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Additional Recovery Techniques

Autor:   •  October 10, 2017  •  Creative Writing  •  1,186 Words (5 Pages)  •  684 Views

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Acontecimientos

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Additional recovery techniques:

After a well has used up the reservoir’s natural drives and all the hydrocarbons possible have been lifted by pumps or gas lift, statistics show that 25 to 95 percent of oil in the reservoir may remain there. This amount of oil can be worth recovering if prices are high enough. The petroleum industry has developed several techniques to produce at least part of this remaining oil.

One thing to keep in mind about additional recovery techniques is that they are expensive and risky. They require special chemicals, equipment, and personnel. And there are no guarantees that a project will work. Of course, the potential rewards are high if a project does work out, but the risk is also high. In most cases, it takes years before a company actually starts recovering any oil from a project. Recovering oil from reservoirs beyond the initial production remains one of the great challenges facing the oil industry.

Waterfllooding:

When the wells drilled into one reservoir stop flowing, the company representative may him a workover contractor to pump, or inject, water into some of them (fig. 1). The wells into which water is pumped become injection wells. This water kills the wells and then sweeps into the reservoir and moves some of the oil that remains in the rock toward other wells in the same reservoir. These producing wells then pump up the oil and water, often by means of a beam pumping unit. Several injection wells surround each producing well. This procedure is called waterflooding.

Sometimes a crew injects a gas, such as natural gas, nitrogen, or flue gas, in alternating steps with water to improve recovery. In this case it is called gas injection.

Something wells from producing wells to injection wells is a workover job, but when they need maintenance, a well servicing contractor does the work on injection wells in old fields. As they do with producing wells, the maintain the pump and repair or replace tubing if corrosion has caused leak or if scale has formed.

Miscible drives:

While waterflooding recovers additional oil from certain reservoirs, it cannot recover all of it. Part of the reason is that oil and water do not mix (they are not miscible). As a result, water will flow past some of the oil and leave it behind. Two processes can improve the amount of oil recovered, chemical flooding and a second type of gas injection.

Chemical flooding:

In chemical flooding, a chemical that causes oil and water to mix can be injected into a reservoir. One chemical that does this is a surfactant. The workover crew injects the surfactant into a well in one of two ways. The first method is to inject a batch, or slug, of water containing the surfactant (fig. 2). The second is to inject an alkaline, or caustic solution. The alkaline solution reacts with the acids normally present in the oil, and the reaction forms a surfactant in the reservoir (fig. 3).

Whether the surfactant is injected or forms in the reservoir, it washes through it (or at least part of it) and moves additional amounts of oil to the producing well.

Often, the crew mixes a special chemical called a polymer with the water and injects it into the well behind the surfactant. The polymer-water mix helps prevent fingering of the surfactant. Remember that fingering occurs when water moves through sections of the reservoir in “fingers” (fig. 2). Fingering leaves portions of the reservoir untouched, portions that contain oil.

Gas injection:

A gas that is not miscible

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