A method comprising: estimating a change in a characteristic of a subterranean formation into which a fluid has been injected via a well extending into the subterranean formation; building a multi-dimensional model balancing mass of the injected fluid, wherein the model is based on the estimated characteristic change; utilizing the model to determine the sensitivity of a borehole gravity tool in the well; measuring gravity with the borehole gravity tool at a plurality of stations along the well; and utilizing the model and the gravity measurements to locate the injected fluid in the subterranean formation.