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Instruments / Technical Area	Publication Details	Published
I13-2-Diamond Manchester Imaging	Verifying pore network models of imbibition in rocks using time‐resolved synchrotron imaging Tom Bultreys , Kamaljit Singh , Ali Q. Raeini , Leonardo C. Ruspini , Pål‐eric Øren , Steffen Berg , Maja Rücker , Branko Bijeljic , Martin J. Blunt Water Resources Research 56 DOI: 10.1029/2019WR026587 Diamond Proposal Number(s): [11587] Open Access Show Abstract ▼ Abstract: At the pore scale, slow invasion of a wetting fluid in porous materials is often modeled with quasi‐static approximations which only consider capillary forces in the form of simple pore‐filling rules. The appropriateness of this approximation, often applied in pore network models, is contested in the literature, reflecting the difficulty of predicting imbibition relative permeability with these models. However, validation by sole comparison to continuum‐scale experiments is prone to induce model overfitting. It has therefore remained unclear whether difficulties generalizing the model performance are caused by errors in the predicted filling sequence or by subsequent calculations. Here, we address this by examining whether such a model can predict the pore‐scale fluid distributions underlying the behavior at the continuum scale. To this end, we compare the fluid arrangement evolution measured in fast synchrotron micro‐CT experiments on two rock types to quasi‐static simulations which implement capillary‐dominated pore filling and snap‐off, including a sophisticated model for cooperative pore filling. The results indicate that such pore network models can, in principle, predict fluid distributions accurately enough to estimate upscaled flow properties of strongly wetted rocks at low capillary numbers.	Jun 2020
I13-2-Diamond Manchester Imaging	Pore-scale dynamics and the multiphase Darcy law Ying Gao , Qingyang Lin , Branko Bijeljic , Martin J. Blunt Physical Review Fluids 5 DOI: 10.1103/PhysRevFluids.5.013801 Open Access Show Abstract ▼ Abstract: Synchrotron x-ray microtomography combined with sensitive pressure differential measurements were used to study flow during steady-state injection of equal volume fractions of two immiscible fluids of similar viscosity through a 57-mm-long porous sandstone sample for a wide range of flow rates. We found three flow regimes. (1) At low capillary numbers, Ca, representing the balance of viscous to capillary forces, the pressure gradient, ∇ P , across the sample was stable and proportional to the flow rate (total Darcy flux) q t (and hence capillary number), confirming the traditional conceptual picture of fixed multiphase flow pathways in porous media. (2) Beyond Ca ∗ ≈ 10 − 6 , pressure fluctuations were observed, while retaining a linear dependence between flow rate and pressure gradient for the same fractional flow. (3) Above a critical value Ca > Ca i ≈ 10 − 5 we observed a power-law dependence with ∇ P ∼ q a t with a ≈ 0.6 associated with rapid fluctuations of the pressure differential of a magnitude equal to the capillary pressure. At the pore scale a transient or intermittent occupancy of portions of the pore space was captured, where locally flow paths were opened to increase the conductivity of the phases. We quantify the amount of this intermittent flow and identify the onset of rapid pore-space rearrangements as the point when the Darcy law becomes nonlinear. We suggest an empirical form of the multiphase Darcy law applicable for all flow rates, consistent with the experimental results.	Jan 2020
I13-2-Diamond Manchester Imaging	Dynamics of enhanced gas trapping applied to CO2 storage in the presence of oil using synchrotron X-ray micro tomography Alessio Scanziani , Kamaljit Singh , Hannah Menke , Branko Bijeljic , Martin J. Blunt Applied Energy DOI: 10.1016/j.apenergy.2019.114136 Diamond Proposal Number(s): [19367] Show Abstract ▼ Abstract: During CO2 storage in depleted oil fields, under immiscible conditions, CO2 can be trapped in the pore space by capillary forces, providing safe storage over geological times - a phenomenon named capillary trapping. Synchrotron X-ray imaging was used to obtain dynamic three-dimensional images of the flow of the three phases involved in this process - brine, oil and gas (nitrogen) - at high pressure and temperature, inside the pore space of Ketton limestone. First, using continuous imaging of the porous medium during gas injection, performed after waterflooding, we observed chains of multiple displacements between the three phases, caused by the connectivity of the pore space. Then, brine was re-injected and double capillary trapping - gas trapping by oil and oil trapping by brine - was the dominant double displacement event. We computed pore occupancy, saturations, interfacial area, mean curvature and Euler characteristic to elucidate these double capillary trapping phenomena, which lead to a high residual gas saturation. Pore occupancy and saturation results show an enhancement of gas trapping in the presence of both oil and brine, which potentially makes CO2 storage in depleted oil reservoirs attractive, combining safe storage with enhanced oil recovery through immiscible gas injection. Mean curvature measurements were used to assess the capillary pressures between fluid pairs during double displacements and these confirmed the stability of the spreading oil layers observed, which facilitated double capillary trapping. Interfacial area and Euler characteristic increased, indicating lower oil and gas connectivity, due to the capillary trapping events.	Nov 2019
I13-2-Diamond Manchester Imaging	Time-resolved synchrotron X-ray micro-tomography datasets of drainage and imbibition in carbonate rocks Kamaljit Singh , Hannah Menke , Matthew Andrew , Christoph Rau , Branko Bijeljic , Martin J. Blunt Scientific Data 5 DOI: 10.1038/sdata.2018.265 Diamond Proposal Number(s): [11587] Open Access Show Abstract ▼ Abstract: Multiphase flow in permeable media is a complex pore-scale phenomenon, which is important in many natural and industrial processes. To understand the pore-scale dynamics of multiphase flow, we acquired time-series synchrotron X-ray micro-tomographic data at a voxel-resolution of 3.28 μm and time-resolution of 38 s during drainage and imbibition in a carbonate rock, under a capillary-dominated flow regime at elevated pressure. The time-series data library contains 496 tomographic images (gray-scale and segmented) for the complete drainage process, and 416 tomographic images (gray-scale and segmented) for the complete imbibition process. These datasets have been uploaded on the publicly accessible British Geological Survey repository, with the objective that the time-series information can be used by other groups to validate pore-scale displacement models such as direct simulations, pore-network and neural network models, as well as to investigate flow mechanisms related to the displacement and trapping of the non-wetting phase in the pore space. These datasets can also be used for improving segmentation algorithms for tomographic data with limited projections.	Dec 2018
I13-2-Diamond Manchester Imaging	Dynamics of snap-off and pore-filling events during two-phase fluid flow in permeable media Kamaljit Singh , Hannah Menke , Matthew Andrew , Qingyang Lin , Christoph Rau , Martin J. Blunt , Branko Bijeljic Scientific Reports 7 DOI: 10.1038/s41598-017-05204-4 Diamond Proposal Number(s): [11587] Open Access Show Abstract ▼ Abstract: Understanding the pore-scale dynamics of two-phase fluid flow in permeable media is important in many processes such as water infiltration in soils, oil recovery, and geo-sequestration of CO2. The two most important processes that compete during the displacement of a non-wetting fluid by a wetting fluid are pore-filling or piston-like displacement and snap-off; this latter process can lead to trapping of the non-wetting phase. We present a three-dimensional dynamic visualization study using fast synchrotron X-ray micro-tomography to provide new insights into these processes by conducting a time-resolved pore-by-pore analysis of the local curvature and capillary pressure. We show that the time-scales of interface movement and brine layer swelling leading to snap-off are several minutes, orders of magnitude slower than observed for Haines jumps in drainage. The local capillary pressure increases rapidly after snap-off as the trapped phase finds a position that is a new local energy minimum. However, the pressure change is less dramatic than that observed during drainage. We also show that the brine-oil interface jumps from pore-to-pore during imbibition at an approximately constant local capillary pressure, with an event size of the order of an average pore size, again much smaller than the large bursts seen during drainage.	Jul 2017
I13-2-Diamond Manchester Imaging	Dynamic fluid connectivity during steady-state multiphase flow in a sandstone Catriona A. Reynolds , Hannah Menke , Matthew Andrew , Martin J. Blunt , Samuel Krevor Proceedings Of The National Academy Of Sciences 4 DOI: 10.1073/pnas.1702834114 Diamond Proposal Number(s): [10605] Show Abstract ▼ Abstract: The current conceptual picture of steady-state multiphase Darcy flow in porous media is that the fluid phases organize into separate flow pathways with stable interfaces. Here we demonstrate a previously unobserved type of steady-state flow behavior, which we term “dynamic connectivity,” using fast pore-scale X-ray imaging. We image the flow of N2 and brine through a permeable sandstone at subsurface reservoir conditions, and low capillary numbers, and at constant fluid saturation. At any instant, the network of pores filled with the nonwetting phase is not necessarily connected. Flow occurs along pathways that periodically reconnect, like cars controlled by traffic lights. This behavior is consistent with an energy balance, where some of the energy of the injected fluids is sporadically converted to create new interfaces.	Jul 2017
I13-2-Diamond Manchester Imaging	Dynamic Pore-scale Reservoir-condition Imaging of Reaction in Carbonates Using Synchrotron Fast Tomography Hannah Menke , Matthew G. Andrew , Joan Vila-comamala , Christoph Rau , Martin J. Blunt , Branko Bijeljic J. Vis. Exp. 120, e53763 DOI: 10.3791/53763 Diamond Proposal Number(s): [11587] Open Access Show Abstract ▼ Abstract: Synchrotron fast tomography was used to dynamically image dissolution of limestone in the presence of CO2-saturated brine at reservoir conditions. 100 scans were taken at a 6.1 µm resolution over a period of 2 hours.	Feb 2017
I13-2-Diamond Manchester Imaging	Dynamic imaging of oil shale pyrolysis using synchrotron X-ray microtomography Tarik Saif , Qingyang Lin , Kamaljit Singh , Branko Bijeljic , Martin J. Blunt Geophysical Research Letters 43, 6799 - 6807 DOI: 10.1002/2016GL069279 Diamond Proposal Number(s): [11587] Open Access Show Abstract ▼ Abstract: The structure and connectivity of the pore space during the pyrolysis of oil shales determines hydrocarbon flow behavior and ultimate recovery. We image the time evolution of the pore and microfracture networks during oil shale pyrolysis using synchrotron X-ray microtomography. Immature Green River (Mahogany Zone) shale samples were thermally matured under vacuum conditions at temperatures up to 500°C while being periodically imaged with a 2 µm voxel size. The structural transformation of both organic-rich and organic-lean layers within the shale was quantified. The images reveal a dramatic change in porosity accompanying pyrolysis between 390 and 400°C with the formation of micron-scale heterogeneous pores. With a further increase in temperature, the pores steadily expand resulting in connected microfracture networks that predominantly develop along the kerogen-rich laminations.	Jul 2016
I13-2-Diamond Manchester Imaging	Reservoir condition imaging of reactive transport in heterogeneous carbonates using fast synchrotron tomography — Effect of initial pore structure and flow conditions H. Menke , M. G. Andrew , M. J. Blunt , B. Bijeljic Chemical Geology 428, 15 - 26 DOI: 10.1016/j.chemgeo.2016.02.030 Diamond Proposal Number(s): [9377] Open Access Show Abstract ▼ Abstract: We investigate the impact of initial pore structure and velocity field heterogeneity on the dynamics of fluid/solid reaction at high Péclet numbers (fast flow) and low Damköhler number (relatively slow reaction rates). The Diamond Lightsource Pink Beam was used to image dissolution of Estaillades and Portland limestones in the presence of CO2-saturated brine at reservoir conditions (10 MPa and 50 °C representing ~ 1 km aquifer depth) at two flow rates for a period of 2 h. Each sample was scanned between 51 and 94 times at 4.76-μm resolution and the dynamic changes in porosity, permeability, and reaction rate were examined using image analysis and flow modelling.	Jun 2016
I13-2-Diamond Manchester Imaging	The Imaging of Dynamic Multiphase Fluid Flow Using Synchrotron-Based X-ray Microtomography at Reservoir Conditions Matthew Andrew , Hannah Menke , Martin J. Blunt , Branko Bijeljic Transport In Porous Media DOI: 10.1007/s11242-015-0553-2 Show Abstract ▼ Abstract: Fast synchrotron-based X-ray microtomography was used to image the injection of super-critical CO2 under subsurface conditions into a brine-saturated carbonate sample at the pore-scale with a voxel size of 3.64μm and a temporal resolution of 45 s. Capillary pressure was measured from the images by finding the curvature of terminal menisci of both connected and disconnected CO2 clusters. We provide an analysis of three individual dynamic drainage events at elevated temperatures and pressures on the tens of seconds timescale, showing non-local interface recession due to capillary pressure change, and both local and distal (non-local) snap-off. The measured capillary pressure change is not sufficient to explain snap-off in this system, as the disconnected CO2 has a much lower capillary pressure than the connected CO2 both before and after the event. Disconnected regions instead preserve extremely low dynamic capillary pressures generated during the event. Snap-off due to these dynamic effects is not only controlled by the pore topography and throat radius, but also by the local fluid arrangement. Whereas disconnected fluid configurations produced by local snap-off were rapidly reconnected with the connected CO2 region, distal snap-off produced much more long-lasting fluid configurations, showing that dynamic forces can have a persistent impact on the pattern and sequence of drainage events.	Aug 2015

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