Preparation and performance of novel temperature‐resistant thickening agent

Abstract

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 ...

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