We establish an operational risk assessment approach for integrated power and gas systems (IPGS) considering varying hydrogen concentrations with high penetration of wind. First, the operational availability of wind generation is formulated considering the stochastic process of wind is developed. Then, an operational risk mitigation scheme (ORMS) is devised to minimize both load shedding and gas security violation. The varying gas composition on the physical properties of IPGS is characterized to fully reflect the impact of alternative gas on the IPGS operation. Moreover, several risk indices, improved from traditional gas security indices, are proposed to evaluate gas security under various uncertainties. An analytical risk evaluation method is used for better computation efficiency. Finally, a test IPGS is utilized to demonstrate the proposed approach. We can find that the proposed operational risk evaluation approach is able to evaluate the weak spot of the IPGS when distributed injections of hydrogen are considered, and the trend of the risk evolution can also be obtained during the operation.