Analysis of flow field characteristics of sand removal hydrocyclone applicable to solid fluidization exploitation of natural gas hydrate.

With the development of economy and society, the consumption of fossil energy is gradually increasing. In order to solve the current energy dilemma, Natural gas hydrate (NGH) is considered as an ideal alternative energy. At the same time, solid fluidization exploitation is an ideal method.

Synthesis and Anticancer Properties of Functionalized 1,6-Naphthyridines.

The burgeoning interest in synthesis and biological applications of 1,6-naphthyridines reflects the importance of 1,6-naphthyridines in the synthetic as well as medicinal chemistry fields. Specially, 1,6-naphthyridines are pharmacologically active, with variety of applications such as anticancer, anti-human immunodeficiency virus (HIV), anti-microbial, analgesic, anti-inflammatory and anti-oxidant activities. Although collective recent synthetic developments have paved a path to a wide range of functionalized 1,6-naphthyridines, a complete correlation of synthesis with biological activity remains elusive.

Application of a Zwitterionic Hydrophobic Associating Polymer with High Salt and Heat Tolerance in Brine-Based Fracturing Fluid.

ZIDPM, a zwitterionic hydrophobic associating polymer, has equivalent positive and negative charges and some hydrophobic monomers with twin-tailed long hydrophobic chains. It exhibits a great heat resistance and salt tolerance to the common salt in formation brine (MgCl, CaCl, NaCl, and KCl), which is attributed to its anti-polyelectrolyte effect and strong association force. High-salinity water (seawater or formation water) can be prepared as a fracturing fluid directly.

Preparation of a Novel Fracturing Fluid System with Excellent Elasticity and Low Friction.

The quaternary polymer was synthesized by radical polymerization and characterized by H NMR. The tests of critical associating concentration and SEM suggest that there is a multilayered and robust network structure in the polymer solution. An excellent elasticity in the polymer solution by the first normal stress difference, viscoelasticity, and thixotropy was observed.

Improving the Thermal Stability of Hydrophobic Associative Polymer Aqueous Solution Using a "Triple-Protection" Strategy.

Because of their high viscoelasticity, Hydrophobic Associative Water-Soluble Polymers (HAWSPs) have been widely used in many industrial fields, especially in oilfield flooding and fracturing. However, one major problem which limits the wide applications of HAWSPs is their weak resistance to high temperatures. Once the temperature increases over 100 °C, the viscosity of the fracturing fluid decreases rapidly, because high temperatures reduce fluid viscosity by oxidizing the polyacrylamide chains and weakening the association of hydrophobic groups.

High Performance Clean Fracturing Fluid Using a New Tri-Cationic Surfactant.

In order to improve the heat resistance of current clean fracturing fluids, a novel cationic surfactant (VES-T), composed of three single-chains and a spacer group, was designed and synthesized as thickener for the fluids. Various performances of such VES-T fluid in the presence of NaSal were evaluated carefully. Study of the rheological properties demonstrated that the fluids with varying concentrations (3⁻5 wt %) of VES-T have excellent thermal stabilities under ultra-high temperatures ranging from 140 to 180 °C.

Study of a Novel Gemini Viscoelastic Surfactant with High Performance in Clean Fracturing Fluid Application.

Gemini surfactant, as a functionally flexible polymer-like material in the aqueous solution, has attracted increased attention in reservoir stimulation of hydraulic fracturing in recent decades. A new Gemini cationic viscoelastic surfactant named JS-N-JS, which has a secondary amine spacer group and two ultra-long hydrophobic tails, was synthesized from erucamidopropyl dimethylamine, diethanolamine, and thionyl chloride as a thickener for hydraulic fracturing fluid. Compared with some Gemini cationic surfactant with methylene spacer, JS-N-JS showed a lower critical micellar concentration (CMC) and higher surface activity due to the hydrogen bond formed between the secondary amine and water molecule intends to reduce electrostatic repulsion, which is more beneficial to be the fracturing fluid thickener.

Preparation of a Hydrophobic-Associating Polymer with Ultra-High Salt Resistance Using Synergistic Effect.

Polymer, SRP-2-1, was synthesized by micellar polymerization and characterized by ¹H NMR. Salt tolerance and viscoelasticity tests verified that the salt resistance of SRP-2-1 was promoted by the synergistic effects of oxyethylene groups, sulfonate, and hydrophobic chains. It is suggested that the structure of SRP-2-1 became more compact with increasing salinity.

CH Nanobubbles on the Hydrophobic Solid-Water Interface Serving as the Nucleation Sites of Methane Hydrate.

The surface hydrophobicity of solid particles plays a critical role in the nucleation of gas hydrate formation, and it was found that the hydrophobic surface will promote this nucleation process, but the underlying mechanism is still unveiled. Herein, we proposed for the first time our new theory that the formation of methane nanoscale gas bubbles on the hydrophobic surface provides the nuclei sites for further formation of methane hydrate. First, we studied the effect of hydrophobicity of particles on the nucleation of hydrate.

Simulation of solute transport through heterogeneous networks: analysis using the method of moments and the statistics of local transport characteristics.

We used a time domain random walk approach to simulate passive solute transport in networks. In individual pores, solute transport was modeled as a combination of Poiseuille flow and Taylor dispersion. The solute plume data were interpreted via the method of moments.

Intrinsic viscosity and rheological properties of natural and substituted guar gums in seawater.

The intrinsic viscosity and rheological properties of guar gum (GG), hydroxypropyl guar (HPG) and carboxymethyl guar (CMG) in seawater and the effects of shear rate, concentration, temperature and pH on these properties were investigated. An intrinsic viscosity-increasing effect was observed with GG and HPG in seawater (SW) compared to deionized water (DW), whereas the intrinsic viscosity of CMG in seawater was much lower than that in DW due to a screening effect that reduced the repulsion between the polymer chains. Regardless of the functional groups, all sample solutions was well characterized by a modified Cross model that exhibited the transition from Newtonian to pseudoplastic in the low shear rate range at the concentrations of interest to industries, and their viscosity increased with the increase in their concentration but decreased with the increase in temperature.

Hydraulic fracture extending into network in shale: reviewing influence factors and their mechanism.

Hydraulic fracture in shale reservoir presents complex network propagation, which has essential difference with traditional plane biwing fracture at forming mechanism. Based on the research results of experiments, field fracturing practice, theory analysis, and numerical simulation, the influence factors and their mechanism of hydraulic fracture extending into network in shale have been systematically analyzed and discussed. Research results show that the fracture propagation in shale reservoir is influenced by the geological and the engineering factors, which includes rock mineral composition, rock mechanical properties, horizontal stress field, natural fractures, treating net pressure, fracturing fluid viscosity, and fracturing scale.

Numerical simulation on open wellbore shrinkage and casing equivalent stress in bedded salt rock stratum.

Most salt rock has interbed of mudstone in China. Owing to the enormous difference of mechanical properties between the mudstone interbed and salt rock, the stress-strain and creep behaviors of salt rock are significantly influenced by neighboring mudstone interbed. In order to identify the rules of wellbore shrinkage and casings equivalent stress in bedded salt rock stratum, three-dimensional finite difference models were established.