Zhaoyang Zhang

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.

Double alkyl chain copolymers as flow improvers for heavy oil

ABSTRACT As flow improvers for heavy crude oil, two oil-soluble copolymers (DM-S-VA, DA-S-VA) were successfully synthesized and characterized by 1H NMR and GPC. A rich alkyl chain and appropriate molecular weight of copolymer play fundamental role in viscosity reduction of heavy oil. Furthermore, synergistic effect of surfactants on polymers can promote the viscosity reduction, and the best formulation can increase the viscosity reduction rate to 78% to oil A. Comparing with the apparent viscosity of the different heavy oil mixing system in a wide shear rate range (0.1–200 s−1), the results show good stability and viscosity reducing effect.

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.