results show that 1) individual roots as well as the root system as a whole adapt to the pattern of water availability to maximize access to water, and that 2) this adaptation increases as water sources become more rare. These results suggest that either plant roots are more sensitive to water gradients than humanmade water sensors by 3-5 orders of magnitude, or they might have developed, like other organisms, mechanisms for water foraging that allow them to find water in the absence of an external gradient in water potential.
'/%3e%3cuse xlink:href='%23a' transform='rotate(23.036 .093 25.536)'/%3e%3cuse xlink:href='%23a' transform='rotate(45.87 1.273 16.18)'/%3e%3cuse xlink:href='%23a' transform='rotate(69.945 .996 12.078)'/%3e%3cuse xlink:href='%23a' transform='rotate(20.66 -19.689 31.932)'/%3e%3c/svg%3e)
