RELIEF WELL INJECTION SPOOL APPARATUS AND METHOD FOR KILLING A BLOWING WELL

Abstract

A relief well injection spool for use in killing a well has a body with a pair of inlets opening to a bore on an interior of the body, a ram body cooperative with the bore of the body so as to selectively open and close the bore, an upper connector affixed to the body and adapted to connect the body to a lower end of a blowout preventer, and a wellhead connector affixed to a lower end of the body. Each of the pair of inlets has a valve cooperative therewith. The upper connector opens to the bore of the body. The wellhead connector is adapted to connect to a relief well wellhead. The wellhead connector also opens to the bore of the body. A floating vessel can be provided so as to deliver a kill fluid into at least one of the pair of inlets.

Claims

1. A relief well injection spool apparatus comprising: a blowout preventer; a relief well drilling system positioned at a surface of a body of water; a pipe extending from said relief well drilling system to said blowout preventer; a body having a pair of inlets opening to a bore on an interior of said body, each of said pair of inlets having a valve cooperative therewith; a ram cooperative with said bore of said body, said ram being selectively movable so as to open and close said bore; an upper connector affixed to said body so as to connect said body to a lower end of said blowout preventer, said upper connector opening to a bore of said body; a wellhead connector affixed to a lower end of said body, said wellhead connector adapted to connect to a relief well, said wellhead connector opening to the bore of said body; and a first line having one end connected to one of said pair of inlets, said first line extending to a surface location, said first line adapted to pass a kill fluid to one of said pair of inlets.

2. The relief well injection spool apparatus of claim 1, said pair of inlets positioned on diametrically opposed locations on said body.

3. The relief well injection spool apparatus of claim 1, said valve comprising: a first valve cooperative with the inlet so as to selectively open and close the inlet; and a second valve positioned in spaced relation to said first valve and cooperative with the inlet so as to selectively open and close the inlet.

4. The relief well injection spool apparatus of claim 3, each of said first and second valves being actuatably by a remotely-operated vehicle.

5. (canceled)

6. The relief well injection spool apparatus of claim 1, further comprising: a floating vessel connected to an opposite end of said first line, said floating vessel having a fluid storage tank and a pump thereon.

7. The relief well injection spool apparatus of claim 1, further comprising: a second line connected to another of said pair of inlets, said second line extending to the surface location.

8. (canceled)

9. The relief well injection spool apparatus of claim 1, further comprising: a drill pipe connected or interconnected to said wellhead connectors, said drill pipe extending to a primary well so as to connect to said primary well at a location below a seafloor.

10. A well killing system for killing a primary well in which the primary well has a wellbore extending to a producing reservoir, the well killing system comprising: a relief wellbore extending through a seabed so as to open to the primary well, said relief wellbore having a relief wellhead at a seafloor; a relief well injection spool affixed to said relief wellhead, said relief well injection spool having a body having an internal bore and a pair of inlets opening to said internal bore, each of said pair of inlets having at least one valve thereon so as to selectively open and close the inlet; a blowout preventer affixed to an end of said relief well injection spool opposite said relief wellhead; and a kill line connected to one of said pair of inlets of said relief well injection spool, said kill line adapted to pass a kill fluid into said relief well injection spool; and a floating vessel connected to said kill line, said floating vessel having a storage tank for the kill fluid and a pump for passing the kill fluid under pressure through said kill line, said kill line comprising a first kill line connected to one of said pair of inlets and a second kill line connected to another of said pair of inlets, said floating vessel comprising: a first floating vessel connected to said first kill line so as to pass the kill fluid to said one of said pair of inlets; and a second floating vessel connected to said second kill line so as to pass the kill fluid to another of said pair of inlets.

11. The well killing system of claim 10, said relief well injection spool having a ram body cooperative with said internal bore of said relief well injection spool, said ram body adapted to selectively close said internal bore of said relief well injection spool.

12. (canceled)

13. (canceled)

14. The well killing system of claim 10, further comprising: a relief well drilling system connected by pipe to said blowout preventer at an end of said blowout preventer opposite said relief well injection spool.

15. The well killing system of claim 10, said at least one valve comprising: a first valve cooperative with the inlet so as to selectively open and close the inlet; and a second valve positioned in spaced relation to said first valve and cooperative with the inlet so as to selectively open and close the inlet.

16. The well killing system of claim 10, further comprising: a manifold connected by said kill line to said one of said pair of inlets of said relief well injection spool, said manifold having the kill fluid therein.

17. The well killing system of claim 16, further comprising: a floating vessel connected by a line to said manifold, said floating vessel having a storage tank for the kill fluid and a pump for passing the kill fluid through said line to said manifold, said manifold being positioned at or adjacent to the sea floor.

18. A method for killing a well, the method comprising: forming a primary wellbore to a producing reservoir, forming a relief wellbore extending so as to open to the primary wellbore; affixing a relief well injection spool to a wellhead of the relief wellbore in which the relief well injection spool has a pair of valved inlets extending to a bore of the relief well injection spool; moving a floating vessel to a surface location above said relief well injection spool, said floating vessel having a storage tank for the kill fluid and a pump for passing the kill fluid under pressure from said storage tank; connecting said floating vessel to a line extending to one of said pair of inlets; and pumping the kill fluid under a pressure greater than a pressure of fluids flowing through the primary wellbore from said storage tank to the inlet; and flowing the kill fluid through the bore of said relief well injection spool, through said relief wellbore, and to said primary wellbore.

19. (canceled)

20. (canceled)

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0058] FIG. 1 is a perspective view of the relief well injection spool of the present invention.

[0059] FIG. 2 is a side elevational view of the relief well injection spool of the present invention.

[0060] FIG. 3 is a cross-sectional view of the relief well injection spool of the present invention is taken across lines 3-3 of FIG. 2.

[0061] FIG. 4 is a diagrammatic illustration of the method of killing a well in accordance with the present invention.

[0062] FIG. 5 is a diagrammatic illustration showing a method of killing a well in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0063] Referring to FIG. 1, there is shown the relief well injection spool 10 in accordance with the present invention. The relief well injection spool 10 includes a diverter inlet spool 12, an upper mandrel 14, a ram body 16, and a wellhead connector 18. The upper mandrel 14 is affixed to the upper side of the diverter inlet spool 12. The ram body 16 is affixed to an lower end of the diverter inlet spool 12 opposite the upper mandrel 14. The wellhead connector 18 is affixed to a lower end of the ram body 16 opposite the diverter inlet spool 12. The wellhead connector 18 is configured so as to connect to the relief well wellhead.

[0064] The diverter inlet spool 12 is configured so as to allow kill fluids to be introduced into the internal bore 20 extending through the diverter inlet spool 12, the ram body 16 and through the wellhead connector 18. In particular, the diverter inlet spool 12 includes a first inlet 22 and a second inlet 24 (not shown in FIG. 1). These inlets 22 and 24 will extend through the body of the diverter inlet spool 12 so as to have an inner end opening to the bore 20. The inlets 22 and 24 will have a diameter typically of 4 1/16 inches. A pair of valves 26 and 28 are configured so as to cooperate with the inlet 22. Valves 26 and 28 are isolation valves that are independently actuatable. The valves 26 and 28 are arranged in spaced relationship. The valve 26 includes a bucket 30. The valve 28 includes a bucket 32. Buckets 30 and 32 are configured so as to allow an actuator associated with an ROV to be used so as to open and close the valves, as required. As such, when the valves 26 and 28 are closed, then the kill fluid cannot flow through the inlet 22.

[0065] The inlet 24 has valves 34 and 36 cooperative therewith. The valves 34 and 36 are configured in the same manner as valves 26 and 28 associated with inlet 22. Valves 34 and 36 include ROV-receiving buckets thereon. Valves 34 and 36 are also isolation valves that are operable so as to open and close the inlet 24 so as to selectively allow the flow of a kill fluid therein. Inlets 22 and 24 are diametrically opposed on the diverter inlet spool. Suitable fluid lines can be connected thereto so as to deliver the kill fluid from a pumping vessel.

[0066] The mandrel 14 is affixed to the upper side of the diverter inlet spool 12. The upper mandrel 18 is configured so as to connect to the bottom of a blowout preventer. The bore 20 will have the same diameter as that of the blowout preventer. This diameter is approximately 18¾ inches.

[0067] The ram body 16 is affixed to the lower end of the diverter inlet spool 12. The ram body 16 includes selectively actuatable rams 40 and 42. These rams 40 and 42, when actuated, can extend across the bore 20 so as to seal the bore. Each of the rams 40 and 42 can have an ROV backup function.

[0068] FIG. 2 is a side view of the relief well injection spool 10. In FIG. 2, it can be seen that the mandrel 14 is located at the upper end of the diverter inlet spool 12. The ram body 16 is positioned below the diverter inlet spool 12. Ultimately, the wellhead connector 18 is affixed by flanges to the bottom of the ram body 16.

[0069] FIG. 3 illustrates a cross-sectional view of the relief well injection spool 10. As can be seen, the bore 20 will extend from the upper mandrel 14, through the diverter inlet spool 12, through the ram body 16, and through the wellhead connector 18. The inlets 22 and 24 are associated with a channel that opens to the bore 20. The valves 26 and 28 will communicate with the channel extending from the inlet 22. Similarly, the valves 34 and 36 will cooperate so as to act upon the channel associated with the inlet 24. It can further be seen that each of the inlets 22 and 24 includes a connector which allows the kill lines to be connected thereto.

[0070] When the kill fluid enters each of the inlets 22 and 24 and flows toward the bore 20, the blowout preventer (mounted upon the mandrel 14) will block upward fluid flow. As such, the kill fluids will flow downwardly in the bore 20 within the ram body 16. The fluids will then flow downwardly through the bore, through the wellhead connector 18 and outwardly into the relief wellbore 15 (as shown in FIG. 4). The ram body 16 is illustrated as having rams 40 and 42 cooperative therewith. The rams 40 and 42 can operate so as to close the bore 20, if desired.

[0071] FIG. 4 shows the use of the relief well injection spool 10 in association with a relief wellbore 50. In FIG. 2, it can be seen that the relief wellbore 50 extends through the seabed 52 so as to communicate with a primary wellbore 54. Primary wellbore 54 will extend from a wellhead 56 to a producing reservoir 58.

[0072] In the case shown in FIG. 4, the wellhead 56 has hydrocarbons 60 gushing therefrom. Hydrocarbons 60 will eventually flow toward the surface 62 of the body of water. As such, the present invention is implemented in those cases when such hydrocarbons 60 cannot be conventionally controlled.

[0073] The relief wellbore 50 is directly drilled through the seabed 52 so as to have one end opening to the primary wellbore 54. The relief wellbore 50 has a relief well wellhead 64 at the seabed 52. It can be seen that the relief well injection spool 10 is affixed to the relief wellhead 64. A blowout preventer 66 is then attached to the mandrel 14 of the relief well injection spool 10.

[0074] So as to allow for a kill fluid to pass through the relief well injection spool 10, through the relief wellhead 64 and into the relief wellbore 50, a pumping vessel 68 is provided adjacent to the relief well drilling system 70. The pumping vessel 68 has a storage tank with the kill fluid therein. The pumping vessel 68 can also include a pump which is cooperative with the kill fluid in the storage tank so as to transfer the kill fluid from the pumping vessel 68 under pressure to the line 72. The line 72 will extend so as to connect with one of the inlets of the diverter inlet spool 12 of the relief well injection spool 10. Another line 76 can extend from another pumping vessel 77 and connect with the other inlet of the diverter inlet spool 12. Alternatively, each of the lines 72 and 76 can extend from the pumping vessel 68 so as to deliver the kill fluid into the relief well injection spool 10 and, ultimately, into the primary wellbore 54 for the purposes of killing the well. The inlets 22 and 24 of the diverter inlet spool 12 are capable of allowing 200 barrels per minute of 2.0 specific gravity mud to be introduced into the relief wellbore 50. As stated hereinabove, when the hydrostatic pressure of the mud within the relief wellbore exceeds the pressure of the producing reservoir 58, the primary wellbore 54 is effectively killed.

[0075] In FIG. 4, it can be seen that there is a pipe 79 which extends from the relief well drilling system 10 to the top of the blowout preventer 66. A kill line 81 will extend from the relief well drilling system 70 and connect with the kill line inlet of the blowout preventer 66. A choke line 83 also extends from the relief well drilling system 70 so as to connect with a choke line inlet of the blowout preventer.

[0076] The relief well injection system 10 is a device that greatly increases the pumping capacity of a single relief well. The relief well injection system is installed on the relief well wellhead 64 beneath the blowout preventer 66 to provide additional flow connections into the wellbore 50. Using high-pressure flex lines, the inlets enable pumping units from the floating vessels 68 and 77, in addition to the relief well rig 70, to deliver a high-rate dynamic kill through a single relief well.

[0077] The relief well injection system 10 is designed with only components that are already used in proven in deepwater environments. The design is also relatively lightweight and modular. This allows the relief well injection system 10 to be transported on land, offshore, and by air freight.

[0078] The relief well injection system 10 performs the following basic functions: (1) connect and sealed to an 18¾ inch/15,000 p.s.i. wellhead housing; (2) provide an 18¾ inch/15,000 p.s.i. connection to the standard subsea blowout preventer 66; (3) provide one additional blowout preventer ram capable of shearing and sealing off the wellbore at 15,000 p.s.i. wellbore pressure when manually actuated (with a remotely-operated vehicle) via a remote subsea accumulator module; and (4) provide two subsea 4 inch horizontal flow line connectors for contingency bore access above the ram in a spool that can be opened or isolated from the wellbore by a pair of valves manually via a remotely operated vehicle.

[0079] In the in event of a blowout, relief well drilling should commence immediately as soon as a suitable rig 70 has been identified and mobilized. While the relief well is drilled, the relief well injection spool can be transported to the location. Preferably, the relief well injection spool 10 is installed prior to the blowout preventer 66, but this is not a requirement. Using downhole ranging techniques, the relief well task force locates the blowing well and directionally steers the wellbore 50 until it is finally aligned to intersect the blowing well at a planned depth. At this point, the kill-string casing will be run and cemented in place. If the relief well injection spool is not already installed, the relief well blowout preventer 66 should be disconnected from the wellhead and the relief well injection spool stack installed on the same wellhead. Subsequently, the blowout preventer 66 is reconnected on top of the relief well injection spool 10 and the flex lines 72 and 76 from the support vessels 68 and 77 are attached to the relief well injection spool inlets 22 and 24 using a remotely operated vehicle. After assembling the entire dynamic-kill pumping system, the relief well controls the final section and intersect the blowout well. Finally, a high-rate dynamic kill is achieved by simultaneously pumping down the relief well rig 70 and the support vessel 68 and 77 through the relief well injection spool 10.

[0080] As an example of a challenging dynamic kill in an offshore environment, the relief well drilled for the 2009 Montara blowout used a combination of the mud and cementing pumps of the rig to achieve a peak kill rate of sixty-eight barrels per minute. In a deep water environment, feasibility studies have shown that, in some cases, a kill rate approximately 100 barrels per minute may be achievable for a single relief well, depending on the available vessel/equipment and the blowout scenario. With current technology, a dynamic kill with a pump rate of 200 barrels per minute is considered far beyond the capability of a single relief well. FIG. 4 actually shows how the relief well injection spool 10, along with the vessels 68 and 77, can actually achieve this desired kill rate.

[0081] With reference to FIG. 4, the total pump rate required at the intersection between the relief wellbore 50 and the primary wellbore 54 is 200 barrels per minute. 40 barrels per matter pumped from the relief well rig 70 down the annulus. 20 barrels per matter pumped from the relief well 70 through the drill pipe 79. The flex line system made of line 72 and 76 extend from the vessels 68 and 77, respectively to the relief well injection spool 10. The surface distance from the support vessels 68 and 77 to the relief well rig 70 is for 500 meters. A 9⅝ inch casing is set prior to the intersection. There is a 5 inch drill pipe in the relief well 50. The maximum achievable pump pressure from the pumps within the vessel 68 and 77 is 550 bar.

[0082] Hydraulic simulations using OLGA-WELL-KILL were carried out for a blowout in 370 meters of water with a 1.2 specific gravity pressure reservoir at 1300 meters true-vertical depth. In this example, the relief well is assumed to intersect at approximately 1290 meters of true-vertical depth, just below the target/blowout well's 9⅝ inch casing shoe. It is assumed that the choke-and-kill lines are four inch lines and the flex lines connected to the relief well injection spool 10 has a five inch diameter. Based on a typical relief well designed with 9⅝ inch casings that just prior to intersecting, dynamic kill simulations with a 1.5 specific gravity mud indicate that a combined pump rate of 200 barrels per minute down a single relief well using the relief well injection spool 10 is unachievable. That is, the pump pressure for the kill plants located on the relief well rig 70 and each of the support vessel 68 and 77 will exceed 1000 bar. However, if only one of the support vessels is used for the dynamic kill, the pump pressure will be less than 500 bar on each kill plant (approximately 11,500 horsepower on the support vessel). Hence, with a typical relief well design, the maximum achievable kill rate is 130 barrels per minute using the relief well injection spool 10.

[0083] FIG. 5 shows a system 100 that is able to achieve the required 200 barrels per minute kill rate. The relief well design will need, in this case, to be optimized. In order to use larger flex lines 102 and 104 from the vessels 106 and 108, respectively, a manifold 110 is placed on the seafloor 112 next to the relief well injection spool 114. It can be seen that the blowout preventer 116 is connected by a pipe 18 to the relief well rig 120 located on the surface 122 of the body of water. A control unit 124 is connected to the relief well injection spool 114 so as to control the operation of the valves allow for the cooperation with the manifold 110. The flex line 114 can flow by way of a lower marine riser package 126. Alternatively, it can flow from pipe 104 into a blowout preventer or to another spool. A flexible flow line 128 can then extend from the lower marine riser package 126 to the manifold 110. The manifold 110 has lines 130 and 132 that are connected to the separate inlets of the relief well injection spool 114.

[0084] In this case, the simulation results indicate that the pressure and the horsepower were achievable for all the kill plants. The maximum pressure and horsepower requirements are on the support vessel kill plants, with 300 bar and 7600 horsepower, respectively. Therefore, a 200 barrel per minute dynamic kill is feasible for a shallow water blowout, if the relief well design is optimized and the relief well injection spool 114 is used.

[0085] Similar to the shallow water blowout example, hydraulic simulations were done for a deep water blowout having a water depth of 1500 meters with 1.2 specific gravity and the pressure reservoir at 5500 meters of true vertical depth. In this case, it was assumed the relief well would intersect at approximately 5450 meters of true vertical depth. This would be just below the 14 inch casing shoe of the blowing well. A 1.75 specific gravity kill mud, in this case, is necessary to bring the well to static conditions. With a typical relief well design (e.g. 9⅝ inch casings set just prior to intersecting), the maximum achievable combined pump rate is 90 barrels per minute (i.e. 20 barrels per minute down the five inch drill pipe, 30 barrels per minute down the four inch choke-and-kill lines, and 40 barrels per minute through the five inch flex lines from each of the support vessels).

[0086] As in the previous example, to achieve the required 200 barrel per minute kill rate, the relief well will need to be optimized with 4.5 inch choke-and-kill lines, six inch flex lines, and a 14 inch casing plus 300 meters of 9⅝ inch liner. The maximum pressure and horsepower requirements are on the support vessel kill plants with 325 bars and 8080 horsepower, respectively. Again, a 200 barrel per minute dynamic kill is also feasible for a deep water blowout if the relief well design is optimized and the relief well injection spool is utilized.

[0087] From the analysis of the relief well injection spool, it was found that the relief well injection spool of the present invention is able to achieve significant benefits over prior offshore blowout control attempts. The relief well injection system can provide cost savings by eliminating casing strings on well designs driven by dynamic-kill requirements. The use of the relief well injection spool will likely move the additional mud and pump storage challenges from the rig to remotely located support vessels. The support vessels can wait to mobilize closer to the time of relief well intersection. As such, the loading of kill fluid can be performed on an onshore terminal while the relief well is drilled. The relief well injection spool can eliminate the necessity of installing additional pumps and storage tanks on the relief well rig. The relief well injection spool also eliminates the use of boats in close proximity to the relief well. As such, safety concerns in this regard are addressed. The relief well injection spool system is independent of the relief well rig and equipment. Hence, any rig could be chosen for the relief well operation. The relief well injection spool will only require a suitable wellhead and blowout preventer connections that fit the relief well. The relief well injection spool and the additional equipment should be pre-fabricated, maintained, and air freightable so as to enhance the mobilization time. As such, the relief well injection spool is an important tool for well-designed oil spill contingency planning. The present invention ensures that a potential worst-case blowout scenario can be killed with a single relief well.

[0088] Typically, the relief well intersection point is as deep as possible, but above the top of the reservoir. This is desirable to achieve a maximum frictional and hydrostatic pressure in the blowing wellbore during the dynamic kill. The relief well injection spool offers benefits on blowouts that do not require a high-rate dynamic-kill rate. Because the relief well injection spool facilitates a higher kill rate than typical relief wells, it may be possible to intersect a blowing well at a shallower depth. Based on the blowout scenario, this can reduce drilling time, eliminate casing strings on the relief well, and, by saving time for a relief-well intervention, it may limit hydrocarbon discharge and pollution from a blowout.

[0089] The simulations presented herein illustrate the clear potential for the relief well injection spool to increase the pump capacity to the relief well wellhead significantly. The relief well injection spool can, in some cases, provide a high rate dynamic kill through a single relief well, which otherwise would have only been possible with multiple relief wells. When planning a high-rate dynamic kill operation using the relief well injection spool, the entire relief well configuration and design will need to be optimized. For shallow, prolific wells with low reservoir pressure, the relief well injection spool can be an alternative to drilling two relief wells. Significant benefits for the relief well injection spool are also possible for deepwater blowouts. Relief wells designed to stop a blowout from deepwater wells are restricted by long choke-and-kill lines for pumping. This bottleneck is removed when introducing additional inlets at the wellhead.

[0090] The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made within the scope of the appended claims without departing from the true spirit of the invention. The present invention should only be limited by the following claims and their legal equivalents.