CREATE TABLE table_name_15 (field VARCHAR(255), geological_trend VARCHAR(255), discovery VARCHAR(255), operator_s_ VARCHAR(255))
Which Field has a Discovery of na, and an Operator(s) of woc, and a Geological Trend of western
    
SQL: SELECT field FROM table_name_15 WHERE discovery = "na" AND operator_s_ = "woc" AND geological_trend = "western"