Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_15338 ( "Client" text, "Years of Operation" text, "Area of Operation" text, "Country" text, "Services" text )

### Question ###
Where is the area of operation that had drilling during the year 1999?

### Accurate SQL ###

SELECT "Area of Operation" FROM table_15338 WHERE "Services" = 'drilling' AND "Years of Operation" = '1999'