Similarities and Differences of Low Salinity Polymer and Low Salinity LPS (Linked Polymer Solutions) for Enhanced Oil Recovery

Linked polymer solution (LPS) is nano-size particles made of hydrolyzed polyacrylamide (HPAM) cross-linked with aluminum citrate. The propagation of LPS has been compared to non-cross-linked polymers at low brine salinity condition. The possible differences in properties and potentials for oil recovery have been investigated using water-wet and intermediate-wet cores. The target oil for polymer flooding (PF) is assumed to be the portion of the reservoir that has been bypassed by water during waterflooding and not the residual oil saturation in flooded zones. Our recent studies have shown that a positive synergy can be obtained by combining low salinity and PF. It has been claimed in the literature that cross-linking polymer such as colloidal dispersion gels (colloidal dispersion gels (CDG), micron-size aggregates) or LPS (nano-size particles) would extend the application of polymers to also include change in residual oil saturation. The results of this study indicated higher pressure buildup when low salinity LPS was propagated through brine saturated cores compared to low salinity polymer solution. The pressure buildup was even stronger for high salinity LPS injection. In two phase flow experiments, both polymer and LPS under low salinity condition, showed approximately similar propagation and oil recovery potential when injected into water-wet and intermediate-wet cores.     

Salinity Selection for a Low Salinity Water-Low Salinity Surfactant Process

A laboratory selection of salinity for a low salinity water-low salinity surfactant (LS-LSS) process is presented in this paper with systematical investigation on surfactant phase behavior, interfacial tension (IFT), and dynamic retention in porous media with IOS2024 and isoamyl alcohol (IAA) as surfactant system. The results show that 0.4 wt% IOS2024 with 1 wt% IAA can provide ultra-low IFT of 10^?3 mN/m at around 3000–4000 mg/L total dissolved solids, but at that salinity range the surfactant retention is very high. The search for an optimum surfactant formulation has to consider solution properties and retention in addition to the low IFT. The salinity for a LS-LSS process should thus not be focused on either optimal salinity or ultra-low IFT, but instead the best choice could be a compromise between the properties in question. The three-phase region, where ultra-low IFT are found, is also associated with high retention values. However, we show that as salinity is increased from a two-phase region with oil solubilized in a water continuous microemulsion, there is a region close to the three-phase boundary which has potential. This region does not give ultra-low, but fairly low (10^?2 mN/m in this case) interfacial tensions, and also significantly lower retention.      

The impact of the natural sciences on archaeology

This article reviews some of the applications of physics to the solution of archaeological problems. The use of magnetic, resistivity and electromagnetic surveying techniques for the location of buried features is described. Various methods of age determination are outlined while the problems associated with radiocarbon dating of organic material and thermoluminescent dating of pottery are discussed in detail. The techniques, including petrological examination, chemical analysis and isotopic analysis, employed in the physical examination of archaeological artefacts are described. Examples of the application of these techniques in establishing the source of the raw materials used in pottery, metal and stone implements and in elucidating the techniques of manufacture of pottery and metal objects are also given.     

Cisplatin Adducts on a GGG Sequence within a DNA Duplex Studied by NMR Spectroscopy and Molecular Dynamics Simulations

The antitumor drug cisplatin (cis‐[PtCl₂(NH₃)₂]) reacts with cellular DNA to form GG intrastrand adducts between adjacent guanines as predominant lesions. GGG sites have been shown to be hotspots of platination. To study the structural perturbation induced by binding of cisplatin to two adjacent guanines of a GGG trinucleotide, we examined here the decanucleotide duplex d[(G₁C₂C₃ G₆T₇‐ C₈G₉C₁₀) ? d(G₁₁C₁₂G₁₃A₁₄C₁₅C₁₆C₁₇G₁₈‐ G₁₉C₂₀)] ( dsCG*G*G ) intrastrand cross‐linked at the G* guanines by cis‐{Pt(NH₃)₂}²⁺ using NMR spectroscopy and molecular dynamics (MD) simulations. The NMR spectra of dsCG*G*G were found to be similar to those of previously characterized DNA duplexes cross‐linked by cisplatin at a pyG*G*X site (py=pyrimidine; X=C, T, A). This similarity of NMR spectra indicates that the base at the 3′‐side of the G*G*–Pt cross‐link does not affect the structure to a large extent. An unprecedented reversible isomerization between the duplex dsCG*G*G (bearing a –Pt chelate) and duplex dsGG*G*T (bearing a –Pt chelate) was observed, which yielded a 40:60 equilibrium between the two intrastrand GG–Pt cross‐links. No formation of interstrand cross‐links was observed. NMR spectroscopic data of dsCG*G*G indicated that the deoxyribose of the 5′‐G* adopts an N‐type conformation, and the cytidines C₃, C₁₅, and C₁₆ have average phase angles intermediate between S and N. The NMR spectroscopic chemical shifts of dsGG*G*T showed some fundamental differences to those of pyG*G*–platinum adducts but were in agreement with the NMR spectra reported previously for the DNA duplexes cross‐linked at an AG*G*C sequence by cisplatin or oxaliplatin. The presence of a purine instead of a pyrimidine at the 5′‐side of the G*G* cross‐link seems therefore to affect the structure of the XG* step significantly.     

Connectivity in Vuggy Carbonates, New Experimental Methods and Applications

The length and spatial distribution of the touching-vugs channels affect the degree of permeability variations and is the main contributor to heterogeneity in vuggy carbonates. Hence, this article focuses on vug connectivity characterization and its impact on fluid flow. A whole core sample was scanned by X-ray computed tomography (CT). Image segmentation was used to obtain a binarized three-dimensional (3D) model of the vuggy pore space. Analysis of the binarized 3D model is used to calculate the correlation function and correlation length for the vuggy pore space. Connectivity analysis of the binarized 3D model shows that 79% of the vugs connected network spanning along the sample. The remaining 21% vug porosity exists in a large number of isolated vugs. The correlation length for the connected vug network is found to be larger than for vugs in general. NMR T ₂ measurements at increasing capillary pressure is tested on the vuggy material and used to investigate the amount of connected- and isolated vugs. The results verify the large fraction of connected vugs. Application of NMR T ₂ measurements in combination with capillary pressure experiments can also reveal matrix properties that play an important role in recovery processes. The transition between non-Fickian and Fickian regimes for tracer/solute transport is studied by laboratory experiments performed at various sample lengths, from cm to m scale. For the largest sample measured in our experiments show that effluent concentration curve conform to the CDE solution, suggesting that the Fickian regime has been established.     

Phenolic compounds,essential oil composition,and antioxidant activity of Angelica purpurascens (Avé-Lall.) Gill

In this study, methanol extracts (MEs) and essential oil (EO) of Angelica purpurascens (Avé-Lall.) Gill obtained from different parts (root, stem, leaf, and seed) were evaluated in terms of antioxidant activity, total phenolics, compositions of phenolic compound, and essential oil with the methods of 2,2-azino-bis(3ethylbenzo-thiazoline-6-sulfonic acid (ABTS•⁺), 2,2-diphenyl-1-picrylhydrazil (DPPH•) radical scavenging activities, and ferric reducing/antioxidant power (FRAP), the Folin–Ciocalteu, liquid chromatography−tandem mass spectrometry (LC−MS/MS), and gas chromatography-mass spectrometry (GC−MS), respectively. The root extract of A. purpurascens exhibited the highest ABTS•⁺, DPPH•, and FRAP activities (IC₅₀: 0.05 ± 0.0001 mg/mL, IC₅₀: 0.06 ± 0.002 mg/mL, 821.04 ± 15.96 µM TEAC (Trolox equivalent antioxidant capacity), respectively). Moreover, EO of A. purpurascens root displayed DPPH• scavenging activity (IC₅₀: 2.95 ± 0.084 mg/mL). The root extract had the highest total phenolic content (438.75 ± 16.39 GAE (gallic acid equivalent), µg/mL)). Twenty compounds were identified by LC−MS/MS. The most abundant phenolics were ferulic acid (244.39 ± 15.64 μg/g extract), benzoic acid (138.18 ± 8.84 μg/g extract), oleuropein (78.04 ± 4.99 μg/g extract), and rutin (31.21 ± 2.00 μg/g extract) in seed, stem, root, and leaf extracts, respectively. According to the GC−MS analysis, the major components were determined as α-bisabolol (22.93%), cubebol (14.39%), α-pinene (11.63%), and α-limonene (9.41%) among 29 compounds. Consequently, the MEs and EO of A. purpurascens can be used as a natural antioxidant source.     

Transition Metal Ion-binding Properties of a 14-Membered N2O2S2- Macrobicyclic Ligand

The selective liquid–liquid extraction of various transition metal cations from the aqueous phase to the organic phase was carried out using a 14-membered N₂O₂S₂-macrobicycle. Metal picrates such as Pb²⁺, Co²⁺, Zn²⁺, Ni²⁺,Cu²⁺ and Cd²⁺ were used in this extraction studies. It was found that the ligand showed moderate selectivity towards Pb²⁺ only among the other metals. The extraction constant (log K _ex) was determined to be 13.8 for Pb²⁺ complex.     

Changes in partial molar volume and isentropic partial molar compressibility of self-association of purine and caffeine in aqueous solution at 1–1600 bar

Ultrasound measurements of purine and caffeine in aqueous solution as function of pressure are reported at 25°C and used to calculate the changes in their partial molar volumes and partial molar compressibilities due to self-association. The effect of pressure is to increase the association. The volume changes are negative for the self-association process, becoming less negative with increasing pressure. This is caused by the monomer in the associated state. The partial molar volume of the monomer in the associated state increases with pressure, contrary to what is expected for nonelectrolytes in water. Hydration of the associated monomer must be a key to this increase. The result suggest that dipole-induced dipole interactions is a possible mechanism for the association process and not hydrophobic interactions. The change in the partial molar compressibility of the association is positive, decreasing with increasing pressure.     

Foam Generation,Propagation and Stability in Porous Medium

Transport in Porous Media - There have been several foam field applications in recent years. Foam treatments targeting gas mobility control in injectors as well as gas blocking in production wells...