Cambridge, United Kingdom
Cambridge, United Kingdom

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Mitchell J.,Schlumberger | Lyons K.,Schlumberger | Howe A.M.,Schlumberger | Howe A.M.,BP Institute for Multiphase Flow | Clarke A.,Schlumberger
Soft Matter | Year: 2015

Viscoelastic polymer solutions flowing through reservoir rocks have been found to improve oil displacement efficiency when the aqueous-phase shear-rate exceeds a critical value. A possible mechanism for this enhanced recovery is elastic turbulence that causes breakup and mobilization of trapped oil ganglia. Here, we apply nuclear magnetic resonance (NMR) pulsed field gradient (PFG) diffusion measurements in a novel way to detect increased motion of disconnected oil ganglia. The data are acquired directly from a three-dimensional (3D) opaque porous structure (sandstone) when viscoelastic fluctuations are expected to be present in the continuous phase. The measured increase in motion of trapped ganglia provides unequivocal evidence of fluctuations in the flowing phase in a fully complex 3D system. This work provides direct evidence of elastic turbulence in a realistic reservoir rock-a measurement that cannot be readily achieved by conventional laboratory methods. We support the NMR data with optical microscopy studies of fluctuating ganglia in simple two-dimensional (2D) microfluidic networks, with consistent apparent rheological behaviour of the aqueous phase, to provide conclusive evidence of elastic turbulence in the 3D structure and hence validate the proposed flow-fluctuation mechanism for enhanced oil recovery. © 2016 The Royal Society of Chemistry.

Hesse M.A.,University of Texas at Austin | Woods A.W.,BP Institute for Multiphase Flow
Geophysical Research Letters | Year: 2010

Carbon capture and storage is currently the only technology that may allow significant reductions in CO2 emissions from large point sources. Seismic images of geological CO2 storage show the rise of CO 2 is influenced by horizontal shales. The buoyant CO2 spreads beneath impermeable barriers until a gap allows its upward migration. The large number and small scale of these barriers makes the prediction of the CO2 migration path and hence the magnitude of CO2 trapping very challenging. We show that steady buoyancy dominated flows in complex geometries can be modeled as a cascade of flux partitioning events. This approach allows the analysis of two-dimensional plume dispersal from a horizontal injection well. We show that the plume spreads laterally with height y above the source according to (y/h)1/2 L, where L is the width of the shales and h is their vertical separation. The fluid volume below successive shale layers, and therefore the magnitude of trapped CO2, increase as (y/h)5/4 above the source, so that every additional layer of barriers traps more CO2 than the one below. Upscaling small scale flow barriers by reducing the vertical permeability, common in numerical simulations of CO2 storage, does not capture the dispersion and trapping of the CO2 plume by the flow barriers. Copyright 2010 by the American Geophysical Union.

Fitzgerald S.D.,BP Institute for Multiphase Flow | Woods A.W.,BP Institute for Multiphase Flow
Building and Environment | Year: 2010

The natural ventilation of a well mixed, pre-heated room with a point source of heating, and openings at the base and roof is investigated. The transient draining associated with the room being warmer than the exterior combined with the convective flow produced by the point source of heat leads to a fascinating series of transient flow regimes as the system evolves to the two-layer steady-state regime described by Linden, Lane-Serff and Smeed [1]. As the room begins to ventilate, a turbulent plume rises from the point source of heat to the ceiling, and typically forms a deepening layer of hot air. However, with a weak heat source, then at some point the ascending plume will intrude beneath the layer of original fluid. Otherwise, the ascending plume always reaches the top of the room as the system evolves to a steady state. We develop a simplified model of the transient evolution and test this with some new laboratory experiments. We conclude with a discussion of the implications of our results for real buildings. © 2010.

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