INTRODUCING CORE-SHELL TECHNOLOGY FOR CONFORMANCE CONTROL

Reservoir heterogeneities can severely affect the effectiveness of waterflooding because displacing fluids tend to flow along high-permeability paths and prematurely breakthrough at producing wells. A Proof-of-Concept (PoC) study is presented while discussing the experimental results of a research on “core-shell” technology to improve waterflooding in heterogeneous oil reservoirs. The proposed methodology consists in injecting a water dispersion of nanocapsules after the reservoir has been extensively flushed with water. The nanocapsules are made of a “core” (either polymeric or siliceous materials), protected by a “shell” that can release its content at an appropriate time, which activates through gelation or aggregation thus plugging the high permeability paths. Additional flooding with water provides recovery of bypassed oil. The initial conceptual screening of possible materials was followed by extensive batch and column lab tests. Then, 3D dynamic simulations at reservoir scale were performed to compensate for the temporary lack of pilot tests and/or field applications

Adsorption and wettability study of methyl ester sulphonate on precipitated asphaltene

Asphaltene precipitation from crude oil and its subsequent aggregation forms solid, which preferentially deposit on rock surfaces causing formation damage and wettability changes leading to loss of crude oil production. To resolve this problem, asphaltene inhibitor has been injected into the formation to prevent the precipitation of asphaltene. Asphaltene inhibitors that are usually employed are generally toxic and non-biodegradable. This paper presents a new environmentally friendly asphaltene inhibitor (methyl ester sulphonate), an anionic surfactant, which has excellent sorption on formation rock surfaces. Result from adsorption study validated by Langmuir and Freundlich models indicate a favourable adsorption. At low volumes injected, methyl ester sulphonate is capable of reverting oil-wet sandstone surface to water-wet surface. Biodegradability test profile shows that for concentrations of 100-5000ppm it is biodegradable by 65-80%

Experimental Study and Performance Investigation of Miscible Water-Alternating-CO 2

This experimental study is aimed at evaluating the performance of the miscible Water-Alternating-CO2 (CO2-WAG) flooding as a function of slug size and WAG ratio based on the ultimate oil recovery in the Sarvak formation. In this research, initially the slim-tube apparatus was used to determine the Minimum Miscibility Pressure (MMP) of the Sarvak heavy oil and CO2 at the constant reservoir temperature. Then, a total of seven core flooding experiments were performed by using the sandstone core samples collected from the Sarvak formation. These experiments were conducted through respective water flooding, miscible continuous CO2 flooding, and miscible CO2-WAG flooding. In the miscible CO2-WAG flooding, different WAG slug sizes of 0.15, 0.25, and 0.50 Pore Volume (PV) and different WAG ratios of 1:1, 2:1, and 1:2 were applied to investigate their effects on the oil Recovery Factor (RF) in the Sarvak formation. The results showed that, in general, the miscible CO2 Enhanced Oil Recovery (CO2-EOR) process is capable of mobilizing the heavy oil and achieving a high and significant oil RF in the Sarvak formation. The miscible CO2-WAG flooding has the highest oil RF (84.3%) in comparison with water flooding (37.7%), and miscible continuous CO2 flooding (61.5%). In addition, using a smaller WAG slug size for miscible CO2-WAG flooding leads to a higher oil RF. The optimum WAG ratio of the miscible CO2-WAG flooding for the Sarvak formation is approximately 2:1. The results also demonstrated that, more than 50% of the heavy oil is produced in the first two cycles of the miscible CO2-WAG flooding. The optimum miscible CO2-WAG flooding has a much less CO2 consumption than the miscible continuous CO2 flooding

Oral biofilm models for mechanical plaque removal

In vitro plaque removal studies require biofilm models that resemble in vivo dental plaque. Here, we compare contact and non-contact removal of single and dual-species biofilms as well as of biofilms grown from human whole saliva in vitro using different biofilm models. Bacteria were adhered to a salivary pellicle for 2 h or grown after adhesion for 16 h, after which, their removal was evaluated. In a contact mode, no differences were observed between the manual, rotating, or sonic brushing; and removal was on average 39%, 84%, and 95% for Streptococcus mutans, Streptococcus oralis, and Actinomyces naeslundii, respectively, and 90% and 54% for the dual- and multi-species biofilms, respectively. However, in a non-contact mode, rotating and sonic brushes still removed considerable numbers of bacteria (24–40%), while the manual brush as a control (5–11%) did not. Single A. naeslundii and dual-species (A. naeslundii and S. oralis) biofilms were more difficult to remove after 16 h growth than after 2 h adhesion (on average, 62% and 93% for 16- and 2-h-old biofilms, respectively), while in contrast, biofilms grown from whole saliva were easier to remove (97% after 16 h and 54% after 2 h of growth). Considering the strong adhesion of dual-species biofilms and their easier more reproducible growth compared with biofilms grown from whole saliva, dual-species biofilms of A. naeslundii and S. oralis are suggested to be preferred for use in mechanical plaque removal studies in vitro

Facilitated diffusion in the dissolution of carboxylic polymers

Carrier-mediated transport plays an important role in the dissolution of carboxylic polymers in aqueous solutions. Experiments with a rotating disk apparatus showed that the rate of polymer dissolution increased significantly with the addition of proton-carriers over the pH range of 6 to 13. The facilitated diffusion phenomenon in the dissolution of carboxylic polymers differs from that in membrane and biological systems in that the transport of polymer chains is not directly facilitated by any carriers. Proton-carriers facilitate the diffusion of hydrogen ions away from the polymer interface. As the concentration of hydrogen ions at the polymer interface decreases, the polymer solubility at the interface increases significantly, leading to a substantial increase in the polymer concentration driving force and, hence, the diffusion rate. A homogeneous chemico-diffusion model that elucidates the effects of the solution pH, the concentration and acidity of carriers, and the polymer acidity on the facilitated diffusion was developed. Good agreement between experimental and theoretical results was achieved. There are optimum values of the carrier's pK a , and of the solution pH which give a maximum facilitation effect. As the diffusion rate of the polymer is increased by the carrier, the overall polymer dissolution process changes from diffusion-limited to disentanglement-limited. © 2005 American Institute of Chemical Engineers AIChE J, 51: 415–425, 2005Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/34253/1/10329_ftp.pd

Comparative Assessment of Status and Opportunities for Carbon Dioxide Capture and Storage and Radioactive Waste Disposal in North America

Aside from the target storage regions being underground, geologic carbon sequestration (GCS) and radioactive waste disposal (RWD) share little in common in North America. The large volume of carbon dioxide (CO{sub 2}) needed to be sequestered along with its relatively benign health effects present a sharp contrast to the limited volumes and hazardous nature of high-level radioactive waste (RW). There is well-documented capacity in North America for 100 years or more of sequestration of CO{sub 2} from coal-fired power plants. Aside from economics, the challenges of GCS include lack of fully established legal and regulatory framework for ownership of injected CO{sub 2}, the need for an expanded pipeline infrastructure, and public acceptance of the technology. As for RW, the USA had proposed the unsaturated tuffs of Yucca Mountain, Nevada, as the region's first high-level RWD site before removing it from consideration in early 2009. The Canadian RW program is currently evolving with options that range from geologic disposal to both decentralized and centralized permanent storage in surface facilities. Both the USA and Canada have established legal and regulatory frameworks for RWD. The most challenging technical issue for RWD is the need to predict repository performance on extremely long time scales (10{sup 4}-10{sup 6} years). While attitudes toward nuclear power are rapidly changing as fossil-fuel costs soar and changes in climate occur, public perception remains the most serious challenge to opening RW repositories. Because of the many significant differences between RWD and GCS, there is little that can be shared between them from regulatory, legal, transportation, or economic perspectives. As for public perception, there is currently an opportunity to engage the public on the benefits and risks of both GCS and RWD as they learn more about the urgent energy-climate crisis created by greenhouse gas emissions from current fossil-fuel combustion practices

Enhanced Oil Recovery (EOR) by Miscible CO2 and Water Flooding of Asphaltenic and Non-Asphaltenic Oils

An EOR study has been performed applying miscible CO2 flooding and compared with that for water flooding. Three different oils are used, reference oil (n-decane), model oil (n-C10, SA, toluene and 0.35 wt % asphaltene) and crude oil (10 wt % asphaltene) obtained from the Middle East. Stearic acid (SA) is added representing a natural surfactant in oil. For the non-asphaltenic oil, miscible CO2 flooding is shown to be more favourable than that by water. However, it is interesting to see that for first years after the start of the injection (< 3 years) it is shown that there is almost no difference between the recovered oils by water and CO2, after which (> 3 years) oil recovery by gas injection showed a significant increase. This may be due to the enhanced performance at the increased reservoir pressure during the first period. Maximum oil recovery is shown by miscible CO2 flooding of asphaltenic oil at combined temperatures and pressures of 50 °C/90 bar and 70 °C/120 bar (no significant difference between the two cases, about 1%) compared to 80 °C/140 bar. This may support the positive influence of the high combined temperatures and pressures for the miscible CO2 flooding; however beyond a certain limit the oil recovery declined due to increased asphaltene deposition. Another interesting finding in this work is that for single phase oil, an almost linear relationship is observed between the pressure drop and the asphaltene deposition regardless of the flowing fluid pressure

Using Vegetation near CO2 Mediated Enhanced Oil Recovery (CO2-EOR) Activities for Monitoring Potential Emissions and Ecological Effects

CO2 mediated enhanced oil recovery (CO2-EOR) may lead to methods of CO2 reduction in the atmosphere through carbon capture and storage (CCS); therefore, monitoring and verification methods are needed to ensure that CO2-EOR and CCS activities are environmentally safe and effective. This study explored vegetation growth rate to determine potential ecological effects of emissions from CO2-EOR activities. Plant relative growth rates (RGR) from plots within an oilfield and reference areas, before and after CO2 breakthrough were used to assess CO2-EOR activities impact surrounding vegetation. The trend for both areas was the decrease in RGR ratio during the study time; however, the decrease in RGR ratio was significantly less in the oilfield area compared to the reference area overall and by subcategories of pine, tree and shrub. Based on data from plant plots, RGR decreased in the reference and oilfield areas except one plot, which increased in RGR. Within the oilfield and reference areas, several species decreased significantly in RGR, but American olive increased in RGR. Vegetation monitoring could provide parameters related to the modeling potential effects of emissions on local ecosystems (species, groups and community) and serve as a necessary component to the monitoring and verification of CO2-EOR and CCS projects. The challenge and limitations of vegetation monitoring were also discussed