All I can find is the odd reference to "estudio en escritorio" as opposed to "investigaciones de campo". Here, for example, at foot of p. A-104 (p. 106 of the file):
http://open_jicareport.jica.go.jp/pdf/12291688.pdf (despite the Japanese URL it's from Nicaragua).
So maybe Hugh's guess is right, since one can find "desktop study" contrasted with "field investigations" in English:
"an initial desktop study; • field investigations using trial pits or boreholes"
https://books.google.co.uk/books?id=TastxSGEEGIC&pg=PA1&lpg=...I'm not very confident about this but I have nothing else to offer.