(Source: Morningstar)

Buckeye GP Holdings (BGH) - Manages a network of refined oil products pipelines and terminals through its subsidiary, Buckeye Partners. Most of the company's assets are found in the Northeast and Midwest, though it also operates terminals and some smaller pipelines in the Southeast and West. Buckeye's pipelines transport a variety of refined petroleum products connecting refineries, storage facilities, other companies' pipelines, and airports. (Source: Morningstar)

Energy Transfer Equity (ETE) - Owns the general partner interests, incentive distribution rights, and about 46% of the outstanding limited partner interests of Energy Transfer Partners. ETP is a master limited partnership primarily engaged in natural-gas transportation and storage and also is the third-largest retail marketer of propane in the U.S., serving more than a million customers in 41 states. (Source: Morningstar)

Chesapeake Energy (CHK) - An independent oil and natural-gas producer. CEO Aubrey McClendon cofounded Chesapeake in 1989 and took it public in 1993. The firm's proved reserves of 11 trillion cubic feet of natural-gas equivalent are located primarily in the Mid-Continent and Appalachian basin. Chesapeake also owns natural-gas gathering and processing assets and several drilling rigs. (Source: Morningstar)

Southern Union (SUG) - Southern Union operates an array of regulated and unregulated assets divided into the transportation and storage, gathering and processing, and distribution segments. The transportation and storage assets, comprising one of the nation's largest LNG terminals and a pipeline network stretching from Texas up through the Midwest and across to south Florida, generate the lion's share of cash flows. (Source: Morningstar)

Cal Dive International (DVR) - Cal Dive International, a marine contractor company, provides underwater services to offshore natural gas and oil firms. These services include manned diving, pipe lay and pipe burial services. It also constructs, inspects, maintains, repairs and decommissions offshore pipeline infrastructure in the Gulf of Mexico, Middle East, Southeast Asia, and Australia. Helix Energy Solutions Group is its parent company. (Source: Morningstar)