Research on uniaxial mechanical properties of synthetic sandstones cemented with epoxy resin adhesives
YAN Min, DENG Jingen, TIAN Deliang, YU Baohua, XIAO Qiangzhong, CHEN Zhuo
1 China Oilfield Services Limited, Tianjin 300459, China 2 National Key Laboratory of Petroleum Resources and Engineering, China University of Petroleum, Beijing 102249, China 3 Tianjin Branch of CNOOC Ltd, Tianjin 300459, China
Synthetic sandstones have been widely used in petroleum, rock and soil engineering for their easy acquisition and controllable properties. However, there are still some differences between the mechanical properties of the artificial and natural cores. In this study, synthetic sandstones were prepared with three different curing systems to investigate the mechanical properties of epoxy resin-cemented cores. The effect of curing systems on the mechanical properties of artificial cores was studied through the comparison of uniaxial stress/strain curves and rock failure forms between the cores cemented with different adhesives. The dominant factors affecting the brittleness of the cycloaliphatic epoxy resin-bonded cores were determined by varying the curing agent ratio, the curing duration, and the catalyst content. Considering the material aging of epoxy products, mechanical tests were conducted on the artificial cores that have been treated with fluids, and the sensitivity of the mechanical properties of the core to fluid was analyzed. The results show that the mechanical properties of epoxy products are related to the type and molecular structure of epoxy resins and curing agents, which lead to the differences in the mechanical properties of the synthetic samples based on different curing systems. The cores cemented with cycloaliphatic epoxy resin have relatively high brittleness. The strain softening was rapid and the apparent failure line was observed on the core surface after the failure of the core. The catalyst can greatly affect both the brittleness and strength of the cycloaliphatic resin-bonded cores. A low content of catalyst may lead to distinct plasticity, while a high content can lower the core strength. A dosage of 3% to 5% is recommended when using DMP-30 as the catalyst. The artificial cores are sensitive to water and mineral oil in different degrees, and the effect of water on strength weakening is more obvious than that of mineral oil. The core lost up to 50% of its strength after two hours’ soaking in water. It is recommended that the sensitivity of core strength to fluids should be considered for research involving mechanical properties of epoxy resin-cemented artificial cores affected by fluids. The results can provide some guidance for reducing the difference in mechanical properties between artificial and natural cores and the application of artificial cores in rock mechanics experiments.
