NEW YORK ( Karvy) -- GT Solar ( SOLR), LDK Solar ( LDK) and Yingli Green Energy ( YGE) emerged as top gainers last week, while InterOil ( IOC), McMoRan Exploration ( MMR) and TransAtlantic Petroleum ( TAT) led the losers' list.GT Solar gained 9.8%, topping the list of energy gainers. During the week, the company announced a new DSS650 Multicrystalline Ingot Growth System. Tom Gutierrez, GT Solar's president and CEO, said in a press release, "GT Solar continues to actively invest in advanced technologies that deliver value to our customers. Our field-tested DSS650 sets a new standard for cost-effective, high volume, multicrystalline silicon ingot growth systems greater than 600 kilograms, which help PV manufacturers lower their production costs and improve their competitive position." Meanwhile, the company has received a $33.3 million order for sapphire crystallization from South Korea-based OCI. Other solar stocks LDK Solar, Yingli, Trina Solar ( TSL) and First Solar ( FSLR) advanced around 6.8%, 6.7%, 4.3% and 4.1%, respectively. EnCana ( ECA) rose 5%. During the week, Western Gas Partners ( WES), a subsidiary of Anadarko Petroleum ( APC), agreed to purchase Encana's Ft. Lupton processing plant in the DJ Basin of northeastern Colorado for $303.3 million. Nexen ( NXY) advanced around 3.8%, after FirstEnergy Capital raised the stock to market perform. Analysts at Haywood Securities, however, downgraded the stock to sector perform. Meanwhile, Nexen announced it will sell its 65% stake in chemical company Canexus for C$477.1 million ($481 million) to a syndicate of underwriters. French oil giant Total ( NXY) rose around 3.6% last week. Total Capital Canada and Total Capital, units of Total, sold around $2 billion of notes in a three-part offering. In the penultimate week, Total acquired interests in four exploration licenses in Argentina, in partnership with YPF ( YPF), to appraise the shale gas potential of these assets. Cabot Oil & Gas ( COG) gained 3% after Morgan Stanley upgraded the stock to overweight with a $45 price target, implying a 15.1% upside from the current level. Energy giants Exxon Mobil ( COG), Royal Dutch Shell ( RDS.A), Sunoco ( SUN) and Chevron ( CVX) posted gains of 3%, 2%, 1.9% and 1.7% last week, respectively. Eni ( E) and El Paso ( EP) were up 2.9% and 2.8% during the week, respectively. RBS upgraded Eni to buy from hold, while Citi raised El Paso to buy from hold.