Wells – Processes – Electric current or electrical wave energy through earth for...
Reexamination Certificate
1999-03-24
2001-02-20
Neuder, William (Department: 3672)
Wells
Processes
Electric current or electrical wave energy through earth for...
C166S272100, C166S302000, C166S272300
Reexamination Certificate
active
06189611
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to providing subterranean fluid flow within a permeable formation.
In the oil production industry, an oil well is typically drilled hundreds or thousands of feet to reach a permeable formation containing an oil reservoir. In this context, a permeable formation refers to any subterranean media through which a fluid may flow, including but not limited to soils, sands, shales, porous rocks and faults and channels within non-porous rocks. When techniques are used to increase or concentrate the amount of fluid in an area of a reservoir, that area is commonly referred to as an enhanced pool.
During the primary stage of oil production, the forces of gravity and the naturally existing pressure in a reservoir cause a flow of oil to the production well. Thus, primary recovery refers to recovery of oil from a reservoir by means of the energy initially present in the reservoir at the time of discovery. Over a period of time, the natural pressure of a reservoir will decrease as oil is taken from the well. In general, as the pressure differential between the reservoir and the well decreases, the flow of oil to the well also decreases. Eventually, the flow of oil to the well will decrease to a point where the amount of oil available from the well no longer justifies the costs of production, including the costs of removing and transporting the oil. Many factors may contribute to this diminishing flow, including the volume and pressure of the oil reservoir, the structure, permeability and ambient temperature of the formation, and the viscosity, composition and other characteristics of the oil.
As the amount of available oil decreases in the primary stage of recovery, it may be desirable to enhance production through the use of secondary or tertiary stages of production. Secondary recovery generally refers to the injection of secondary energy into the reservoir to enhance oil flow to a production well. Secondary recovery methods include, for example, injecting materials such as steam, air or natural gas into a reservoir to displace oil in the direction of a production well.
Tertiary recovery generally refers to processes that attempt to recover oil beyond the conventional primary and secondary recovery methods. Tertiary processes include such techniques as miscible fluid displacement, microemulsion flooding, thermal methods, and chemical flooding methods. Such methods may be technologically sophisticated and entail considerable financial risk because of the level of financial investment required.
One method of enhancing oil production is to inject a solvent into a reservoir that is miscible both in oil and in the brine waters found in the reservoir. As an example, natural gas may be injected into a reservoir at a sustained pressure to cause the gas to diffuse into the reservoir and extract some of the hydrocarbons from the oil. The resulting light hydrocarbon solvent is generally miscible with both the oil and the brine found in the reservoir.
Generally, as a miscible solvent passes through a reservoir, some of the oil is displaced in an accumulating oil bank in the path of the solvent, and some of the oil is dissolved in the solvent. The mixture of oil and solvent may be referred to as a miscible bank. As the miscible bank moves through the formation, it increases in oil content, and the outer boundary of the miscible bank may eventually be indistinguishable from the oil bank being displaced.
An advantage to the miscible solvent approach is that such solvents can generally wash oil from formations that might otherwise remain clinging to a formation if non-miscible displacement fluids were used. In some applications, it may be desirable to conduct secondary or tertiary reservoir injections in stages. For example, an initial miscible solvent injection stage may be followed by subsequent sweeping stages where gasses or nonmiscible liquids are injected to displace the oil-enriched solvent that may remain in the formation.
Steam flooding is another technique that may be used to enhance recovery. With this technique, steam is injected into a reservoir to displace the oil and increase the reservoir temperature, thereby providing a decrease in the viscosity of the oil. Some of the steam diffusing into the reservoir may also serve to distill lighter hydrocarbon fractions from the oil, resulting in a miscible bank preceding the injected steam. In addition, some of the steam may form a nonmiscible displacement bank as it condenses to water. The advantages of steam flooding include relatively inexpensive production costs, and the fact that steam carries a large amount of heat per unit of mass.
Another method of enhancing recovery involves heating a reservoir at the site of a production well to create a heated zone of oil. The advantages of such processes may include higher reservoir pressure, lower oil viscosity, and causing the oil to swell due to heat effects. Such methods may be referred to in this respect as in situ heating methods. As an example, a heated production zone may be achieved by periodically injecting steam into the reservoir at the production well.
In general, recovery enhancement techniques can be used either individually, successively or in combination. However, typically even where secondary or tertiary recovery methods are implemented, there eventually comes a point when the production available from a well has diminished below a threshold economic level, and the costs of production are no longer justified. Such a situation may be exacerbated where the implementation of enhanced recovery methods has imposed a significant increase to production costs.
Thus, due to the economic balance between diminishing oil recovery and the expense of enhanced production, in many cases, well production may be discontinued where there is still a substantial amount of oil remaining in a reservoir, but it is simply too difficult or expensive to produce.
SUMMARY OF THE INVENTION
The invention features systems and methods of providing a subterranean fluid flow by radiating electromagnetic energy into a permeable formation.
In general, in one aspect, the subterranean fluid flow through the permeable formation is provided by positioning an electromagnetic device in a borehole of an applicator well and radiating electromagnetic energy into the permeable formation to vaporize material within the formation, thereby propagating a material displacement bank away from the applicator well and through the formation.
In another aspect, a subterranean fluid flow may be propagated to enhance oil recovery. In still another aspect, a subterranean fluid flow may be propagated to enhance gas recovery, including hydrocarbon gasses such as natural gas and methane, and non-hydrocarbon gasses such as sulfur. Additionally, in another aspect, a subterranean fluid flow may be propagated to provide subterranean material abatement.
Thus, the methods described above provide a significantly more effective and relatively inexpensive approach for providing a subterranean fluid flow. Moreover, the methods can be advantageously implemented in a wide variety of applications including, for example, enhanced oil or gas well recovery and pollution abatement.
Embodiments of each of the above aspects of the invention may include one or more of the following features. The methods may be applied in an autogenic manner. That is, the electromagnetic energy is provided into the reservoir without injecting external materials such as gases or liquids into the formation. Thus, the difficulty and expense of injecting external materials into a reservoir is eliminated. Another advantage of autogenic energy injection is that, because the reservoir volume is not artificially increased, cessations of energy injection may be used to provide increased control and even to reverse displacement bank propagation.
A production well, spaced away from the applicator well, is used to pump fluids from an enhanced pool formed by the displacement bank. In some applications, a formation pressure relief station is used to
Fish & Richardson P.C.
KAI Technologies, Inc.
Neuder William
LandOfFree
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