Xiaojiang Yang

A novel gemini viscoelastic surfactant (VES) for fracturing fluids with good temperature stability

A category of gemini surfactants with novel structures were designed and synthesized as thickening agents of clean fracturing fluids in this research. The desired products were characterized by high resolution mass spectrometry (ESI-HRMS) and infrared spectrometry (FT-IR GX). Fluid samples with a formula of 5 wt% of products and 1 wt% of KCl were evaluated. The SEM studies revealed a good network microstructure and obvious viscoelasticity, which is favorable for a proppant suspension. Furthermore, the evaluation of their rheological properties at high temperatures revealed good thermal stabilities of these fluids up to 139 °C, particularly for VES-M (the spacer for the surfactant using methylamine and epoxy chloropropane). Comparative analysis of the rheological properties showed that since long chains of N-substituents in the middle of the molecules could enhance steric hindrance and rigidity, it is unfavorable for molecular entanglement and increases the viscosity of the VES aqueous solution. Proppant-support and gel breaking evaluations were also performed. It can be seen that nearly 100% proppant suspension was observed for 180 min at ambient temperature and complete gel breaking was achieved.

Novel terpolymers as viscosity reducing agent for Tahe super heavy oil

The four components of extra-heavy oil (saturates, aromatic, resins, asphaltene) were analyzed by chemical separation. The terpolymers with different contents of styrene (S), alkyl chain (MM/DM), and vinyl acetate (V) were designed, synthesized and employed as the viscosity reducers for super heavy oil. Thus, structure and average molecular weight of the oil-soluble terpolymers were measured by Fourier-transform infrared (FTIR) and gel permeation chromatography (GPC), respectively. Comparing with the apparent viscosity of heavy oil in a wide range of shear rates (0.1–200 s−1) and temperatures (25–75 °C), it can be seen that optimal efficiency could be achieved to reduce viscosity when the terpolymer has a high percentage of long-chain alkyl. Furthermore, the molar ratio between long-chain alkyl groups and aromatic ring as well as molecular weight of terpolymers play a fundamental role in viscosity reduction of super heavy oil.

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. Until now, this is the highest temperature that the VES fracturing fluid could bear. The VES-T/NaSal fluid exhibited good viscoelasticity and proppant-suspending capability, which was attributed to the three-dimensional network formed by entangled wormlike micelles. Furthermore, the VES fracturing fluids can be completely gel broken by standard brines within 2 h. Thus, the VES-T synthesized in this work has a good prospect for utilization during the development of ultra-high temperature reservoirs.

Effective Synthesis of Benzyl 3-Phenylpropiolates Via Copper(I)-Catalyzed Esterification of Alkynoic Acids with Benzyl Halides Under Ligand-Free Conditions

Abstract We developed an efficient way to prepare benzyl 3-phenylpropiolates via copper-catalyzed coupling between corresponding benzyl halides and alkynoic acids under ligand-free condition. This methodology is also suitable for aromatic and α,β-unsaturated acids. The desired esters could be obtained in good yields.Graphical AbstractWe developed an efficient way to prepare benzyl 3-phenylpropiolates via copper-catalyzed coupling between corresponding benzyl halides and alkynoic acids under ligand-free condition. This methodology is also suitable for aromatic and cinnamic acids. The desired esters could be obtained in good yields.

Investigation on Problems of Wastewater from Hydraulic Fracturing and Their Solutions

AbstractThe global energy landscape has significantly changed in the past several years because horizontal drilling and hydraulic fracturing enable unconventional oil and gas extraction from previously inaccessible shale formations. However, opportunities and challenges coexist. Large volumes of freshwater consumed and wastewater discharge increasingly affect the environment and ecosystem. Much freshwater is pumped into deep formations during hydraulic fracturing process, and flowback with high-salinity brines, producing large volumes of wastewater. Such wastewater contains not only many toxic chemicals and high levels of total dissolved solids, but also abundant stratigraphic minerals and radioactive substances, which may pose a serious risk to the surrounding environment and public health. One of the greatest challenges for current oil and gas extraction is handling those wastewaters in a reasonable and efficient way. This paper described the current methods for dealing with these challenges and put forward some suggestions and expectations for future management of water resources in hydraulic fracturing. Graphical Abstract

Novel Hydrophobic Associating Polymer with Good Salt Tolerance

A hydrophobic associating polymer named DiPHAM (acrylamide/sodium acrylamide-2-methylpropanesulfonic/sodium acrylate/N,N-di-n-dodecylacrylamide) with good salt tolerance was synthesized via photo-initiation polymerization. The critical association concentration (CAC) of DiPHAM was determined by viscosity changes to be 490 mg/L with different DiPHAM concentrations and particle sizes varied under such dynamic conditions. The influences of aqueous metal ions with different charges on its aqueous solution were investigated by measuring apparent viscosity, viscoelasticity, thixotropy, rheology, and particle size, and by SEM observation. The apparent viscosity of the DiPHAM solution was affected by metal ions to some extent, but the viscosity of the polymer can be still maintained at 55 mPa·s under 20 × 104 mg/L NaCl. Divalent metal ions show greater impact on DiPHAM aqueous solutions, but the polymer solutions showed resistance to the changes caused in viscosity, structure, and viscoelasticity by Ca2+ and Mg2+ ions. The salt tolerance of DiPHAM is due to the combination of hydrophobic association, the electrostatic shield, and double layer compression of the hydration shell. Increasing the ion concentration enhances the dehydration and further compresses the hydration shell, making the non-structural viscosity decrease, even “salting out”. Measurements of rheological properties showed that DiPHAM solutions could maintain a relatively high viscosity (0.6%-71 mPa·s/0.3%-50 mPa·s) after 120 min of continuous shearing (170 s−1) at 140 °C. Under high-salinity (5000 mg/L Ca2+/3000 mg/L Mg2+) conditions, the solution with 0.6 wt% DiPHAM still maintained a high viscosity (50 mPa·s/70 mPa·s) after continuously shearing for 120 min at 120 °C and 170 s−1. The good salt tolerance of DiPHAM can lead to a variety of applications, including in fracturing fluids for enhanced oil recovery (EOR) and in sewage treatment.

Advances in waterless fracturing technologies for unconventional reservoirs

ABSTRACT The application of conventional hydraulic fracturing technology has been greatly restricted especially in areas with water shortage and traffic inconvenience. At the same time, concern grows about water resources and environmental protection. More environmentally friendly new fracturing technologies, such as waterless fracturing technologies, can also make an important contribution to oil and gas exploitation. This paper reviews several kinds of waterless fracturing fluid technologies, including their working mechanisms, technical features, advantages, and disadvantages. This paper then explores the economics of the various technologies, and prioritizes them based on their advantages and disadvantages. It provides a reference point for theoretical research on and the practical application of waterless fracturing.

Palladium-catalyzed synthesis of diarylbenzenes from coupling reactions between equal amount of diiodoarenes and arylboronic acids

We reported a highly effective Pd-catalytic system for the synthesis of diarylbenzenes through Suzuki-type reaction between equal amount of diiodoarenes and arylboronic acids. This preferential oxidative addition resulted in such high selectivity.

Pd-catalyzed oxidative olefination of arenes with olefins via C–H activation: Retention of the leaving group

Pd-catalyzed direct oxidative olefination of arenes with olefins via C–H activation is described in the absence of any chelating directing groups. For Pd-catalyzed oxidative coupling between arenes and allyl acetate, it was observed the retention of the leaving group.