(For a Reuters live blog on U.S., UK and European stock markets, click LIVE/ or type LIVE/ in a news window) July 15 (Reuters) - European stocks fell for a second straight session on Thursday, as oil stocks slid on lower crude prices, while wind energy companies tumbled after Siemens Energy’s downbeat margin outlook. The pan-European STOXX 600 index slipped 0.4% by 0719 GMT, with oil & gas sector falling 3.3%. UK-listed oil majors Royal Dutch Shell and BP fell almost 3%, as crude prices fell on expectations of more supplies after a compromise between top OPEC producers. Siemens Energy dropped 11% after it scrapped its margin target as wind power division Siemens Gamesa was hit by higher-than-expected raw material and product ramp-up costs. Siemens Gamesa fell 16%, while shares in wind turbine maker Vestas slid 6.9%. (Reporting by Sruthi Shankar in Bengaluru; editing by Uttaresh.V)