Flow characteristics and reaction properties of carbon dioxide in microtubules and porous media

Methane hydrate exists in huge amounts in certain locations, in sea sediments and the geological structures below them, at low temperature and high pressure. Production methods are in development to produce the methane to a floating platform. There it can be reformed to produce hydrogen and carbon dioxide, in an endothermic process. Some of the methane can be burned to provide heat energy to develop all needed power on the platform and to support the reforming process. After separation, the hydrogen is the valuable and transportable product. All carbon dioxide produced on the platform can be separated from other gases and then sequestered in the sea as carbon dioxide hydrate. In this way, hydrogen is made available without the release of carbon dioxide to the atmosphere, and the hydrogen could be an enabling step toward a world hydrogen economy.

The storage of carbon dioxide and acid gases in deep geological formations is considered a promising option for mitigation of greenhouse gas emissions. An understanding of the primary mechanisms such as convective mixing and geochemistry that affect the long-term geostorage process in deep saline aquifers is of prime importance. First, a linear stability analysis of an unstable diffusive boundary layer in porous media is presented, where the instability occurs due to a density difference between the carbon dioxide saturated brine and the resident brine. The impact of geochemical reactions on the stability of the boundary layer is examined. The equations are linearised, and the obtained system of eigenvalue problems is solved numerically. The linear stability results have revealed that geochemistry stabilises the boundary layer as reaction consumes the dissolved carbon dioxide and makes the density profile, as the source of instability, more uniform. A detailed physical discussion is also presented with an examination of vorticity and concentration eigenfunctions and streamlines' contours to reveal how the geochemical reaction may affect the hydrodynamics of the process. We also investigate the effects of the Rayleigh number and the diffusion time on the stability of a boundary layer coupled with geochemical reactions. Nonlinear direct numerical simulations are also presented, in which the evolution of density-driven instabilities for different reaction rates is discussed. The development of instability is precisely studied for various scenarios. The results indicate that the boundary layer will be more stable for systems with a higher rate of reaction. However, our quantitative analyses show that more carbon dioxide may be removed from the supercritical free phase as the measured flux at the boundary is always higher for flow systems coupled with stronger geochemical reactions.

The purpose of this work is to study the effect of carbon dioxide oil solubility on the aggregation of asphaltene associates and decrease of oil permeability of sandstones. Consideration is given to the interaction variants of oil and carbon dioxide in a free volume before being injected into a porous medium and immediately in the porous medium. The influence of oil composition on the aggregation of asphaltene associates is studied. The effect of the dissolved carbon dioxide on associate dispersion in oil is examined through oil filtering in sandstones. If asphaltene aggregation occurs in a porous medium it causes pore plugging leading to reduced permeability, complicates the development of carbon dioxide injection wells and, as a result, prevents from achieving the planned indicators of oil production and oil recovery. It is found that in the case when oil interacts with carbon dioxide in the free volume before being injected into a porous medium, the increase in the volume of filtered oil and the concentration of carbon dioxide dissolved in oil, and decrease in sandstone permeability reduce the relative mobility of oil with the dissolved carbon dioxide. The significant influence of sandstone permeability on the experimental results indicates that the sizes of asphaltene aggregates are comparable to the sizes of small pores. We have not observed complete attenuation of filtration after passing of oil with dissolved carbon dioxide through sandstones. Based on the analysis of changes in oil composition and properties carried out in the laboratory experiments on oil displacement by carbon dioxide rims, it has been determined that aggregation of asphaltene associates takes place under immediate contact of oil and carbon dioxide in a porous medium. The higher the asphaltene content in oil, the lower the formation permeability, whereas tight formations feature a more significant decrease in permeability.

A several-fold increase in the flow rate of liquids in synthetic and natural sandstone cores was observed upon application of direct electrical current. These results present the possibility of using direct electric treatment to stimulate wells or enhance water injectivity. Introduction Electroosmosis has long been applied in soil engineering, and there are several patents granted on the removal of water from clayey and silty soils by electroosmosis. These techniques have been used successfully in Germany, England, the U.S.S.R. and Canada in drying water-logged soils for heavy construction. Casagrande documented a good example of electroosmosis in a large-scale soil drying operation in Salzgitter, Germany, during the construction of a double-track railway cutting in a loose loam deposit. Well electrodes were 7.5 m deep and 10 m apart. Before the application of electrical potential, the water flow rate was 0.4 cu m/day/20 wells. potential, the water flow rate was 0.4 cu m/day/20 wells. An electrical potential of 180 v and 19 amps/well increased the flow rate to 60 cu m/day/20 wells, or 150 times the original rate. We and our colleagues have conducted extensive research on the effect of direct electrical current on permeability of sandstone cores. In some of these permeability of sandstone cores. In some of these earlier experiments the flow rate of water was increased by as much as 32-fold on application of direct electrical current, whereas in other cases the increase in flow rate was only about twofold. It was not clear as to why the volumetric rate of flow increased much more in some cases than in others. It was concluded that there is a possibility of using direct electrical current to enhance the injectivity of water in waterflood systems, or simply to increase the rate of production in tight formations. Amba et al. have discussed production in tight formations. Amba et al. have discussed the economics. Amba et al. reported a 175 percent increase in flow rate at 1.5 psi pressure drop upon application of a potential gradient of 4.5 v/cm and a current density of 0.28 milliamp/sq cm. Chilingar et al. reported a 33.7-fold increase in water flow rate at 3.0 psi pressure drop upon application of a potential gradient pressure drop upon application of a potential gradient of 7.5 v/cm and a current density to 20 milliamp/sq cm. Adding CaCl2 (0.1 to 0.5 percent by weight) to the flowing liquid increased the electrosmotic flow rate and resulted in electrochemical changes in the porous medium. These changes were evidenced by porous medium. These changes were evidenced by the higher final permeability upon discontinuation of the treatment (hysteresis effect). Chilingar et al. discovered, however, that the volumetric rate of flow increased to a lesser degree on using concentrated formation brines. Tikhomolova studied the displacement of immiscible liquids in a porous medium. She compared the effectiveness of displacement caused by capillary forces only (imbibition) with that of displacement owing to application of an electric field to the system (electroosmotic displacement) in relation to the capillary radii of powder systems. Based on her experiments, electroosmosis substantially increases the rate of displacement of nonpolar kerosene over the entire range of particle sizes studied (16 to 20, 12 to 16, 8 to 12, and 4 to 8 microns). The influence of electroosmosis increases with decrease in size of silica particles and with increase in backpressure applied to the system. JPT P. 830

A 6M digital twin for modeling and simulation in subsurface reservoirs

The flow characteristics of different gases such as air, helium and carbon dioxide and internal convection heat transfer between the solid particles and the fluid in mini/micro porous media were studied experimentally. The test sections for fluid flow and heat transfer were made of sintered bronze particles with average diameters of 225 μm, 125 μm, 90 μm and 40 μm. The experimentally measured friction factors with consideration of compressibility for air, helium and carbon dioxide in the porous media with average diameters of 225 μm and 125 μm agree well with the known correlation for normal size porous media (the correlation of Aerov and Tojec), especially at the relatively high Reynolds numbers. The experimentally measured friction factors for air, helium and carbon dioxide in the porous media with average diameters of 90 μm are slightly less than the correlation of Aerov and Tojec at the relatively low Reynolds numbers. The experimental values for the friction factors for air, helium and carbon dioxide in the microporousmedia with 40 μm average diameters are much less than the correlation of Aerov and Tojec. The results show that rarefaction effects occur in air, helium and hydrogen flows in the microporous media with particle diameters less than 90 μm. The internal convection heat transfer coefficients between particles and fluid for air, helium and carbon dioxide in the micro porous media were determined experimentally.

Coupling covariance matrix adaptation with continuum modeling for determination of kinetic parameters associated with electrochemical CO2 reduction

Mayo Clinic, Rochester, Minnesota. roy.tk@mayo.eduCapnography: Clinical Aspects. Edited by J. S. Gravenstein, M.D., Dr. med. h.c., Michael B. Jaffe, Ph.D., and David A. Paulus, M.D. Cambridge, United Kingdom, Cambridge University Press, 2004. Pages: 441. Price: $120.00.Practicing anesthesiologists and intensivists have come to take capnography for granted in the monitoring of surgical and critically ill patients. Although many standard anesthesiology texts contain a chapter about this important and useful technique, a comprehensive up-to-date treatment of the subject is not easy to find. Capnography: Clinical Aspects fills this void.The book is a multiauthored effort edited by two academicians and an engineer working in industry. The editors acknowledge significant overlap between chapters and characterize the book as more of a “symposium” than a textbook. There is adequate continuity of style between chapters, but as with any book written in this format, some chapters are more interesting to read than others.The book is organized into four parts. The first part is meant to be clinical and describes the interaction of respiratory, cardiovascular, and metabolic systems in determining the amount of exhaled carbon dioxide as measured by capnography. This is followed by parts on basic carbon dioxide physiology, the history of capnography, and the technology of capnography.The clinical part is divided into four sections: Ventilation, Circulation, Metabolism, and Organ Effects. The ventilation section is further divided into subsections on breathing assessment, airway management, monitoring of ventilation, weaning, and special situations. The first chapter (written by two of the editors) is a well-written introduction to time-based capnogram interpretation, the most commonly used form of capnography in the operating room setting. Of particular value is the introduction to the volume-based capnogram, a topic not commonly detailed in anesthesia texts. Subsequent chapters discuss capnography outside the operating room and in the prehospital setting for airway management, in particular to confirm tracheal intubation. The chapter on airway management in the intensive care unit includes a section on using capnography to confirm proper orogastric and nasogastric tube placement. The chapter on airway management in the operating room includes sections on confirming tracheal intubation and recognizing endobronchial tube placement.The chapter describing the use of capnography to monitor ventilation during anesthesia includes interesting comments on the Food and Drug Administration checkout relevant to capnography. This chapter also includes sections on equipment troubleshooting and how capnograms can be affected by positioning, pulmonary pathology, and several particular situations such as one-lung ventilation, laparoscopy, neurosurgery, cardiac surgery, tourniquet release, and high-frequency jet ventilation. Other chapters in this section focus on the use of capnography during transport and how it can be used in the field as a way to avoid deleterious effects of unintentional hyperventilation after intubation.A particularly comprehensive chapter describes the unique physiology and technological limitations of capnography in neonates and infants. Other chapters describe capnography in the sleep laboratory, capnography as a feedback tool for behavioral therapy in various disorders, and how the capnogram is affected by alterations in physiologic and technical limitations in high- and low-pressure environments.Chapters are also included on sedation and noninvasive ventilation. These chapters are valuable for their descriptions of how end-tidal carbon dioxide can be sampled during spontaneous ventilation in nonintubated patients and the clinical utility and limitations of end-tidal carbon dioxide as a method of estimating arterial carbon dioxide tension (PCO2) in noninvasive ventilation.Chapters relevant to critical care describe the use capnography to optimize tidal volume, alveolar minute ventilation, and positive end-expiratory pressure to wean patients from mechanical ventilation. These chapters also describe the use of volumetric capnography to assess carbon dioxide production and how the capnogram is affected by positive end-expiratory pressure, unilateral lung injury, tracheal gas insufflation, and various high-frequency ventilation modes.The circulation subsection includes chapters on how end-tidal carbon dioxide monitoring can be used to assess circulatory status during cardiopulmonary resuscitation and for prognostication during cardiac arrest in medical patients as well as the use of end-tidal and tissue carbon dioxide monitoring techniques to assess oxygen delivery in shock states. This section includes an elegant physiologic description of changes in alveolar dead space with pulmonary embolism and the use of capnography in diagnosis and treatment of pulmonary emboli and gas embolization in addition to a chapter on the utility of volumetric capnography for estimating arterial PCO2in patients with acute respiratory distress syndrome.The chapter on noninvasive pulmonary blood flow measurement describes complete and partial carbon dioxide rebreathing techniques as alternatives to invasive cardiac output monitoring. A variety of clinical scenarios illustrating the use of these techniques sets this chapter apart from other descriptions of this topic.The metabolism subsection includes a single chapter describing alterations in normal physiology induced by surgery and anesthesia that affect carbon dioxide elimination. The chapter discusses alterations in ventilation, circulation, and carbon dioxide metabolism that are influenced by temperature alterations, various anesthetic techniques, and pharmacologic agents as well as particular intraoperative situations such as laparoscopy, tourniquet release, vascular cross clamping, and cardiopulmonary bypass.The final chapter of the ventilation section describes the effects of hypercapnia and hypocapnia on tissue oxygenation and perfusion, focusing on the central nervous system, respiratory system, and cardiovascular system. This is an excellent introduction to the effect of carbon dioxide at the organ, tissue, and cellular/molecular level and could have been included in the section on physiology.The physiology section includes a chapter on carbon dioxide pathophysiology, which describes inherited and acquired mitochondrial and enzyme disorders as well as pharmacologic agents that alter carbon dioxide production. The chapter also discusses carbon dioxide embolism and the increase in PCO2during apnea testing for brain death. There is a complete if somewhat standard chapter on acid–base physiology, followed by an excellent description of how capnography can provide information on ventilation/perfusion mismatch from a physiologic standpoint, including examples of various disease states. Subsequent chapters describe clinical correlates of alterations in normal time and volume capnographic tracings and how capnograms can provide clues to the underlying pathophysiology.A particularly interesting chapter in this section summarizes a biomedical engineering approach to illustrate the underlying anatomical and physiologic processes that result in a normal volumetric capnogram. A mathematical model that accounts for bronchial airway structure, gas convection and diffusion, and the carbon dioxide release from alveolar capillary blood is shown to generate a computed washout curve that shows remarkable agreement with an experimentally measured capnogram from a healthy human subject. This illustrates the utility of physiologic modeling as a useful tool for investigating potentially complex pathophysiologies without placing patients at risk.A unique historical section describes the evolution of time and volumetric capnography with many interesting anecdotes, as well as a first-person account by Smalhout, an early proponent of capnography. A selection of capnographic tracings corresponding to clinical events that he made over a 20-yr period is one of the highlights of this book. Without reading this section of the book, few people would realize that the impetus for carbon dioxide analyzer development was to investigate the cause of death in patients who turned out to be rebreathing due to a channeling issue through carbon dioxide absorption devices, or that carbon dioxide analyzers enabled a reduction in mortality for polio patients by allowing clinicians to titrate ventilation to expired carbon dioxide instead of adjusting ventilation based on their weight.The technological section fulfills the editors’ wishes for providing clinicians with information necessary to appreciate the mechanism, design, and limitations of devices for measuring carbon dioxide. Various chapters address technical specifications and standards (e.g. , accuracy, range, drift, response time, interfering gases, alarm systems, calibration) for carbon dioxide analyzers and describe technological limitations for flow measurement, required to estimate carbon dioxide production. Another chapter describes various methods for carbon dioxide detection, including infrared, photoacoustic, colorimetric, and mass spectrometry methods. Unfortunately, Raman spectroscopy is not included simply because it is not currently commercially available. This chapter also includes a discussion of mainstream versus sidestream carbon dioxide analyzers.The book ends with a mini-atlas of capnographic waveforms typifying various physiologic states, which is useful although not exhaustive.As the editors acknowledge, there is a fair amount of redundancy; as an example, the fact that highly sensitive colorimetric carbon dioxide indicators can yield false positives with esophageal intubation is mentioned in multiple chapters along with the fact that false negatives in cardiac arrest have led to the removal of correctly placed endotracheal tubes. Other recurring themes include the predictive value of end-tidal carbon dioxide in assessing arterial PCO2and the utility of volumetric capnography. In general, I found the multiple perspectives to be helpful instead of confusing or irritating. As with any book, the onus is on the reader to formulate his or her judgment with the assistance of the most recent literature.The overall introduction to the book and the introduction chapters for each section are very short and could have been used to provide the reader with a more substantial description of the basic concepts or objectives of each section. The section and subsection titles are somewhat arbitrary, and some chapters are in fact assigned to their own sections. Although the terminology is relatively consistent, the book could also use a more comprehensive list of abbreviations and acronyms used in various chapters. I found most of the typographical and page-setting errors to be minor (with the exception of a reference to “title” volumes). In spite of these limitations, the book admirably maintains its focus on capnography; readers interested in the latest tissue oxygen tension (PO2) monitoring techniques, for example, will have to look elsewhere.In summary, Capnography: Clinical Aspects is a very readable introduction to a topic addressed by few textbooks. It is useful as a reference primarily because of its comprehensive index and contains much information useful to the practitioner of critical care as well as anesthesiology. It addresses the physiologic and technological considerations that need to be understood to make capnography a clinically useful tool and should be standard reading for those who depend on it as a basic anesthetic monitor.Mayo Clinic, Rochester, Minnesota. roy.tk@mayo.edu

Thermodynamic effects of cycling carbon dioxide injectivity in shale reservoirs

The object of this study was to determine if crude oil could be produced successfully by a process of crude oil vaporization using carbon dioxide repressuring. This process appears to have application to highly fractured formations where the major oil content of the reservoir is contained in the non-fractured porosity with little associated permeability. Crude oil was introduced into the windowed cell and carbon dioxide was charged to the cell at the desired pressure. A vapor space was formed above the oil, and the crude oil-carbon dioxide mixture was allowed to come to equilibrium. The vapor phase was removed and the vaporized oil collected as condensate. Samples of all produced and unproduced fluids were analyzed. Tests were also performed to evaluate the amount of vaporized oil that can be produced by rocking from a high to a lower pressure. The carbon dioxide repressuring process was applied to a sand-filled cell to investigate the performance in a porous medium. A test was performed to evaluate how the condensate recovery changes as the size of the gas cap in contact with the oil changes. Introduction This study has been directed toward a relatively new process of vaporization of crude oil designed to increase ultimate production of hydrocarbons through the application of carbon dioxide to an oil reservoir. Suggested advantages of carbon dioxide repressuring of a petroleum reservoir are: - reduction in viscosity of liquid hydrocarbons due to the solubility of carbon dioxide in crude oil, - swelling of the reservoir oil into a larger liquid-oil volume with a resulting increase in production and decrease in residual oil saturation due to an increase in the relative permeability to oil, - displacement of more stock-tank oil from the reservoir since the residual liquid is a swelled crude oil, and - gasification of some of the hydrocarbons into a carbon dioxide-hydrocarbon vapor mixture. Balanced against these advantages are several detrimental factors which must be evaluated; i.e., high compression costs and corrosion of well equipment and flow lines. Some of the more outstanding contributions to the study of carbon dioxide injection have been reviewed in order to furnish a basis for a continuation of research pertaining to this method. The literature reviewed has been limited to that dealing with carbon dioxide repressuring processes or with carbon dioxide-crude oil-natural gas phase behavior. Articles relating to carbonated water injection and literature published on the use of low pressure carbon dioxide gas injection in water flooding have not been included in this study. In 1941 Pirson suggested the high pressure injection of carbon dioxide into a partially depleted reservoir for the purpose of causing the reservoir oil to vaporize and thus produce the oil as a vapor along with the carbon dioxide gas. By reducing the pressure on this produced mixture of hydrocarbons and carbon dioxide at the surface, it was proposed to separate the hydrocarbons from the carrier gas. He theorized that essentially all the oil in a reservoir could be produced by simply injecting enough carbon dioxide to vaporize the residual oil. This present investigation deals with the vaporization of a crude oil by carbon dioxide, the molecular weight and gravity of the vaporized oil product and the characteristics of the residual oil after several repressuring cycles with carbon dioxide. An attempt is made to evaluate the merits of a vaporization process for the crude oil rather than a flow process where the oil recovery is determined by relative permeability considerations. Such a vaporize of crude oil by carbon dioxide repressuring appears to have possible use in a highly fractured formation where the major oil content of the reservoir is contained in the non-fractured porosity with little permeability. The carbon dioxide flows into the fractures, contacts the crude oil in the matrix and vaporizes part of the crude oil; this vaporized oil is produced and recovered and the carbon dioxide is reinjected again. The specific problem of this study is to attempt to answer this question; Can crude oil be produced successfully (technically, but without economic considerations) from a petroleum reservoir by a process of vaporization of the crude oil by carbon dioxide repressuring?

Reactivity of dolomite in water-saturated supercritical carbon dioxide: Significance for carbon capture and storage and for enhanced oil and gas recovery

This study concerns the construction and operation of a laboratory model of a non-recharged (pressure depletion) two-phase geothermal reservoir. The primary emphasis was directed towards the significance of vapor pressure lowering phenomena caused by interfacial tension in a consolidated porous medium. Preliminary runs were made which porous medium. Preliminary runs were made which indicated vapor pressure lowering effects as large as 15 psia in a consolidated porous medium at geothermal system temperatures of 220 deg. F to 290 deg. F. Model construction and operating details are given. Introduction In a single-component vapor-liquid system, vaporization occurs whenever the vapor phase absolute pressure is equal to or less than the vapor pressure of the liquid at the system temperature. pressure of the liquid at the system temperature. The solid line on Fig. 1 shows the vapor pressure vs. temperature for a flat liquid surface. However, within a porous medium, interfaces should be curved and the solid line on Fig. 1 may not be appropriate. In order to understand geothermal reservoir behavior, it is important to define the vapor pressure curve for conditions correct for geothermal reservoirs. Many factors are known to affect pressure temperature phase diagram for reservoir fluids. Among these are solution of solids, gases, and liquids in the liquid phase and the composition of both phases. Geothermal liquids are known to contain large amounts of salts in solution in some cases, and geothermal steam often contains non-condensible gases (carbon dioxide a major constituent). Another important factor is caused by the rock. Capillarity and adsorption phenomena also may affect vapor pressure of fluids in pore space of rocks. We will neglect the effects of materials in solution in the following and direct attention toward development of a geothermal model and study the vapor pressure of a pure liquid and boiling in a porous medium. Because capillary pressure is known to affect vapor pressure in a pressure is known to affect vapor pressure in a porous medium, we expect capillary pressure to be porous medium, we expect capillary pressure to be a major factor in this study. The relationship between capillary pressure and water content for a water-wet porous medium has been studied for both drainage and imbibition for water saturations greater than the practical irreducible wetting phase saturation, S wi. The portion to the right of the dotted line in Fig. 2 portion to the right of the dotted line in Fig. 2 represents conventional capillary pressure-water saturation curves. The dotted line represents the conventional concept of irreducible wetting phase saturation. We speculate that there must be phase saturation. We speculate that there must be drainage and imbibition curves to the left of the conventional Swi. Calhoun, et al., have provided perhaps the only quantitative information available for the low water saturation region less than Swi. The transfer of liquid from a flat surface to the pore space of a core caused by the lower vapor pore space of a core caused by the lower vapor pressure of the liquid within the core was pressure of the liquid within the core was observed. The lower vapor pressure was apparently the result of the capillary pressure caused by curved surfaces within the core. The Calhoun, et al., work was performed at 97 deg. F for high permeability cores (permeability 700 md or more). permeability cores (permeability 700 md or more).The hysteresis between drainage and imbibition in the low liquid content region on Fig. 2 could be caused by a difference in adsorption and capillarity. As liquid enters a dry core, it would form layers on the surface until liquid content became high enough for interfaces to meet and form curved surfaces. On desaturation, the liquid interfaces should remain connected to low liquid contents. Normally, one would expect increasing temperatures to decrease capillary pressure effects because surface and interfacial tensions normally decrease with temperature increase. However, Sinnokrot, et al., found that Swi increased with temperature increase for several sandstone cores.

Experimental investigation of the asphaltene deposition in porous media: Accounting for the microwave and ultrasonic effects

Although sufficient capacity exists in theory to substantially increase the geological storage of CO2 to limit or reverse the effects of climate change, various challenges remain to be addressed regarding sustained, unimpeded and prolonged injectivity of CO2 into the various types of target reservoirs. Improved understanding of the physics and chemistry of subsurface CO2 flow for the purposes of geological storage is required. As CO2 is injected, geochemical reactions between CO2, brine, and minerals will occur, and this can lead to formation damage which compromises the injectivity of the CO2, either by fines migration or the precipitation of various undesirable solids, e.g., scale, hydrates, and ice. There are various near-well treatments available to maintain or restore injectivity. However, effective selection and deployment of these treatments requires improved understanding of the underlying damage mechanisms that occur during CO2 geological injection and storage. This understanding requires effective experimental protocols to generate field-representative phenomena reproducible at the laboratory scale. The current paper aims to highlight key operational challenges related to CO2 injection in low-temperature environments at various pressures. A new approach is provided in this paper to assess injectivity impairment phenomena, and their remediation, both at the laboratory scale. A novel core flooding-based testing apparatus was used to measure permeability changes of a porous core medium during injection of liquid or gaseous carbon dioxide across a range of saturations, temperatures, and pressures. This demonstrates the effect on injectivity of various formation-damage mechanisms, including formation of CO2 hydrates. The new dynamic dual-phase injection test rig was designed, built, and used to assess a range of conditions expected during CO2 injection either into deep saline aquifers or depleted oil and gas reservoirs. Injection of CO2 into a brine-saturated porous core medium, with manipulation of the pressure into the hydrates-formation envelope, resulted in severe blockages in the core sample. Manipulation of the temperatures and pressures at specific trajectories allowed for determination of CO2 hydrates blockages. Reproduction of injectivity impairment under a variety conditions, saturations and flow rates demonstrated the ability to form, dissipate, and reform CO2 hydrates within a porous medium. The equipment allows for near wellbore treatment assessment (including inhibition, remediation, prevention and induced fractures methods) which are now being developed exclusively as CO2-specific additives to manage injectivity and well integrity. This paper presents new laboratory workflow for the dynamic assessment of CO2 injection into reservoirs, determining under which specific operating conditions CO2 injectivity is impaired due to formation of various solids. This apparatus surpasses existing methods outlined in literature which mostly rely on static measurements of fluids rather than dynamic measurements in reservoir core, a much more field representative scenario for geological carbon storage.

The applications of carbon dioxide sequestration in brine-saturated reservoirs, \nas well as recovery of oil from oil-wet reservoirs, involve the injection of a less-\nviscous, non-wetting fluid into a porous medium occupied by a more-viscous, wetting \nfluid: i.e., drainage with an unfavorable viscosity ratio. In these cases, there is \na competition between capillary fingering and viscous fingering. \n In standard treatments of two-phase flow in porous media, the flow is assumed \nto be compact, with a uniform residual saturation behind a front, which advances \nlinearly with time. This view of two phase flow is inconsistent with the cases of \nfractal capillary fingering at zero capillary numbers, and fractal viscous fingering \nresulting from injection of an inviscid fluid. \nEarlier work has shown that when the flow characteristics are not precisely at their \nfractal limit, the fractal fingering behavior crosses over to standard behavior at a \ncharacteristic time which is inversely related to the distance of the flow \ncharacteristics from their fractal limit. This earlier work was limited to \ncrossover from one type of fractal fingering to standard flow. \n We present results from pore-level modeling for a range of capillary numbers \nand unfavorable viscosity ratios. The results are analyzed to determine how the \ncompeting capillary and viscous fingerings cross over to compact flow. These \nresults are compared with predictions of a scaling hypothesis based upon experience \nwith the aforementioned, simpler fractal-to-compact crossovers from one type of \nfractal fingering to standard/compact flow.