Shanshan Dai

Copolymer SJ-1 as a Fluid Loss Additive for Drilling Fluid with High Content of Salt and Calcium

A ternary copolymer of 2-acrylamide-2-methyl propane sulfonic acid (AMPS), acrylamide (AM), and allyl alcohol polyoxyethylene ether (APEG) with a side chain polyoxyethylene ether SJ-1 were designed and synthesized in this work. Good temperature resistance and salt tolerance of “” of AMPS, strong absorption ability of “amino-group” of AM, and good hydrability of side chain polyoxyethylene ether of APEG provide SJ-1 excellent properties as a fluid loss additive. The chemical structure of ternary copolymer was characterized by Fourier transform infrared (FTIR) spectroscopy. The molecular weight and its distribution were determined by gel permeation chromatography (GPC). The API fluid loss of drilling fluid decreased gradually with the increasing concentration of NaCl and CaCl2 in the mud system. SJ-1 was applied well in the drilling fluid even at a high temperature of 220°C. Results of zeta potential of modified drilling fluid showed the dispersion stability of drilling fluid system. Scanning electron microscopy (SEM) analysis showed the microstructure of the surface of the filter cake obtained from the drilling fluid modified by SJ-1.

CO2-/N2-Triggered Viscoelastic Fluid with N,N-Dimethyl Oleoaminde-Propylamine and Sodium p-Toluenesulfonate

In this article, a new type of CO2-triggered switchable wormlike micelles based on N,N-dimethyl oleoaminde-propylamine (DOAPA) and sodium p-toluene sulfonate (SPTS) mixed in a molar ratio of 1:1 is studied. With inlet of CO2, DOAPA molecules are protonated to form quaternary ammonium. The electrostatic attraction between quaternary ammonium and SPTS results in assembled structures and formation of a viscoelastic wormlike fluid. These results are proved by rheological methods in this study. Upon the release of CO2, the quaternary ammonium is deprotonated back to tertiary amines, the assemble structures are split, and water-like fluid is obtained. Such a reversible transition of viscosity between high and low can be repeated several times with or without CO2. This transition of the micromolecular structure is proved by 1H NMR and conductivity. As well, the process of viscosity reduction can be controlled by the flow rate of N2 addition.

Molecular dynamic simulations of the core–shell microsphere of nanosilica grafted by acrylamide acrylic acid copolymer PAMAA: study of its microstructure and interaction between microsphere and additives

Nanosilica grafted by acrylamide (AM) acrylic acid (AA) copolymer (PAMAA) is designed in this study to make a functional material, where nano-SiO2 provides the rigidity and strength and the copolymer the elasticity and flexibility. The resulting microsphere with a core–shell structure is able to enter, expand, shut off and be removed from deep layers of oilfields. Qualitative results can be easily obtained from normal experimental methods, but many quantitative relationships are still missing. To solve the problem mentioned above, molecular dynamic (MD) simulation is applied in this work to study the microstructure of microspheres and the interaction between microsphere and additives. Aqueous solutions (S1), as well as solutions with sodium dodecyl sulfate (SDS, S2), dodecyl trimethyl ammonium bromide (DTAB, S3), and alcohol ethoxylate (AEO, n = 3, S4) are built. The non-bond energy, radius of gyration (ROG) of microsphere, radial distribution function (RDF) for microsphere–additive pairs and mean square displacement (MSD) of polymer chains in these 4 different solutions are calculated at 325 K, 350 K and 375 K. The results show that addition of surfactants leads to a more stretched out polymer chain structure. The hydration effect and mobility of the polymer chain increase in both aqueous and surfactant solutions as temperature increases.

An Advanced Method for the Preparation of Erucyl Dimethyl Amidopropyl Betaine and Acid Solution Properties

Abstract In this paper, an improved method for the preparation of erucyl dimethyl amidopropyl betaine (EDAB) was provided. The synthesis conditions were investigated. N,N-dimethyl-N′-erucyl-1,3-propylenediamine was synthesized by the reaction of erucic acid with N,N-dimethyl-1,3-propylenediamine at 170°C for 7 h, and then the intermediate was reacted with sodium chloroacetate in the mixture of methanol and water (3:7 v/v) at 60°C. The product was obtained after 6 h. The compounds were confirmed by IR and 1H-NMR. The properties of EDAB acid solution were also studied. The results indicated that viscosity of acid solution increased with decreasing hydrochloric acid concentration and was mainly controlled by surfactant concentration and temperature. The viscosity of an acid solution was maximum when the concentration of hydrochloric acid was at 15 wt%.

Molecular dynamics simulations on the interaction between microsphere and water in nanosilica/crosslinked polyacrylamide microsphere aqueous solution with a core–shell structure and its swelling behavior

Abstract In this study, nanosilica/crosslinked Polyacrylamide (PAM) microsphere with a core–shell structure is designed to make a functional material, where nanosilica provides the rigidity, stiffness and strength, the crosslinked PAM provides the flexibility and elasticity. The structure mentioned above make the resulting microspheres to be able to enter, expand, shut off and be removed from deep layers of oilfields. A methodology to create the nanosilica/crosslinked PAM microsphere with a core–shell structure has been developed, and molecular dynamic (MD) simulations are applied to successfully study the interaction between the microsphere and water in aqueous solution of nanosilica/crosslinked PAM microsphere and its swelling behavior. Results including the interaction energies (Einter) between nanosilica and crosslinked PAM, Einter between the microsphere and water molecules, radius of gyrations (Rg) of the microsphere, the radial distribution functions of microsphere-water pairs, the mean square displacements and the diffusion coefficients (D) of water are calculated and analyzed in detail. The experimental results of particle diameter tested from dynamic light scattering have been used to verify the simulation results of swelling behavior. Graphical Abstract The interaction between nanosilica/crosslinked PAM microsphere and water in aqueous solution and its swelling behavior are studied.

Molecular dynamic simulation of core–shell structure: study of the interaction between modified surface of nano-SiO2 and PAMAA in vacuum and aqueous solution

Abstract The interaction between acrylamide acrylicacid copolymer (PAMAA) and the modified surface of nano-SiO2 is investigated using the molecular dynamic (MD) simulation. The binding energies (Ebinding) of interface, the concentration profiles of PAMAA and functional groups (carboxyl and acylamino) of corresponding model, the mean square displacements (MSD) and diffusion coefficients (D) of PAMAA in four systems with different modifiers are all calculated at 325 K in vacuum. Vinyl trimethoxy silane (VTEOS) shows best modification effect in the systems mentioned above. Furthermore, the effects of temperature on the interaction between VTEOS modified surface of nano-SiO2 and PAMAA are studied at 300, 325, 350, 375 and 400 K in aqueous solution. Interesting results show that, water molecular layer reduces with the increase of temperature, and then improves the interaction between PAMAA and VTEOS modified surface of nano-SiO2. The corresponding Ebinding of interface, the radial distribution functions (RDF) of carbon atoms on the surface and oxygen atoms of water molecules, the concentration profiles of PAMAA on the surface of nano-SiO2, the MSD and D of PAMAA are all studied seriously to find the reason of this counterintuitive phenomenon.