"The boom in natural gas prices has been good for North American producers and their investors, both of which continue to be upbeat on the sector as share prices also keep rising," says Bill Martin.

In his exceptional BullMarket.com, he looks at SandRidge Energy (NYSE: SD), where its billionaire CEO as well as a director have continued to buy shares, despite the stock trading near "peak levels."

"Oklahoma City-based SandRidge focuses on the exploration, development, and production of oil and gas in the West Texas Overthrust, East Texas, and Mid-Continent (Oklahoma) regions.

"President, and CEO Tom Ward purchased 460,000 shares at $48.95 on May 19th/20th, which increased his already substantial holdings to nearly 36.95 million shares, or a 25.27% stake.

"It was the first purchase for Ward since he announced in March his attention to buy up to $100 million in stock on the open market this year. His only other open-market purchase came in November 2007, when he took down 4.17 million shares at $26.00 in the company's initial public offering.