Related Application

[0001] This application claims priority from Australian Patent Application Number 2022900070, the contents of which are incorporated in entirety by reference.

Field

[0002] The present invention relates to an apparatus and method for clearing solids from a well.

Background

[0003] The production of oil and gas typically involves drilling a well into a region in which oil and gas deposits are located. The bore of the well is normally cased with an outer casing. Oil, gas or water enters into the outer casing and is raised to the surface. Wells that are used to provide water operate in a similar manner.

[0004] In some wells, the oil, gas or water in the deposit is under sufficient pressure that it rises to the surface through the bore of the well without requiring any pumping. However, many wells do not have sufficient pressure for this to occur. In wells that initially do raise the oil, gas or water to the surface without requiring pumping, as production from the well goes on, the pressure inside the well can drop and, following a period of production, the pressure in the well may no longer be sufficient to raise the produced fluid to the surface.

[0005] Artificial lift is a means of assisting a gas, oil or water well to lift fluids from the bottom of the well to the surface.

[0006] Many wells that require artificial lift use down hole pumps to provide the artificial lift. A typical problem that occurs with the use of pumps, such as progressive cavity pumps (PCP pumps), is solids can build up in the bottom of the well to a point where the pump intake is blocked. At this stage, the pump stops pumping production fluid. One currently used solution to overcome this issue involves treating the well with a “flush by” where the rotor is pulled from the pump and fluid is pumped through the tubing and PCP stator to clear out the intake. This is usually a short-term solution. Experience has shown that it will eventually be necessary to pull out the tubing, followed by a clean out of the bottom of the well and a new pump is then run into the well. [0007] An alternative solution to cleaning out solids build-up at the bottom of the well is to run a bailer. A bailer is like a large syringe with a check valve on the bottom. In this cleanout method, the PCP rotor and stator and associated tubing are pulled out of the hole and the bailer is run into the hole. Fluid and solids are sucked into the tubing through the check valve and the tubing is pulled to the surface, where the tubing is unloaded into buckets. This is a slow and messy process. There may still be some problems with managing the well-control while carrying out this operation, especially if the well cannot be kept full in over-balanced pressure control when there is a chance that the well will flow, creating a dangerous working situation.

[0008] Even in wells that do not require artificial lift, the build-up of solids, such as sand and gravel, in the bottom of the well, can compromise production from that well. Thus, periodic cleaning out of such wells may be required to retain satisfactory production.

[0009] It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.

[0010] Throughout the specification, “up-hole” is to be taken as reference to a direction toward a top of the well and “downhole” is to be taken as reference to a direction toward a bottom of the well.

Object

[0011] It is an object of the invention to provide an apparatus and method to clear solids from a well to facilitate continued and reliable operation of the well.

Summary

[0012] In one aspect, there is provided an apparatus for clearing solids from a well including a housing with a jet pump, for positioning in a production string of the well, a tailpipe string carrying an elongate body to project out of a downhole end of the production string, a coupling to connect to inner tubing positioned within the production string for providing pressurised fluid to drive the jet pump, and a conduit which bypasses the jet pump in order to deliver pressurised fluid into the tailpipe string, wherein the tailpipe string includes a nozzle assembly to jet pressurised fluid into the well in order to agitate and stir up solids adjacent the elongate body and the elongate body includes an intake screen through which the solids are suctioned into an internal channel of the apparatus which is in fluid communication with an inlet of the jet pump, and wherein the jet pump has an exit for pumping the solids into a space between the apparatus and the production string in order to force the solids up-hole and out of the well.

[0013] In one implementation, the nozzle assembly includes at least one nozzle at a nosing end of the tailpipe string.

[0014] In one implementation, the nozzle assembly includes at least one nozzle at an up-hole location relative to the screen to maintain agitation of the solids before being suctioned through the intake screen.

[0015] In one implementation, the apparatus includes a seal arrangement below the exit of the jet pump to seal against the production string to preventfluids in the production string above the seal arrangement travelling in a downhole direction

[0016] In one implementation, the apparatus is configured to be mounted to an existing seat in the production string and the tailpipe string has a reduced diameter to pass through the seat to exit the downhole end of the production string.

[0017] In one implementation, the tailpipe string is dimensioned to pass through the opening from which a rotor of a P CP pump has been extracted.

[0018] In one implementation, the tailpipe string is dimensioned to pass through the opening from which a rod pump has been extracted.

[0019] In one implementation, the coupling includes a diverter to direct power fluid delivered through the inner tubing into both the conduit which extends into the tailpipe/tubing and the jet pump.

[0020] In another aspect, there is provided a method of extracting solids from a well using the apparatus described above, including attaching the apparatus to an inner tubing which supplies power fluid to the apparatus, feeding the apparatus down the well and supplying the power fluid through the inner tubing to agitate solids in the well and suction the agitated solids into the apparatus and out of the jet pump exit to thereby force the solids up-hole for extraction from the well.

[0021] In one implementation, the method includes jetting pressurised fluid through nozzles positioned above and below the screen to maintain a dilute slurry of agitated solids adjacent the intake screen of the apparatus.

[0022] In one implementation, the method further includes jetting pressurised fluid through nozzles positioned above and below the screen to maintain a dilute slurry of agitated solids adjacent the intake screen of the apparatus and also reduce the particle size of particles in the slurry such that they are compatible with the screen intake.

[0023] In one implementation, nozzles to jet the pressurised fluid are positioned such that the nozzles generate an intense turbulent cloud which acts to generally maintain an unblocked screen by ejecting blocked particles from the screen thereby permitting continuous operation.

[0024] In one implementation, the method includes firstly removing a rotor and rotor string of a PCP pump from an opening in a stator of a production string and deploying the apparatus through the stator such that the tailpipe string extends through a resultant opening, downhole of the production string.

Brief Description of the Drawings

[0025] The invention is more fully described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

[0026] Figure l is a sectioned view of part of a well and apparatus;

[0027] Figure 2 is a sectioned view of another part of the well and apparatus; and

[0028] Figure 3 is a sectioned view of another part of the well and apparatus.

Detailed Description

[0029] Figure 1 shows a well 1 with a down hole 2 including a wellbore 3 and a bore casing 4. [0030] A production string 5 in the form of outer tubing 6 is positioned within the well 1. Inner tubing 7 is arranged within the outer tubing 6. The inner tubing 7 is connected to an apparatus 10 via a coupling 11. The inner tubing 7 provides power fluid to the apparatus 10.

[0031] The apparatus 10 includes a housing 12 that carries a jet pump 13 which includes one or more inlets 14, a restriction throat 15, an expansion chamber 16 and an exit 17 through a wall 18 of the housing 12, which opens into an a space 19 between the apparatus 10 and the production string 5.

[0032] A conduit 20 extends through the housing to bypass the jet pump 13. The conduit 20 is coupled to a diverter 21 that splits power fluid from the inner tubing 7 between the jet pump 13 and the conduit 20.

[0033] The conduit 20 is formed of connected first and second sections 22, 23 that extend downhole from the jet pump 13. A manifold 24 provides fluid communication for extracted fluid and solids to travel up-hole to the inlet 14 of the jet pump through channel 25.

[0034] A seal arrangement 26 is provided below the exit 17 of the jet pump 13 and the housing 12 to seal against the production string 5 and prevent fluids above the seal arrangement 26 travelling in a downhole direction

[0035] Figure 2 illustrates a connection part 27 that couples the housing 12 to further tubing/tailpipe string 30.

[0036] The part 27 includes formations 31 to allow the tailpipe to pass through but pevent the seal arrangement passing through a seat 32 of the production string 5. The seat 32 may, for example, be a stator (not shown) for a previously removed rotor of a top tag PCP pump, although the seat 32 may be of any form suitable for the apparatus 10 to engage with. In either case, the seat 32 has a reduced diameter opening 34 and the tailpipe string 30 has a similarly reduced diameter to allow the tailpipe string 30 to pass through the opening 34.

[0037] The tailpipe string 30 may also be dimensioned to pass through the opening 34 from which a rod pump has been extracted. In that case, the method of installation involves firstly removing a rod pump and rod string of a rod pump from a seat 32 in a production string 5 and passing the apparatus 10 through an associated pump seating nipple such that the tailpipe string 30 extends through a resultant opening, downhole of the production string 5 toward a bottom of the well 1.

[0038] A junction 35 provides a connection between the second section 23 and a third section 36 of the conduit 20, which is concentric and central of the tailpipe string 30. A manifold 37 is also provided to allow fluid communication between and extraction passage 38 in the tailpipe string 30 and the channel 25.

[0039] After passing though the opening 34, the tailpipe string 30 extends downwardly into the well 1, beyond the downhole end 38 of the production string 5.

[0040] Figure 3 shows the tailpipe string 30 as including a tubular elongate body 40. The body

40 has an extraction screen 41 and a nozzle assembly 42. A nosing end 43 of the body 40 has one or more nozzles 44, below the screen 41, and one or more nozzles 45 up-hole of the screen 41. The one or more nozzles 44, 45 may be angled in various orientations.

[0041] Fluid from a lower section 46 of the conduit 20 is jetted out from the nozzles 44, 45 to stir up and agitate solids 47 at a bottom 48 of the well 1. The one or more nozzles 44 may be used to displace solids 47 from the bottom 48 of the well 1 and allow the nosing end 43 to penetrate fill 49 in the well 1. The displaced solids 47 adjacent the body 40 are kept in an agitated fluid state as a dilute slurry, as a result of the pressurised fluid exiting the nozzles 44, 45, until being vacuumed into the body 40 through the intake screen 41, which has multiple apertures 50 to allow passage of the solids 47. The vacuuming process is facilitated by the jet pump 13, described with reference to Figure 1, generating suction to draw the solids 47 into an internal channel 51, which is in fluid communication with the inlet 14 of the jet pump 13 via the extraction passage 38. The solids 47 are entrained into the jet pump 13 and ejected through the exit 17 and into the space between the apparatus 10 and the production string 5 and forced up to the top of the well 1, for surface extraction.

[0042] As a result of jetting pressurised fluid through nozzles 44, 45 positioned above and below the screen 41, the solids 47 can be maintained in a dilute slurry adjacent the intake screen

41 of the apparatus 10. The pressurized fluid also reduces the particle size of the solids in the slurry such that the particles are compatible with the apertures in the screen intake. [0043] The nozzles 44, 45 are positioned to generate an intense turbulent cloud which acts to generally maintain an unblocked screen by ejecting blocked particles from the screen thereby permitting continuous operation.

[0044] The apparatus 10 has been described above with reference to being deployed througha PCP pump stator or alternatively the apparatus may be deployed through a rod pump nipple however it is possible for the apparatus 10 to be deployed through any generally open tubing arrangement.

[0045] The seal arrangement 26 also provides facility for the apparatus 10 to function continuously at any depth in the welll shallower than the seated depth such that the intake screen 41 can continuously clean through an interval of fill 49 in the wellbore 3.

[0046] The invention has also been described in relation to prior extraction of a pump rotor and string however the invention can also be used to simply clear solids from a well, for continued and reliable well production even if a pump is not used. The operation of the apparatus 10 has also been described with reference to interaction with a production string 5 however it is possible of the apparatus 10 to similarly operate against the bore casing 4, if the production string 5 is not present in the well 1.

[0047] The method of the present invention provides reliable functionality as additional power fluid is circulated above and below the intake screen 41 to agitate the solids 47 in the well 1. The power fluid delivered to the tailpipe string 30 is from the same source of power fluid delivered to the jet pump 13 through the inner tubing 7, which effectively results in drawing off the additional power fluid upstream of the jet pump 13 and directing the additional power fluid to the bottom of the tailpipe string 30.

[0048] An important discovery of the inventors which was not apparent prior to testing was that the nozzle 44 at the nosing end 43, although effective in creating a slurry of the fill 49, limits the extent of the slurry to below the nozzle 44. The conditions and turbulence in the wellbore 3 are not sufficient to deliver the slurry generated by nozzle 44 up to the screen 41. Therefore, the role of nozzle 44 is preferably only to assist in breaking up any partially compacted fill 49 encountered that may otherwise form an impenetrable barrier to the nosing end 43 of the tailpipe string 30. [0049] A breakthrough in performance was observed with the addition of bypass nozzles 45 which generate a turbulent cloud of slurry in the wellbore 3 in the region around the intake screen 41.

[0050] With the present invention, a turbulent slurry of known dilution, say 5-25% slurry concentration in the wellbore 3 at the point of the vacuum intake screen 41, can be maintained.