Canadian Natural Resources Limited, or CNRL or Canadian Natural, is an oil and gas exploration, development and production company with its corporate head office in Calgary, Alberta. Along with its core area Western Canadian Sedimentary Basin (WCSB),, CNRL also has North Sea and offshore West Africa fields. By 2011, with a production of 121,000 barrels (19,200 m3), CNRL was Canada's largest oil company and Canada's "single biggest conventional heavy oil producer." By 2009 CNRL ranked number 251 on the Forbes Global 2000 list.