Master limited partnership and energy infrastructure exchange traded funds were trading near all-time highs as investors look for investment alternatives in a shaky market and capitalize on the shale oil expansion.

For instance, the Global X MLP & Energy Infrastructure ETF (NYSEArca: MLPX) was hovering around $18.1 per share before dipping 0.7% Tuesday. MLPX has gained 10.7% year-to-date.

According to a recent Fitch Ratings report, Non-Traditional MLP Assets (Changing Mix, Changing Risk), non-traditional MLP Investments continue to support hydraulic fracturing. MLPs can also serve as a stable investment due to their low volatility and revenue source.

“In some cases, these operations exhibit favorable characteristics of traditional pipelines such as longer-term contractually supported revenues, strong counterparties, and low volatility,” according to a press release.

While MLPs are associated with the energy sector, they have a low correlation to energy prices, along with the broader equities markets, as the assets act like a toll-road in the nation’s energy infrastructure. Consequently, these companies will generate a steady revenue stream as oil continues to flow.

Moreover, MLPs have a historically low correlation with the S&P 500, which helps diversify a portfolio.

Fitch expects MLPs will play a large role in the U.S. energy sector as shale operations expand. [Increased Investment Activity Could Energize Energy ETFs]