# Browsing by Subject "Multiphase"

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Item Analytical solutions of pressure-production tests with permanent multisensors in oil gas and water zones(2019-09-12) Rodriguez Roman, Jesus; Sepehrnoori, Kamy, 1951-; Daigle, Hugh; DiCarlo, David; Ezekoye, Ofodike; Okuno, RyosukeShow more The petroleum industry has invested millions of dollars in developing technologies for improving the monitoring methods for wells. These wells may have up to eight pressure sensors, recording infrastructure, and data transmission. The information from the sensors is at the disposal of the analyst immediately after the measurements are performed to make decisions about the exploitation of the reservoir. The usage of this information has not been completely useful because there are no developments in the literature on how to evaluate the combination of the pressure behaviors obtained through the sensors. Additionally, they present a high complexity as a result of the interrelationship between phases. The present work develops analytical pressure solutions for several cases, considering information from gauges at different fluid zones in the reservoir (Gas-cap, oil zone, and aquifer). The author presents approximations for both homogeneous and naturally fractured reservoirs and shows specialized graphs for the analysis of particular cases. Also, an analytical solution is developed to define the movement of the gas-oil contact. In this work, an approach to the study multiphase flow in the oil zone and a semi-analytic method to calculate properties for each phase are presented. All the proposed solutions are validated through the comparison of analytical and numerical solutions are denoting good agreements. Additionally, the researcher establishes approaches for the evaluation of production systems through well-test analysis using analytic solutions.Show more Item Characterization of structured packing via computational fluid dynamics(2014-12) Basden, Michael Allen; Bonnecaze, R. T. (Roger T.); Eldridge, R. BruceShow more CFD simulations were used to study single phase and multiphase flows through structured packing. Simulations utilizing a high fidelity, digital copy of a packing element were validated against experimental results for both single phase and multiphase flows. Single phase simulations were carried out on a variety of periodic packing elements to examine the impact of packing channel geometry on pressure drop. Multiphase simulations on periodic elements were used to examine the effect of hydrodynamic properties and boundary conditions. Single-phase simulations of nitrogen flow through the high fidelity geometry produced via X-ray CT scans showed average deviations less than 15% when compared to experimental measurements. This error was reduced to 7% when a mesh utilizing prism layers to accurately resolve the boundary layer was used. With a validated model for single phase flow, the application of CFD to packing design was investigated on periodic geometries with varied packing parameters (e.g. channel corrugation angle and channel side length). It was found that current industrial packings have channel geometries maximizing pressure drop, indicating some degree of optimization around channel geometry is possible depending on separation needs. Multiphase simulations using the Volume of Fluid model examined the effects of liquid density, viscosity, surface tension, and contact angle on small-scale packing geometries. Contact angle had the most pronounced influence on predicted wetting, and simulations demonstrated that using experimentally determined static contact angles was not an appropriate choice for the simulation contact angle. The predicted influence of surface tension qualitatively matched experimental data for wetted area. Liquid viscosity and density also demonstrated qualitative agreement with semi-empirical models derived from experimental data. Experimental data collected via absorption of CO2 into 0.1 mol/L NaOH were compared to simulation predictions using a geometry generated via X-ray CT scans. Wetted area predictions matched experimental data best when a fully wetting static contact angle (0°) was used, yielding simulated results 3.4% lower than experimental data on average. Irrigated pressure drop and holdup predictions were significantly higher than experimental data.Show more Item Development of a multiphase flow simulator for drilling applications(2017-08) Calvache Mejia, Sebastian; Sepehrnoori, Kamy, 1951-; Ribeiro, Paulo RShow more Drilling, or gas kick, simulators are becoming prevalent in industry due to their ability to replicate wellbore conditions that are not feasible in a laboratory setting. This is becoming more desirable as deeper wells are being explored. One of the biggest dangers that could happen during drilling operations is the onset of a gas kick. This occurs when a zone in the formation whose pressure is higher than that of the wellbore is breached. This allows for the undesired influx of formation fluids into the wellbore. If left uncontrolled, it could develop into a blowout. Gas kick simulators allow for testing of procedures that could be used to contain kicks at such depths. Furthermore, the use of drilling simulators could provide more insight into other phenomena. These include wellbore breathing and fracture ballooning, that cause similar kick symptoms at the surface and lead to expensive misdiagnosis, and the dissolution of gas into oil based mud, which could delay the identification of a kick. This thesis investigates the development of the initial integration of a drilling simulator into UTWELL, the wellbore simulator program developed at The University of Texas at Austin, by implementing a gas kick module. The transport equations of mass and momentum conservation were discretized using a Semi-Implicit Homogeneous Method over a one dimensional staggered grid. The multiphase phenomena were modelled using a Drift Flux approach as opposed to a mechanistic, Two Fluid approach. This was due to increased stability of the solution and faster computation time, despite the risk of loosing accuracy. The simulator was successful at simulating single phase flows for fluids with distinct rheology models, and with wellbores with discontinuities in the geometry. When attempting to simulate the well control of a gas kick in water based mud, the results were mixed. Attempt at simulating a `Floating Mud Cap' method failed due to the simulator's inability to perform drainage functions that allow for the raising and lowering of the mud level in the wellbore. However, the simulator was successful at capturing the behaviour of the gas kick as it entered and migrated through the wellbore, matching literature results. The simulator was compared to experimental data gathered from a test well. Three different scenarios were tested: No Drillstring, Semi-Submerged Drillstring and Drillstring at the Bottom. In all three cases, there was a good match between the experimental and simulation results for the bottomhole and choke pressures. The pit gain was severely overestimated in the 'No Drillstring' and 'Semi-Submerged Drillstring Case', however this was due to a higher influx of simulated gas having entered the wellbore during simulations. The 'Drillstring at the Bottom' simulation matched well with all data and with other simulators. Recommendations included full integration and testing of a compositional model to simulate oil based mud cases, implementation of automatic choke control and special flux splitting techniques in the discretization in order to better handle pressure waves caused by discontinuities.Show more Item Evolution equations in physical chemistry(2009-05) Michoski, Craig E.; Vasseur, Alexis F.; Stanton, John (John F.); Gamba, Irene M.; Wyatt, Robert E.; Souganidis, Panagiotis E.; Henkelman, GraemeShow more We analyze a number of systems of evolution equations that arise in the study of physical chemistry. First we discuss the well-posedness of a system of mixing compressible barotropic multicomponent flows. We discuss the regularity of these variational solutions, their existence and uniqueness, and we analyze the emergence of a novel type of entropy that is derived for the system of equations. Next we present a numerical scheme, in the form of a discontinuous Galerkin (DG) finite element method, to model this compressible barotropic multifluid. We find that the DG method provides stable and accurate solutions to our system, and that further, these solutions are energy consistent; which is to say that they satisfy the classical entropy of the system in addition to an additional integral inequality. We discuss the initial-boundary problem and the existence of weak entropy at the boundaries. Next we extend these results to include more complicated transport properties (i.e. mass diffusion), where exotic acoustic and chemical inlets are explicitly shown. We continue by developing a mixed method discontinuous Galerkin finite element method to model quantum hydrodynamic fluids, which emerge in the study of chemical and molecular dynamics. These solutions are solved in the conservation form, or Eulerian frame, and show a notable scale invariance which makes them particularly attractive for high dimensional calculations. Finally we implement a wide class of chemical reactors using an adapted discontinuous Galerkin finite element scheme, where reaction terms are analytically integrated locally in time. We show that these solutions, both in stationary and in flow reactors, show remarkable stability, accuracy and consistency.Show more Item Harmonic rejection mixers for wideband receivers(2013-05) Rafi, Aslamali Ahmed; Viswanathan, T. R., doctor of electrical engineering; Hassibi, ArjangShow more This dissertation presents novel Harmonic Rejection (HR) Mixer architectures to obtain a high level of harmonic rejection. This is achieved by reducing the sensitivity to mismatches in devices operating at high frequencies. Consequently, the HR performance for this mixer architecture is primarily determined by resistor and capacitor matching at low intermediate frequencies (IF). Since large resistor areas can be used at relatively less power penalty in the low frequency IF section, superior HR performance is realized. A design fabricated in 110 nm CMOS process, rejects up to the fi rst 14 local oscillator (LO) harmonics and achieves 3rd, 5th and 7th HR ratios in excess of 52, 54 and 55 dB respectively, without any calibration or trimming. This mixer architecture also rejects flicker noise, has improved image rejection (IR) and second-order input-intercept-point (IIP2) performance. By using a clock N times the desired LO frequency, this scheme rejects the (N-1)th LO harmonic only by an amount of 20log(N-1) dB. A new technique is presented that enables better HR for the (N-1)th harmonic while preserving the level of rejection for other harmonics. This mixer fabricated in 55 nm standard CMOS process has a programmable number of 8, 10, 12 or 14 mixer phases and achieves an improvement of 29 dB for the (N-1)th harmonic while achieving 52 dB of rejection for the 3rd harmonic. It also rejects flicker noise and has an IIP2 performance of 68 dBm. The mixers presented in this dissertation set the state-of-the-art in HR performance for single-stage mixers with configurable number of phases without using any calibration or trimming.Show more Item Pore-scale modeling of the impact of surrounding flow behavior on multiphase flow properties(2009-08) Petersen, Robert Thomas; Balhoff, Matthew T.; Bryant, Steven L.Show more Accurate predictions of macroscopic multiphase flow properties, such as relative permeability and capillary pressure, are necessary for making key decisions in reservoir engineering. These properties are usually measured experimentally, but pore-scale network modeling has become an efficient alternative for understanding fundamental flow behavior and prediction of macroscopic properties. In many cases network modeling gives excellent agreement with experiment by using models physically representative of real media. Void space within a rock sample can be extracted from high resolution images and converted to a topologically equivalent network of pores and throats. Multiphase fluid transport is then modeled by imposing mass conservation at each pore and implementing the Young-Laplace equation in pore throats; the resulting pressure field and phase distributions are used to extract macroscopic properties. Advancements continue to be made in making network modeling predictive, but one limitation is that artificial (e.g. constant pressure gradient) boundary conditions are usually assumed; they do not reflect the local saturations and pressure distributions that are affected by flow and transport in the surrounding media. In this work we demonstrate that flow behavior at the pore scale, and therefore macroscopic properties, is directly affected by the boundary conditions. Pore-scale drainage is modeled here by direct coupling to other pore-scale models so that the boundary conditions reflect flow behavior in the surrounding media. Saturation couples are used as the mathematical tool to ensure continuity of saturations between adjacent models. Network simulations obtained using the accurate, coupled boundary conditions are compared to traditional approach and the resulting macroscopic petrophysical properties are shown to be largely dependent upon the specified boundary conditions. The predictive ability of network simulations is improved using the novel network coupling scheme. Our results give important insight into upscaling as well as approaches for including pore-scale models directly into reservoir simulators.Show more Item A predictive model for sand production in poorly consolidated sands(2010-12) Kim, Sung Hyun, 1983-; Sharma, Mukul M.; Prodanovic, MasaShow more This thesis presents a model for the process of sand production that allows us to predict the stability of wellbores and perforation tunnels as well as mass of sand produced. Past analytical, numerical, and empirical models on material failure and erosion mechanisms were analyzed. The sand production model incorporates shear and tensile failure mechanisms. A criterion for sand erosion in failed sand was proposed based on a force balance calculation on the sand face. It is shown that failure, post failure sand mechanics and flow-dominated erosion mechanisms are important in the sand production process. The model has a small number of required input parameters that can be directly measured in the lab and does not require the use of empirical correlations for determining sand erosion. The model was implemented in a numerical simulator. Three different experiments using different materials were simulated and the results were compared to test the model. The model-generated results successfully matched the sand production profiles in experiments. When the post-failure behavior of materials was well-known, the match between the simulation and experiment was excellent. Sensitivity studies on the effect of mechanical stresses, flow rates, cohesion, and permeability show qualitative agreement with experimental observations. In addition, the effect of two-phase flow was presented to emphasize the importance of the water-weakening of the sand. These results show that catastrophic sand production can occur following water breakthrough. Finally the impact of increasing sand cohesion by the use of sand consolidation chemicals was shown to be an effective strategy for preventing sand production.Show more Item Simulation and analysis of the multiphase flow and stability of co-extruded layered polymeric films(2011-08) Chabert, Erwan; Bonnecaze, R. T. (Roger T.); Paul, Don R.Show more The flow and stability of co-extruded layers of different polymers in a forced assembly process is studied computationally to determine the extent of the stable process window and the types of instabilities that occur. Recent advances in layer-multiplying co-extrusion of incompatible polymers have made possible the fabrication of multilayered nanostructures with improved barrier, thermal and mechanical behavior. However, existing layering techniques are very sensitive to mismatches in viscosity and elasticity of the co-extruded polymers which often give rise to layer non-uniformity and flow instabilities, such as encapsulation. Simulations of the flows inside the feedblock and the successive multiplier dies of the multi-layering system are used to track the interface and predict instabilities and degrees of encapsulation as a function of process parameters, primarily the flow rates and rheology of the polymers. Encapsulation is found to be negligible in practice in the feedblock even for large viscosity contrasts and differences in elasticity between the two co-extruded polymers. Encapsulation or pinch-off of interfaces is more severe in the multiplier dies when there the rheologies of the polymers differ. A secondary flow due to the second normal stress differences for non-Newtonian fluids is primarily responsible for the encapsulation. A new multiplier design is proposed and simulated. The pressure drop in the proposed design is half that of the current design, which is useful for extruding highly elastic materials. Further, the degree of encapsulation is also reduced. The results of the simulations are validated with experimental measurements of pressure drop and flow visualization provided by research collaborators.Show more