Hydrogeochemistry of Gandhar oil field waters, Cambay Basin, India

摘要

Hydrogeochemical interpretation of Gandhar oil field waters integrating log calculated salinities and other geological data suggests presence of three different hydrogeological regimes. The north eastern zone represents chloride-calcium type of waters in static equilibrium, with different degree of metamorphism indicating more favourable conditions to hold hydrocarbons. In the main Gandhar field waters are more saline showing higher coefficient values indicating maximum static condition. In the southern part of Gandhar the bicarbonate-sodium type of waters show moderate salinities with lesser degree of sealing nature. Tectonic analysis along with hydrogeochemical parameters infer possible hydrocarbon migration from south-east/southwest of Gandhar towards north-east resulting in accumulation in stratigraphic/structurally favourable positions during Miocene tilt. Presence of lesser salinities towards down dip is possibly due to mixing of Olpad waters during this tilt. Absence of hydrocarbons in GS-7 and GS-10 sands in Gandhar is due to opening of the hydrogeological system of these sands towards north-east.