Performance of PAM/PEI gel system for water shut‐off in high temperature reservoirs: Laboratory study

A polymer gel is one of the common remediate methods to either reduce or totally block excessive water production in oilfields. Some systems demonstrated an excellent performance in treating the problem like polyacrylamide tert‐butyl acrylate (PAtBA)/polyethylenimine (PEI). In this study, polyacrylamide (PAM) was introduced as a cheap alternative to PAtBA that can tolerate high salinity reservoirs. The thermal stability of the PAM/PEI polymeric gel in saline water was examined at 150°C (302F). Samples prepared in sea water showed better stability compared with distilled and field water. Dynamic rheology and core‐flooding experiments were used to evaluate the PAM / PEI gel system at high temperatures. NaCl and NH₄Cl were evaluated as a possible retarders for delaying the gelation time in order to achieve a successful placement. NH₄Cl was found to be more effective retarder. Core‐flooding tests were conducted in sandstone and carbonate cores. The subject polymer gel was injected at rates typical of those in field applications. The injectivity of PAM/PEI was tested in Berea sandstone cores with initial permeability of ～45 mD. The post‐treatment of the system showed a permeability reduction of ～94% for a period of two weeks. The injectivity in low permeability carbonate cores required more retardation compared with the injectivity in sandstone cores. The gel reduced the permeability to brine in Indiana limestone core by 99.8% for more than 5 months. Rheology of cured gel samples indicated that the gel strength needs about one day of curing in the core for the strength to stabilize. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41869.     

Effect of feed pressure on the performance of the photovoltaic powered reverse osmosis seawater desalination system

This paper describes the potential of the development of a seawater desalination system that combines the technologies of reverse osmosis (RO) and photovoltaic (PV) to deliver 100 m³/day of sweet water. Silicon cells are chosen for the PV array and the polyamide thin-film composite seawater Filmtec membranes are selected for the RO system. The software ROSA is adopted to study the influences of the feed pressure on the performance of the system. It is found that as the feed pressure increases, the specific energy of the plant decreases but the percentage of recovery increases.     

Proportional damping approximation using the energy gain and simultaneous perturbation stochastic approximation

The design of vector second-order linear systems for accurate proportional damping approximation is addressed. For this purpose an error system is defined using the difference between the generalized coordinates of the non-proportionally damped system and its proportionally damped approximation in modal space. The accuracy of the approximation is characterized using the energy gain of the error system and the design problem is formulated as selecting parameters of the non-proportionally damped system to ensure that this gain is sufficiently small. An efficient algorithm that combines linear matrix inequalities and simultaneous perturbation stochastic approximation is developed to solve the problem and examples of its application to tensegrity structures design are presented.     

47—THE FORM TAKEN BY THREADS LAID ON A MOVING BELT. PART II: MECHANISMS AND THEORY

It is shown that the form of a laid-down thread can be expressed mathematically by the equation of a modified cycloid when the speed ratio between the feed and the belt is within a certain range. The experimental form is found to be reasonably close to the theoretical form. The theoretical form can be predicted if the radius of the circular coil with the belt stationary, the feed speed, and the belt speed are known, The condition for laying down the thread in a form of overlapping loops is deduced. A strobo-photographic method is used to clarify the existence of different mechanisms under different conditions.     

A Screening Technique for Fabric Handle

An objective screening technique for fabric handle is presented. This method is based on the use of a simple device fitted to a tensile testing machine, and measures the force generated while passing a fabric specimen through a ring. The method proved capable of detecting differences in fabric handle between comparable fabrics, as illustrated by studies on shirting fabrics, and on fabrics with functional finishes. The results were validated by comparison with measurements of fabric mechanical properties obtained from the KESF (Kawabata Evaluation System for Fabrics). The handle force measurement gives a summed single value result for fabric handle.     

SOLVENT EXTRACTION OF PAKISTANI COALS (ii): EXTRACTION AND CHARACTERIZATION OF METHANOL-BENZENE EXTRACTS

Structural characterization of the solvent extracts from four different Pakistani lignitic coals has been carried out by their proximate, elemental analysis and FT-Infrared and ¹H n.m.r. spectra. The yield of each extracts was greater with 1:1 benzene-methanol mixture in comparison to the total yield obtained by separate extractions with benzene and methanol. The extracts contained significantly less amount of ash and fixed carbon along with an increase in the percentage of volatile matter. The FTIR and ¹H n.m.r. spectra indicated that basically all the extracts contained less condensed aromatic rings in comparison to the coal. The FTIR spectra showed sharp well resolved peaks which have been assigned to various functional groups.

The ¹H n.m.r. spectra were used to obtain average structural parameters for all the extracts. A detailed analysis of the FTIR and n.m.r. spectra of the coal and their extracts provided an important in-sight into the differences between various extracts and also between various coals and their corresponding extracts.     

Simultaneous kinetic method for the determination of vitamin C, citrate and oxalate employing the Kalman filter

A kinetic method for the determination of vitamin C, citrate and oxalate in their mixture is described. The method involves the use of cerium(IV) as an oxidant and measurement of reaction rates spectrophotometrically by following the decrease in absorbance of cerium(IV) at 410 nm. The adaptive Kalman filter was used for data manipulation and analysis. It is shown that the use of the Kalman filter is superior to the classical differential kinetic methods owing to its suitability for the determination of analytes that react with a single reagent and exhibit a reaction rate constant ratio of less than 1.5. The results obtained were found to be highly precise and accurate even in the presence of some expected interferents.     

The effect of inlet parameters on the performance of packed tower-regenerator

An investigation on the operation of packed tower for the regeneration of liquid desiccant is presented. A theoretical model demonstrating the effect of the system parameters is described. The experimental results are plotted to illustrate the effect of air and liquid parameters on the output variables. The regeneration process is shown to be highly dependent on the air inlet conditions, namely, temperature, humidity and flow rate. Also, the effects of the liquid temperature, concentration and flow rate is discussed. Data obtained were correlated to estimate the rate of water evaporation (regeneration rate) from values of variables that influence the rate of mass transfer in the column.     

The mode features of an annular sector microstrip antenna

A rigorous analysis of the features of the modes of an annular sector printed microstrip antenna is presented. General expressions for its radiation field are derived by using the cavity model. The expressions are used to study the radiation patterns, radiation peak in the broadside direction, and beamwidth of different structures for various sector angles, widths, and modes of excitation. This includes the special cases of quarter-, half-, three-quarters-, and ideal-gap open-ring structures. Compared to a closed ring, the results indicate that the TM₁₂ mode is superior to the TM₁₁ mode with regard to the radiation properties in the annular sector as its angle approaches 2π     

Chemical reactions in crosslinking of copolymers of ethylene and vinyltrimethoxy silane

The crosslinking reactions of a new type of polyethylene, an ethylene vinyltrimethoxy silane (EVS) copolymer, when reacted with water has been studied. Samples of EVS were treated in water at 90°C. The kinetics of the crosslinking was followed by measuring the gel content and by determination of the content of different structures (? Si? OCH₃,? Si? OH, and ? Si? O? Si? ) using FT-IR. The observations show that a maximum gel content of 70-75% is obtained after 25 h treatment in water at 90°C. On the other hand, the absorption index for the crosslinks, ? Si? O? Si? , continues to increase until about 100 h, i.e., more crosslinks seem to be formed without a simultaneous increase in gel content. Mechanical measurements showed decreased elongation at break even after very long treatments. Thermo-oxidative degradation is, however, also responsible for the change in mechanical properties. For properly stabilized samples, the decrease in elongation leveled off after about 100 h of treatment. This indicates that the crosslinks formed after 25 h mainly should be within the already existing gel. The observed synergistic effect of crosslinking and thermo-oxidative degradation emphasizes the importance of a proper stabilizing system.