Graft-modified polybutadiene(PB) latex was synthesized and used as an admixture to improve the performance of oilwell cement. Results showed that the addition of latex to pure cement slurry can significantly reduce th...Graft-modified polybutadiene(PB) latex was synthesized and used as an admixture to improve the performance of oilwell cement. Results showed that the addition of latex to pure cement slurry can significantly reduce the fluid loss of the cement slurry. When the dosage was 8%, the fluid loss was only 38 mL, and the fluidity of the cement slurry was improved. With an increasing amount of latex, the fluidity of the cement slurry increased continuously. The toughness of cement was significantly enhanced, whose average elastic modulus was 4.2 GPa. Scanning electron microscopy revealed that the filter cake of the cement slurry with latex was thin and dense, and the surface was coated with a layer of latex film. The microstructure of the cement stone showed a high density, and an interweaving mesh network formed in the cement. The results of cement hydration heat analysis and X-ray diffraction showed that latex inhibited the hydration of cement; the effect was stronger under a larger amount of latex. It is indicated that the graft-modified PB latex has great potential to replace the conventional styrene-butadiene rubber(SBR) latex for cementing in the future.展开更多
Fundamental mechanics of gas hydrates is of importance to evaluating geomechanical and geotechnical properties of gas hydrate deposits,but it remains largely unexplored yet due to insufficient direct experimental tech...Fundamental mechanics of gas hydrates is of importance to evaluating geomechanical and geotechnical properties of gas hydrate deposits,but it remains largely unexplored yet due to insufficient direct experimental techniques and high-quality of gas hydrate samples.Here,classic molecular dynamic(MD)simulations are used to study the fracture mechanics of three main methane clathrate hydrates of sI,sII and sH types.The results show that the mechanical properties of those three methane clathrate hydrates are intrinsically different and are degraded by the presence of nanocracks.They show brittle facture and different fracture toughness.In terms of energy release rate,they are ranked as sH>sI>sII.Moreover,the three methane clathrate hydrates with nanocracks can be explained by a modified Griffith criterion.Moreover,it is intriguingly identified tip amorphization during the crack propagation process of the three methane clathrate hydrates,and sH methane clathrate hydrate with specific nanocrack exhibits slower crack propagation than other two methane clathrate hydrates.展开更多
基金supported by the National Science and Technology Major Project of China (No. 2016ZX05020-004)
文摘Graft-modified polybutadiene(PB) latex was synthesized and used as an admixture to improve the performance of oilwell cement. Results showed that the addition of latex to pure cement slurry can significantly reduce the fluid loss of the cement slurry. When the dosage was 8%, the fluid loss was only 38 mL, and the fluidity of the cement slurry was improved. With an increasing amount of latex, the fluidity of the cement slurry increased continuously. The toughness of cement was significantly enhanced, whose average elastic modulus was 4.2 GPa. Scanning electron microscopy revealed that the filter cake of the cement slurry with latex was thin and dense, and the surface was coated with a layer of latex film. The microstructure of the cement stone showed a high density, and an interweaving mesh network formed in the cement. The results of cement hydration heat analysis and X-ray diffraction showed that latex inhibited the hydration of cement; the effect was stronger under a larger amount of latex. It is indicated that the graft-modified PB latex has great potential to replace the conventional styrene-butadiene rubber(SBR) latex for cementing in the future.
基金This work was supported by the National Natural Science Foundation of China(Grants 11772278,11904300 and 12002350)the Jiangxi Provincial Outstanding Young Talents Program(Grant 20192BCBL23029)。
文摘Fundamental mechanics of gas hydrates is of importance to evaluating geomechanical and geotechnical properties of gas hydrate deposits,but it remains largely unexplored yet due to insufficient direct experimental techniques and high-quality of gas hydrate samples.Here,classic molecular dynamic(MD)simulations are used to study the fracture mechanics of three main methane clathrate hydrates of sI,sII and sH types.The results show that the mechanical properties of those three methane clathrate hydrates are intrinsically different and are degraded by the presence of nanocracks.They show brittle facture and different fracture toughness.In terms of energy release rate,they are ranked as sH>sI>sII.Moreover,the three methane clathrate hydrates with nanocracks can be explained by a modified Griffith criterion.Moreover,it is intriguingly identified tip amorphization during the crack propagation process of the three methane clathrate hydrates,and sH methane clathrate hydrate with specific nanocrack exhibits slower crack propagation than other two methane clathrate hydrates.
