MXPA99010394A - Conduit cleaning material and process - Google Patents

Abstract

Novel abrasive particles for cleaning conduits, particularly subterranean wellbores are described. The particles are rounded, preferably spherical, and have a hardness of 80 to 200 Vickers. The particles are preferably made of non-metallic material such as Calcite pellets. The new abrasives cause significantly less damage to the well tubulars than sand.

Description

MATERIAL AND PROCESS CLEANER OF DUCTS The present invention relates to abrasives and to an improved method for cleaning ducts, particularly hydrocarbon wells using a jet-shaped fluid loaded with said abrasives.

BACKGROUND OF THE INVENTION It has been common practice for many years to run a continuous return tube (widely known in the industry as "coil tubing") in a well to perform operations using the circulation of treatment fluids and cleaners such as water, oil, acid, corrosion inhibitors, hot oil, nitrogen, foam, etc. The coil pipe being preferably continuous rather than joined, runs in and out of a well with continuous movement of the pipe through a spiral injector pipe. The spiral tube is frequently used to circulate cleaning fluids through a well for the purpose of removing sand bridges, inlays and similar obstructions at the bottom of the borehole. Often such obstructions are very difficult and occasionally impossible to remove due to the inability to rotate the coil tube and pierce such obstructions. The tubulars of the wells vary from non-perforated and perforated pipelines, larger diameter casing, production piping and wire-lined or slotted pgzo casing. The tubular wells often re-clog or cover with corrosion products, sediments and hydrocarbon deposits. The deposits may consist of silicates, sulfates, sulfur, carbonates, calcium and organic growth. It is desirable to perform well-type drilling operations through the use of coil tubing that can be rapidly drawn into and out of a well in addition to performing the usual operations that require only fluid circulation. The same type of service in wells can be carried out several small diameter working strands. The present invention can be used with such work strings and is not limited to a spiral tube. For many years, high-pressure fluid jet systems have been used to clean the inner diameter of tubular wells. Examples of such systems were described in the following - U.S. Patent Nos: 3,720,264, 3,811,499, 3,829,134, 3,850,241, 4,088,191, 4,349,073, 4,441,557, 4,442,899, 4,518,041, 4,919,204, 5,181,576 or 5,337,819.

The abrasive of choice in the current practice of cleaning wells is sand, although other abrasive particles of different technical fields are known. For example, the use of non-spherical flint or steel pellets is described in U.S. Patent No. 4,482,392. The hardness of the material described is well above 50 on a Rockwell C scale. A well cleaning method using coil tubing is described in the application of International Patent WO 91/11270. This comprises the use of an abrasive mixture of carrier fluid and abrasive particles, a pump system for pressurizing said mixture and a coil pipe unit with a jet jet head. The abrasive is characterized as round and its effects on the pipes are described as limited to a blasting action. No specific examples of such abrasive are given. In view of the aforementioned prior art, it is an object of the invention to provide an improved abrasive for application in the cleaning of ducts, particularly applications in the cleaning of wells.

COMPENDIUM OF THE INVENTION The objects of the invention are achieved by the abrasives and methods as set out in the appended independent claims. The abrasive particles according to the invention are round and have a hardness of 80 to 200 Vickers (measured with a load of 50 g). This value is less than the hardness of the steel shot described in the .Patent US No. 4,482,392 referred to above. It was found that novel abrasives, although effectively removing scale, cause only limited erosion of the tubular wells. Erosion of tubular wells can be further limited by ensuring that the abrasive particles are essentially spherical. Essentially spherical in the context of this invention is defined as having no other systematic preferential form than an ideal sphere, although each individual particle may deviate more or less in this way. It was further found that the removal of solid deposits can be accelerated by the choice of material within the range of 120 to 190 Vickers, even more preferably, from the range of 155 to 185 Vickers. In addition, the preferred abrasives according to the invention have a material density or GE of more than 2000 kg / m3, more preferably within the range of 2000 kg / m3 to 5000 kg / m3. It should be noted that the given density refers to the density of a single pellet of the abrasive material. The abrasives are preferably selected from non-metallic materials, such as minerals or ceramics. The ceramics can be for example particles of the clay type that are produced by processes that ide rolling and spray drying to make spherical shapes. The required hardness can then be generated by calcination at temperature during the specified period. The minerals are taken from the deposit of earth as rocks, then crushed to produce particles. These particles (for example, Calcite, Dolomite, Barite) can be acquired with the correct hardness and size, but usually tend to be angular. However, using for example a wet rolling process, it is possible to produce spherical particles. Materials such as calcium, barium and zinc or derivatives thereof, such as sulfates, carbonates, phosphates can be produced as spherical particles by precipitation or in rotating pump type reactors. These have the correct hardness and can be made in the correct size and shape. Importantly, granule reactors are used to reduce carbonate (CaCOs) or phosphate levels in cold water. These produce spherical particles with the correct properties (iding particles normally known as calcite beads, which contain precipitated calcium carbonate). Calcite beads are especially advantageous for the purpose of this invention and are available in large quantities at economical prices. In addition, the beads are preferably graded to select a size range of 0.1 mm to 1-mm in diameter. It should be noted that the abrasives according to the present invention are round to limit the damage to the steel pipes to be cleaned. However, such damage is tolerable for the materials mentioned above, specifically, calcite-based materials could also be used in other forms, for example angular. The "described materials can be used for a wide range of jet cleaning applications, which ide the separation of deposits from interior surfaces, pipes, furnace tubes, tubular wells, etc. Abrasives can also be applied to separate the filter cake inside. These and other features of the invention, the preferred embodiments and variants thereof, and advantages will be appreciated and understood by those skilled in the art of the detailed description and drawings hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 illustrates the erosion of the steel depending on the blasting time of some abrasives; FIGURE 2 illustrates the separation of the deposits depending on the distance of the shot for different abrasives; FIGURE 3 schematically shows a tool for jet cleaning.

MODE (S) FOR CARRYING OUT THE INVENTION This invention is now described with reference to the accompanying drawings. The respective operation of the different abrasive materials can be tested using a standard test equipment. The results of which are illustrated by figures 1 and 2. For the tests a water-abrasive mixture at 2.5% (by weight) was prepared. The tested materials ided Olivina with hardness Vickers of around 700, Dolomite (hardness: 200) and calcite - (hardness: 150) as well as pearls of calcite graduated (hardness: 180) with spherical shape. The slurries were pumped through a 2.8 mm diameter nozzle at a pressure of 180 bar (18 MPa) (jet speed approximately 200 m / sec). The objective of the jet was to a steel plate and, after the blasting, the depth of the hole was measured to quantify the damage caused by the abrasives. The results illustrated by figure 1 were measured at a constant distance (section) between the jet nozzle and the 15 mm steel plate. The time of the jet varied between 40 and 105 seconds (as marked on the abscissa).

The measured depth of the hole in the steel plate (in mm) was marked on the ordinate. The results that refer to the Olivine slurry are marked by squares, those of dolomite with a triangle and for calcite and the calcite pellets with circles and crosses, respectively. Notably, the damage caused by the round pellets is about an order of magnitude less than those caused by the angular Olivin (sand) and even less than the damage caused by the angular calcite, which has approximately the same hardness or even less. The effectiveness of the abrasives with respect to the separation of deposits was tested in a sample of barium sulfate. Barium sulfate, together with calcium sulfate and calcium carbonate, is a common component of well deposits (scale). During these tests, illustrated by Figure 2, the jet traveled in a circular path over barium sulfate at a constant speed of 60 mm / sec, while the distance varied between 6 and 10 nozzle diameters (2.4 and 3.2 mm) (on the abscissa). The ordinate shows a depth of the normalized slit. The results for the different materials are marked as in figure 1. Surprisingly the calcite pellets showed a higher cutting rate than even the very hard and angular sample of Olivina although the operation at increased distances seems to fall at a faster rate. Also, the performance of pellets compares favorably with that of angular calcite and dolomite. Other possible abrasive materials may consist of annealed steel shot to control its hardness. This material shows similar performance to Calcite pellets, however, it is significantly more expensive and heavier. Another alternative could be pellets of plastic material loaded with a heavy mineral, usually barium sulfate. Common applications of the novel abrasives include well-cleaning operations as illustrated in Figure 3. The underground well-cleaning equipment consists of a spool of coil tubing 31 usually mounted on a truck 32. Connected to the spool is a cleaning fluid tank 33, a reserve reservoir and feeder for the abrasive material 34. A mixer 35 produces the applied abrasive slurry to remove the reservoir. A pump unit 36 generates the pressure to circulate the slurry through the coil pipe 37 and the bore 38. The coil pipe 37 is fed through the anti-burst sealing stack (OAE) 381 into the tubular wells 382. A return pipe 371 in the upper end portion of the well tubulars closes the flow cycle through which the cleaning fluid is pumped. Also included in the flow cycle (not shown) are the separators to recover the cleaning fluid- and / or the abrasives. In operation, the coil pipe with a jet supply head 372 at its end lowered to the well 38 at a predetermined depth at which the tanks 383 must be removed. Then, the grout containing the abrasive is discharged through the nozzles of the jet supply head, removing the scale at a rate that depends on the deposits, the speed of the jet and the distance.

Claims (25)

1. CLAIMS The abrasive particles, when used to clean ducts in hydrocarbon wells, are characterized in that said particles are round and have a hardness of 80 to 200 Vickers.
2. The particles of claim 1, wherein the particles have an essentially spherical shape.
3. The particles of claim 1, wherein the particles have a diameter of 0.1 to 1 mm.
4. The particles of claim 1, wherein the particles have a material density of more than 2000 kg / m3.
5. The particles of claim 1, wherein the particles consist of non-metallic material.
6. The particles of claim 1, wherein the particles contain mineral material.
7. The particles of claim 6, wherein the particles consist of sulfates, carbonates, phosphates or other calcium, barium or zinc derivatives.
8. The particles of claim 7, characterized in that the particles consist of calcite pellets.
9. The particles of claim 1, wherein the particles consist of beads of plastic material loaded with a mineral material having a density greater than that of the plastic material.
10. 10. The particles of claim 9, wherein the mineral material consists of barium sulfate.
11. 11. The particles of claim 1, wherein the particles consist of ceramic material.
12. 12. The particles of claim 11, wherein the ceramic material is a type of clay and the particles are produced by processes that include rolling and spray drying.
13. 13. The particles of claim 11, wherein the particles are produced by processes that include calcination at a predetermined temperature for a predetermined time.
14. 14. The particles of claim 1, wherein the particles are produced using a pellet reactor.
15. 15. The particles of. Claim 1, wherein the particles are produced by a process that includes the reduction of carbonate levels in water
16. 16. The particles of claim 15, wherein the process includes the reduction of carbonate levels in cold water.
17. 17. A method for cleaning a pipeline in a hydrocarbon well comprising the steps of: - descending a head with nozzle mounted on a part of a lower end of a hollow tubular in the well, and - pressurizing a fluid to be discharged. through said nozzle head to a predetermined location within the well, wherein the fluid contains abrasive particles that are round and have a hardness of 80 to 200 Vickers 8.
18. The method of claim 17, wherein the particles have a essentially spherical shape 19.
19. The method of claim 17, wherein the particles have a diameter of 0.1 to 1 mm 0.
20. The method of claim 17, wherein the Ticles consist mainly of calcite.
21. The method of claim 17, wherein the particles consist of beads of plastic material loaded with a mineral material.
22. 22. The method of claim 21, wherein the mineral material consists of barium sulfate.
23. 23. The method of claim 17, wherein the particles consist of ceramic material.
24. The method of claim 23, wherein the ceramic material is a type of clay and the particles are produced by processes that include rolling and spray drying.
25. 25. The method of claim 17, wherein the particles are produced using a pellet reactor. The method of claim 17, wherein the particles are produced by a process that includes the reduction of carbonate levels in cold water.