US3618662A

US3618662A - Gas anchors

Info

Publication number: US3618662A
Application number: US90508A
Authority: US
Inventors: Harry G Cambern
Original assignee: Individual
Current assignee: Individual
Priority date: 1970-11-18
Filing date: 1970-11-18
Publication date: 1971-11-09
Anticipated expiration: 1988-11-09

Abstract

A gas anchor in combination with a downhole pump. The anchor has an upper terminal end connected to a pump intake and a lower terminal end in the form of an inverted cone from which there upwardly depends a skirt member which forms an annulus therebetween. An inverted frustum of a cone circumferentially encloses a marginal portion of the tubular body and forms a conical annulus therebetween with the second annulus being spaced apart from the first annulus by guide means. Apertures placed in communication with each annulus provides a liquid flow path to the pump to enable gas to be separated from liquid as flow occurs into the tubular body.

Description

United States Patent Primary Examiner-James A. Leppink Attorney-Marcus L. Bates ABSTRACT: A gas anchor in Combination with a downhole pump. The anchor has an upper terminal end connected to a pump intake and a lower terminal end in the form of an inverted cone from which there upwardly depends a skirt member which forms an annulus therebetween. An inverted frustum of a cone circumferentially encloses a marginal portion of the tubular body and forms a conical annulus therebetween with the second annulus being spaced apart from the first annulus by guide means, Apertures placed in communication with each annulus provides a liquid flow path to the pump to enable gas to be separated from liquid as flow occurs into the tubular body.

PATENTEDuuv 9 usm /N VE/V TOE. HARRY GCAMBERN BY MARCUS LBATES H/s flGENT BACKGROUND OF THE INVENTION It is a common practice to employ afonn of gas anchor in conjunction with a downhole production pump so as to preclude admixture of gas with the liquid flowing from a production formation into the suction of the pump. When the gas anchor is affixed to the lower terminal end of the working barrel of the pump, and the pump is run into-the hole, various expedients incorporated into the anchor efiect a separation between the gas and oil by causing the oil to flow along a particular flow path. The separated gas moves upward by reason of its lower density and generally escapes through or into the space between the casing and the tubing and hence through the side outlet of the well head.

in lowering a string of tools into a borehole with the gas anchor placed in underlying relationship with respect to the pump, and where parafiin has accumulated within the borehole, difficulty will be experienced when the pumping operation is initiated for the reason that the pump will often be plugged with this waxy residue. Various expedients have heretofore been proposed in order to prevent the occurrence of such plugging, such as, for example,.the provision of a brittle cast iron disc member that can be broken out by dropping a weight down through the tubing from the surface.

It is therefore desirable to provide an efiicient gas anchor which separates gas from the liquid which flows into the suction side of a downhole pump. It is also desirable to provide a SUMMARY OF THE INVENTION The present invention broadly comprehends an improved gas anchor for use in combination with a downhole pump with the anchor effecting a separation between the gas and liquid so as to preclude admission of gas to the working barrel of the pump. More specifically, the invention comprehends an elongated tubular body axially aligned with the borehole and the pump and placed in underlying relationship with respect to the pump intake so that fluid flow through the pump must also occur through the tubular body. The separation of the gas from the liquid is effected by two annular areas spaced apart from each other by guide means. The lowermost annulus is formed by an upstanding skirt member which terminates in a cone with the apex of the cone forming the lowermost portion of the anchor. The second annulus is in the fonn of an inverted frusto cone which provides an inverted conical annulus. Apertures formed within a sidewall of the tubular body communicates each of the annular areas with interior of the tubular body.

Upon the anchor being run into the hole on the end of a pump or pump tubing, the anchor penetrates a strata of wax, whereupon the apertures associated with the anchor are protected by the members forming the annular areas so as to preclude entrance of the wax into the anchor interior. After the pump is set in place and production initiated, fluid flow must occur about the outer members forming the annular areas thereby causing separation of the gas and liquid to occur because of the velocity of the fluid together with the lower density of the gas. This action causes the separated gas to flow upward about the exterior of the anchor while liquid flows into the tubular body of the anchor and into the suction area of the downhole pump.

It is therefore a primary object of the present invention to provide an improved gas anchor.

Another object of the present invention is the provision of a gas anchor which can satisfactorily penetrate wax formations located within a borehole.

A still further object of the present invention is the provision of a gas anchor which effects separation between liquid and gas more efiiciently than gas anchors of the prior art.

A still further object of the present invention is the provi sion of a gas anchor which is low in cost, efficient in separation, simple in design, and rugged in construction.

These and various other objects and advantages of this invention will become readily apparent to those skilled in the art upon reading the following detailed description and by referring to the accompanying drawings.

BRlEF DESCRIPTION OF THE DRAWINGS DETAILED DESCRlPTlON OF THE PREFERRED EMBODIMENT Disclosed in FIG. 1 is a downhole pump assembly 10 below which gas anchor 12 is disposed in underlying relationship. The gas anchor is connected to a shoe or collar 14 which in turn is connected to the lowermost end portion 15 of the pump. A longitudinally extending passageway indicated by nu- 'meral 16 flow connects the gas anchor to the pump suction or intake.

A polish rod 17 reciprocates the pump to cause well fluid to exit at 18. Wellhead 19 supports tubing 21 within which sucker rod 22 is disposed. The pumphousing 23 includes the piston, valves, and working

barrel

24, 25, 26, and 27 therein. the details of which are unnecessary to discuss since the specific pump along with its various mechanisms can take on several difierent forms and therefore is not considered a part of the present invention.

The gas anchor, which forms the essence of the present invention, includes a tubular body 28 which can be of any length, and is axially aligned with the borehole and with the pump. Optionally provided within the upper portion of the tubing which connects the anchor to the pump is a number of radially spaced-apart ports 29. Guides 30 are attached to the tubular body and radiate therefrom. The guides have a major dimension in cross section which is substantially equal to the major diameter of the inverted frusto cone 31.

A second guide means 32 is similar to the upper guide means and is attached to the tubular body at a location which separates the inverted frusto cone from upstanding circumferentially disposed skirt member 33. The skirt member has a lowermost portion attached to an inverted cone which terminates at apex 34 with the apex forming the lower extremity of the gas anchor.

The various members are welded together as indicated at 35, 35, however, those skilled in the art will realize that other fabrication techniques such as threaded connections can be substituted for some of the welded connections.

The inverted frusto cone upwardly diverges from the tubular body and terminates at edge portion 36. The lowermost portion of the frusto cone engages the upper extremity of a collar 37, although the collar 37 could be dispensed with and the tubular body could be one continuous length of tubular goods.

The skirt member terminates as a circumferentially extending edge portion 38 which is spaced apart from the tubular body, and is attached at 39 to the uppermost portion of the lower inverted cone. Centrally aligned within the inverted cone is a collar 40 which is threadedly connected to and forms a portion of the tubular body. Triangular-shaped apertures 41 interconnect annular area 42 with the interior of the tubular body.

The inverted frusto cone forms a conical annulus at 43 with apertures 29 flow connecting the annulus with the interior of the tubular body.

OPERATION The tubular body 28, which may be comprised of one or more joints of tubular goods, is threadedly secured to the shoe or collar 14 which forms the suction side of a downhole pump. As the downhole pump and gas anchor assembly is run into the borehole, deposits of paraffin may be encountered at some depth below the surface. The specific design and construction of the gas anchor precludes the pump intake from being obstructed by the waxy deposits. In particular it will be noted that apex 34 will penetrate a waxy formation while the skirt member 33 prevents wax or paraffin deposits from entering triangular apertures 41. As the anchor penetrates the waxy formation, the inverted frusto cone 31 prevents the paraffin from plugging the apertures 29'. The inverted cones usually clears a sufficient tunnel through the paraffin deposit so that aperture 29 are unaffected by the deposits. However, should the uppermost apertures 29 become plugged as the pump continues its travel toward the bottom of the borehole, experience shows that the aperture are soon cleared of the deposit because of the solubility of the hydrocarbons with respect to the parafiins. As the assembly continues traveling downhole,

guides

3 and 32, which may be spaced apart from each other a considerable distance, maintain the gas anchor centrally aligned within the borehole.

Separation between the gaseous and liquid phase of the hydrocarbons flowing from the production formation is effected because of the particular flow path the mixture must follow. In order for liquid to flow into apertures 41 the mixture of gas and liquid must first flow upwardly past apex 34 and skirt member 33. As the flow reverses itself in a manner indicated by the arrow at number 42, the difference in the specific gravity between the liquid and gas phase effects a first separation so that gas-free liquid enters apertures 41 while the separated gas continues uphole within the annulus formed between the gas anchor and the casing. The lower extremity of the longitudinal passageway of the gas anchor is now filled with liquid. As liquid and gas continues to flow up about the exterior of the gas anchor and inverted frusto cone 31, the liquid follows the flow path indicated by the arrow at numeral 43 and accordingly the mixture is subjected to a secondary separation. The separated liquid enters apertures 29' which communicates the interior of the gas anchor with the annulus. The separated gas continues uphole towards the foot of the pump.

Those skilled in the art will now realize that the separated gas is forced against the inside peripheral wall of the casing at a spaced apart distance away from the tubular body 28. Apertures 29 are present as a safety feature in the event that the lowermost ports or apertures 41 together with ports 29 should for some unforseen reason become clogged with debris. Should flow stoppage occur, it will become evident because of the action of the downhole pump as it becomes locked with gas, thereby indicating that the entire apparatus must be removed from the borehole and serviced. it is highly unlikely that both lower ports will become plugged except under unusual conditions.

Accordingly, the present combination of a downhole pump and gas anchor prevents gaseous flow from a hydrocarbonproducing formation from entering into the pump intake. The elongated tubular body of the gas anchor is axially aligned with the pump and provided with means at 14 for connecting the upper terminal end of the anchor to the pump intake. The lower terminal end of the gas anchor at 34 is in the form of an inverted cone. A skirt member 33 is spaced apart from and circumferentially encloses a lower marginal portion of the tubular body so as to form annulus 42 therebetween, with the skirt having an upper free portion 42 and a lowermost edge portion at 39. The lowermost edge portion is connected to the upper extremity of the last said inverted cone.

Inverted frusto cone 31 has a free upper edge portion 36 which is spaced apart from and circumferentially extends about the tubular body 28, with the lowermost edge portion of the cone being attached to the tubular body at a location 35 which is also spaced apart from the upper edge portion 38 of the skirt member 33. A conical annulus 43 is formed between the frusto cone and the tubular body. Apertures 29 flow connect the interior of the tubular body and the frustoconical annulus. Accordingly, production fluid must flow over the skirt member 38 in order to flow into the annulus at 42 and over inverted cone member 31 and into annulus 43 in order to enter apertures 29'. This action effects a separation between the liquid and gaseous phase of the production fluid flowing from a hydrocarbon-producing formation into the suction end of the downhole pump.

Those skilled in the art will comprehend fabricating the present anchor into a unitary device by welding and the like. Others will envision fabricating the entire apparatus from plastic and plasticlike materials and such changes in design and construction are considered obvious variations of the present invention.

lclaim:

1. In combination with a downhole'pump, a gas anchor for preventing gaseous flow from a hydrocarbon-producing formation into the pump intake;

said anchor having an elongated tubular body axially aligned with the pump; means connecting an upper terminal end of the anchor to the pump intake; the lower terminal end of said anchor being in the form of an inverted cone;

a skirt member circumferentially enclosing and spaced apart from a lower marginal portion of said tubular body to form an annulus therebetween, said skirt member having an upper free edge portion and a lowermost edge portion, said lowermost edge portion being connected to the upper extremity of said cone; means forming apertures which flow-connect the annulus to the interior of said tubular body;

an inverted frusto cone having a free upper edge portion spaced apart from and circumferentially extending about said tubular body, the lowermost edge portion of said frusto cone being attached to said tubular body at a location spaced apart from the upper edge portion of said skirt member to thereby form a conical annulus therebetween; means forming apertures which flow-connect the interior of said tubular body with the conical annulus, whereby:

liquid must flow over the skirt member and into the annulus in order to enter the lower apertures, and, liquid must flow over the inverted cone member and into the annulus in order to enter the upper apertures.

2. The combination of claim 1 and further including radially spaced apart guide means attached to said tubular body and located between said skirt member and said inverted frusto cone; said guide means being radially spaced apart and describing a diameter which is substantially equal to the diameter of said skirt member.

3. The combination of claim 1 wherein the skirt member has a diameter substantially equal to the major diameter of said inverted frusto cone.

4. The combination of claim I and further including upper and lower spaced apart guide mean attached to said tubular body;

said upper and lower guide means being spaced apart from one another by said inverted frusto cone;

said frusto cone and said skirt member being spaced apart from one another by said lower guide means.

5. The combination of claim 4 wherein said upper and lower guide means include radially spaced apart planar members having a major diameter substantially equal to the major diameter of said skirt members;

said skirt member having a major diameter substantially equal to the major diameter of said frusto cone.

6. The combination of claim 1 wherein there is further included means forming apertures within said tubular body at a location intermediate said frusto cone and the upper terminal end of said tubular body.

Claims

1. In combination with a downhole pump, a gas anchor for preventing gaseous flow from a hydrocarbon producing formation into the pump intake; said anchor having an elongated tubular body axially aligned with the pump; means connecting an upper terminal end of the anchor to the pump intake; the lower terminal end of said anchor being in the form of an inverted cone; a skirt member circumferentially enclosing and spaced apart from a lower marginal portion of said tubular body to form an annulus therebetween, said skirt member having an upper free edge portion and a lowermost edge portion, said lowermost edge portion being connected to the upper extremity of said cone; means forming apertures which flow-connect the annulus to the interior of said tubular body; an inverted frusto cone having a free upper edge portion spaced apart from and circumferentially extending about said tubular body, the lowermost edge portion of said frusto cone being attached to said tubular body at a location spaced apart from the upper edge portion of said skirt member to thereby form a conical annulus therebetween; means-forming apertures which flow-connect the interior of said tubular body with the conical annulus, whereby: liquid must flow over the skirt member and into the annulus in order to enter the lower apertures, and, liquid must flow over the inverted cone member and into the annulus in order to enter the upper apertures.

4. The combination of claim 1 and further including upper and lower spaced apart guide mean attached to said tubular body; said upper and lower guide means being spaced apart from one another by said inverted fruSto cone; said frusto cone and said skirt member being spaced apart from one another by said lower guide means.

5. The combination of claim 4 wherein said upper and lower guide means include radially spaced apart planar members having a major diameter substantially equal to the major diameter of said skirt members; said skirt member having a major diameter substantially equal to the major diameter of said frusto cone.