A method includes collecting a first set of borehole gravity data at a first time step along a length of a first wellbore and collecting a second set of borehole gravity data at the first time step along a length of a second wellbore. The method also includes interpolating a third set of borehole gravity data at the first time step in an area between the first wellbore and the second wellbore using the first and the second sets of borehole gravity data. Further, the method includes determining a first fluid saturation and a fluid saturation change over time in a reservoir containing the first wellbore and the second wellbore using the first set, the second set, and the third set. Moreover, the method includes controlling wellbore production operations or wellbore injection operations at the first wellbore based on the fluid saturation change.