Abstract
In this paper, sepiolite was treated by acid activation, coupling agent treatment, and sulfonation modification. The purpose of this study was to explore the changes in the fluidity and mechanical properties of sepiolite cement slurry before and after modification. Therefore, the comprehensive properties of unmodified sepiolite fiber (HPS) and acid activation-coupling agent treatment-sulfonated sepiolite fiber (S-O-H-HPS) in oil-well cement slurry were evaluated. FT-IR and microscopic mechanism of cement paste fracture surface before and after sepiolite modification were analyzed. The results showed that HPS can effectively improve the toughness of cement paste, but when the content of HPS was more than 1%, the fluidity of cement paste deteriorated sharply and the compressive strength decreased gradually. The addition of S-O-H-HPS can significantly improve the fluidity and stability of HPS slurry. Without affecting the compressive strength, it can effectively improve the flexural strength and impact strength and reduce the elastic modulus of cement paste. The mechanism analysis showed that S-O-H-HPS can not only form network structure in cement paste but also improve the toughness of cement paste by forming a bridge. This also explains why the strength of S-O-H-HPS cement paste does not decrease significantly with the increase of S-O-H-HPS.
Highlights
Cementing operation is very important in drilling engineering. e main purpose of cementing is to seal the oil, gas, and water layers in the wellbore, protect the casing of oil and gas wells, prolong the life of oil and gas wells, and increase the production of oil and gas wells [1,2,3,4]
According to the principle of super-hybrid composite [7], improving the plasticity of cement sheath and enhancing the deformation ability of cement sheath can effectively deal with these defects [8]. e dynamic mechanical properties of cement paste can be effectively changed by adding fillers of appropriate types and characteristics in the cement slurry
It was difficult to agitate the slurry when the dosage was increased to 3% or more; even if the dosage of the dispersant was increased, it was difficult to improve, which was consistent with the defect of conventional fibers when they were used as tougheners for cement. e fluidity index n of S-O-H-HPS admixture cement slurry decreased slowly with the increase in S-O-H-HPS (0%–9%). e decrease of n value was obviously smaller than that of HPS admixture cement slurry
Summary
Cementing operation is very important in drilling engineering. e main purpose of cementing is to seal the oil, gas, and water layers in the wellbore, protect the casing of oil and gas wells, prolong the life of oil and gas wells, and increase the production of oil and gas wells [1,2,3,4]. E dynamic mechanical properties of cement paste can be effectively changed by adding fillers of appropriate types and characteristics in the cement slurry. It can reduce the elastic modulus of cement sheath and prevent the appearance of microcracks and microannulus and improve the flexural and shear strengths of cement sheath. E dynamic mechanical properties of the cement sheath are affected and improved by adding fiber structural material into cement composition, and the stress field at the crack tip is shielded to improve the fracture toughness of the cement slurry system. Mechanical property tests showed that the maximum load and toughness increased by about 25% and 80%, respectively. Li et al [11] investigated the effect of methylcellulose and carboxymethyl cellulose on carbon
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