Gas separation: processes – Degasification of liquid – Plural successive degassing treatments
Reexamination Certificate
1999-10-15
2001-10-09
Smith, Duane S. (Department: 1724)
Gas separation: processes
Degasification of liquid
Plural successive degassing treatments
C095S253000, C096S156000, C096S183000, C096S207000, C096S215000, C166S075120, C166S105500
Reexamination Certificate
active
06299672
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to systems for producing fluids such as oil and gas from geological formations via subterranean wells. More particularly, the invention relates to a technique for producing flowable materials by extracting fluids from one or more wells and depositing the fluids in a gathering or collection facility where the fluids may separate into gas and liquid components for conveyance to a collection or processing point.
BACKGROUND OF THE INVENTION
A wide range of completion techniques have been devised and are presently in use for producing useful flowable substances, such as oil and gas, from subterranean deposits. In production wells having sufficient natural pressure to force the fluids to a collection point, typically at the earth's surface, the wells may be exploited directly without artificial pumping means. Where, however, the well pressures are insufficient for this purpose, various types of pumps are employed to raise the fluids to the earth's surface. These pumps may be located at least partially below the earth's surface, with pumping elements or rods extending to the location of the fluid. However, in many applications, it is preferable to use a submersible pumping system deployed in the well and driven electrically to displace the wellbore fluids under pressure sufficient to convey them to the collection or processing point.
In many pumping systems used to extract petroleum and similar products from production wells, the production rate may be hampered by the presence of fluids of lesser interest, or by elevations through which the fluids must be raised. Specifically, in many petroleum wells, liquid phase components of wellbore fluids are mixed or disbursed with gaseous phase components. Separators may be employed to at least partially extract the gaseous phase components for production of the petroleum, or the liquid and gas may be allowed to separate over time via gravity, where the dispersion permits. However, such techniques may not always present the most economical solution from the point of view of actual production rates. Accordingly, wellbore fluids may be raised to the earth's surface and stored in a gathering station, typically an above-ground container, where gas-phase components are allowed to slowly migrate from the liquid-phase components.
While such collection stations are generally effective for separating the wellbore fluid components from one another, they are not without drawbacks. For example, depending on the well production volume and collection schedules, the collection stations may occupy significant space. Also, such collection stations are not generally permitted or desirable in environmentally sensitive areas, near residential areas, and so forth.
In addition to problems associated with separation of wellbore fluid components, production from groups of wells having mixed gas and liquid components is often limited by the hydraulic head required to raise the fluids to the collection point. Specifically, because the production rate of fluid typically declines as the hydraulic head increases, a collection point at a substantially raised position with respect to the wellhead can result in poor production rates. This is particularly problematic in wells that are located some distance from the collecting station, and in sub-sea wells from which production fluids must be raised to an elevated production vessel or a platform, or to a distant collection point.
Several concepts have been used to separate gas-phase from liquid-phase components in production fluids with sub-sea facilities. However, these sub-sea facilities have not been used as permanent production facilities because of their low availability and their unreliability. For example, in the case of pump failure the flow of production well fluid has to be secured for safety reasons during pump repair or replacement. In the case of electrical failure the flow of production well fluid has to be secured if there is insufficient storage volume available.
There is a need, therefore, for an improved technique for producing fluids from production wells which provides efficient production rates; allows separation of wellbore fluid components; is widely available; and is reliable enough for use as a permanent production facility. Moreover, there is a need for a technique which can be applied in a wide variety of environments, including land-based wells, sub-sea wells, wells in environmentally sensitive areas, and the like.
SUMMARY OF THE INVENTION
The present invention provides a novel technique for producing wellbore fluids. The technique utilizes a system for separating gas from liquid in production well fluid. The system includes a separation unit which is comprised of a storage tank able to store production well fluids, a first separation stage to separate gas from liquid, a second separation stage located in series with the first separation stage, and an electrical pumping system disposed in the storage tank to pump liquid out of the storage tank.
According to another aspect of the invention, a system is provided for producing fluids from a production well and for removing a portion of gas from production well fluids. The system is comprised of a plurality of separator units and a fluid transport system. Each separator unit includes a gas/liquid separation stage to separate a gas from a production well fluid, a storage tank for receiving at least a portion of the production well fluid, and a plurality of electric submergible pumping systems disposed in each storage tank to pump fluid from the storage tank. The fluid transport system is used to transport the production well fluid from a production well to the plurality of separator units.
According to another aspect of the invention, a method is provided for producing gas and liquid from a production fluid by separating at least a portion of the gas contained in the production fluid from the liquid contained in the production fluid. The method includes the steps of pumping a production fluid containing a gas and a liquid from at least one production well to at least one separator unit. The separator unit includes a plurality of gas/liquid separators, a submergible storage tank and a plurality of electric submergible pumping systems. The method further includes separating at least a portion of the gas from the production fluid through the use of the plurality of gas/liquid separators. The method further includes pumping the liquid stored from the submergible storage tank to a remote location and conveying the separated gas from the submergible storage tank.
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Camco International Inc.
Fletcher Yoder & Van Someren
Smith Duane S.
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