Counter-current Technique Research Articles

A Novel Assisted Gas–Oil Countercurrent EOR Technique for Attic Oil in Fault-Block Reservoirs

As the mature oil fields have stepped into the high water cut stage, the remaining oil is considered as potential reserves, especially the attic oil in the inclined fault-block reservoirs. A novel assisted gas–oil countercurrent technique utilizing gas oil countercurrent (GOC) and water flooding assistance (WFA) is proposed in this study to enhance the remaining oil recovery in sealed fault-block reservoirs. WFA is applied in our model to accelerate the countercurrent process and inhibit the gas channeling during the production process. Four comparative experiments are conducted to illustrate enhanced oil recovery (EOR) mechanisms and compare the production efficiency of assisted GOC under different assistance conditions. The results show that WFA has different functions at different stages of the development process. In the gas injection process, WFA forces the injected gas to migrate upward and shortens the shut-in time by approximately 50% and the production efficiency improves accordingly. Compared with the basic GOC process, the attic oil swept area is extended 60% at the same shut-in time condition and secondary gas cap forms under the influence of WFA. At the production stage, the WFA and secondary gas cap expansion form the bi-directional flooding. The bi-directional flooding also displaces the bypassed oil and replaced attic oil located below the production well, which cannot be swept by the gas cap expansion. WFA inhibits the gas channeling effectively and increases the sweep factor by 26.14% in the production stage. The oil production increases nearly nine times compared with the basic GOC production process. The proposed technique is significant for the development of attic oil in the mature oil field at the high water cut stage.

Measurement of Spontaneous Imbibition Capillary Pressure, Saturation and Resistivity Index by Counter Current Technique at Net Reservoir Stress and Elevated Temperature

Capillary pressure and resistivity index spontaneous imbibition experiments by the porous plate method, in a core holder at elevated temperature and net reservoir stress, are both difficult and time consuming special core analysis measurements to perform. In this type of experiment, low capillary forces act against a low permeable porous plate and only one face of the cylindrical core sample is in capillary contact with the fluid saturated porous plate. In this paper, core samples having different lithology, petrophysical properties and wettability are analysed by counter current spontaneous imbibition, starting at initial water saturation (Swi), at net confining pressure and elevated temperature. Synthetic brine is used as the wetting phase and Isopar L mineral oil as the non-wetting phase. This methodology is applied to investigate and evaluate how to obtain more reliable, more efficient and faster saturation imbibition data combined with electrical measurements, during spontaneous imbibition measurements. Resistivity index (RI), saturation exponent (n) (by single saturation equilibrium point using Archie’s second law RI= Sw-n) and wettability information using representative fluids, confining pressure and temperature are also obtained by applying this specific counter current imbibition technique and improved procedural approach.

Evaluation of enantioselective nonaqueous ion-pair capillary electrophoresis as screening assay in the development of new ion exchange type chiral stationary phases

This study evaluates how enantioselectivity values for the separation of chiral N-derivatized amino acids achieved in non-aqueous ion-pair CE with cinchona alkaloid derived chiral counter-ions are related quantitatively to those obtained in enantioselective anion-exchange chromatography with the same selectors immobilized on silica supports. Three different setups of CE experiments, viz. a conventional total filling technique (TFT), a countercurrent technique (CCT), and a partial filling technique (PFT), were investigated and were tested in terms of the goodness of fit of correlations between apparent electrophoretic and chromatographic a values. Both selectands and selectors have been varied. Correlation coefficients higher than 0.95 are commonly obtained with all three CE techniques, yet even better fits are found for TFT-CE and CCT-CE. The common premise for the good correlations is the equal molecular recognition mechanism in ion-pair and ion-exchange modes, both involving ionic interactions as driving force for selectand-selector association, and the fact that separation selectivity in both techniques is primarily determined by the difference of the binding constants of (R) and (S) enantiomers with the chiral selector, i.e. the intrinsic or thermodynamic enantioselectivity. Factors related to the separation technique, which also influence apparent enantioselectivity and possibly contribute to a deterioration of the fit, are discussed. The good correlations prove that enantioselective ion-pair CE may be used as screening method in the development and optimization of ion-exchange type chiral stationary phases.

Complex formation between Escherichia coli lipopolysaccharide O antigen and capsular K antigen as detected by immunoelectrophoresis

Many Escherichia coli of serotypes commonly found in the normal intestine and in extraintestinal diseases, and having capsular antigens of the low molecular group called group II, will, in simple saline extracts, produce complexes between some or all of the lipopolysaccharide molecules and some of the polysaccharide K molecules. Non-complex-forming and complex-forming strains with the same O and K can be found. The complexes are thermostable but are disrupted by some detergents. O-K complex formation may lead to misinterpretation of immunoprecipitation results; one example is the counter current technique used for K determination of E. coli. In this technique O antigen lipopolysaccharide may, when complexed to K polysaccharide, mimic a K antigen. The possible implications of O-K complex formation during the infection process, especially for antibody formation need to be examined.

Enzymic saccharification of pretreated wheat straw

Studies of pretreatment of wheat and its subsequent saccharification by Trichoderma reesei cellulases are reported. Steam explosion was found to be the most effective of the pretreatment methods tested. Data are presented describing the effect of enzyme and substrate concentration on the rate and degree of hydrolysis. Significant inhibition of the cellulases was observed when sugar concentrations were 6% or higher. This inhibition increased when glucose and ethanol were present simultaneously. Adsorption of enzymes to the substrate was followed during a 24-h hydrolysis period. An initial rapid and extensive adsorption occurred, followed by a short desorption period that was followed in turn by a further increased adsorption peaking after 3 h. Intermediate removal of hydrolysate, particularly in combination with a second addition of enzyme, clearly improved the yield of saccharification compared to an uninterrupted hydrolysis over a 24-h period. Thus, a 74% yield of reducing sugars was obtained. Furthermore, an increase in the amount of recoverable enzymes was observed under these conditions. Evidence is presented that suggests that a countercurrent technique, whereby free enzymes in recovered hydrolysate are adsorbed onto new substrate, may provide a means of recirculating dissolved enzymes.

Arteriography in old age--an assessment of the risks and technique (author's transl)

Of 1,263 arteriograms performed over a period of two and a half years, there were 166 patients aged 70 years or more. The indications, angiographic findings and results have been examined retrospectively. In seven patients only was it impossible to carry out the examination because of advanced vascular disease in the pelvis. Most examinations could be performed as planned. In three patients there were minor complications without consequence. In one patient the external iliac artery was occluded following catheter angiography, but this was disobliterated during a subsequent operation which would have been carried out in case. The severity of vascular calcification as seen on plain films gives no indication regarding the difficulties during catheterisation. If aortography by catheter is impossible, we demonstrate the aorta retrogradely by a counter-current technique, using the Hettler instrument. The Hettler technique does not increase the risk and has certain advantages for the examination of older patients.

Solvent extraction of the lanthanide elements, scandium, uranium and thorium using tetracycline as complexing agent

Hydrogen ion dependence and extractant dependence of the extraction of the lanthanide elements, scandium, uranium and thorium into a solution of tetracycline in benzyl alcohol have been determined. Possiblity of using the tetracycline-benzyl alcohol system for separation of the lanthanide elements present in a mixture, as well as for the separation of uranium from those elements was tested. In the first case discontinuous countercurrent technique was used. In the second case a single step solvent extraction procedure was applied.

Separation of phenolic O-glucuronides and phenolic sulphate esters by multiple liquid-liquid partition

A liquid-liquid partition method is described for the separation of phenolic O-glucuronides from the corresponding phenolic sulphate esters and of the different compounds within the two classes of conjugates. The method, which involves a countercurrent technique with continuous flow of the solvents, is suitable for the isolation of these metabolic conjugates from biological fluids (bile and urine).

Application of Craig Countercurrent Extraction Techniques to the Purification of Dyes

The theory of countercurrent extraction as a criterion of purity is described. Application of the theory fully established the purity of two disperse dyes that had been separated by the countercurrent technique. The use of the method to show that a mixture of materials is such is discussed. Its limitation with regard to ionic compounds is also discussed.

Application of modified counter-current technique to the determination of tungsten in molybdenum

More than trace amounts of molybdenum interfere in the determination of tungsten by the dithiol method. A simplified counter-current extraction method is described which allows the determination of 5 p.p.m. or more of tungsten in a molybdenum matrix. The optimum conditions for the separation were a 6 M HCL-2.4 M HF medium and methyl isobutyl ketone as extractant; the percentage extractions in a single pass were 85% and 15% for molybdenum and tungsten, respectively.

Fractionation of nucleic acids in aqueous polymer two-phase systems

1. The partition coefficients of some different preparations of nucleic acid from different sources have been determined in the polymer phase systems dextran: methylcellulose: water and sodium dextran sulphate: methylcellulose: water. 2. For nucleic acids of different molecular sizes, the negative logarithm of the partition coefficient was found to increase nearly proportionally with increasing sedimentation coefficient. 3. In the counter-current experiment with thymus DNA, the distribution after each transfer changed in such a way that, according to the above-mentioned relation between sedimentation and partition coefficients, the low molecular fractions of the heterogeneous DNA moved with the top phase. Soluble RNA has also been separated from a mixture with thymus DNA and the separation was checked with a pyrimidine analysis. 4. Thymus DNA has been fractionated by the counter-current technique. After a few transfers, analysis in the ultracentrifuge showed a fractionation of the material and each tube contained DNA with a more homogeneous sedimentation coefficient distribution—the higher the tube number, the lower the coefficient. 5. In most systems, an interface layer of nucleic acid is formed. This can be used to obtain a more homogeneous thymus DNA. 6. The adsorption of nucleic acid at the interface can also be used as an analytical tool. A few per cent of high molecular RNA, in a preparation of soluble RNA, can be detected by the formation of an interface layer in a suitable polymer phase system. 7. Contaminated DNA from phage T2 was shown to deviate strongly from the main relation between the sedimentation coefficient and the partition coefficient. When the preparation was dialysed, and thus freed from parts of the contaminating substances, which are probably amines, the negative logarithm of the partition coefficient increased towards a better agreement with the main relation.

The nonspecific fluorescent material in estrogen extracts from the urine of pregnant women.

INTRODUCTION URINARY estrogen extracts are known to contain some nonspecific material which can 1) induce the Kober reaction, or 2) fluoresce following the addition of acid. Using the countercurrent technique of fractionation, the fractions resembling estrone, estradiol and estriol have been found to represent only 30 per cent of the total fluorescence in urinary extracts from normal adults and 70 to 75 per cent during pregnancy (1). Although the nonspecific material may bear no relation to the estrogenic hormones, there is the possibility that it is made up of compounds which are either hormones themselves or intermediary metabolites of estrogens. Such a possibility has been suggested by the work of Lieberman et al. (2), Zondek and Finkelstein (3) and Slaunwhite (4). In an attempt to characterize this nonspecific fluorescent material, we previously reported the separation of two fractions designated as “E4” and “E5” (1). It is the purpose of the present paper to describe certain of the properties of “Fra...

Nidulin and ustin; two chlorine-containing metabolic products of Aspergillus nidulans.

A MOULD, isolated by Kurung1 in 1944 and considered to be a strain of Aspergillus ustus (Bain.) Thom and Church, was shown to produce a metabolic liquor which possessed a marked antibiotic activity towards Mycobacterium tuberculosis and M. ranae. Afterwards, Hogeboom and Craig2, by application of a counter-current technique, were able to isolate, from an ethereal extract of this mould and its substrate, two crystalline products, called compound I and compound II, which showed a very high activity against M. ranae. Doering, Dubos, Noyce and Dreyfus3, using the same strain of mould, isolated a number of chlorine-containing metabolic products, one of which was proved to be identical with Hogeboom and Craig's compound I. Doering et al. proposed the name ‘ustin’ for this compound, established its empirical formula (C19H15O5Cl3) and published a superficial account of some of its chemical properties.