Energy stocks' current rally may or may not last, but oil and gas as energy sources have robust long-term prospects. Growing global energy demand is expected to be met by a combination of renewable and conventional energy sources. Additionally, few segments, such as petrochemicals, have viable alternatives to fossil fuels yet. So, buying fundamentally strong oil and gas stocks with robust growth prospects can surely generate attractive returns in the long term. Here are three high-yield energy stocks trading near rock-bottom prices to consider buying right now.

Chevron

Integrated oil and gas giant Chevron's (NYSE:CVX) stock has risen nearly 12% in 2021. Still, it is 18% off its 52-week high and 28% off its three-year high. The stock offers an attractive yield of around 5.5%.

CVX Chart

CVX data by YCharts

Chevron has increased its dividends for 32 consecutive years. The company can easily cover its dividends using its cash flow from operations at $55 per barrel Brent -- the international benchmark crude oil price. Much of CVX's production is outside the U.S.  While that's the price level currently, there is no guarantee that oil prices will remain near current levels. However, Chevron's resilience at lower prices differentiates it from peers.

Chevron management says it can reduce its capital expenditures, suspend share repurchases, and minimize operating costs if oil prices remain low, as was the case in 2020. These actions should allow the company to maintain its balance sheet strength and dividends even at Brent prices of around $30 per barrel. Moreover, Chevron has the strongest balance sheet among its peers. 

CVX Financial Debt to Equity (Quarterly) Chart

CVX Financial Debt to Equity (Quarterly) data by YCharts

As the above graph shows, Chevron's debt-to-equity and debt-to-capital ratios are the lowest among its top peers. Chevron's strong balance sheet and capital discipline positions it well for periods of low oil prices. At the same time, it allows the company to make discretionary acquisitions, such as that of Noble Energy, at attractive terms.

Valero Energy

Low refining margins have pressured refining stock prices, including that of Valero Energy (NYSE:VLO). The stock is off 33% from its 52-week high and offers an attractive yield of nearly 6.5%. The refiner is likely to report weak fourth-quarter performance due to persistently low refining margins. That may keep the stock price under pressure in the near term.

However, Valero is one of the most well-positioned refiners to benefit from an eventual recovery in refining margins. Its refining cash operating expenses per processed barrel are among the lowest in its peer group. Additionally, Valero continues to invest in projects that improve connectivity to feedstocks as well as improve margins. This disciplined approach to investments allowed Valero to generate the highest average free cash flow among its peer group in the past. 

VLO Free Cash Flow (Quarterly) Chart

VLO Free Cash Flow (Quarterly) data by YCharts

Moreover, its free cash flow has been less volatile than that of its top peers. 

Finally, Valero is expanding its renewable diesel capacity significantly. With the planned expansion in 2021, the company's renewable diesel capacity will more than double from its current level. Low-carbon fuel policies in California, Canada, and the EU have driven the demand for renewable diesel. Other states are also considering similar policies, which could further boost demand. Valero's renewable diesel operations, though small currently, have generated healthy and growing cash flow over the years.

A pile of $100 bills.

Image source: Getty Images.

ONEOK

ONEOK (NYSE:OKE) stock has risen nearly 15% so far in 2021, outperforming both Valero Energy and Chevron. Still, the stock is off 43% from its 52-week high. It also offers an alluring yield of nearly 8.5%. ONEOK stock slumped big time in 2020. A key reason was that the company's distributable cash flow (broadly EBITDA less interest, tax, and maintenance capital expenditures) slumped in the second quarter and wasn't sufficient to cover its dividend. A steep fall in oil and gas production impacted the company's gas gathering and processing earnings.

ONEOK's performance, however, improved in the third quarter supported by strong growth in natural gas liquid (NGL) volumes. The company's dividend coverage improved, too. Yet its debt level remains elevated.

OKE Financial Debt to EBITDA (TTM) Chart

OKE Financial Debt to EBITDA (TTM) data by YCharts

ONEOK expects double-digit earnings growth in 2021. Unless commodity prices fall to the levels seen in April last year, ONEOK should be able to achieve its anticipated earnings growth. Notably, based on its guidance midpoint, it grew earnings by around 8% even in the challenging year of 2020.

Moreover, the company expects to spend only $300 million to $400 million on growth projects annually until the production volumes rise substantially to justify an increase in expenditure. Increased earnings and reduced capital expenditure should allow ONEOK to reduce its debt over time. That should help drive its stock higher in the long term. This makes its attractive yield sustainable, too.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.