Furqan Hussain

Abstract: Enhanced coalbed methane (ECBM) core flooding experiments are a direct way to observe the gas displacement process, the competitive adsorption and the effect of coal swelling and shrinkage on coal permeability. This study reports two ECBM experiments. In the first experiment, pure N2 is injected (N2-ECBM) to a coal sample saturated with CH4 while, in the second experiment, pure CO2 is injected (CO2-ECBM) to the same coal sample cleaned and resaturated with CH4. We record the volumes and composition of the effluent gas with respect to time. Then the gas rate and gas composition are history matched using a commercial reservoir simulator. The results show that the breakthrough of N2 occurs earlier than CO2 breakthrough (after approximately 0.1 day of injection compared to 0.43 day). The recovery factor of CH4 is 71% for the N2-ECBM and 86% for the CO2-ECBM at a 10%-molar percentage of CH4 in the produced gas stream. The N2 injection causes moderate increases in coal permeability whereas the injection of CO2 reduces coal permeability significantly. The maximum strain of CO2 injection is higher at the initial stage of CO2 injection but decreases after several days of injection. The extended Langmuir adsorption model predicts the compositional adsorption amounts of N2 and CH4 better for the N2-ECBM than for the CO2-ECBM. A co-optimisation concept is presented to analyse the coupling of ECBM with CO2 storage which shows that early times CO2 storage efficiency is higher than CH4 recovery efficiency. Later CO2 storage efficiency decreases due to CO2 production and CH4 recovery dominates the co-optimisation.

Abstract: Permeability decline during waterflooding by varying water composition, in particular with low salinity or high pH water, has been observed in numerous laboratory studies This has been explained by the lifting, migration and subsequent plugging of pores by fine particles Recently, mathematical models have been presented to investigate the concept of using this permeability decline for mobility control during a waterflood Now, these models need to be tested against observations during a core flood test This paper presents a systematic laboratory study to investigate the underlying physics mechanisms for improved oil recovery as a consequence of injecting low-salinity water Three sister plugs of Berea sandstone were used in the experiments The first plug was subjected to single-phase waterflood for permeability measurements with varying salinities from 4 (high-salinity) to 0 (low-salinity) g/L NaCl Core permeability decreased from 495 to 60 md, confirming the effect of changing water composition on permeability The second plug saturated with high-salinity water was subjected first to primary oil flood (using Soltrol) to the connate water saturation and then to a benchmark waterflood using the same water The oil recovery was noted and the core was restored to the connate water by a secondary oil flood Finally, low-salinity waterflood was carried out and oil recovery was recorded Experimental observations were interpreted using a numerical model In order to check the reproducibility of the observations, the same experimental procedure was applied on the third plug Results confirmed the reproducibility of the observations Significant decrease in water relative permeability by approximately 50% and some decrease in residual oil saturation by about 5% were observed during the low-salinity waterflood in comparison with the high-salinity waterflood Treatment of the low-salinity coreflood data by a numerical model reveals the decrease in water relative permeability with increasing water saturation at high water saturations This observation is explained by the expansion of rock surface exposed to low-salinity water during the increase of water saturation The laboratory data matched by the numerical model shows a high surface exponent value (nA=30), which is explained by a sharp surface area rise at high water saturations The abnormal behavior of water relative permeability in response to low-salinity waterflood has resulted from matching water permeability increase at low water saturations and decrease at high saturations

Abstract: bility due to large permeability contrasts. The most accurate upscaling technique is employing Darcy’s law. A key part of the study is the establishment of porosity transforms between highresolution and low-resolution images to arrive at a calibrated porosity map to constraint permeability estimates for the whole core.

Abstract: Produced water during coal seam gas (CSG) production carries fines. A few laboratory studies reported in open media suggest that fines migration can cause variation in coal permeability during water flow. However, a detailed laboratory study has not been reported so far to explain this variation in coal permeability. The characterization of coal and produced fines and water quality may shed light on the root causes of variation in coal permeability. This paper presents an experimental study on an anthracite coal sample from a CSG field in China to investigate the impact of fines migration on coal permeability. Proximate, petrographic and XRD tests are conducted for a robust characterization of the coal sample. The coal sample is first covered with Araldite epoxy to minimize any confining stress effect during the flow test. Then the coal sample is saturated with filtered distilled water which is also injected to the coal sample. The injection pressure is kept constant during the flow and the production rate is measured continuously to calculate permeability. Once the measured permeability stabilizes, the injection pressure is increased to see the effect of pressure gradient on fines migration and permeability variation. Effluent water is collected frequently and analyzed by a laser particle counter to determine the concentration and size of the produced fines. The fines are then separated from the water samples using membrane filters and analyzed under a scanning electron microscope and electron dispersive X-ray (SEM–EDX) to investigate their composition and morphology. The proximate test shows 9.6% ash (air-dried-basis) in the coal sample while the low-temperature ashing XRD shows kaolinite (38.5%), illite (26.2%) and chloride (2.8%) clay in the mineral matters. Production of fines and permeability increases and decreases are observed during water injection. The permeability decrease is attributed to the blockage of cleats by fines whereas the permeability increase indicates the mobilization of trapped fines. The characterization of produced fines shows that the majority of fines are clay particles with some coal fines also observed.

Abstract: This paper presents an experimental and numerical study that delineates the co-optimization of carbon dioxide (CO2) storage and enhanced oil recovery (EOR) in water-alternating-gas (WAG) and simultaneous-water-and-gas (SWAG) injection schemes. Various miscibility conditions and injection schemes are investigated. Experiments are conducted on a homogeneous, outcrop Bentheimer sandstone sample. A mixture of hexane (C6) and decane (C10) is used for the oil phase. Experiments are run at 70 degrees C and three different pressures (1,300, 1,700, and 2,100 psi) to represent immiscible, near-miscible, and miscible displacements, respectively. WAG displacements are performed at a WAG ratio of 1: 1, and a fractional gas injection (FGI) of 0.5 is used for SWAG displacements. The effect of varying FGI is also examined for the near-miscible SWAG displacement. Oil recovery, differential pressure, and compositions are recorded during experiments. A co-optimization function for CO2 storage and incremental oil production is defined and calculated by use of the measured data for each experiment. The results of SWAG and WAG displacements are compared with the experimental data of continuous-gas-injection (CGI) displacements. A compositional commercial reservoir simulator is used to examine the recovery mechanisms and the effect of mobile water on gas mobility.Experimental observations demonstrate that the WAG displacements generally yield higher co-optimization function than CGI and SWAG with FGI = 0.5 displacements. Numerical simulations show a remarkable reduction in gas relative permeability for the WAG and SWAG displacements compared with CGI displacements, as a result of which the vertical-sweep efficiency of CO2 is improved. More reduction of gas relative permeability is observed in the miscible and near-miscible displacements than in the immiscible displacement. The reduced gas relative permeability lowers the water-shielding effect, thereby enhancing oil recovery and CO2-storage efficiency. More water-shielding effect is observed in SWAG with FGI = 0.5 than in WAG. However, increasing FGI from 0.5 to 0.75 in the near-miscible SWAG displacement shows a significant increase in oil recovery, which is attributed to reduced water-shielding effect. So, an optimal FGI needs to be determined to minimize the water-shielding effect for efficient SWAG displacements.

Abstract: The validity of the cubic law for laminar flow of fluids through open fractures consisting of parallel planar plates has been established by others over a wide range of conditions with apertures ranging down to a minimum of 0.2 µm. The law may be given in simplified form by Q/Δh = C(2b)3, where Q is the flow rate, Δh is the difference in hydraulic head, C is a constant that depends on the flow geometry and fluid properties, and 2b is the fracture aperture. The validity of this law for flow in a closed fracture where the surfaces are in contact and the aperture is being decreased under stress has been investigated at room temperature by using homogeneous samples of granite, basalt, and marble. Tension fractures were artificially induced, and the laboratory setup used radial as well as straight flow geometries. Apertures ranged from 250 down to 4µm, which was the minimum size that could be attained under a normal stress of 20 MPa. The cubic law was found to be valid whether the fracture surfaces were held open or were being closed under stress, and the results are not dependent on rock type. Permeability was uniquely defined by fracture aperture and was independent of the stress history used in these investigations. The effects of deviations from the ideal parallel plate concept only cause an apparent reduction in flow and may be incorporated into the cubic law by replacing C by C/ƒ. The factor ƒ varied from 1.04 to 1.65 in these investigations. The model of a fracture that is being closed under normal stress is visualized as being controlled by the strength of the asperities that are in contact. These contact areas are able to withstand significant stresses while maintaining space for fluids to continue to flow as the fracture aperture decreases. The controlling factor is the magnitude of the aperture, and since flow depends on (2b)3, a slight change in aperture evidently can easily dominate any other change in the geometry of the flow field. Thus one does not see any noticeable shift in the correlations of our experimental results in passing from a condition where the fracture surfaces were held open to one where the surfaces were being closed under stress.

Abstract: Background Engineering student team projects are frequently used to meet professional learning outcomes. Industrial and organizational psychologists study teams in the industry settings for which we prepare students, yet this research does not effectively inform engineering education. Purpose This research review sought to demonstrate the relevance of literature on teams literature from industrial and organizational psychology to engineering education and to identify implications for practice and future directions for research. Scope/Method Phase 1 systematically reviewed 104 articles published from 2007 to 2012 describing engineering and computer science student team projects and sought to answer the following questions: What professional learning outcomes have been met by team projects? What negative student team behaviors have faculty sought to minimize? What literature has been used to inform development of teamwork outcomes? Phase 2 reviewed five team effectiveness constructs selected according to the results of Phase 1: social loafing, interdependence, conflict, trust, and shared mental models. Examples from Phase 1 articles and our own work explain how this research informs facilitation and assessment of engineering student teams. Conclusions Engineering faculty sought to achieve a variety of outcomes through team projects, including teamwork, communication, sustainability, and consideration of global/societal design context. They sought to avoid social loafing and conflict while building trust to ensure equal team effort. That few Phase 1 articles engaged the literature about team effectiveness indicates there is great opportunity to apply industrial and organizational psychology research to engineering education.

Abstract: A unique contrast agent technique using X-ray micro-computed tomography (micro-CT) was developed for studying micrometer-sized features in coal. The technique allows for the visualization of coal fractures not visible with conventional imaging methods. A Late Permian medium volatile bituminous coal from Moura coal mine was imaged and the resulting three-dimensional coal cleat system was extracted for fluid flow simulations. The results demonstrate a direct relationship between coal lithotype and permeability, i.e. bright coals offer more permeability than dull coals. However, there was no direct relationship between porosity and permeability for any given lithotype. Scanning electron microscope and energy dispersive spectrometry (SEM–EDS) together with X-ray diffraction (XRD) methods were used for identifying mineral matter at high resolution. After segmentation of the micro-CT image, mineral phase was removed from the segmented data and it was found that permeability was significantly improved by increasing cleat void space and connectivity; suggesting that enhanced recovery methods could target de-mineralization techniques. Overall, only the epigenetic mineral phases in the bright band influenced permeability while lithotype had a stronger impact on permeability than porosity. Coal lithotype and mineralization are important evaluation criteria when considering coal seam gas development sites.

Abstract: We explore the fully coupled thermo-hydro-mechanical-chemical (THMC) response of CO2 enhanced CBM recovery (CO2-ECBM) considering the coupling relationships of competitive sorption of binary gas and dissolved gas in water (C), gas and water transport in two phase flow (H), thermal expansion and non-isothermal gas sorption (T), and coal deformation (M). The THMC model is developed, validated then applied to simulate CO2 enhanced recovery. Parametric studies are completed, systematically switching-off components of the thermal (T) and hydraulic (H) coupling, to provide insights into key processes controlling ECBM recovery and key factors. The evolution of permeability is strongly dependent on coal matrix swelling/shrinkage induced by gas adsorption/desorption, expansion by thermal effects, and compaction by effective stress. Reservoir permeability first decreases, then rebounds before continuously decreasing to low magnitude. Ignoring the impact of water migration overestimates CH4 production, and ignoring heat transfer underestimates. The high injection pressure and initial permeability will promote fluid mixture transport, resulting in an increase in production and sequestration; conversely, high injection temperature and water saturation will result in a decrease. Delaying injection start time is shown to counter the low average production rate and early CO2 breakthrough resulting from early injection (beginning at ∼2500 days for this case).

Abstract: Sizeable amounts of connected microporosity with various origins can have a profound effect on important petrophysical properties of a porous medium such as (absolute/relative) permeability and capillary pressure relationships. We construct pore-throat networks that incorporate both intergranular porosity and microporosity. The latter originates from two separate mechanisms: partial dissolution of grains and pore fillings (e.g. clay). We then use the reconstructed network models to estimate the medium flow properties. In this work, we develop unique network construction algorithms and simulate capillary pressure–saturation and relative permeability–saturation curves for cases with inhomogeneous distributions of pores and micropores. Furthermore, we provide a modeling framework for variable amounts of cement and connectivity of the intergranular porosity and quantifying the conditions under which microporosity dominates transport properties. In the extreme case of a disconnected inter-granular network due to cementation a range of saturations within which neither fluid phase is capable of flowing emerges. To our knowledge, this is the first flexible pore scale model, from first principles, to successfully approach this behavior observed in tight reservoirs.