The aim of this work was to prepare a novel dendritic branched nano-thickening agent by free radical polymerization of acrylamide (AM), acrylic acid (AA), sodium p-styrene sulfonate, dimethyl diallyl ammonium chloride, and multiwalled carbon nanotubes. The as-synthesized nano-thickening agent was characterized by Fourier transform infrared, Raman spectra, transmission electron microscope, 1 H-NMR, and thermogravimetric analysis (TGA). Compared with the pristine polymer and partially hydrolyzed polyacrylamide (HPAM), thickening capacity, temperature resistance, and salt tolerance properties of the nano-thickening agent considerably improved, and the viscosity of 0.5% nano-polymer solution was 126.5 mPaÁs. Additionally, the properties of the nano-gel prepared by nano-thickener, such as temperature and shear tolerance, viscoelasticity, sand carrying capacity, and gel breaking performance, were evaluated showing the satisfactory performance of the nano-gel under high temperature condition. The results indicated that the nano-thickener has potential applications in the field of oil and gas production.

In this article, a novel kind of temperature-resistant thickening agent (LK) was copolymerized with acrylamide, acrylic acid, sodium p-styrenesulfonate, and dimethyl diallyl ammonium chloride via free radical copolymerization. The polymerization conditions were optimized by the single-variable method. Subsequently, the structure of the copolymer was characterized through Fourier transform infrared spectroscopy and proton nuclear magnetic resonance.Thermal gravimetric analysis demonstrates that the thickening agent LK has an excellent ability of temperature-resistance and the degradation temperature of the copolymer is higher than 300°C. The 3-dimensional network structure formed in the fracturing fluid was observed via experimental results of scanning electron microscopy. Several aspects of the properties of fracturing gel system, such as temperature and shear tolerance, salt resistance and viscoelasticity, and gel breaking and filter loss were evaluated. Results indicates that the fracturing gel system presents good comprehensive performances under high-temperature condition. KEYWORDSfracturing fluid, temperature resistance, thickening agentWith the continuous increase of oil and gas consumption and the decline of conventional oil and gas production, the unconventional oil and gas resources such as shale gas, tight sandstone gas, and coal bed methane have already attracted great attention from the countries all over the world. 1,2 As is known to all, fracturing has proved to be an effective method to increase production and water injection in oil and gas field; thus, it has been widely used in low-permeability reservoirs.And thickening agent is not only an important part in water-based fracturing fluid but also the most core ingredient. 3 Guar and its derivatives are widely used to stimulate the oil and gas wells because of its advantages such as the strong viscosity and good temperature resistance. However, fracturing fluids based on guar and its derivatives are usually broken down by chemical breakers, then many insoluble residues might be left behind, which can cause blockages of the flow channels and a decrease of the formation production rate. 4,5 Compared with natural polymers, synthetic polymers are characterized by strong thickening ability, easy to get, strong heat resistance, low residue content, easy to control the molecular structure, and so on. [6][7][8][9] The traditional synthetic polymers are mainly composed of partially hydrolyzed polyacrylamide, characterized by poor temperature resistance. 10 To enhance the temperature and shear resistance performance of the fracturing fluid, it needs to improve the molecular weight or increase the usage concentration, which will lead to higher costs and formation damages. [11][12][13][14] To solve the above-mentioned problems, sodium p-styrenesulfonate (PS) and dimethyl diallyl ammonium chloride (DMDAAC) are introduced into the copolymer. Sodium p-styrenesulfonate contains rigid group with good thermal stability.The rigid groups are usually larger, which can ...

A novel temperature-resistant fluid loss reducer FL is obtained by free radical copolymerisation. Thermal gravimetric analysis demonstrates that the fluid loss reducer FL has a strong temperature-resistance capability and its degradation temperature is higher than 440°C. An experiment investigating the effect of FL on the comprehensive performance of oil well cement slurry shows that filter loss can be controlled within 50 ml when the dosage of FL is 1·0% of the total mass of cement and quartz powder under the ultra-high-temperature condition of 200°C (bottom-hole circulating temperature). Cement slurry with FL exhibits good comprehensive performance under high-temperature and ultra-high-temperature conditions. The working mechanisms of the fluid loss reducer FL are studied and the compressible ‘viscoelastic adsorbed layer’ perspective is proposed, which could explain the excellent ability to control the filter loss of cement slurry under high temperature.