Generation of electricity during the injection of a dense fluid into a subterranean formation

DETAILED DESCRIPTION Briefly, the invention provides an improved method for the injection of a dense fluid through an injection well and into a subterranean formation which has a connate fluid pressure less than the available downhole pressure of the dense fluid in the injection wall.
In the method, a fluid engine/generator is positioned in the injection well and the fluid to be injected is flowed through the fluid engine/generator enroute to the subterranean formation, thereby providing motive power for the generation of electricity.
The electricity is transmitted to the surface for use in a conventional manner.
In one embodiment of the method of this invention, a normally gaseous fluid, such as a gas condensate, is injected under pressure through an injection well into a subterranean oil-bearing formation to miscibly displace the oil through the formation to a production well.
The downhole pressure of the fluid is controlled at the desired displacement pressure, and electrical energy is produced, by flowing the fluid through a fluid engine/generator positioned in the well, thereby converting the potential energy represented by the downhole fluid pressure in excess of the desired displacement pressure to electrical energy.
Compression requirements are minimized by controlling the formation pressure at the desired displacement pressure.
The method of this invention allows production of electrical energy from a previously unused energy source without adversely affecting, and in some cases actually beneficially affecting, the injection operation.
The method provides electricity at relatively remote locations and results in an environmental benefit in that it reduces or eliminates the necessity of environmentally objectionable alternative energy sources, such as the burning of fossil fuel to fire a power plant.
The method may be used to smooth out the peak load of a geothermal power plant, or reduce the amount of power purchased or generated in costly surface facilities to supply energy for enhanced oil recovery processes