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After about three years of enthusiastic drilling , during which most of the initially promising wells showed precipitous and mysterious production declines , the area was dubbed " the world 's largest unrecoverable oil reserve . "
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: location, person, organization 
Text: {0} 
Answer:
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