Refrigeration – Vortex tube – e.g. – ranque
Reexamination Certificate
1999-04-05
2001-03-06
Doerrler, William (Department: 3744)
Refrigeration
Vortex tube, e.g., ranque
C062S617000
Reexamination Certificate
active
06196004
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to employing a vortex tube to condense hydrocarbons and water, and more particularly, to a simple method and apparatus to permit preliminary separation of hydrocarbons and water from a pressurized gas stream leaving a separator at a well location.
2. Description of the Prior Art
Various applications of both the heating and cooling aspects of the vortex tube are known in the art. The current invention discloses a method and apparatus for condensing water and a plurality of hydrocarbons entrained in a pressurized gas stream leaving a separator at a well location. The pressurized gas stream leaves the separator during a first time period and enters the vortex tube. Through the cooling action of the vortex tube, a first plurality of hydrocarbons and water are condensed and sent to a first reservoir. The temperature in the vortex tube is not low enough to condense a second plurality of hydrocarbons, which remain in the gaseous state and are sent to a second reservoir for sale. The pressurized gas stream is terminated during the well recharge phase. This termination period occurs for a second time period. The ratio of the second time period to the first time period is generally chosen to be greater than unity (one), although it may be greater than zero.
During the well recharge phase, the vortex tube is not being employed. However, other actions are occurring. The use of a vortex tube in low pressure gas stream and a method to cyclically operate the same has not been contemplated by the prior art.
So, although the vortex tube has been employed in oil well applications, no prior art provides for its cyclical use, being on during the well flow phase and being discontinued during the well recharge phase. Other advantages of the present invention over the prior art also will be rendered evident.
SUMMARY OF THE INVENTION
Gas wells which produce relatively small amounts of liquids are abundant in the United States. These wells are characterized by a low head pressure, typically 200 psi or less, and employs a lift pump or a plunger lift to bring the gas, water, and liquid hydrocarbons to the surface. Once brought to the surface, this mixture is field processed. Once the mixture is field processed, the various components are sold. Wells of this type constitute the great majority of oil wells. These wells have a general property where the well pressure will not exceed an upper pressure, regardless of how long the valve which empties the well itself is closed.
Generally speaking, there are two common methods for producing salable gas and oil. The first type are wells which employ a lift pump. The lift pump is a device which pumps oil and gas through the well's tubing until a specified final pressure is achieved at the casing head. When this specified final pressure is achieved, the oil and gas are permitted to flow to the field processing devices which produce salable gas and oil. The specified final pressure is generally achieved after a certain number of lift cycles occur during a certain period of time.
The second type of well employs a plunger lift. The plunger lift is a device which operates as a natural pump. When the plunger is closed, pressure builds up in the casing naturally as a function of time based on sub-surface reservoir pressure. A plunger is opened when a specified final pressure is achieved in the casing. When the plunger is opened gas and oil are permitted to flow to the field processing devices which produce salable gas and oil. This specified final pressure is also generally achieved after a certain time period.
Both of these common well types share that characteristic that they start at an initial pressure and proceed to a specified final pressure during a certain time interval. After the specified time interval, the well unloads and gas and liquids are allowed to flow. The period of time in which both of these common well types flow is generally constant. The specified final pressure may be ascertained by a pressure transducer. Field operations most often employ a simple timer, as well recharge and discharge characteristics are well known.
During the flow phase, the mixture of gas, hydrocarbons, and water flow through a pipe from the well to a field processing apparatus. Post processed products are routed to a gas purchasers sales line, and waste products are stored for remediation.
Current field processing techniques generally involve a two step process. First, oil and water separation, and second, further treatment for the removal of any remaining water prior to the introduction of the gasses to the sales line as follows. Initially, the gas stream flows from the well into a separator. Oil and water generally condense into liquid as the gas stream expands from the well head into the larger volume of the separator. The resultant mixture of oil and water separate due to their different densities, and are routed to separate holding tanks, one for the crude oil and one for the water. The crude oil is sold, and the water is remediated or disposed of in an environmentally responsible fashion. A second step treats the mixture of natural gasses which do not condense in the separator. The gasses pass to a heat treatment device which elevates the gas temperature. This separates the gas mixture from the water vapor. Whether or not this processing step is employed is determined by the amount of water vapor present in the separator gas effluent. The water free gas mixture is then routed directly to the gas sales line.
The instant invention is directed to a method of cycling the pressurized gas stream from the separator into a vortex tube to permit further condensation of hydrocarbons as well as any water which may be present in certain time ratios based on the time the well takes to recharge, and the flow time of the well. It includes a separator, the separator having a valved entrance connected to the well and three valved exits. During the time period when the well flows, the first valve is opened and the mixture from the well enters the separator. Again, oil and water generally condense into liquid as the gas stream expands from the well head into the larger volume of the separator. The resultant mixture of oil and water separate due to their different densities. A first valved exit would open and route the noncondensed gasses into the vortex tube. Once the well stops flowing and enters its recharge phase, this valve will close. A second valved exit would open and route the crude oil to a crude oil reservoir. A third valved exit would open and route the liquid water to a water holding reservoir.
During the period of time when the first valved exit is open, the pressurized gas stream leaves the separator, and enters the vortex tube. The vortex tube has two exits. A first exit is considered to be the cold exit. A second exit is considered to be the hot exit. By the cooling action of the vortex tube, a plurality of hydrocarbons with a temperature of condensation below that developed by the vortex tube will condense. These fluids will be routed into an intermediate crude oil holding tank or reservoir through the first exit.
This reservoir will include an valved entrance and four valved exits. The valved entrance will permit the condensates and any cold gasses to enter the reservoir during the flow phase of the well. After the flow phase, condensates again will separate according to their different densities. A first valved exit will open and permit the cooled gasses to pass to the gas sales line. During this time period, the well is recharging and the mixture present in this reservoir begins to warm. A second valved exit will open and permit butane which has returned to the gaseous state to be collected in a butane reservoir. This valve will remain open for a time period. A butane compressor may be employed in some applications. After the time period, this valve will close. A third valved exit routes the fluid hydrocarbons to the crude oil holding tank. A fourth valved exit will rout
Lewis W. Stan
Lindberg Roderick L.
Doerrler William
Hamill Jr. Tom
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