WO2015120511A1

WO2015120511A1 - A fines and sand removal system for wells

Info

Publication number: WO2015120511A1
Application number: PCT/AU2015/000084
Authority: WO
Inventors: Ian Gray
Original assignee: Ian Gray
Priority date: 2014-02-17
Filing date: 2015-02-17
Publication date: 2015-08-20

Abstract

A separator (7) and method for separating fine and coarse particles that are carried by a production fluid during production of a well to reduce downtime and pump wear. The finer fraction is withdrawn with the produced fluid to the surface while the coarse particle fraction falls by gravity to the base of the well. Production fluid is forced through a conical shaped annulus in a separator (7). The inner conical surface of the annulus includes a radial slot through which the produced fluid is drawn laterally and then upwardly along with the finer particles. The width of the conical-shaped annulus can be adjusted by changing the relative axial position of conical-shaped valve members (16, 17) by a threaded connection (12) between base member (14) and pipe (10). The width of the radial slot between the separator members (16, 17) can also be adjusted by a threaded connection between rod (18) and spider (13).

Description

BACKGROUND OF THE INVENTION

Wells are frequently drilled to produce fluids contained in rock formations. The wells may be completed by a variety of means which normally include a cemented casing located in the upper zone of the well. The casing may extend through the production zones, in which case it is a conventional practice to perforate the cemented casing to provide a fluid connection to the formation. Alternatively, the producing zones of the well can be screened or simply left bare. A frequent problem is that the formation produces particulate matter together with other fluids. Such wells are often referred to as sand or fines producers. The former term is generally used in the case of wells where the producing formation is sandy, while the latter term is used in the case of coal seam gas wells. The sand or fines originate from breakage or deterioration of the formation. The particulate m atter may also constitute the sand used in the hydrofracturing process. The production of fines or sand from the fonnation may completely or partially fill the wellbore and prevent further production. In this case, it is necessary to remove the particulate matter from the well and restore it to operation. Such well restoration operations, referred to as workovers, not only take the well out of production for a period of time, but also incur significant costs. The particulate material that is produced usually has a range of particle sizes, but it is common for the majority of the particulate matter to have a finer particle size.

While pumping the production fluid from the formation to the surface, if the velocity of the fluid in the wellbore is adequate to lift or sweep the particle matter into the production tubing, then the particles may be removed from the well. However, this is frequently not the case, and the majority of the sand or fines produced from the formation sink to the lower zone of the well, eventually blocking it from further production or severely affecting the production efficiency.

Well pumps have varying capabilities for handling fines. Some pumps can pass the finer particles without any problems. Progressive cavity pumps are particularly well suited for this purpose.

Having an adequate production flow rate to lift particles from the well provides a potential solution for removing particulate matter from the well and avoiding workovers. However, it is frequently not possible or desirable to lift the more coarse particles because the fluid flow velocity in the production tubing is too slow, or the pump being used will not reliably pass the coarse material. SUMMARY OF THE INVENTION

The fine fraction often constitutes the larger portion of the solid material being produced within a well. Accordingly, the removal of the fine fraction will therefore significantly reduce the required frequency of well workovers. A feature of the invention is to separate the finer proportion of the particulate matter from the larger material by entrainment of the finer material in the fluid stream being pumped to surface. The coarse material is not carried by the fluid stream and thus settles by gravity to the bottom of the wellbore.

The prime use of this feature is in near vertical wells, where the production zones of the well bore are located above the intake to the production tubing, or pump inlet, and such wells are producing sand or fines along with fluid to be lifted to surface. In this situation, the inlet to the production tubing is extended below the production zone and is equipped with a separator. The separator entrains the production fluid together with the fine fraction of the solids and lifts the same to the surface.

The mechanism by which the separator functions is by guiding the fluid and particle stream through an annulus surrounding the separator. Formed within the annulus is an internal annular slot into which the produced fluid is drawn at increased speed, much like the function of a restriction. The fluid flows into the slot is at a sufficient velocity such that the finer fraction of particles is drawn into the fluid stream, while the coarser fraction cannot follow the flow path and thus continue to gravitate downwardly through the annulus and to the sump of the well. To achieve this action, the annulus and slot are of suitable sizes, taking into consideration the fluid flow rate and particle sizes. By forming the annular slot between external and internal cone members, the width of the spacing therebetween can be adjusted by a change in the relative axial position between the two cone-shaped members. In a preferred embodiment, the slot through which the well fluid is drawn is adjustable and is formed within the inner cone. In accordance with an aspect of the invention, the annulus and internal annular slot may be adjusted to accommodate the fluid and particle size encountered.

The size of the annulus allows the coarse particles to pass downwardly therethrough, while the annular slot is constructed to provide a sufficient velocity of fluid flow therein so that the finer particles are also drawn into the annular slot.

The separation characteristics of the separator are adjusted to gather particles below a particular particle size, and can be adjusted to provide a separation with a fairly precise cut point in a particle size distribution.

The separator is constructed with a diameter approximate to the size of the well bore, and for this reason there is a possibility that the separator may risk becoming jammed on casing imperfections, or by coarse material if the separator is being withdrawn from the well with the pump or production tubing. This risk is reduced by constructing the outer part of the separator from an elastomer. In the preferred embodiment, the separator is constructed so that in the event it becomes jammed in the borehole, it tears off the tubing to which it is attached. The tubing torn off is constructed of material that is drillable. With this construction, the consequences of the separator becoming jammed in the borehole are greatly reduced. These requirements are readily met by constructing various components of the separator with plastic or soft alloys, and providing the separator with an elastomeric skirt.

The separator of the invention is particularly suitable for coal seam gas wells where the well continues to produce fines for the period of time that the well produces water. In such cases, the well casing diameter is large so as to enable a pump to be installed downhole for gas to pass up the well annul us while water and particles pass downwardly from the production zone to the pump inlet. The pump type well adapted for use with these wells is a progressive cavity pump which will pass fine particles of coal without damage.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a drawing of a portion of a production well with a perforated casing which produces both fluid and sand or fines, and with the separator attached to the bottom end of a production tube connected to a downhole pump.

Figure 2 is a drawing that illustrates the details of a separator constructed according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 illustrates the installation of the separator (7) within the borehole of a drilled well (1 ). Installed within the well borehole (1) is a casing (2). In this embodiment, the annulus between the casing (2) and the well bore (1 ) is cemented and has been perforated (3) to enable flow of the production of fluid from the formation surrounding the perforations (3). The perforations (3) produce formation fluid as well as particulate matter into the cased wellbore. Installed within the cased well bore is a production tubing (4) to which a pump (5) is attached at the bottom end thereof. Attached to the bottom end of the pump (5) is a stub tube (6) of sufficient length to extend below the perforations (3) fonned through the casing (2). Attached to bottom end of the stub tube (6) is the separator (7). Formation fluid and particles flow downwards within the cased well bore from the perforations (3) and then into the separator (7). The fluid and finer particles are drawn laterally into the separator (7), up the stub tube (6), through the pump (5), and up the production tubing (4) to surface. More particularly, the production fluid carries with it the finer particles in a downwardly path in the cased borehole, and then is drawn into the separator (7) and flow upwardly, thus changing the direction of the flow path. The more coarse fraction of the particles (8) are heavier and more dense than the fine particles and thus cannot follow this abrupt change in fluid flow direction. As such, the coarse particles pass through the separator (7) and settle downwardly by gravity in a sump at the base of the cased wellbore. As will be described in more detail below, the separator (7) is constructed with an orifice or slot through which the production fluid must flow so that the velocity thereof is increased during the change in direction of fluid flow. The increased velocity of the production fluid during the change in direction carries with it the fine particles, but the coarse particles have too much momentum to follow the fluid flow path. Thus, the coarse particles continue on a downward flow path to the sump of the cased wellbore.

Figure 2 illustrates an embodiment of the separator (7) of Figure 1. The separator (7) is shown installed within a perforated casing (2), below the perforations (3). Attached to the top of the separator (7) is the stub tubing (6) which has a lower threaded part (10). A threaded sleeve (1 1) is threadably connected to the lower threaded part of the stub tubing (6). The threaded sleeve (1 1) is attached to plural arms (12), each of which is connected by a respective shear pin (20) to a corresponding annular conical-shaped base member (14). The base member (14) is preferably constructed of a drillable material. The annular base member (14) is equipped with an elastomeric skirt (15) that engages the inside surface of the casing (2) to prevent fluid flow around it. Located at the lower end of the threaded tube (10) are adjustable conical-shaped valve members (16, 17). The valve members (16, 17) are axially spaced apart to provide an annular orifice through which the production fluid and fine particles pass. Formed within the threaded tube (10) at its end is a spider (13). Attached in the centre of the spider (13) is a threaded rod (18) which carries with it the valve member (16). Valve members (16) and (17) constitute an inner cone, and are spaced from the outer annular cone-shaped base member (14). The spacing between the cone-shaped valve members (16) and (17) and the conical inside surface of the base member (14) can be adjusted by screwing the threaded sleeve (1 1) up or down on the threaded tube (10). The spacing of the slot between valve members (16) and (17) is adjusted by screwing the lower valve member (16) up or down on the threaded rod (18), and then locking it in place using a lock nut (19). By making the base member (14) adjustable with respect to the valve members (16) and (17), the spacing of the passageway of the production fluid and the particulate matter flowing past the valve member slot can be adjusted.

In operation, production fluid and particles flow under formation pressure downwards within the well between the casing (2) and the tubing (6). The production fluid and particles then enter the conical -shaped annular space between the inner conical surface of the base member (14) and the two separator members (16) and (17). The production fluid and the fine particles are drawn laterally through the slot between the valve members (16) and (17,) and then upwardly through the threaded tube 10 and the stub tube (6). The production fluid and the fine particles effective make a U-turn. The coarse particles are also carried downwardly by the production fluid, but continue on to the sump (not shown) at the base of the well. Because the coarse particles are heavier than the fine particles, the coarse particles are not able to make the U-turn and continue on the downward path to the sump.

In the event that problems occur in the production of fluid from the well, the withdrawal of the tubing (6) from the well may be required. If the upward movement causes the base member (14) to become jammed in the casing (2,) then the shear pins (20) are designed to fail and leave the base member (14) downhole. The arms (12) are designed to be sufficiently deformable that they will not jam on any imperfections or particles within the casing (2), and thus will not prevent the withdrawal of the remainder of the separator ( 7). The base member (14) is designed to be drillable so that it can be drilled out if it jams in the casing (2). In another embodiment, both the elastomeric skirt (15) and the base member (14) are constructed out of an elastomer that will deform and thus resist being jammed in the well bore.

While the preferred and other embodiments of the invention have been disclosed with reference to a specific separator and method of operation and manufacture thereof, it is to be understood that many changes in detail may be made as a matter of engineering choices without departing from the spirit and scope of the invention, as defined by the appended claims.

Claims

CLAIMS What is Claimed is:

1. A device for use in a well bore, said device for separating finer solid components of particles from coarser solid components being produced with fluids, said separator enables the finer solid components to be lifted with the fluids to the surface whilst allowing the coarser solid components to settle in the well bore, said separator comprising; said separator attached to the base of a conduit located within a well, said separator is located in the well below a fluid entry point into the well, and said conduit carries the fluids and selected particles being produced from the formation to the surface; said separator having spaced-apart inner and outer conical-shaped walls forming a conical-shaped passageway through which the well fluid passes substantially downwards at an angle to the vertical, and said inner conical-shaped wall having an annular extraction slot into which the wellbore fluids and finer solid components are drawn and coupled upwardly in said conduit, whilst the coarser solid components fall under the force of gravity to the base of the well.

2. The device according to claim 1 , wherein said separator includes a circuitous path for carrying the fluids, said circuitous path being such that said finer solid components can follow but the coarser solid components cannot follow.

3. The device according to claim 2, wherein said extraction slot is spaced from said outer conical -shaped wall by a space that is adjustable by rotating a threaded connection to permit adjustment of an operating flow rate of the fluid and to adjust a fine cut point of the particles being lifted by the fluid out of the well.

4. The device according to claim 1 , wherein said inner conical-shaped wall comprises a valve with said extraction slot formed therein, and said valve comprises two parts that are axially adjusted to adjust a spacing of the extraction slot.

5. The device according to claim 1 , wherein said separator engages with an inner surface of said casing with an elastomeric seal so that the fluids flow through said passageway.

6. The device according to claim 4, wherein said separator further includes a tube having a threaded part, and said outer conical-shaped wall defines a base member that includes a corresponding threaded part that engages with the threaded part of said tube, wherein adjustment of the base member on said tube adjusts a size of said passageway for fluids.

7. The device according to claim 6, wherein said valve includes a stationary member and a movable member, said movable member is threadably attached to said tube to adjust a size of said extraction slot.

8. The device of any of the claims above where said separator is used below a well pump.

9. A method of separating coarse particles from fine particles carried in a fluid stream flowing from a formation into a well, and carrying the fluid stream with the fine particles to the surface while allowing the coarse particles to be carried downwards to the base of the well, said method comprising; extending a tubing down a well cased with a perforated casing or screen, the fluid stream and particles passing from the formation through the casing perforations or screen into the well; extending a separator coupled to the tubing to a location in the well below the perforations in the casing; allowing the well fluid and particles to pass substantially downwards through a passageway at an angle to the vertical, where said passageway includes an inner conical surface and an outer conical surface; and carrying the finer particles with the fluids through an extraction slot formed in said inner conical surface so that the finer particles move from a downwardly direction to an upwardly direction, and allowing the coarse particles to fall under the force of gravity to the base of the well.

10. The method according to claim 9, wherein said extraction slot and said passageway are arranged in an axisymmetric manner with said extraction slot being connected to the conduit carrying the well bore fluids to a hole collar along with the finer particles.

1 1. The method according to claim 9, further including adjusting a spacing between said extraction slot and the outer wall of said passageway by rotating a threaded connection so as to permit adjustment of an operating flow rate and a fine cut point of the particles being lifted out of the well.

12. The method according to claims 9 to 1 1 , where the separator is used below a well pump.

13. The method according to claim 12 utilising the device of claims 1 to 4.

14. The method of preventing the build up of particles in the base of a well using the separator of claims 1 to 4 to extract fine particles with the fluid stream.

15. The method to prevent pump damage caused by lifting coarse particles through the pump with the produced well fluids by using the method of claim 14.