Wang, Tao, Wu, Jingtao, and Yang, Jian
Journal of Futures Markets, Vol. 28 Issue 10, p. 993-1011

Using high-frequency returns, realized volatility and correlation of the NYMEX light, sweet crude oil, and Henry-Hub natural gas futures contracts are examined. The unconditional distributions of daily returns and daily realized variances are non-Gaussian, whereas the distributions of the standardized returns (normalized by the realized standard deviation) and the (logarithms of) realized standard deviations appear approximately Gaussian. The (logarithms of) standard deviations exhibit long-memory, but the realized correlation between the two futures does not, implying rather weak inter-market linkage in the long run. There is evidence of asymmetric volatility for natural gas but not for crude oil futures. Finally, realized crude oil futures volatility responds with an increase in the weeks immediately before the OPEC events recommending price increases.