Jincheng Mao

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.

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

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.

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.