I am proof-reading a thesis.

In REVIEW OF PREVIOUS LITERATURE, there are paras -

"Purohit (2007) conducted a study regarding the assessment of CDM potential of BGPP in India. The annual CER potential of BGPP, annual gross potential availability of biomass and gross potential of BGPP in India had been estimated to 58 MT, 74 MT and 31 GW respectively."

OR

Miccio et al. (2008) conducted a study on the efficiency of biomass gasification (a thermodynamic predictive tool) in ICFB.

I corrected the word 'STUDY' as 'STUDIES' but my MS WORD software shows it wrong, but STUDY is correct to the s/w. What is the correct - study or studies?

I have read somewhere that the word 'study' means 'to read', 'to pursue a course' (as verbs) or the room, in which one studies (as NOUN) or study room (as ADJECTIVE, meaning same).

Please tell me what is correct?

In this case, he did/performed/ran/conducted ONE study (but may have run multiple studies before and after in order to amass and fine-tune his data).

"Studies" could mean my school work -- "I am doing so well in all my studies."

"Study" could mean examining something closely -- "She decided to study the spider a bit closer by using a magnifying glass." or "She decided to study hard this semester."

In this case, "study" is correct.