Design and execute the wellbore — from the first wellhead to total depth — that makes it possible to reach and produce oil and gas reserves. In India, the role concentrates at ONGC (Mehsana, Sibsagar, Rajahmundry, Barmer, Mumbai High), Oil India (Duliajan, Assam), Cairn Oil & Gas (Barmer, Rajasthan), Reliance E&P (KG-D6), and the oilfield services majors (Schlumberger, Halliburton, Baker Hughes, Weatherford) that run drilling contracts across all these fields. Day-to-day work spans well-planning (trajectory design in WellPlan / Landmark, casing programme sizing, pore-pressure and fracture-gradient analysis), drilling-fluid engineering (mud-weight selection, inhibitive WBM/OBM design, hydraulics calculations), bottomhole assembly design (PDC bit selection, RSS / steerable motor choice, LWD/MWD string), directional drilling supervision, well-control execution under IWCF protocols, and cementing and casing-running operations. The IIT-ISM Dhanbad petroleum-engineering stream and PDEU Gandhinagar are the primary feeders; B.Tech in Mechanical or Chemical Engineering with a GATE-level drilling-engineering elective also enters ONGC and OFS. Senior drilling engineers progress to Drilling Superintendent (site authority for all operations), Wells Manager (multi-rig campaign), or Drilling Manager (country or asset-level).