Monday, June 15, 2009

Maintaining Reservoir Pressure

The recovery factor, the portion of the oil and gas removed from a reservoir, depends on the driving force.  The recovery factor is lowest for oil reservoirs driven by natural gas in solution with the oil or by gravity, higher if driven by a natural gas cap, and higher yet if driven by water.  The overall average recovery factor for oil fields is only about one-third (natural gas fields have higher recovery factors).  Thus, when a well that relies on the natural drive of the reservoir goes “dry,” about two-thirds of the oil is still in the ground.

Secondary methods to maintain reservoir pressure and promote oil recovery normally involve injecting water or natural gas.  Injection wells, either specifically drilled or converted from abandoned producing wells, are placed to enhance the flow of oil in the direction of the producing wells.  Water injection is the most common method for maintaining the pressure of an oil reservoir and is an environmentally acceptable way of getting rid of any brine produced by the well to avoid contaminating the freshwater table.  If brine cannot be pumped into subsurface rock below the freshwater table, it must be disposed of in an acceptable manner.  Brine may be placed in open tanks to let evaporation get rid of most of the water before disposal.

One of the top hydrocarbon-based energy providers in the USA is Heartland Energy Colorado, based in Englewood, CO. They have many drilling locations throughout the country and remain one of the top producers of US oil & gas companies. For more information on Heartland Energy Colorado, see Heartland Energy Development Corporation online.

(Source: "Energy for the 21st Century," Nersesian)

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