Ultralow-frequency wave and test particle models are used to investigate the pitch angle and energy dependence of ion differential fluxes measured by the Van Allen Probes spacecraft on 6 October 2012. Analysis of the satellite data reveals modulations in differential flux resulting from drift resonance between H + ions and fundamental mode poloidal Alfvén waves detected near the magnetic equator at L ∼ 5.7. Results obtained from simulations reproduce important features of the observations, including a substantial enhancement of the differential flux between ∼20 and 40 ∘ pitch angle for ion energies between ∼90 and 220 keV and an absence of flux modulations at 90 ∘ . The numerical results confirm predictions of drift-bounce resonance theory and show good quantitative agreement with observations of modulations in differential flux produced by ultralow-frequency waves.
Key Points:• ULF wave and test particle models are used to investigate the pitch angle and energy dependence of H + fluxes observed by Van Allen Probes • Trapping of a population of drift-resonant ions in a range of L is observed • The dependence of the drift-resonance energy on pitch angle leads to butterfly shaped ion distributions
Stand-alone sand screen (SAS) is proven to be effective for sand control in unconsolidated sands in thermal wells. The characteristic design parameter to specify SAS is the aperture size, while the Open to Flow Area (OFA) is chosen to balance between the mechanical integrity of the screen, the completion cost, and the plugging risk. The objective of this study is to compare the performance of common SAS types for a certain geological condition.
A series of three-phase large-scale sand retention tests (SRTs) is performed on slotted liner, wire-wrapped screen, and punched screen coupons. The tests are performed using two common representative PSDs of the McMurray Formation. The test matrix includes the common aperture sizes and OFA for each screen and PSD based on the current best practices in the industry. The test procedure is designed to mimic the near wellbore flow velocities, with three-phase flow ranging from 0%-100% water cut and produced gas-oil ratio ranging from 0-277 scf/bbl. The gas flow was supposed to simulate the steam breakthrough incidents. Live measurements are obtained of the sanding amount and pressure drops along the sand-pack and across the screen. Screen plugging is assessed after the completion of each test.
The sanding and flow performance are shown to be a function of the aperture size, PSD, near-wellbore flow velocities, and the water cut. In low fluid flow rates, all the screen types show minimal pressure drops and perform similarly. As near-wellbore velocities increase or gas flow occurs, pressure drops show a significant increase for all devices. Results show OFA, aperture size, and screen type affect the pressure drop and sanding. In all cases, the produced sand in three-phase flow is the determining design parameter for the upper-bound acceptable aperture. The gas flow is observed to accompany large amounts of sanding for larger aperture sizes. Further, test results indicate high pressure drops for three-phase flow conditions. Test results reveal the complexity of the interaction between different design parameters, which affect the sand and flow performance, hence, necessitating an SRT test for each specific case.
This paper presents the results of physical model testing of different standalone screens in terms of flow performance and sand control. This will help to identify the main factors that influence the performance of each specific screen type and develop the rationale for the screen type selection in new developments.
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