Gravity interpretation workflow in injection wells

A method, comprising:

• determining total porosity of a subterranean formation into which a fluid has been injected via a well extending into the subterranean formation;
• estimating time-lapse variation of the porosity based on the total porosity, perforation data and injection data;
• building a time-lapse density model based on the estimated time-lapse variation of the porosity, formation matrix density data and injected fluid density data;
• and
• projecting a borehole gravity tool response at a plurality of stations along the well based on the time-lapse density model.

An apparatus, comprising:

• means for performing at least one of a first method and a second method, wherein the first method comprises:
• 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;
• and wherein the second method comprises:
• determining total porosity of the subterranean formation into which the fluid has been injected via the well;
• estimating time-lapse variation of the porosity based on the total porosity, perforation data and injection data;
• building a time-lapse density model based on the estimated time-lapse variation of the porosity, formation matrix density data and injected fluid density data;
• and
• projecting a borehole gravity tool response at a plurality of stations along the well based on the time-lapse density model.