149 research outputs found
Effect of oil on foam flow in porous media modeled by the Stochastic Bubble Population model
No full textThe Stochastic Bubble Population (SBP) model invented in 2006 by Prof. Dr. Zitha has been improved to take in account for the oil presence in the porous medium through which foam flows. The assumptions of the SBP model are that foam flow in porous media is a complex fluid and bubble generation is a stochastic process. The SBP model is a simple model as it describes the net bubble generation using three parameters: maximum bubble density, bubble generation and bubble destruction coefficients. Oil present in the porous medium through which foam flows destabilizes the foam indicating that there is a bubble destruction coefficient not equal to zero, which in turn is dependent on the prevailing oil saturation. In this paper we first introduce the modifications made for taking in account the presence of oil in the porous medium. Then we consider the SBP model for the case of a strong foam, thus bubble destruction coefficient equal to zero and perform a sensitivity analysis. Afterwards, the SBP model is considered again but then for the case of a destabilized foam, thus bubble destruction coefficient not equal to zero and perform another sensitivity analysis. Finally, the cases of zero and nonzero oil presence in the porous medium are compared with each other.Civil Engineering and GeosciencesGeoscience & Engineerin
Formation of Methane and Carbon Dioxide Hydrates in Bulk and in Porous Media
No full textGashydraatvorming is een kristallisatieproces. Dit proces bestaat uit twee fases, respectievelijk nucleatie (de vorming van nucleatie kernen) en hydraatgroei (degroei van kleine nucleatiekernen tot grote hydraatkristallen). Deze twee fases van het kristallisatieproces worden in het binaire systeem gekenmerkt door de nucleatietijd en de halfwaardetijd. De resultaten laten een afname zien in nucleatietijd naar mate oververzadiging en roersnelheid toenemen. Bovendien vermindert de nucleatietijd als gevolg van het geheugeneffect wanneer de experimenten worden uitgevoerd met `gebruikt' water. Dit geheugeneffect is beschreven door andere auteurs [98, 149] en kan worden verklaard door het bestaan van (water) hydraatstructuren na dissociatie van gashydraten. De structurering van de water-moleculen is waarschijnlijk gewaarborgd door de overvloed aan waterstofbruggen in de waterfase bij lage temperaturen door de aanwezigheid van opgeloste gastmoleculen. De tweede fase, de daadwerkelijke groei van gashydraten, bleek ongevoelig te zijn voor veranderingen in de mate van oververzadiging. De groei neemt toe met een verhoging van de roersnelheid; echter, het geheugeneffect van water heeft een licht negatief effect op de groei van het gashydraat. Daarom is niet nucleatie, maar kristalgroei de snelheidslimiterende stap tijdens gashydraatvorming. Uit experimenten in het binaire systeem bleek ook, dat, bij gelijke mate van oververzadiging, de kristalgroei van CO2 hydraten sneller is dan van CH4 hydraten. Dit wijst er op dat, kinetisch gezien, de vorming van CO2 hydraten gunsitiger is dan de vorming van CH4 hydraten. Bevindingen resulterend van experimenten in het ternaire systeem ondersteunen deze theorie. In het ternaire systeem blijken bij iedere geteste initiele druk CO2 moleculen makkelijker te vangen in kooien van watermoleculen dan CH4 moleculen (Hoofdstuk 4). Ondanks dat de CH4 concentratie in de gevormde gashydraten toeneemt met de initiele druk, bevatten de ontstane gashydraten nog steeds meer CO2 dan CH4. De formatie van methaanhydraat bij lage druk (lager dan de evenwichtsdruk van de H - Lw - V curve voor het CH4 + H2O systeem) wordt bevestigd. Dit betekent dat de aanwezigheid van een `makkelijkere' gashydraatvormer, zoals CO2, er voor kan zorgen dat de CH4 hydraat wordt gestabiliseerd. Experimenten, waarbij van een gasmix van 50/50 CH4/CO2 gashydraten worden gevormd, lieten zien dat de hoogste CH4 en CO2 scheidings effcientie wordt behaald bij een druk lager dan 3.5 MPa. Hierbij wordt in de gasfase een verandering van 18% van de initiele CH4 molfractie gevonden. Bulkexperimenten hebben tastbaar bewijs geleverd dat CH4 in de al gevormde methaanhydraten kan worden uitgewisseld met CO2 zonder dat er dissociatie van de gashydraten optreedt (Hoofdstuk 4). Echter, de vervanging vindt plaats op een zeer geringe diepte, vlakbij het scheidingsvlak tussen de gasfase en de gashydraten. Hierdoor functioneren CO2-rijke hydraatlagen als een schild en belemmeren verdere penetratie van CO2 in dieper gelegen methaanhydraatlagen en werken de migratiestroom van CH4 naar de gasfase tegen. Ten gevolge hiervan is het noodzakelijk dat eerst dissociatie van de CO2 hydraatlagen plaats vindt, alvorens er CH4 vrij kan komen uit de lager gelegen gashydraatlagen. Als gevolg is een lagere druk dan de evenwichtsdruk nodig voor de dissociatie van de CH4 hydraten. De CO2 hydratvorming werd ook bestudeerd in een kern bestaand uit gelijmde glazen kralen (Hoofdstuk 5). De vorming van gashydraat in dit poreuze medium werd voornamelijk waargenomen in het bovenste gedeelte van de horizontal gepositioneerde kern waar gas en connaat water zich bevinden. In het onderste gedeelte van de kern, voornamelijk gevuld met de CO2 verzadigde waterige vloeibare fase, werd een lokale distributie van gashydraatvorming geconstateerd, die moeilijk te detecteren valt op CT beelden. Drie verschillende regimes konden onderscheiden worden in het proces van gashydraat vorming: een reactie gelimiteerd regime, een di®usie gelimiteerd regime en een pre-evenwichtsregime. Uit de data komt naar voren dat de temperatuur en de snelheid waarmee het gas geinjecteerd wordt weinig invloed hebben op de vorming van gashydraten. Modelleren en numerieke simulaties van gelijktijdige methaanwinning en CO2 injectie in een klasse II gashydraat accumulatie hebben aangetoond dat door injectie van CO2 de productie van CH4 stijgt in vergelijking tot de methaanproductie door alleen drukvermindering (Hoofdstuk 6). In het beste geval nam de totale CH4 productie toe met 60% door de injectie van CO2. Ook kan uit de experimenten worden geconcludeerd dat CO2 op een effciente wijze kan worden opgeslagen in de vorm van hydraten. Slechts 2 mol% van het geinjecteerde CO2 werd hergeproduceerd. Uit de simulaties blijkt dat CO2 hydraten zich direct onder de lagen met CH4 hydraten vormen; de warmte die vrij komt bij deze CO2 hydraten formatie versterkt de verdere dissociatie van CH4 gashydraten.Geoscience & EngineeringCivil Engineering and Geoscience
Immiscible foam for enhancing oil recovery
No full textGrowing worldwide oil demand increased the need of new and efficient oil recovery methods. Gas injection in oil reservoirs is deemed one of the most widely used methods to increase oil recovery. However, the full potential of gas injection is often not realized due to poor vertical and areal sweep efficiency of the gas. Foaming could be a potential solution to mitigate the above challenges in gas-flood processes. This thesis aims to study the behavior of foam in natural sandstone previously subject to water flooding. It provides new insight into processes that could be highly relevant for the application of enhanced oil recovery (EOR) in clastic reservoirs. The main premise of this thesis is that whether stable foam can be generated in the presence of ware-flood residual oil and if so, can such foam increase oil recovery beyond water/gas flooding? These questions were addressed by performing systematic bulk and porous media studies. Firstly, the bulk foaming characteristics of several commercial surfactants were investigated to examine the effects of oil phase on the foamability and foam stability. A foaming agent, the AOS surfactant, which forms a stable foam in the presence of alkane-type oils, was thus identified. Secondly, the flow of that surfactant foam in natural sandstone was studied in the absence of oil. Effects of surfactant concentration and injection velocity on the foam mobility and foam propagation were examined in detail. Mechanisms involved in the foam mobility reduction were also explored. Knowledge obtained from the above part formed a basis for further study of the behavior of foam in porous media in the presence of oil. Thirdly, foam flow in water-flooded sandstone was studied with the aid of X-ray CT scanner, enabling us to provide evidence that stable foam could be obtained in the presence of oil. More significantly, we proved that foam displaced additional oil from water-flooded sandstone. Incremental oil recovery by foam was as much as 23±2% of the oil initially in place after injection of four pore volumes compared to only 5.0±0.5% for gas flooding at the same conditions. These results support the idea that foam is potentially an effective EOR method.Geoscience & EngineeringCivil Engineering and Geoscience
Formation dry-out and injectivity impairment during CO2 storage in saline aquifers
No full textThis research concerns the geological storage of CO2 and in particular injectivity impairment problems related to salt precipitation. Drying and salt precipitation in geological formations can have serious consequences for upstream operations in terms of injectivity and productivity. This can negatively affect the performance of injection and production wells and can even lead to well clogging, which is a serious risk for such operations.Geoscience & EngineeringCivil Engineering and Geoscience
Polymer gels for water control: NMR and CT scan studies
No full textAs oil and gas reservoirs mature, larger volumes of water are produced. These large volumes of produced water need to be separated, processed, treated and re-injected into the reservoir. All of these processes impose extra costs to the hydrocarbon production. Water rates can increase until production from a certain field is no longer economical. Therefore, there is a need to reduce water production. Depending on the nature of the problem, mechanical or chemical methods can be applied to remediate the excessive water problem. This research focused on the use of chemical methods for water shut-off. More specifically, this work is concerned with polymer gels for totally blocking excessive water production. Polymer gels are widely utilized for water shut-off. These chemicals are based on a polymer, a cross-linker and water. The solution is mixed at the surface. In such a case, it is a liquid. Then, this liquid (referred to as gelant) is injected into the target zone of the reservoir. After that, the well is shut-in for a certain time. During this shut-in time, the polymer and the cross-linker of the said gelant react to form a gel. Once the well is put back on production, the formed gel blocks the water flow. In fact, gels can also be applied in injection wells to divert water flow to less permeable zones in order to improve reservoir sweep efficiency. Research presented in this thesis established a systematic investigation methodology for an existing water shut-off chemical. A widely applied chemical is the polyacrylamide tert-butyl acrylate (PAtBA) cross-linked with polyethyleneimine (PEI). First, the gelation mechanisms of this system were explored in terms of published literature. Then, Carbon-13 Nuclear Magnetic spectroscopy (C-13 NMR) was used for analyzing the structural changes of the PAtBA copolymer. Gas Chromatography was used for analyzing gas products of the PAtBA thermal decomposition with and without the presence of PEI. The NMR studies indicated that gelation can take place at the amide groups of the PAtBA. Therefore, a more cost-effective polymer to be cross-linked with PEI was proposed, namely, simple polyacrylamide homopolymer (PAM). Research was then devoted to detailed analysis of the proposed system (PAM cross-linked with PEI). Bulk studies were conducted to address its thermal stability and gelation time at various conditions. High temperature glass tubes were used for thermal stability studies and steady shear viscometry was used for measurement of gelation time. The investigation was extended to porous media where the ability of the PAM/PEI system to reduce permeability of reservoir cores was examined. The system was efficient in reducing permeability of reservoir cores to zero for 7 weeks at 90oC (194oF). The displacement of the gel from porous media with low viscosity brine was examined with the aid of Computed Tomography. The brine was found to create a flow path within the rock containing the gel after a certain yielding pressure. Then, brine followed this path where no multiple branched fingering was observed. The fingering brine saturation was measured from the CT measurements and compared to theoretical models. In addition, the pressure behavior during gel extrusion from the rock matrix was compared to existing models. The yielding pressure was found to be a function of polymer content of the cured gel.Civil Engineering and Geoscience
Enhanced transport phenomena in CO2 sequestration and CO2 EOR
No full textThe results of this thesis give insight into the (mass)-transfer during flow of gases, especially CO2, in various gas-liquid systems. A number of experiments was performed to investigate the transport phenomena through interfaces with and without surfactant monolayers. The observed phenomena have been incorporated into physical models to predict the fate of CO2 overlaying a bulk liquid or liquid saturated porous media. Moreover, dynamics of (CO2)-foam flow in oil-free and oil-saturated porous media was studied using X-ray tomography.GeotechnologyCivil Engineering and Geoscience
Method of drilling with magnetorheological fluid
No full textA method of drilling a bore hole into a stratum, wherein via the drill hole drilling fluid is introduced and fed to the drill head. In order to avoid dilution or leak-off of the drilling fluid the same is in accordance with the invention a magnetorheological drilling fluid, and when an undesirable pressure difference occurs between the drilling fluid at the height of the drill head and a fluid present in the stratum surrounding the drill head, a magnetic field is applied. The inventions also provide a permanent solution.Civil Engineering and Geoscience
Underground storage of Diesel fuel oil in Salt Caverns
No full textApplied Earth ScienceGeoscience & EngineeringCivil Engineering and Geoscience
Method to form a barrier in a reservoir with a magnetorheological fluid
No full textThe invention relates to a method of winning oil from a source via a bored well, wherein a magnetorheological fluid is introduced into the source via the bored well to re duce the water content of the oil won. Oil drilling is resumed in the presence of a magnetic field, thereby increasing the oil yield and/or decreasing the water content of the drilled oil.Civil Engineering and Geoscience
Water Injectivity Prediction: Experiments and Modeling
No full textDecline in injectivity due to suspended solids in injected water is a wide spread phenomenon in water injection projects. Reliable prediction of injectivity through experiments and modeling is very essential under such circumstances. A model for predicting the injectivity during internal filtration taking into account particle dispersion, retention kinetics, nonlinear filtration, permeability reduction and viscosity functions was proposed. Subsequently, the analytical model for external filtration was coupled with the numerical model for internal filtration using the concept of transition time to predict the overall decline in injectivity. Core flood experiments using hematite suspensions for various particle concentrations (1-5 ppm) were conducted in Bentheim sandstone cores to quantify the injectivity. Simultaneously, X-ray CT scanning was performed under dynamic conditions to obtain deposition profiles along the core at different times. From microscopic analyses and visual observations, it was found that surface deposition in the porous medium and face plugging at the inlet of the core were responsible for decline in injectivity. A good agreement was obtained between the modeled and experimental results showing the validity of the retention function. Further, the effect of various parameters (particle concentration, number of grids etc.) on injectivity was investigated. Finally, the results from the study help the operators in planning and design of water management strategy for improved oil recovery projects.Petroleum EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
- …
