Addition of melamine formaldehyde (MF) as a crosslinker containing hydroxymethyl to partially hydrolyzed poly(acrylamide) (HPAM) generated covalently crosslinked in situ gels through chemically nucleophilic attack by hydroxymethyl groups to amide in an HPAM backbone, which was demonstrated by FTIR spectrum analysis and rheological studies. NH₄Cl could act as a catalyst to reduce the gelation time from 7 days in dilute water to 8 h in the presence of 0.8 wt % NH₄Cl. Compared to high-temperature HPAM/phenol/formaldehyde and HPAM/Cr³⁺ gel systems, this gel has better adhesion and higher strength over a broad range of temperature from 60 to 100 °C under reservoir conditions with a denser and hook-like three-dimensional microstructure. Pressure-bearing capacity experiments demonstrated that the gel could efficiently plug high pressure from underneath to seal the wellbore, attributing to its high strength and good adhesion. This study could aid petroleum engineers in applying soft materials on controlling the pressure via polymer gels.

Conventional preformed particle gels suffer from insufficient salt tolerance and weak mechanical properties after water absorption, which reduce the water shutoff effect in mature oilfields. In this paper, a nanocomposite particle gel (NCPG) is synthesized by copolymerization of acrylamide (AM) and 2-acrylamido-2-methylpropane sulfonic acid (AMPS) using laponite RD (LPT) as a physical cross-linker and N,N-methylene-bisacrylamide (MBA) as a chemical cross-linker via in situ free radical polymerization. Compared with the NCPG without LPT, both the swelling rate and mechanical properties of NCPG added with LPT are found to be improved. In addition, the pore sizes of the network of the swollen NCPG are smaller than those of the sample without LPT, and the thermal stability is also slightly enhanced. The swelling rate of NCPG increases with increasing AMPS concentration. The water absorbency of NCPG first increases and then decreases with increasing MBA and APS concentrations. The NCPG is sensitive to alkaline medium due to the presence of sulfonic acid groups on the molecular chains of the NCPG. The synthesized NCPG exhibits good salt tolerance at 80 °C in formation water. The plugging rate of the NCPG to a sand-pack is above 90%, and the residual resistance factor reaches 19.2 under reservoir conditions. These results indicate that the NCPG may have potential application for water shutoff treatment in mature oilfields.

The gelation process of organically polymer gel was investigated by dynamic thickening measurements. Rheological measurements were used to evaluate the viscosity of the gel. During the gelation process, high temperature resulted in higher rate of crosslinking. Rigid and stable gel was formed in neutral and alkaline media, and the higher of the pH value, the faster of the gelation process. However, gel could not be formed in acid condition. Moreover, the rate of crosslinking increased with the increase of concentration of polymer and crosslinker. The addition of NH₄Cl elongated the gelation time significantly, but played a negative role in the gel strength, while a rigid gel was formed in the presence of Sodium acetate or trisodium citrate dehydrate. This paper summarizes the results and discusses how various parameters affect the gelation process of the gel. GRAPHICAL ABSTRACT

Nanoparticles have been widely applied to treat emulsion-containing wastewater in the form of chemical demulsifiers, such as SiO₂, Fe₃O₄, and graphene oxide (GO). Owing to their asymmetric structures and selective adsorption, Janus nanoparticles show greater application potential in many fields. In the present work, the novel magnetic Janus graphene oxide (MJGO) nanoparticle was successfully prepared by grafting magnetic Fe₃O₄ to the surface of the JGO, and its demulsifying ability to treat a crude oil-in-water emulsion was evaluated. The MJGO structure and its magnetic intensity were verified by Fourier-transform infrared spectra (FTIR), transmission electron microscopy (TEM), X-ray diffraction (XRD), and magnetization saturation (MS) tests. Compared with GO and JGO, MJGO displayed the superior efficiency (>96%) to demulsify the crude oil-in-water emulsion, which can be attributed to the reduced electrostatic repulsion between MJGO and the emulsion droplets. Furthermore, the effects of pH and temperature on the demulsification performance of MJGO were also studied. Lastly, the recyclability of MJGO largely reduced the cost of demulsifiers in separating crude oil and water. The current research presents an efficient and recyclable demulsifier, which provides a new perspective for the structural design of nanomaterials and their application in the field of demulsification.

In the process of petroleum exploitation, in order to effectively inhibit the corrosion damage of acid to metal equipment. Mannich base corrosion inhibitors are generally added to inhibit the corrosion damage of acid. In order to enhance the solubility of Mannich base corrosion inhibitor. This paper intends to introduce hydrophilic groups to enhance the solubility of the Mannich base corrosion inhibitor. In this paper, two efficient corrosion inhibitors 3-(2-hydroxyethylamino)-1-phenylpropan-1-one (MY1) and 3-(2-aminoethylamino)-1-phenylpropan-1-one (MY2), were synthesized based on the Mannich reaction, using formaldehyde, acetophenone and ethanolamine/ethylenediamine as reaction raw materials. The corrosion inhibition performance of the inhibitor on N80 steel in 15% (mass fraction) hydrochloric acid solution was studied by means of the static weight loss method, electrochemical test and optical contact angle analysis. It could be seen from the static weight loss method that the corrosion rate in the hydrochloric acid solution before and after adding 0.7% (mass fraction) corrosion inhibitor concentration decreased from 129.39 g·m⁻²·h⁻¹ to 1.45 g·m⁻²·h⁻¹ and 2.79 g·m⁻²·h⁻¹, respectively. The corrosion inhibition rate could reach 98%, indicating that both inhibitors had good corrosion inhibition performance, and the corrosion inhibition effect of MY1 was better than that of MY2. It was found from the electrochemical tests that the two inhibitors were mixed corrosion inhibitors mainly inhibiting the anodic reaction, and both inhibitors belonged to spontaneous adsorption, and their adsorption behaviors followed the Langmuir adsorption isotherm. In addition, the surface of N80 steel was characterized by SEM, EDS elemental mapping and contact angle measurement. The results show that a dense hydrophobic film is formed on the surface of the steel sheet after the addition of a corrosion inhibitor, which prevents corrosion.

Metal centralizers suffer high frictional resistance, high self-weight, and severe pore shrinkage after perforation in deep, highly deviated, and horizontal wells. Targeting the performance demands of adhesive casing centralizers, this study uses epoxy resin as the matrix, introduces amino modification, and regulates inorganic filler composites to prepare an amino-modified epoxy resin composite centralizer material, followed by systematic property tests. The optimal formula of modified epoxy resin:curing agent:UR300 accelerator:amino-modified silica:silicon carbide:alumina is 100:10:1:1:35:20 and delivers superior comprehensive performance. Its compressive strength reaches 136.61 MPa with a Shore hardness of 92.32 HD, low linear expansion, and favorable thermal compatibility with steel casings. Hardness remains stable after 168 h of aging at 150 °C, and the material maintains low friction at ambient and elevated temperatures. After 30-day immersion in acidic, alkaline, and high-salinity fluids, its compressive strength retention exceeds 86% with a slight variation in volume and mass, while adhesion strength reaches 2.667 MPa at a pipe-wall roughness of 12.12 μm. Combining high strength, heat resistance, corrosion resistance, and strong adhesion, the material suits complex downhole conditions and supports the field application of resin composite centralizers.