In this paper, we investigated the use of Ni-19.5-Ru-0.05/CGO as catalysts for associated gas pre-reforming to convert higher hydrocarbon and obtain higher methane content. To increase the content of methane, we perform catalytic pre-reforming experiments at 8 bars. Ni-Ru/CGO fully converted the C-2-C-5 hydrocarbons at 500 degrees C. However, the conversion of C-2-C-5 hydrocarbons decreased from 100% to 80% as the SCR decreased from 3.0 to 1.0. Catalytic degradation occurred at temperatures below 300 degrees C. Comparing the commercial pre-reforming catalyst (C11PR, produced by Stid-Chemie) with Ni-Ru/CGO catalysts, Ni-Ru/CGO outperformed C11PR under the same conditions. We performed long-term tests with Ni-Ru/CGO. Each long-term test lasted over 900 h. Initially, the methane yield was approximately 60%, and the higher hydrocarbons were fully converted. After 900 h, the methane yield was approximately 55%, and dramatically reaching to 50% at 920 h. Simultaneously, the C-2-C-5 hydrocarbon yield increased to approximately 8%. After the long-term test, we analyzed the tested catalysts and determined that catalytic degradation occurred due to carbon deposition on the catalyst surface. (C) 2017 Elsevier Ltd. All rights reserved.