Oil recovery primary

Primary oil recovery is the production of oil driven to wellbores by the energy of fluids under pressure in the reservoir. As reservoir pressure is reduced by oil production, additional recovery mechanisms may operate. One is natural water drive as water from an adjacent more highly pressured formation is forced into the oil-bearing formation by the pressure differential between the formations. Gas drive, expansion of a gas cap above the oil as... 

The primary oil recovery takes advantage of the pressure exerted by the natural gases which force s the oil through the wells. 

Primary oil recovery oil recovery utilizing only naturally occurring forces. 

In primary oil recovery from underground reservoirs, the capillary forces described by the Young and Young-Laplace equations are responsible for retaining much of the oil (residual oil) in parts of the pore structure in the rock or sand. It is these same forces that any secondary or enhanced (tertiary) oil-recovery-process strategies are intended to overcome [2,133,421,690,691]. In an oil-bearing reservoir the relative oil and water saturations depend upon the distribution of pore sizes in the rock. The capillary pressure in a pore is... 

Enhanced Oil Recovery The third phase of crude-oil production, in which chemical, miscible fluid, or thermal methods are applied to restore production from a depleted reservoir. Also known as tertiary oil recovery. See also Primary Oil Recovery, Secondary Oil Recovery. 

Fig. 5.1.2 Five-spot pattern of injection and production wells typically used in post-primary oil recovery operations...

Initial or primary oil recovery is accomplished primarily by use of the inherent energy of the oil reservoir—that is, the pressure of the gases and volatile hydrocarbons trapped under high pressures and temperatures in the rock formation. For shallow wells, mechanical pumping may be used. Additional recovery may be accomplished by the injection of water or steam into the rock to maintain a high pressure in the system and force additional oil to the surface through production wells. The use of such mechanisms can normally result in the recovery of about 40% of the potential oil in the formation. Beyond that point, more drastic (and more expensive) measures must be employed. Such measures may involve the use of surfactants and polymers for the alteration of the interfacial and rheological properties of the oil deposit and the fluids injected to facilitate movement of the crude toward production wells. 

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