Patent Grant
10961827
None.
This invention relates, in general, to a method and apparatus for perforating wells, and more particularly to tubing conveyed perforating systems with safety features.
Without limiting the scope of the present invention, its background will be described with reference to perforating a hydrocarbon bearing subterranean formation with a shaped-charge perforating gun, as an example.
After drilling the section of a subterranean well bore that traverses a hydrocarbon bearing subterranean formation, individual lengths of metal tubular casings are typically secured together to form a casing string that is positioned within the well bore. The casing string increases the integrity of the well bore and provides a path through which fluids from the formation may be produced to the surface. Conventionally, the casing string is cemented within the well bore.
To produce fluids into the casing string, the casing string may be perforated with a perforating gun containing multiple shaped explosive charges actuated by a firing head. A variety of different firing heads and perforating guns are known in the prior art. In some embodiments, when the firing head is actuated, a primary explosive is detonated and ignites a booster charge connected to a primer cord. The primer cord transmits a detonation wave to the shaped charges, which are activated to create explosive gas jets for penetrating well casing and the surrounding geologic formations.
It is known that perforating guns and associated apparatus can be configured as an electric wireline perforating (“EWP”) system or a tubing conveyed perforating (“TCP”) system. Each of these systems, as they are known in the prior art, has advantages and disadvantages. EWP systems utilize electrical detonators that may be initiated by an electrical signal. Because an electrical signal is used to initiate detonation, it is critical that all well equipment, including the wellhead, derrick and logging unit, be properly grounded before perforating operations are started. To avoid inadvertent detonation, electrical detonators should not be utilized during electrical or static-generating dust storms. Moreover, perforating operations involving electrical detonators should not be performed while a mobile transmission set (e.g., a radio or telephone) is in operation within a predetermined distance of the well and/or a perforation truck.
In view of potential safety issues associated with EWP systems, TCP systems are often preferred in the industry. TCP systems require hydraulic pressure and/or mechanical force in order to initiate the perforating gun, which eliminates accidental electrical firing from, for example, stray voltage from cathodic protection (low voltage electrical source between well head, casing, and fluids to prevent corrosion), or surface power generation (cell phone or radio transmission, overhead lines, or welding), or lighting strike, among others. TCP systems allow the attachment of firing heads after the perforating guns are positioned in the well bore. In fact, recommended safety practices (as established by API RP67) for TCP systems include the use of a minimum 10-ft safety spacer to be run at the top of the perforating gun string, between the firing head and first loaded charge, so that the guns are positioned below ground level before installing the firing head. In contrast, EWP systems typically require the wiring and/or installing of an electrical detonator on the surface, making these type EWP perforating guns “live” on the surface. TCP system firing head explosive components are also typically designed with additional safety features to prevent accidental firing, such as minimum no-fire impact requirements and matched geometry of the firing pin and a percussion initiator.
An example of a TCP system is one that includes a mechanical firing head (“MFD”); e.g., a firing head designed to actuate upon impact from a dropped device (often referred to as a “drop bar”). In these systems, a drop bar is typically dropped within the TCP string at the appropriate moment. Gravity forces the drop bar downward and into contact with a firing head. There are several different firing heads known in the prior art. For example, the firing head may have a firing pin (or other mechanical element) mechanically held in place (e.g., by one or more shear pins). When the drop bar is dropped, the drop bar will impact a structural element (e.g., a firing piston assembly) portion of the firing head that is either connected with the firing pin or impacts the firing pin. The force of the impact shears the shear pin(s) heretofore holding the firing pin in place. The firing pin is thereby actuated to engage a percussion initiator, which in turn actuates the perforating gun to create the casing perforations. Some prior art TCP systems utilize a safety firing head (sometimes referred to as “safety mechanical firing head”, or “SMFD”), that uses hydraulic pressure to positionally lock the firing pin rather than a shear pin. In these SMFD devices, once certain conditions are met (e.g., sufficient hydraulic pressure within the well bore), the firing pin is unlocked and can be actuated by a drop bar.
While TCP systems have been proven relatively safe over time, there is nonetheless value in improving the safe operation of TCP systems. For example, a TCP system that utilizes a mechanical firing head can encounter a scenario wherein a drop bar is dropped to impact a firing head, but the firing head does not initiate and the perforating gun does not cause perforation of the casing string. There are several potential reasons that such a failure may occur, including: a collapse in the tubing used to convey the TCP guns to proper depth; a shoulder inside the tubing (e.g., a no-go if installed incorrectly); fill from pipe scale; fill from drilling mud when solids come out of suspension (water-based mud); the drop bar impacts the firing pin, but the shear pin holding the firing pin does not shear due to improper assembly or insufficient energy; the drop bar impacts the firing pin, but the firing pin is worn and therefore does not possess the proper geometry to cause initiation of the percussion initiator; the drop bar impacts the firing pin, and the firing pin impacts the percussion initiator, but the percussion initiator does not initiate, etc.
In those instances wherein a prior art firing head/perforating gun is defectively actuated, the uninitiated energetic material is a significant safety concern. The protocol in such instances typically is to retrieve (“fish”) the drop bar using wireline conveyed retrieval equipment (sometimes referred to as a “pulling tool”). It is not, however, always possible to retrieve a drop bar in this manner. If it is not possible to retrieve the drop bar, then the entire unfired firing head/perforating gun may be retrieved. In some instances, it is necessary to make a decision regarding whether to retrieve the unfired perforating gun with the drop bar still inside the firing head. Retrieval in this manner includes the risk that the unfired perforating gun may initiate at an unintended time, thus perforating the casing at an undesirable depth. Even if the drop bar is retrieved, the potential for unintended firing still exists.
According to an aspect of the present disclosure, a tubing conveying perforating system is provided. The system includes a perforating gun and a firing head. The firing head includes a housing, a firing pin and a percussion initiator. The firing pin is configured to degrade over a predetermined period of time from an initial state to a degraded state, and in the degraded state the firing head is inoperable.
According to another aspect of the present disclosure, a firing head is provided. The firing head includes a firing pin and a percussion initiator. The firing pin is configured to degrade over a predetermined period of time from an initial state to a degraded state, and in the degraded state the firing head is inoperable.
According to another aspect of the present disclosure, a method of operating a firing head is provided. The method includes: disposing a firing head in communication with a perforating gun within a casing string of a well bore, which well bore contains well bore fluids, wherein the firing head includes a firing pin and a percussion initiator, and wherein the firing pin is configured to degrade over a predetermined period of time from an initial state to a degraded state, and in the degraded state the firing head is inoperable; determining whether the firing head has failed to actuate the percussion initiator; and permitting an ingress of well bore fluid into the housing and in communication with the firing pin.
In any of the aspects and embodiments of the present disclosure, the firing pin may be configured to mate with the percussion initiator in the initial state, and does not mate with the percussion initiator in the degraded state.
In any of the aspects and embodiments of the present disclosure, the firing pin may include a protruding end surface, and the percussion initiator may include a depression, and the protruding end surface mates with the depression.
In any of the aspects and embodiments of the present disclosure, the protruding end surface may be substantially conically shaped, and the depression may be substantially conically shaped.
In any of the aspects and embodiments of the present disclosure, the firing pin may include a material that degrades by one or more of dissolution, erosion, swelling, chemical change, or electrochemical reaction when in contact with one or more well bore fluids.
In any of the aspects and embodiments of the present disclosure, the firing pin may include a material having a mechanical strength that decreases when in contact with one or more well bore fluids.
In any of the aspects and embodiments of the present disclosure, the firing head housing may include a port that is selectively openable to an open configuration, and in the open configuration is configured to allow an ingress of well bore fluid into the housing and in communication with the firing pin.
In any of the aspects and embodiments of the present disclosure, the housing may include a port sealed by a plug, and a step of permitting an ingress of well bore fluids into the housing may include maintaining the firing head within the casing string a period of time adequate for the plug to fail to an open configuration, and in the open configuration the port is configured to allow well bore fluids into the housing in communication with the firing pin.
In any of the aspects and embodiments of the present disclosure, the firing head housing may include a port sealed by a plug, and a step of permitting an ingress of well bore fluids into the housing may include creating a pressure within the casing string adequate to cause the plug to fail to an open configuration, and in the open configuration the port is configured to allow well bore fluids into the housing in communication with the firing pin.
In any of the aspects and embodiments of the present disclosure, the firing head housing may include a port sealed by a valve, and a step of permitting an ingress of well bore fluids into the housing may include creating a pressure within the casing string adequate to cause the valve to open and allow well bore fluids into the housing in communication with the firing pin.
It is noted that various connections are set forth between elements in the following description and in the drawings. It is noted that these connections are general and, unless specified otherwise, may be direct or indirect and that this specification is not intended to be limiting in this respect. A coupling between two or more entities may refer to a direct connection or an indirect connection. An indirect connection may incorporate one or more intervening entities. It is further noted that various method or process steps for embodiments of the present disclosure are described in the following description and drawings. The description may present a method and/or process steps in a particular sequence. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the description should not be construed as a limitation.
Aspects of the present disclosure include a TCP firing head 20 that can selectively be rendered inoperable, a TCP system 16 that uses such a firing head 20, and a method of operating such a firing head 20. In most embodiments, the present disclosure firing head 20 includes a housing 22, a firing pin 24, and a percussion initiator 26 (e.g., see
In some embodiments of the present disclosure, the firing head 20 includes a firing pin 24 and a percussion initiator 26 having mating geometries; e.g., the percussion initiator may include a contact surface having a depression 38 (e.g., the female half of the mating pair) that mates with a protruding end surface 40 of the firing pin 24 (e.g., the male half of the mating pair). The percussion initiator 26 is configured such that under normal operating circumstances, the percussion initiator 26 will not detonate unless contacted with a firing pin 24 having a protruding end surface 40 that mates with the percussion initiator contact surface depression 38. In these embodiments, a portion of the firing pin 24 (e.g., the protruding end surface 40) comprises a degradable material that causes the portion of the firing pin 24 to change under certain well bore conditions (temperature, exposure to well bore fluids, etc.) from an initial geometry to a second geometry that cannot mate with the percussion initiator contact surface depression 38 in a manner adequate to cause the percussion initiator 26 to actuate. The change in geometry thus renders the TCP system 16 inoperable. In an alternative embodiment, the contact surface depression 38 of the percussion initiator 26 may include a degradable material that prevents actuation by the firing pin 24.
In some embodiments of the present disclosure, the firing head 20 includes a firing pin 24 that is configured to possess mechanical strength sufficient to impact the percussion initiator contact surface and cause initiation of the percussion initiator 26. In these embodiments, at least a portion of the firing pin 24 comprises a degradable material that causes the mechanical strength of at least a portion of the firing pin 24 to decrease to a point wherein the firing pin 24 no longer possesses mechanical strength sufficient to impact the percussion initiator contact surface and cause initiation of the percussion initiator 26.
The term “degradable material” as used herein may be any material that is configured to degrade by one or more mechanisms such as, but not limited to, dissolving, erosion, swelling, undergoing a chemical change, electrochemical reaction, or any combination thereof.
Degradation by swelling may involve absorption by the degradable material of aqueous fluids or hydrocarbon fluids present within the well bore environment such that the mechanical properties of the degradable material degrade or fail. In degradation by swelling, the degradable material absorbs the aqueous and/or hydrocarbon fluid until the firing pin 24 is no longer able to cause initiation of the percussion initiator 26; e.g., lacks mechanical strength or has changed geometry to a degree that it is no longer able to cause initiation of the percussion initiator 26.
Degradation by dissolving or eroding may involve a degradable material that is soluble or otherwise susceptible to an aqueous fluid or a hydrocarbon fluid, such that the aqueous or hydrocarbon fluid is not necessarily incorporated into the degradable material (as is the case with degradation by swelling), but the degradable material becomes soluble or erodes upon contact with the aqueous or hydrocarbon fluid and within a useful period of time the firing pin 24 is degraded to a degree that the firing pin 24 is no longer able to cause initiation of the percussion initiator 26.
Degradation by undergoing a chemical change may involve breaking the bonds of the backbone of the degradable material (e.g., a polymer backbone) or causing the bonds of the degradable material to crosslink, such that the degradable material becomes brittle and within a useful period of time the firing pin 24 is degraded to a degree that the firing pin 24 is no longer able to cause initiation of the percussion initiator 26.
The present disclosure is not limited to a material that degrades at any particular rate, as long as the rate of degradation (and therefore the minimum total amount of time) is useful for the application at hand. For most applications, a material that degrades an amount that is sufficient to make the firing head 20 inoperable within a maximum of about twenty four hours (24 hrs.) is acceptable. In some applications, a material that degrades an amount that is sufficient to make the firing head 20 inoperable within a range of time of about one to twelve hours (1-12 hrs.) is preferred. The aforesaid period of time necessary for adequate degradation may, of course vary depending on factors such as the type of degradable material selected, the conditions of the well bore environment, and the like.
Examples of acceptable degradable materials include borate glass, polyglycolic acid (PGA), polylactic acid (PLA), a degradable rubber, degradable polymers, galvanically-corrodible metals, dissolvable metals, dehydrated salts, thermoplastic polymers, and any combination thereof. With respect to degradable polymers used as a degradable material, a polymer is considered to be “degradable” if the degradation is due to, in situ, a chemical and/or radical process such as hydrolysis, oxidation, or UV radiation. Degradable polymers, which may be either natural or synthetic polymers, include, but are not limited to, polyacrylics, polyamides, polyanhydrides, polyolefins (e.g., polyethylene, polypropylene, polyisobutylene, etc.), polyglycolic acid, and polylactic acid. With respect to galvanically-corrodible metals used as a degradable material, the galvanically-corrodible metal may be configured to degrade via an electrochemical process in which the galvanically-corrodible metal corrodes in the presence of an electrolyte (e.g., brine or other salt-containing fluids present within the well bore). Examples of galvanically-corrodible metals include, but are not limited to, gold, gold-platinum alloys, silver, nickel, nickel-copper alloys, nickel-chromium alloys, copper, copper alloys (e.g., brass, bronze, etc.), chromium, tin, aluminum, iron, zinc, magnesium, and beryllium.
As indicated above, aspects of the present disclosure can be used with a variety of different firing head 20 configurations and therefore is not limited to any particular configuration unless otherwise stated herein. To illustrate aspects of the present disclosure, a particular firing head 20 example is shown in
A non-limiting example of a percussion initiator 26 that can be used with the present disclosure firing head 20 is produced by the Fike Corporation of Blue Springs, Mo., USA.
Given an adequate amount of force, the mating geometries of the depression 38 and the protruding end surface 40 permit the impact of the firing pin 24 to cause the percussion initiator 26 to actuate. Absent the mating geometries, impact between the firing pin 24 and the percussion initiator 26 will not cause the percussion initiator 26 to actuate.
According to an aspect of the present disclosure, the present disclosure may include a firing head 20 having a firing pin 24 with a protruding end surface 40 comprising a degradable material that degrades (e.g., changes geometry) under certain well bore conditions (temperature, exposure to well bore fluids, etc.). In an initial non-degraded form, the firing pin protruding end surface 40 possesses a geometry that mates with the depression 38 of the percussion initiator 26 and therefore can cause actuation of the percussion initiator 26. However, the degraded form of the firing pin protruding end surface 40 geometry no longer mates with the depression 38 of the percussion initiator 26 and therefore cannot cause actuation of the percussion initiator 26. Hence, the firing head 20 (and therefore the perforating gun 18) of the TCP system 16 is rendered inoperable.
The non-limiting firing head 20 embodiment shown in
In the operation of the present disclosure (e.g., see
Pursuant to the present disclosure and in the event the firing head 20 does not actuate the percussion initiator 26, the present disclosure provides a mechanism and/or methodology wherein the firing head 20 may be rendered inoperable within a useful period of time. For example, embodiments of present disclosure firing heads 20 may be configured to permit the ingress of well bore fluids into the housing interior cavity 32, thereby exposing the firing pin 24 to the well bore fluids; e.g., via a port disposed within the firing head housing. The well bore fluids, in turn, can within a useful period of time cause the firing pin 24 to degrade to an extent wherein the firing pin 24 is no longer configured in a form able to initiate the percussion initiator 26, thereby rendering the firing head 20 inoperable. As stated above, the specific mechanism by which the firing pin 24 degrades may vary depending upon the particular embodiment; e.g., the protruding end surface 40 of the firing pin 24 may dissolve, erode, or swell to a form wherein it no longer mates with a depression 38 formed in the percussion initiator 26; or the firing pin 24 may degrade such that it no longer possesses sufficient mechanical strength to actuate the percussion initiator 26, etc.
In some instances, it may be difficult to determine whether a firing head 20 has been completely actuated (e.g., if the TCP system 20 does not include a mechanism for determining whether the firing head 20 has initiated, whether the firing head 20 has initiated the percussion initiator 26, etc.) or undesirable to make such a determination. In those instances, or as a matter of regular course, a TCP system 16 according to the disclosure may be operated such that the firing head 20 is not removed from the well bore until the firing head 20 is known to be inoperable. For example, a TCP system 16 may include a firing head 20 that will become inoperable after a predetermined period of time within the well bore (e.g., a firing head housing having a port that permits an ingress of well bore fluids into the housing interior cavity 32, thereby exposing a firing pin 24 having a degradable material to the well bore fluids). In these instances, the firing head 20 is held within the well bore and only removed after the expiration of the predetermined amount of time. Hence, there is no need to determine if the firing head 20 has successfully actuated.
While various embodiments of the present disclosure have been disclosed, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the present disclosure. For example, the present disclosure as described herein includes several aspects and embodiments that include particular features. Although these features may be described individually, it is within the scope of the present disclosure that some or all of these features may be combined with any one of the aspects and remain within the scope of the present disclosure. Accordingly, the present disclosure is not to be restricted except in light of the attached claims and their equivalents.
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