Unsgaard, Tom (Solagaten 20, STAVANGER, N-4009, NO)
|1.||A feed pump (1) for supply of drive fluid to a sand removal apparatus (10) in an underground well (2), in which the sand removal apparatus (10) comprises a sand chamber (12) and a jet pump (14), the jet pump (14) being of an arrangement capable of pulling sandcontaining fluid into the sand chamber (12), c h a r a c t e r i s e d i n that the feed pump (1) is located in proximity of the sand removal apparatus (10) and is of an arrangement capable of receiving drive fluid locally, the feed pump (1) together with the sand removal apparatus (10) being movable in underground well (2).|
|2.||The feed pump (1) according to claim 1, c h a r a c t e r i s e d i n that the feed pump (1) and the sand removal apparatus (10) constitute an assembly arranged to be able to be lowered down into the underground well (2) by means of a cable.|
|3.||The feed pump (1) according to claim 2, c h a r a c t e r i s e d i n that the assembly of the feed pump (1) and the sand removal apparatus (10) is arranged to be able to be placed in the underground well (2) by means of a well tractor.|
During production of oil and gas a continuously occurring problem consists in sand being torn loose form the formation and is entrained into the well. Sand entrained with the flow of oil or gas, so-called produced sand, may cause great dam- age to production equipment both within and outside of the well.
The amount of produced sand increases with an increasing flow rate, and an important measure against sand production thus is to restrict the flow rate. Measuring equipment for detect- ing produced sand has been developed, thereby allowing sand- reducing measures to be initiated before the damage is so great that the production equipment must be repaired.
Moreover, it is common to reinforce formations that easily yield sand, for example by injecting sand having a binder added thereto, for example sand/gravel mixed with an adhesive of a mixture type termed"adhesive gravel". Several types of filters are also known, and which may be installed in the well to prevent loose sand from becoming entrained up through the well.
After being used for some time, the lower part of the well is filled with loose sand, and it becomes increasingly difficult to maintain an acceptable flow rate. During workover of a well it is therefore common to attempt to remove loose sand that has collected at the bottom of the well. Loose sand may also result from drilling or other work in the well, and such sand is sought removed prior to production start.
Norwegian patent publication 306027 discusses a sand removal apparatus comprising a container having a closable inlet for liquid mixed with entrained sand, and a separate outlet asso- ciated with the suction side of a jet pump. The jet pump is the driving device of the apparatus and is supplied with en- ergy from a supply pipe extending to surface.
The apparatus according to said patent publication thus pre- supposes that a pipe connection, for example in the form of a pipe string or a coiled tubing, is inserted down into the well, the apparatus being connected to the lower end portion of the connection pipe.
A relatively comprehensive set of equipment must be present at the well in order to carry out pipe string and coiled tub-
ing operations of this type, and sand removal employing prior art equipment therefore is relatively expensive.
The object of the invention is to remedy the disadvantages of prior art.
The object is achieved according to the invention by means of the features disclosed in the description below and in the subsequent claims.
Sand removal work of this type is significantly simplified if the sand removal apparatus is adapted to be inserted into the well by means of cable equipment.
By providing the sand removal apparatus according to NO 306027 with a local feed pump that is arranged to supply the jet pump (ejector) of the apparatus with drive fluid, the sand removal apparatus is also well suited for being con- nected and for being inserted into a well by means of a ca- ble.
In a preferred embodiment the drive fluid feeder comprises a feed pump driven by means of electric power from surface via a wire associated with the cable.
The feed pump is arranged to pump fluid from the feed pump surroundings in the well onto the drive side of the jet pump.
A joint assembly of the feed pump and the sand removal appa- ratus is also well suited for enabling its transport into the well by means of a well tractor, for example.
In the following, a non-limiting example of a preferred em- bodiment is described and illustrated in the attached draw- ings, in which: Figure 1 shows a sand removal apparatus provided with a feed pump mounted thereon, in which arrows indicate fluid flow di- rections; and Figure 2 shows a sand removal apparatus provided with a packer mounted thereon.
On the drawings, reference numeral 1 denotes a feed pump dis- posed in a well 2, and feed pump 1 is supplied with energy via a wire 6 from surface.
Feed pump 1 is connected to the lower end portion of a cable 8 (wireline). Cable 8 extends to surface, and wire 6 is a part of cable 8.
The outlet of feed pump 1 is connected to a sand removal ap- paratus 10.
Sand removal apparatus 10 comprises a sand chamber 12 and a jet pump 14. The lower portion of sand chamber 12 is provided with an inlet 16 for sand-mixed fluid. Inlet 16 is of an ar- rangement capable of being closed by means of a check valve 18.
A filter 20 is provided inside of sand chamber 12. Filter 20 covers an outlet (not shown) from sand chamber 12, the outlet
When sand removal apparatus 10 and feed pump 1 are disposed at the bottom portion of well 2, feed pump 1 is started by supplying feed pump 1 with electric power via wire 6. Fluid flows via inlet openings 24 of feed pump 1, through feed pump 1 and onto jet pump 14, whereby an underpressure is created at the suction side of jet pump 14. Fluid containing entrained sand 26 thus flows through inlet 16 and check valve 18 and into sand chamber 12. Sand is cleaned from the fluid in filter 20, and the fluid flows onwards to jet pump 14, from which the fluid together with the fluid from feed pump 1 emanate into well 2 via outlet 22 of jet pump 14.
A portion of the fluid emanating from jet pump 14 flows down towards the bottom portion of well 2 and carries away sand 26 located down in well 2, prior to re-entering inlet 16.
When sand chamber 12 is filled, feed pump 1 and sand removal apparatus 10 are pulled up to surface by means of cable 8 in order to be emptied.
In figure 2, jet pump 14 is provided with a packer 38 of an arrangement capable of closing against the wall of well 2. In this embodiment, the jet pump may contribute to lift the relatively heavy fluids employed during well workovers to surface, thereby allowing a faster production start-up in a well 2.
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