ASYMMETRIC INITIATED SHAPED CHARGE AND METHOD FOR MAKING A SLOT-LIKE PERFORATION
A shaped charge is configured to make a non-circular perforation into a casing. The shaped charge includes a case having a side wall that extends between an open top region and a base; an asymmetric initiation insert configured to fit within the case; an explosive material placed over the asymmetric initiation insert and in contact with the side wall of the case; and a liner placed over the explosive material, to hold the explosive material within the case. The asymmetric initiation insert has a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points, that correspond to the first and second channels.
Embodiments of the subject matter disclosed herein generally relate to shaped charges and associated perforations made in the casing of a well, and more specifically, to a shaped charge that is configured to be asymmetrically initiated for generating a slot-like jet of material for perforating the casing to obtain a slot-like perforation profile.
Discussion of the BackgroundIn the oil and gas field, once a well is drilled to a desired depth H relative to the surface, and the casing protecting the wellbore has been installed and cemented in place, it is time to connect the wellbore to the subterranean formation and to extract the oil and/or gas. This process of connecting the wellbore to the subterranean formation may include a step of plugging with a well a previously fractured stage of the well, a step of perforating a new stage of the casing with a perforating gun system (that includes plural guns) such that plural channels are formed to connect the subterranean formation to the inside of the casing, a step of removing the perforating gun system after all the desired stages have been perforated, and a step of pumping to the surface the oil that enters the casing through the formed plural channels.
However, after the oil pressure in the formation becomes smaller than the hydrostatic pressure in the well, the natural oil flow from the formation into the casing diminishes, and the oil production ceases, although oil is still trapped in the formation. For these wells, a fracturing operation may be applied to extend their lifespan. A typical fracturing operation uses a slurry of a proppant (sand) and a liquid (water), which is pumped into each stage at high rates. The slurry enters then through the holes (perforations) made by the gun system into the casing, into the channels made in the formation by the same gun systems and hydraulically fractures the formation to open up the channels and allow the remaining oil to flow into the casing.
The amount of the slurry that flows through each perforation made into the casing may vary based upon a variety of factors. For example, one such factor is the shape of the perforation. The shape of the perforation depends on the type of the shaped charged used in the gun system for perforating the casing. The typical shaped charge is shown in
The problem with these symmetrical shaped charges is that there is only one initiation point A of the explosive material 112 and thus, when the liner 114 collapses due to the pressure generated by the explosion of the explosive material 112, the jet of material 140 formed from the liner 114 is very symmetrical about the longitudinal axis Y (i.e., is shaped as a cylinder), and this jet, when penetrating the casing (not shown) and the formation (not shown) would typically generate a round perforation and a round channel, respectively.
Having round perforations in the casing and/or round channels in the formation has been found over time to pose the following problem. Assuming that the diameter of the perforations is D1, and the average diameter of the particles in the slurry is D2, which is smaller than D1, over time, if the D1 is not at least six times larger than D2, the particles start to accumulate at the edge of the perforation and over time, they form a bridge, which diminishes if not suppresses the amount of the slurry that flows from the casing into the formation. This is undesirable because the fracturing operation relies on the slurry travelling at a desired rate from the casing into the formation.
To prevent this problem, there are efforts in the field to make slot-type perforations instead of round perforations. A slot-type perforation is understood herein to be a perforation or hole that is made in the casing with a shaped charge and has a shape more similar to a rectangle or square, i.e., a slot, than to a circle. In other words, a slot-type perforation is a non-circular perforation. To obtain slot-type perforations, various shaped charge manufacturers have tried to make the shaped charge non-symmetrical along the Y axis, by either manipulating the shape of the case, by providing plural initiation points by making corresponding plural holes into the case, or by adding various inserts in the explosive material to influence the shaped of the jet 140.
However, such approaches are complicated as they required to modify the case for making more initiation points, or to make an asymmetrical case, or to add various inserts in the explosive material. Further, such approaches are case specific, meaning that each shaped charge manufacturer has to modify differently its manufacturing process. Furthermore, these approaches cannot be used with the existing shaped charge's cases, and thus, require further investments and developing new manufacturing capabilities.
The slot-type perforations are also used for plug and abandonment operations. At the end of life of the well, special procedures are implemented for sealing the well and ensuring that the formations around the well are pressure isolated so that contamination between different formations is minimized. For these operations, non-circular slots are desired to be made in the casing of the well.
Thus, there is a need to form slot-type perforations into the well's casing with an existing shaped charge's case, and to achieve these results with an easy to manufacture shaped charge, that require inexpensive modifications when compared to a traditional shaped charge.
SUMMARYAccording to an embodiment, there is a shaped charge for making a non-circular perforation into a casing. The shaped charge includes a case having a side wall that extends between an open top region and a base, an asymmetric initiation insert configured to fit within the case, an explosive material placed over the asymmetric initiation insert and in contact with the side wall of the case, and a liner placed over the explosive material, to hold the explosive material within the case. The asymmetric initiation insert has a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points, that correspond to the first and second channels.
According to another embodiment, there is a perforating gun for perforating a casing in a well and the perforating gun includes a casing and a shaped charge provided within the casing and configured to make a non-circular perforation into the casing. The shaped charge includes an asymmetric initiation insert having a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points, that correspond to the first and second channels. The first and second initiation points make the shaped charge for form a non-circular perforation into the casing.
According to still another embodiment, there is a method of manufacturing a shaped charge that generates a non-circular perforation in a casing. The method includes providing a case for the shaped charge; placing an asymmetric initiation insert within the case; orienting angularly the asymmetric initiation insert relative to the case to achieve a desired orientation of the non-circular perforation relative to the casing; placing an explosive material over the asymmetric initiation insert and in contact with a side wall of the case; and placing a liner over the explosive material, to hold the explosive material within the case. The asymmetric initiation insert has a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points at the top surface, which correspond to the first and second channels.
The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one or more embodiments and, together with the description, explain these embodiments. In the drawings:
The following description of the embodiments refers to the accompanying drawings. The same reference numbers in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Instead, the scope of the invention is defined by the appended claims. The following embodiments are discussed, for simplicity, with regard to a perforating gun system used for perforating a casing in a well. However, the embodiments discussed herein may be used for guns in another context.
Reference throughout the specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with an embodiment is included in at least one embodiment of the subject matter disclosed. Thus, the appearance of the phrases “in one embodiment” or “in an embodiment” in various places throughout the specification is not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics may be combined in any suitable manner in one or more embodiments.
According to an embodiment, a shaped charge includes, in addition to a case, an explosive material, a liner, and a booster material, an asymmetric initiation insert that makes (1) the explosive material to be initiated from at least two different locations, and (2) the initiation to be asymmetrical relative to a longitudinal axis Y of the shaped charge's case. The longitudinal axis Y may be a symmetry axis for the case, but not for the asymmetric initiation insert. In one application, the longitudinal axis is a symmetry axis for each element of the shaped charge, but for the asymmetric initiation insert. The asymmetric initiation insert may be made of an inexpensive material, for example, plastic, resin, or even a metal. In one application, the asymmetric initiation insert may be 3D printed. In another application, the asymmetric initiation insert may be added to any existing shaped charge case, i.e., any shaped charge can be retrofitted to have the asymmetric initiation insert. The asymmetric initiation insert can be added manually or automatically by a robot to the shaped charge's case. The details of the asymmetric initiation insert are now discussed in more detail with regard to the figures.
An asymmetric initiation insert 220 is placed inside chamber 218, close to the base 212. The insert 220 is shaped in this embodiment to have a frustoconical body, i.e., a truncated cone. In one application, the top surface of the frustoconical body is curved (e.g., convex) and the bottom surface is flat. In one application, the asymmetric initiation insert 220 is in direct contact to the base 212. Although the asymmetric initiation insert 220 is shown in
Returning to the embodiment shown in
To allow the fire wave to propagate from the cord 217 to the explosive material 230, the asymmetric initiation insert 220 may have two or more channels 226 that extend through the entire body of the insert (
The two initiation points are asymmetrical, i.e., they are not provided on the longitudinal axis Y. Further, the two initiation points are provided while the base 212 of the case 210 has only one passage 216. In addition, the two initiation points 228A and 228B are on the top surface 220A of the body 221, i.e., within the top surface 220A. The embodiment illustrated in
The number of the channels 226 made in the body 221 of the insert 220 may vary from 2 to N, where N is a natural number between 3 and 30. The angular distribution of the channels 226 relative to the top surface 220A is illustrated in
While
While
The embodiments discussed herein illustrate various possibilities of providing two or more initiation points for the explosive material 230. Also, the embodiments discussed herein alter the speed of the explosive initiation at the different points so that the shockwave and pressure generated by the explosion of the explosive material 230 does not happen in a radial or circular pattern, as with the traditional shaped charge of
Because this novel insert 220 would make the shaped charge 200 to generate a slot-type perforation into the casing of the gun system, it is possible to orient the insert to obtain the slot-type oriented in a desired way relative to the casing of the gun system. In this regard,
The capabilities of the inserts 220 discussed above have been tested as now discussed.
The disclosed embodiments provide methods and systems for generating a slot-like hole perforation into a casing of a well, by using at least an asymmetric initiated shaped charge. It should be understood that this description is not intended to limit the invention. On the contrary, the exemplary embodiments are intended to cover alternatives, modifications and equivalents, which are included in the spirit and scope of the invention as defined by the appended claims. Further, in the detailed description of the exemplary embodiments, numerous specific details are set forth in order to provide a comprehensive understanding of the claimed invention. However, one skilled in the art would understand that various embodiments may be practiced without such specific details.
Although the features and elements of the present exemplary embodiments are described in the embodiments in particular combinations, each feature or element can be used alone without the other features and elements of the embodiments or in various combinations with or without other features and elements disclosed herein.
This written description uses examples of the subject matter disclosed to enable any person skilled in the art to practice the same, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims.
Claims
1. A shaped charge for making a non-circular perforation into a casing, the shaped charge comprising:
- a case having a side wall that extends between an open top region and a base;
- an asymmetric initiation insert configured to fit within the case;
- an explosive material placed over the asymmetric initiation insert and in contact with the side wall of the case; and
- a liner placed over the explosive material, to hold the explosive material within the case,
- wherein the asymmetric initiation insert has a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points, that correspond to the first and second channels.
2. The shaped charge of claim 1, wherein the top surface of the body is convex.
3. The shaped charge of claim 1, wherein the top surface of the body is part of a sphere of a given radius R.
4. The shaped charge of claim 1, wherein the asymmetric initiation insert fits tightly over the base and side wall of the case so that no explosive material is present at an interface between the asymmetric initiation insert and the case.
5. The shaped charge of claim 1, further comprising:
- a booster material placed in a conduit formed in the base of the case,
- wherein the conduit is configured to drive a flame from the booster material to the first and second channels of the asymmetric initiation insert.
6. The shaped charge of claim 1, further comprising:
- a booster material placed in a conduit formed in the base of the case,
- wherein the booster material is in direct contact with the first and second channels.
7. The shaped charge of claim 1, wherein each of the first and second channels is fully formed within the body of the asymmetric initiation insert.
8. The shaped charge of claim 1, wherein each of the first and second channels is partially open to a side of the asymmetric initiation insert.
9. The shaped charge of claim 1, wherein the first and second channels are cylinders having a constant radius.
10. The shaped charge of claim 1, wherein the first and second channels are conical frustums.
11. A perforating gun for perforating a casing in a well, the perforating gun comprising:
- a casing; and
- a shaped charge provided within the casing and configured to make a non-circular perforation into the casing,
- wherein the shaped charge includes an asymmetric initiation insert having a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points, that correspond to the first and second channels, and
- wherein the first and second initiation points make the shaped charge to form a non-circular perforation into the casing.
12. The perforating gun of claim 11, wherein the shaped charge comprises:
- a case having a side wall that extends between an open top region and a base;
- the asymmetric initiation insert is configured to fit within the case;
- an explosive material placed over the asymmetric initiation insert and in contact with the side wall of the case; and
- a liner placed over the explosive material, to hold the explosive material within the case.
13. The perforating gun of claim 12, wherein the top surface of the body is convex.
14. The perforating gun of claim 12, wherein the top surface of the body is part of a sphere of a given radius R.
15. The perforating gun of claim 12, wherein the asymmetric initiation insert fits tightly over the base and side wall of the case so that no explosive material is present at an interface between the asymmetric initiation insert and the case.
16. The perforating gun of claim 12, wherein the shaped charge further comprises:
- a booster material placed in a conduit formed in the base of the case,
- wherein the conduit is configured to drive a flame from the booster material to the first and second channels of the asymmetric initiation insert.
17. The perforating gun of claim 12, wherein each of the first and second channels is fully formed within the body of the asymmetric initiation insert.
18. The perforating gun of claim 12, wherein the first and second channels of the asymmetric initiation insert are cylinders having a constant radius.
19. The perforating gun of claim 12, wherein the first and second channels of the asymmetric initiation insert are conical frustums.
20. A method of manufacturing a shaped charge that generates a non-circular perforation in a casing, the method comprising:
- providing a case for the shaped charge;
- placing an asymmetric initiation insert within the case;
- orienting angularly the asymmetric initiation insert relative to the case to achieve a desired orientation of the non-circular perforation relative to the casing;
- placing an explosive material over the asymmetric initiation insert and in contact with a side wall of the case; and
- placing a liner over the explosive material, to hold the explosive material within the case,
- wherein the asymmetric initiation insert has a body that includes first and second channels that extend from a bottom surface to a top surface of the body, so that a detonation at the bottom surface is directed to first and second initiation points at the top surface, which correspond to the first and second channels.
Type: Application
Filed: Mar 2, 2021
Publication Date: Mar 10, 2022
Inventor: Wenbo YANG (Kennedale, TX)
Application Number: 17/189,366