Abstract
Oil well cement is a brittle material, which can not ensure the long‐term sealing integrity of oil and gas wells when used in cementing operations directly. As a kind of polymer emulsion material, epoxy resin emulsion has a bright future for improving the properties of the cement slurry. Epoxy resin emulsion was added to oil well cement and its workability and mechanical properties were studied, the stress‐strain behavior of cement samples was evaluated, and the microstructure was observed by scanning electron microscope (SEM) and X‐ray diffraction (XRD). The results show the epoxy resin emulsion used in oil well cement will affect the fluidity, but the rheological property of cement slurry with different content of resin meets the construction requirements. The resin reduces the water loss of cement paste and has no adverse effect on the thickening time. The compressive strength of cement stone decreases with the increase in resin content. When the content of resin is 6%, the flexural strength and impact strength of the cement sample are the largest, and 50.7% and 20.2% higher than that of the specimen without resin, respectively, after curing for 28 days. Further comparison shows that epoxy resin emulsion can improve the mechanical properties of oil well cement better than styrene‐butadiene rubber latex. Meanwhile, the resin obviously improves the deformability and decreases the elastic modulus of cement stone. Compared with pure cement, resin cement slurry has no extra hydration products, but the formation of hydrated calcium silicate is inhibited. The microstructure shows that the resin forms a polymer film in the cement matrix and interweaves with cement hydration products, thus improving the flexibility of cement paste.
Highlights
Cementing operation is important for oil and gas well construction; its fundamental purpose is to achieve interlayer sealing, support and protect casing, preventing fluid channeling between different formations under the pressure difference [1,2,3]
Considering the safety of cementing operation, the thickening time must be measured in the same temperature and pressure of the downhole and taken as the basis of construction operation [16]. e water loss of cement slurry is the free water that can be filtered through a definite area of pores under specified temperature and pressure difference. e excessive water loss will cause premature dehydration, change the thickening time, and reduce the strength of cement paste, resulting in problems such as annulus bridge blockage and interlaminar flow [17]
Evaluation data of rheology is listed in Table 2. e thickening time and water loss of resin cement slurry are shown in Figures 1 and 2, respectively
Summary
Cementing operation is important for oil and gas well construction; its fundamental purpose is to achieve interlayer sealing, support and protect casing, preventing fluid channeling between different formations under the pressure difference [1,2,3]. Some studies have shown that the cement slurry with polymer materials is helpful to enhance the resistance ability of oil well cement to stress and to achieve long-term sealing [5,6,7]. Polymer emulsion is one of the most commonly used polymers in oil well cement Adding polymer emulsion, such as styrene-butadiene latex and ethylene vinyl acetate copolymer emulsion, to cement slurry, the mechanical properties and durability of cement slurry can be significantly improved due to the action of the polymer [5, 8]. E modification mechanism of polymer emulsion on the properties of cement paste is mainly the formation of the polymer film and the close combination of membrane and cement hydration products [9]. The cohesive force of the modified cement is improved, forming a more cohesive microstructure and reducing the number of microcracks inside the cement matrix
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