Wells – Processes – Producing the well
Patent
1989-02-27
1991-05-14
Kisliuk, Bruce M.
Wells
Processes
Producing the well
166 53, 417 54, 417108, E21B 4312, E21B 4318
Patent
active
050147897
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method for startup of production in an oil well, and, more generally, to a method of control of oil production.
The production fluid recovered from an oil well normally comprises a mixture of oil products, water and gas in varying proportions. Under some circumstances, in order to facilitate flow to the surface, a suitable gas is injected into the well production casing, such as towards its lower end, whereby to be entrained in the production liquid. This has the effect of reducing the effective density of the fluid whereby to improve flow to the surface. When starting up production in a well where this gas lift technique is used , some difficulty may arise in that the gas as admitted, may instead of being homogenously entrained in the production fluid, "break out" and form large discrete regions of gas within the well casing. The phenomenon known as "slugging", whereby irregular flow of production fluid from the well occurs, will then arise. This irregular flow is due to alternating flows of gas and production of fluid from the well. Generally, this phenomenon arises because too much gas is injected relative to the quantity of production fluid flowing up the well production casing. Slugging is an undesirable phenomenon since it results in waste of gas, which may be in relatively short supply Slugging also disrupts the orderly processing of the production fluid and may lead to damage to the oil reservoir. Furthermore, if the balance of gas is too great the entire flow of fluid may be cut off.
In one aspect, the invention has for its object to provide a method to startup of oil production in an oil well which lessens the possibility of occurrence of slugging.
In one aspect, the invention provides a method of startup of oil production in an oil well, wherein gas is injected into the well fluid to be recovered whereby to facilitate lifting of the fluid, characterised in that while controlling the inlet flow of the said gas, valve means controlling fluid flow from the well is progressively opened. Preferably, the flow rate of fluid from the well is monitored and the rate of opening of the valve means is varied whereby to reduce the rate of opening on detection of an increase in flow rate which is greater than a predetermined rate. The inlet flow of the gas may be maintained substantially constant.
The invention also provides a method of controlling oil production in an oil well using gas injection to facilitate lifting, wherein the flow rate of fluid from the well is monitored and a flow regulating device in the flow path from the well is controlled in accordance with the monitored flow rate to reduce the flow rate when the flow rate, as monitored, is indicative of onset of slugging, such as when an increase in flow rate is detected.
The invention is further described by way of example only with reference to the accompanying drawings in which:
FIG. 1 is a diagram of an oil well adapted for practising the present invention;
FIG. 2 is a diagram illustrating the manner in which a well outlet control choke in the well of FIG. 1 is controlled; and
FIG. 3 is a diagram illustrating the manner of control of the well outlet control choke.
In FIG. 1, an oil well production casing 10 is shown as having an outer casing 12 and an inner casing 14. The inner casing 14 extends into the oil reservoir 16 from which oil containing fluid is to be recovered, for flow of the fluid up the casing 14 and thence away from the well via a suitable outlet duct 20. The outer casing 12 is connected via a duct 22 to a source 24 of pressurized gas. The inner casing 14 has apertures at suitable positions such as adjacent the base thereof for admission of gas in to the casing 14. The so admitted gas is entrained in the fluid flowing up casing 14 whereby, in accordance with conventional practice, to lessen the effective density of the fluid and to facilitate lifting of the fluid to the surface for outflow along duct 20.
Duct 20 is shown as having a valve or "choke" 28 positioned therein, this being operable to close o
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Clarke Neville
Winter Thomas H.
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