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Inorganically crosslinked polymers have been intensively implemented for conformance control treatments in oil and gas wells at low temperatures (<90°C) because of their faster gelation time compared to organically crosslinked gels. Crosslinkers such as chromium acetate are known to be toxic, and aluminium‐based alternatives have been introduced. This study aims to investigate the impact of aluminium acetate (AlAc) particle size on the gelation kinetics of polyacrylamide (PAM)‐based gels at a pH of 5 and temperature of 75°C. Moreover, bentonite is used as an additive to delay the crosslinking of PAM/AlAc gels. Reducing the particle size increases the specific surface area of the particles and provides more crosslinking sites. Therefore, lower PAM concentrations (up to 5 wt.%) could be used without AlAc settling. Using 7 wt.% PAM/1 wt.% AlAc with sizes of 25 and 48 μm revealed a crosslinking time of 17 and 115 min, respectively. The addition of bentonite at low crosslinker concentrations (0.5–1 wt.%) did not decrease the gel strength of 7 wt.% PAM/1 wt.% AlAc significantly. The gelation time was extended after adding 1 wt.% bentonite to the formulation where the delay was attributed to the adsorption of AlAc on the bentonite surface that was illustrated by molecular simulation. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations based on DFT are employed to study the electronic structure and binding affinity of chelators used in the removal of iron sulphide scales. Three chelating agents, EDTA, HEDTA, and DTPA, are considered in this work. The complexes showed a coordination number of 5, 6, and 7 for Fe2+ and Fe3+ ions with HEDTA, EDTA, and DTPA, respectively. However, regarding EDTA, Fe3+ could coordinate with an additional water molecule and form a seven‐coordinate complex. The calculated binding energies agreed with the experimental stability constants of the chelators in the order DTPA > EDTA > HEDTA for both Fe2+/Fe3+ complexes. The binding free energies showed a spontaneous reaction with Fe3+ having a stronger binding affinity than Fe2+ due to electrostatic forces. This investigation provides insights regarding how chelators that are applied in iron sulphide scale removal may be designed by increasing the number of nitrogen atoms to above the number of carboxylate groups. [ABSTRACT FROM AUTHOR]

Five new gold(I) complexes of carbene and selenone ligands ( 1 – 5 ) having the general formula, [Au(IPr)(selenone)]PF 6 were synthesized by the reaction of [Au(IPr)Cl] ( 0 ) with selenones (IPr = 1,3-Bis(2,6-di-isopropylphenyl)imidazol-2-ylidene and selenone = 1,3-imidazolidine-2-selenone, N- ethyl-1,3-imidazolidine-2-selenone, N -propyl-1,3-imidazolidine-2-selenone, N,N′ -dimethyl-1,3-imidazolidine-2-selenone and N,N′ -diethyl-1,3-imidiazolidine-2-selenone for 1 – 5 respectively). The complexes were characterized by elemental analysis, IR and NMR ( 1 H, 13 C, 77 Se) spectroscopy, and two of them by X-ray crystallography. The X-ray diffraction analysis of complexes 2 and 4 revealed that they were composed of [Au(IPr)(Selenone)] + and PF 6 − ions. In the complex ions, gold(I) atom adopts a linear geometry. In vitro cytotoxicity was appraised for all complexes against HCT15, A549 and MCF7 cancer cell lines. The IC 50 values showed that the complexes exhibited poor activity as compared to cisplatin. However, the complex 1 showed a promising anticancer activity (IC 50 = 33 ± 1 μM) similar to that exhibited by cisplatin (32 ± 2 μM) against HCT15 (human colon cancer) cell line. The molecular docking analysis showed the potential inhibitory capacity of the gold complexes with thioredoxin reductase with complex 4 having the highest binding affinity with a score of −34.45. The interactions of the gold complexes with tryptophan and lysozyme were studied electrochemically using Cyclic and Square Wave Voltammetry. [ABSTRACT FROM AUTHOR]

A common problem that faces the oil and gas industry is the formation of iron sulfide scale in various stages of production. Recently an effective chemical formulation was proposed to remove all types of iron sulfide scales (including pyrite), consisting of a chelating agent diethylenetriaminepentaacetic acid (DTPA) at high pH using potassium carbonate (K 2 CO 3 ). The aim of this molecular modeling study is to develop insight into the thermodynamics and kinetics of the chemical reactions during scale removal. A cluster approach was chosen to mimic the overall system. Standard density functional theory (B3LYP/6-31G*) was used for all calculations. Low spin K 4 Fe(II) 4 (S 2 H) 12 and K 3 Fe(II)(S 2 H) 5 clusters were derived from the crystal structure of pyrite and used as mimics for surface scale FeS 2 . In addition, K 5 DTPA was used as a starting material too. High spin K 3 Fe(II)DTPA, and K 2 S 2 were considered as products. A series of K m Fe(II)(S 2 H) n complexes ( m = n -2, n = 5-0) with various carboxylate and glycinate ligands was used to establish the most plausible reaction pathway. Some ligand exchange reactions were investigated on even simpler Fe(II) complexes in various spin states. It was found that the dissolution of iron sulfide scale with DTPA under basic conditions is thermodynamically favored and not limited by ligand exchange kinetics as the activation barriers for these reactions are very low. Singlet-quintet spin crossover and aqueous solvation of the products almost equally contribute to the overall reaction energy. Furthermore, seven-coordination to Fe(II) was observed in both high spin K 3 Fe(II)DTPA and K 2 Fe(II)(EDTA)(H 2 O) albeit in a slightly different manner., Competing Interests: The authors declare no competing financial interest.