Oil well perforators

Abstract

An oil and gas well shaped charge perforator capable of providing an exothermic reaction after detonation is provided, comprising a housing (2), a high explosive (3), and a reactive liner (6) where the high explosive is positioned between the reactive liner and the housing. The reactive liner (6) is produced from a reactive composition which is capable of sustaining an exothermic reaction during the formation of the cutting jet. The composition is a pressed i.e. compacted particulate composition comprising at least two metals, wherein one of the metals is present as spherical particulate, and the other metal is present as a non-spherical particulate. There may also be at least one further metal, which is not capable of an exothermic reaction with the reactive composition, present in an amount greater than 10% w/w of the liner. To aid consolidation a binder may also be added.

Claims

1. A reactive oil and gas well shaped charge perforator liner comprising: a reactive composition of at least two metals wherein the liner is a compacted particulate composition comprising a spherical metal particulate and a non-spherical metal particulate, wherein the at least two metals are selected such that they produce, upon activation of the shaped charge liner, an electron compound, wherein the non-spherical metal particulate is selected from Ce, Fe, Co, Li, Mg, Mo, Ni, Nb, Pb, Pd, Ta, Ti, Zn, or Zr, wherein the non-spherical particulate has an average longest dimension of less than 300 microns, wherein the average longest dimension of the non-spherical metal particulate is at least twice the diameter of the spherical particulate, wherein the non-spherical particle has an aspect ratio of from 50:1 to 200:1, wherein the liner further comprises at least one further metal particulate, which is substantially inert with the at least two metals and the further metal is present in an amount greater than 10% w/w of the liner, and wherein the at least two metals and at least one further metal are uniformly dispersed to form an admixture.

2. The liner according to claim 1, wherein the electron compound is a Hume-Rothery compound having an electron to atom ratio of 3/2.

3. The liner according to claim 1, wherein the more malleable of the at least two metals is selected as the spherical metal particulate.

4. The liner according to claim 1, wherein the spherical metal particulate is aluminium.

5. The liner according to claim 1, wherein the non-spherical metal particulate is selected from Group VIIIA, VIIA, and IIB of the periodic classification.

6. The liner according to claim 1, wherein the non-spherical metal particulate is selected from Ni, Pb, and Ti.

7. The liner according to claim 1, wherein the non-spherical metal particulate is selected from a flaked, rod-shaped or ellipsoid particulate.

8. The liner according to claim 7, wherein the non-spherical metal particulate has an aspect ratio of greater than 2:1.

9. The liner according to claim 8, wherein the non-spherical metal particulate has an aspect ratio in the range of from 10:1 to 200:1.

10. The liner according to claim 1, wherein the non-spherical metal particulate has an average longest dimension in the range of 2-50 microns.

11. The liner according to claim 1, wherein the spherical metal particulate has an average diameter of 50 microns or less.

12. An oil and gas well shaped charge perforator comprising a liner according to claim 1.

13. A method of completing an oil or gas well using one or more shaped charge perforators according to claim 12.

14. A perforation gun comprising one or more perforators according to claim 12.

15. A method of completing an oil or gas well using one or more perforation guns according to claim 14.

16. A method of completing an oil or gas well using one or more shaped charge liners according to claim 1.

17. A method of producing a reactive shaped charge liner according to claim 1, the method comprising: providing a composition of at least two metals; and compacting said composition to form a liner, wherein the composition comprises a spherical metal particulate and a non-spherical metal particulate.

Description

DESCRIPTION OF THE DRAWINGS

(1) In order to assist in understanding the invention, a number of embodiments thereof will now be described, by way of example only and with reference to the accompanying drawing, in which:

(2) FIG. 1 is a cross-sectional view along a longitudinal axis of a shaped charge device containing a liner according to the invention;

(3) FIG. 2 is a sectional view of a well completion in which a perforator according to an embodiment of the invention may be used;

(4) FIG. 3 is a schematic representation of an explosive anvil system used to test reactive compositions for use in the liner of the invention; and

(5) FIG. 4 is an XRD trace for a non-spherical/spherical NiAl particulate composition tested in the system of FIG. 3.

DESCRIPTION OF THE INVENTION

(6) FIG. 1 is a cross-sectional view of a shaped charge, typically axially-symmetric about centre line 1, of generally conventional configuration comprising a substantially cylindrical housing 2 produced from a metal (usually, but not exclusively, steel), polymeric, GRP or reactive material according to the invention. The liner 6 according to the invention has a wall thickness of typically 1 to 5% of the liner diameter, but may be as much as 10% in extreme cases and to maximise performance is of variable liner thickness. The liner 6 fits closely into the open end 8 of the cylindrical housing 2. High explosive material 3 is located within the volume enclosed between the housing and the liner. The high explosive material 3 is initiated at the closed end of the device, proximate to the apex 7 of the liner, typically by a detonator or detonation transfer cord which is located in recess 4.

(7) One method of manufacture of liners is by pressing a measure of intimately mixed and blended powders in a die set to produce the finished liner as a green compact. Alternatively, intimately mixed powders may be employed in the same way as described above, but the green compacted product is a near net shape allowing some form of sintering or infiltration process to take place.

(8) Modifications to the invention as specifically described will be apparent to those skilled in the art, and are to be considered as falling within the scope of the invention. For example, other methods of producing a fine grain liner will be suitable.

(9) With reference to FIG. 2, there is shown a stage in the completion of a well 21 in which the well bore 23 has been drilled into a pair of producing zones 25, 27 in, respectively, unconsolidated and consolidated formations. A steel tubular casing 9 is cemented within the bore 23. In order to provide a flow path from the production zones 25, 27 into the annulus that will eventually be formed between the casing 9 and production tubing (not shown) which will be present within the completed well, it is necessary to perforate the casing 9. In order to form perforations in the casing 9, a gun 11 is lowered into the casing on a wireline, slickline or coiled tubing 13, as appropriate. The gun 11 is a generally hollow tube of steel comprising ports 15 through which perforator charges of the invention (not shown) are fired.

EXAMPLES

(10) Experiments were conducted to compare the reactive behaviour of the following samples, using similar initial density and shock loading conditions: a NiAl composition comprising a 1:1 molar ratio of spherical Ni particulates and spherical Al particulates, each of size 7-15 micron. a NiAl composition comprising a 1:1 molar ratio of flaked Ni particulates (44 micron by 0.37 micron, aspect ratio 119:1) and spherical Al particulates (5-15 micron).

(11) The TMD of all tests samples was about 60%.

(12) Referring to FIG. 3, an explosive anvil system 30 was used to test the samples, the system comprising a steel anvil 31, a steel cover plate 32, SX2 explosive 33 and an RP80 detonator 34. The sample to be tested was placed in recess 35 in anvil 31.

(13) Initial tests were conducted using a 6 mm thickness of SX2. The skilled person will realise that thresholds depend on the type of shock loading and accordingly, the loadings quoted in respect of the anvil tests do not necessarily equate with the loading in a shaped charge.

(14) The samples were subjected to shock and recovered for analysis. It was found that the Ni flake/AI sphere sample according to the invention had undergone close to 100% reaction to form an intermetallic compound. X-ray diffraction (XRD) analysis confirmed that the main reaction products were NiAl and Ni.sub.2Al.sub.3, with traces of Ni.sub.5Al.sub.3 and Ni.sub.3Al (see FIG. 4).

(15) In contrast, approximately 5% of the spherical Ni/spherical Al sample reacted to form an intermetallic compound. The test was repeated using a 9 mm thickness of SX2. It was found that increasing the explosive loading increased the extent of reaction to about 10%.

(16) It can be concluded that, under identical loading conditions, a reactive composition comprising a spherical metal particulate and non-spherical metal particulate produces more energy. Conversely, a desired energy output can be obtained at a lower detonation threshold. It follows that a shaped charge liner according to the invention provides similar benefits. For small charges in particular, liners according to the invention can be used to maximise the volume of the shaped charge jet at high temperature, thereby ensuring that more thermal work is put into the target.

(17) It will be understood that the present invention has been described above purely by way of example, and modification of detail can be made within the scope of the invention. Each feature disclosed in the description and (where appropriate) the claims and drawings may be provided independently or in any appropriate combination.