US2517198A

US2517198A - Gas anchor

Info

Publication number: US2517198A
Application number: US694510A
Authority: US
Inventors: Walton E Gilbert
Original assignee: Shell Development Co
Current assignee: Shell Development Co
Priority date: 1946-09-03
Filing date: 1946-09-03
Publication date: 1950-08-01
Anticipated expiration: 1967-08-01

Description

W. E. GILBERT Aug. 1, 1950 GAS ANCHOR Filed Sept. 3, 1946 1 lrwenTor-Z WcJTon E. Gilber-T BL hTs MTorneg.

Patented Aug. 1, 1950 UNITED STATES PATENT OFFICE Walton E. Gilbert, New York, N. Y.;, assignor to Shell Development Company, San Francisco, Calili, a corporation of Delaware Application September 3,1946, Serial No. 694,510

This invention relates to'gas anchors and pertains more particularly to gas anchors and separators adapted for use in the pumping of oil wells.

A pumping well normally comprises a string of easing, a string of tubing depending within the casing, a pump attached to the lower end of the tubing string and a gas anchor attached to the pump over the suction inlet of said pump, the object of said gas anchor being to promote better separation of gas from the oil by providing a long and tortuous path to the suction end of the pump.

Oil flowing into the bottom of a well often contains large quantities of gas which, unless separated from the oil, are drawn into the pump. The displacement capacity devoted to the compression of this gas in a pump reduces its liquid capacity. Also, the power required to compress any free gas entrained with the oil drawn into an oil-well pump is largely wasted. It is therefore necessary, insofar as is practicable, to exclude the entry of gas into the pump in order to minimize the size and initial cost of the pumping system as Well as the operating and maintenance costs.

Since pump efliciencies and capacities are adversely affected by the depth of the well, the trend toward deeper wells increases the need for better gas-liquid separation at the pump. Furthermore, the trend toward drilling wells of smaller diameter adds emphasis to the need for betterseparation of the oil and gas by means of a gas anchor, as it is well known that the performance of gas anchors in present use is directly related to the hydraulic radius of the gas anchor down-pass which is limited by the oil-well bore. In modern oi1-well pumping, liquid displacement efficiencies of less than 60% are by no means uncommon, even though attention has been given to securing gas anchors of the best available types. I

It is therefore an object of this invention 1; provide. an improved gas anchor or separating device of simple and rugged design adapted to separate gas from oil that is to be pumped.

Another object is to provide an efficient gas anchor of large capacity for a given diameter which can be readily attached to awell pump to be located near the bottom of a well.

A further object is to provide a gas anchor ofisuch design .thathigh separationyefiiciency is maintained when anchors of small diameterare constructed.

"Ifhese and other objectsof this invention will 6 Claims. (Cl. 103-203) be understood from the following detailed description of the preferred embodiment of the invention and from the accompanying drawings, wherein: 3

Fig. 1 is a diagrammatic view, partlyin crosssection, of thegas anchor of the present invention.

Fig. 2 is a cross-sectional view on the line 2-2 of Fig. 1.

Fig. 3 is a detail view of a side-wall segment of thegas anchor in Fig. 1. V

Fig. 4 is a cross-sectional view on the line 4-4 of Fig. 3.

Figs. 5 and 6 are diagrammatic views, partly in cross-section, showing slightly modified embodiments of the gas anchor of the present inventio-n.

For clarity, the present gas anchor will be described hereinbelow with regard to the illustrated embodiments thereof, it being understood that the present invention is in no way restricted to said illustrated embodiments, but has a, scope defined only in the claims attached to the present specification.

Referring more in detail to the drawing:

The reference numeral l0 designates the gas anchor of the present invention which i-sremovably attached, usually by means of screw-threads, to the lower end of apump I I carried at thelower end of astring f tubing (not shown here) within the casing l2. Since bore-holes nearly always have a. deflection, however slight, from the vertical, the anchor is shown in its preferred position against the low side of the casing.

The gas anchor l0 comprises a pump inlet or delivery tube 28, an intake unit is and a reservoir tube E4. The intakeunit I3 is a tubular member internally threaded at its upper end1 or neck l5 for threaded attachment to the externally threaded lower end of the pump ll. Formed on the peripheral wall of the intake unit, starting just below the neck and extending the length of the unit l3, are helical, downwardly sloping, fluid channels or grooves ii. The direction of this downwardly spiraling conduit may be reversed one or more times as shown at J8 in order to reduce the velocity of the liquid flow. A plurality of fluid inlet openings or perforations l9 extend from the trough bottoms of channels ll through'the Wall 28 of the intake to the axial bore 2!. Located in the channels Ill on the downstream sideoi' each of the perforations!!! are ridge-shaped baflle elements or liquid velocity spoilers l 6, lying atsuchan angle thatthey continuously deflect the lower and denser part of the liquid stream in the channel I'I through the perforations I9 into the axial bore 2I of the intake I3. A desired number of discharge ports 22 in the neck I of the intake I3 serve as outlets for gas to escape from the axial bore 2I of the intake into the bore 23 of the casing I2. A slightly modified embodiment of this invention, as shown in Fig. 5, may have a separate short tubular collar or section of drill tubing 3|, provided with a desired number of discharge ports 32, in threaded attachment between the neck 33 of the intake tube 34 and the lower end of the pump I I. However, openings 32 may be dispensed with, if desired, as sufficient escape means for the ascending gases are provided by the perforations I9.

An internally threaded coupling 24 forms a fluid tight connection between the externally threaded lower end of the intake I3 and upper end of the reservoir tube I4. This reservoir tube I4 is a downwardly extending tubular section having a closed bottom end 25 and of such a length as to hold a quantity of oil sufficient to maintain the level of oil in the reservoir normally above the suction end 21 of the delivery tube 28 to the pump during the operation of said pump.

The externally threaded upper end 29 of the delivery tube 28 is in screw-threaded attachment with the internally threaded suction port 36 of the pump I I, said suction port being usually centrally located in the bottom face of the end of the pump. Thus, the delivery tube 28 is suspended within the intake unit I3 and the reservoir tube I4 and is of such length that the suction end 21 of the tube extends to a point near the closed end 25 of the reservoir tube I4 but at a sufficient distance above the closed end of said tube to allow for the accumulation of sediment. The delivery tube 28, suspended within intake tube I3 and reservoir tube l4, may be p0- sitioned in any manner but is preferably mounted eccentrically against the sides of said tubes thus I providing an improved flow passage in tubular elements I3 and I4.

The present apparatus is operated with the gas anchor Ii] and pump II immersed in the gas-oil mixture at the bottom of well casing I2. Best results are obtained when the gas anchor is eccentrically positioned in the Well casing I2, as shown in Figs. 1 and 2, and preferably on the low side of the casing wall. Boreholes very often have inclinations from vertical which exceed three degrees at pump depths. In such cases the desired positioning of the gas anchor against the low side of the borehole may be accomplished by locating any centering device, such as a tubing anchor no closer than 100 feet above the pump. In cases of boreholes having only slight inclinations from vertical, eccentric positioning of the gas anchor and pump assembly may be easily obtained by using a slight dog-leg, or lateral oifset in the tubing string several joints above the pump.

restricted space on either side of the line of contact between the gas anchor intake I3 and the inner sidewall of the casing I2.

The improved oil-gas separation obtainable with the present gas anchor is due essentially to the following features: first, the well fluid is subjected to a centrifugal force efiect prior to its entry into the anchor, and, second, said well fluid is fed into the anchor by gravity, whereas with most conventional anchors the anchor is filled by the pump suction which tends to draw in gas along with the liquid. Thus, in the operation of the present anchor, the gas-oil mixture first settles in the series of helical downwardly sloping channels I1 of the intake unit I3, and flows by gravity in a circuitous path. During this travel the fluid stream is subjected to a centrifugal force effect tending to promote the separation of the entrained gas from the oil due to the difference in specific gravities of the two fluids. The gas, on being separated from the oil, rises out of the channels I1 and escapes up the outside of the gas anchor intake I3.

The heavier oil continues its circuitous flow in the channels. As the oil stream passes the fluid inlet openings IS, the velocity spoilers l6 continuously divert the least gasified portions of said oil stream through said inlet openings I9 in the wall 20 of the intake and into the axial bore 2| of said intake where the oil drops into the oil reservoir tube I4 of the anchor. Any small amount of gas that finds its Way into the axial bore 2| of the anchor rises to the upper end of said bore 2i where it is discharged through gas outlet ports 22. Oil accumulating in the oil reservoir tube I4 enters the suction end 2'! of the delivery tube 28 and is drawn by suction up said tube 28 and into pump II.

In another modification of the present invention, as shown in Fig. 6, the gas anchor It! may be constructed as a single tubular unit wherein the reservoir 35 tube forms integrally the lower portion, the intake tube 36 forms the central portion and the neck I5 forms the upper portion of said unit, while all other features of this embodiment are substantially similar to the gas anchor described above. In this or other embodiments the intake unit or tube comprises a plurality of longitudinally arranged sections said sections comprising a plurality of spiralling trough channels, the direction of said spiralling channels in each section being preferably reversed in relationship to those of the adjacent section.

I claim as m invention:

1. For use with a Well pump, a gas anchor comprising a tubular member closed at its lower end, port means serving as gas outlet means near the upper end'of the space inside and outside thereof, spiralling trough channel means formed on the outside of said tubular member throughout a substantial portion of the length thereof, a plurality of perforations serving as fluid inlets through said portion of said tubular member, said perforations being in communication between the inside of said tubular member and said channel means, and an imperforate delivery tube extending within said tubular member, said delivery tube having its lower end open to the space within said tubular member at a point near the lower closed end thereof, whereby only the liquid accumulating within the lower portion of said tubular member is raised through said delivery tube.

2. For use with a well pump, a gas anchor comprising in combination, an intake unit, port means serving as gas outlet means near the upper end of said intake unit in communication between the space inside and outside thereof, a downwardly extending reservoir tube coaxially attached to the lower end of the intake unit and having a closed lower end, spiralling trough channel means formed on the outside of the intake unit throughout the length thereof, a plurality of perforations serving as fluid inlets through said intake unit in communication between said channel it means and the inside of the intake unit, and an imperforate delivery tube extending within said intake unit and reservoir tube, said delivery tube having its lower end open to the space within said reservoir tube at a point near the lower closed end thereof, whereby only the liquid accumulating within the lower portion of said reservoir tube is raised through said delivery tube,

3. For use with a well pump, a gas anchor comprising in combination, an intake unit, port means serving as gas outlet means near the upper end of said unit in communication between the space inside and outside thereof, a downwardly extending reservoir tube coaxially attached to the lower end of the intake unit and having a closed lower end, spiralling trough channel means formed on the outside of the intake unit throughout the length thereof, a plurality of perforations serving as fluid inlets through said intak unit in communication between said channel means and the inside of the intake unit, transverse baflle elements in the bottom of said trough channel means opposite each of the communicating perforations, and an imperforate delivery tube extending within said intake unit and reservoir tube, said delivery tube having its lower end open to the space within said reservoir tube at a point near the lower closed end thereof, whereby only the liquid accumulating within the lower portion of said reservoir tube is raised through said delivery tube.

4. For use with a well pump, a gas anchor comprising in combination, a tubular collar, port means serving as gas outlet means in said collar in communication between the space inside and outside thereof, an intake unit having its ends secured to the lower end of said collar, a downwardly extending reservoir tube coaxially attached to the lower end of the intake unit and having a closed lower end, spiralling trough channel means formed on the outside of the intake unit through out the length thereof, a plurality of perforations serving as fluid inlets through said intake unit in communication between said channel means and the inside of the intake unit, and an imperforate delivery tube extending within said collar, intake unit and reservoir tube, said delivery tube having its lower end open to the space within said reservoir tube at a point near the lower closed end thereof, whereby only the liquid accumulating 6 within the lower portion of said reservoir tube is raised through said delivery tube.

5. For use with a well pump, a gas anchor comprising in combination, an intake unit, port means serving as gas outlet means near the upper end of said unit in communication between the space inside and outside thereof, a downwardly extending reservoir tube coaxially attached to the lower end of the intake unit and having a closed lower end, spiralling trough channel means formed on the outside of the intake unit throughout the length thereof, said spiralling trough channel means comprising a plurality of longitudinally arranged sections, the direction of the spiralling trough channel means in each section being reversed with regard to that of the adjacent section, a plurality of perforations serving as fluid inlets through said intake unit in communication between said channel means and the inside of the intake unit, and an imperforate delivery tube extending within said intake unit and reservoir tube, said delivery tube having its lower end open to the space within said reservoir tube at a point near the lower closed end thereof, whereby only the liquid accumulating within the lower portion of said reservoir tube is raised through said delivery tube.

6. For use in a well installation, a well pump having an intake at its lower end, a gas anchor comprising a tubular member closed at its lower end, means for securing said tubular member at its upper end to the lower end of the well pump, spiralling trough channel means formed on the outside of said tubular member throughout a substantial portion of the length thereof, aplurality of perforations through said portion of said tubular member, said perforations being in communication between the inside of said tubular member and said channel means, and an imperforate delivery tube extending within said tubular member, said delivery tube having its upper end in communication with the pump intake and its lower end open to the space within said tubular member at a point near the lower closed end thereof, whereby only the liquid accumulating within the lower portion of said tubular member is conveyed to the pump intake through said delivery tube.

WALTON E. GILBERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,628,900 Neilsen May 1'7, 1927 2,104,339 Arutunoff Jan. 4, 1938 2,398,339 Watts Apr. 9, 1946