Twelve precision gravity surveys have been carried out at the Bulalo Field since production began in 1979. Eight precision leveling surveys have been carried out over this same period to monitor elevation changes at the same benchmarks (BMs). The Bulalo Field has experienced a maximum free-air gravity (FAG) change of about –600 mgals. A maximum subsidence of about 0.5 m can also be observed in the area. Mass calculations based on the gravity data indicate a recharge from upflow and perimeter aquifers of about 42%. The gravity data has also been successfully used as an independent calibration constraint for the Bulalo reservoir simulation model.