"In any industry, one of the most sure-footed means of keeping profits steady is to own the suppliers of production means -- the old 'invest in the picks and shovels' approach," explains Neil George in Personal Finance.

He says, "For refiners, it means pipe, compressors, and the other bits used to crack crude into further profitable products." Here, he looks at a trio of favorites: Dresser-Rand Group Inc. (NYSE: DRC), Shaw Group Inc. (NYSE: SGR), and Tenaris (NYSE: TS).

"Dresser Rand is a leading global producer of highly specialized compressors and turbines, nearly 95% of which are used in the energy business. Compressors are used extensively in refineries; they're a crucial part of equipment used to process heavy and sour crude oils. The reactions used to process these more-complex crudes require generating extreme pressure and temperature.

"Dresser's products are also used to process Canadian oil sands. Dresser is also involved in some high-tech deepwater equipment work. The company has designed a subsea compressor and separator for Norway's Statoil.

"This equipment literally sits on the seafloor; the compressor helps to separate gas from oil and transport these commodities by subsea pipeline to distant floating production platforms.