Yes you can get admission in post graduate diploma course in drilling after passing diploma course in drilling technology .. here I am giving you some information about it ..

PGD courses :
POST GRADUATE DIPLOMA IN PETROLEUM REFINERY AND PETROCHEMICALS
POST GRADUATE DIPLOMA IN PETROLEUM EXPLORATION
PG Diploma in Oil Well Drilling Technology

Colleges for courses in India :
Dibrugarh University,
Dibrugarh, Assam, India, Dibrugarh,
Assam, India- 786004

ANNA UNIVERSITY
CHENNAI Tamil nadu

Dr. Babasaheb Ambedkar Marathwada University
Aurangabad City