WO2017123827A1 - Dynamic offshore vessel positioning technique - Google Patents

Abstract

A technique for safely maintaining a vessel adjacent a rig. The technique includes utilizing a global positioning system (GPS) of the vessel to establish a target location and concentric zones about the location, a first closer to the target location and a second about the first. In this way, thrusters of the vessel may be operated at selective power levels depending on which zone the vessel resides in. Additional features such as a remote release device and floatation capability and a weight on the hose may also be employed. In total, a fuel efficient system that allows for safer and more available vessel use even in circumstances of more severe weather is provided.

Description

DYNAMIC OFFSHORE VESSEL POSITIONING TECHNIQUE

CROSS REFERENCE TO RELATED APPLICATIONS)

[0001] This Patent Document claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application Serial Number 62/279,254, entitled Method for Enhanced Station Keeping While on Dynamic Positioning, filed on January 15, 2016, which is incorporated herein by reference in its entirety.

BACKGROUND

[0002] Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years, well architecture has become more sophisticated where appropriate in order to help enhance access to underground hydrocarbon reserves. For example, as opposed to land based oilfields accommodating wells of limited depth, it is not uncommon to find offshore oilfields with wells exceeding tens of thousands of feet in depth. Furthermore, today's hydrocarbon wells often include a host of lateral legs and fractures which stem from the main wellbore of the well toward a hydrocarbon reservoir in the formation.

[0003] The above described fractures may be formed by a fracturing operation, often referred to as a stimulation operation. The stimulation or fracturing operation, involves pumping of a fracturing fluid at high pressure into the well in order to form the fractures and stimulate production of the hydrocarbons. The fractures may then serve as channels through the formation through which hydrocarbons may reach the wellbore. The indicated fracturing fluid generally includes a solid particulate referred to as proppant, often sand. The proppant may act to enhance the formation of fractures during the fracturing operation and may also remain primarily within fractures once formed. In fact, the fractures may remain open in part due to their propping open by the proppant.

[0004] The above described stimulation operations may be quite challenging to carry out in offshore circumstances. That is, the ability to store massive volumes of proppant and other constituents at an offshore well platform for such operations is generally not practical. The platform is of limited footspace and already accommodates more regularly needed well service equipment, hardware, an entire workforce and even housing and supplies for the workforce. Thus, accommodating large volumes of stimulation materials that are not essential throughout the life of the well is less practical.

[0005] However, instead of attempting to store such materials at an offshore platform, a stimulation vessel capable of supplying sufficient materials for the operations may be navigated to the vicinity of the platform. In this way, massive quantities of stimulation materials may be kept offsite until needed for the stimulation operations.

[0006] A stimulation vessel may be equipped with several thrusters for positioning in a specific location on the water adjacent the platform during operations. High pressure hoses of about 100 meters in length may then be hooked up to equipment at the platform in order to deliver fracture materials in support of the operations. For example, the vessel may be kept at a target location about 25 meters from the platform with the hose having some slack allowing for some range in movement of the vessel on the water.

[0007] Of course, keeping the vessel near a safe targeted location may be quite important. For example, the vessel drifting too far from the platform may risk hose damage or breaking and an interruption of operations, not to mention spillage of fracturing slurry materials into the sea. By the same token, the vessel is likely to be 3,000-10,000 metric tons or more. Thus, accidental ramming of the vessel into the platform could also lead to damage, even if at relatively slow speeds due to the massive size of the vessel and platform. This may pose a risk to equipment, operations and the like.

[0008] Due to underwater architecture and other factors, the vessel is not generally anchored. Therefore, the vessel is equipped with a dynamic positioning system that is used to keep the vessel in the targeted zone of safety for delivery of materials as indicated above. The system is used to automatically control the above mentioned thrusters in response to waves and general motion of the sea. Thus, the reliability of the system is particularly important during times of more severe weather.

[0009] As a matter of protocol, the dynamic positioning system is programmed with redundancy, for example, to utilize no more than 45% of available power so as to always leave the vessel with at least half of its power in reserve. Further, as noted, the vessel is in relatively close proximity of the platform. Thus, any significant turbulence or "excursion" from wave swells, heights or other weather related issues is likely to lead to the need for an immediate and significant thruster response in order to hold the vessel in position.

[0010] Unfortunately, the continual need for immediate dramatic thruster response not only risks utilizing greater than 45-50% power but it is also an inefficient manner of operating the vessel. That is, the weather forecast may not only help to determine if positioning of the vessel is practical and safe but also how efficient it is to keep the vessel safely positioned from a fuel cost standpoint. Therefore, as a practical matter, many offshore platforms are simply considered unserviceable by stimulation vessels or other large supply carriers under certain weather conditions, often dictated by the time of year. SUMMARY

[0011] A method of dynamic positioning of a vessel adjacent an offshore rig is disclosed. The method includes establishing a first power response zone for the vessel at a given distance from the rig and a second power response zone for the vessel at another distance from the rig that is less than the given distance and encompasses the first zone. The vessel is then positioned at a target location in the first power response zone. Thus, positioning thrusters of the vessel may be operated at a first predetermined power level to direct the vessel to the target location when straying therefrom in the first power response zone. Similarly, the thrusters may be operated at a second power level greater than the first power level to direct the vessel to the target location when straying therefrom and reaching into the second power level response zone.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Fig. 1 is an overview of an offshore oilfield with a rig serviced by a vessel employing an embodiment of a dynamic positioning system.

[0013] Fig. 2 is a top view of the vessel of Fig. 1 employing the dynamic positioning system to remain within a predetermined region.

[0014] Fig. 3 is a top view of potential vessel positions adjacent the offshore rig and enabled by the dynamic positioning system

[0015] Fig. 4A is a chart plotting occurrences of significant wave heights in a zone around the offshore rig that encompasses the predetermined region of Fig. 2.

[0016] Fig. 4B is a chart and table illustrating increased productive vessel time for rig operations due to the dynamic positioning system in spite of Fig. 4A wave heights. [0017] Fig. 5A is a side view of an embodiment of a remotely actuatable release device for securing a hose from the vessel to the rig and for releasing the hose back.

[0018] Fig. 5B is another overview of the rig serviced by the vessel and utilizing a laterally movable weight for centering of the hose therebetween.

[0019] Fig. 6 is a flow-chart summarizing an embodiment of employing a dynamic vessel positioning system.

DETAILED DESCRIPTION

[0020] In the following description, numerous details are set forth to provide an understanding of the present disclosure. However, it will be understood by those skilled in the art that the embodiments described may be practiced without these particular details. Further, numerous variations or modifications may be employed which remain contemplated by the embodiments as specifically described.

[0021] Embodiments are described with reference to certain offshore applications serviced by a rig with the aid of a vessel. For example, stimulation applications utilizing a supply of stimulation fluid provided by the vessel is described. However, a variety of different well applications may take advantage of the unique techniques for tethering a vessel to an offshore structure such as a rig or even another vessel as detailed herein. In fact, for any circumstance in which a vessel is to be positioned adjacent a rig, appreciable benefit may be realized from establishing multiple zones with different thruster power responses to maintain the vessel at an appropriate distance from the rig.

[0022] Referring now to Fig. 1, an overview of an offshore oilfield 101 is shown with a rig 150 serviced by a vessel 110 employing an embodiment of a dynamic positioning system. The system includes a standard user interface, display screen, GPS functionality and other conventional features. For example, with brief added reference to Fig. 2, a portion of the display 200 may be seen where multiple geographic zones 250, 275 are represented about a target location 100. Returning to Fig. 1, the target location 100 for the vessel 110 is at a predetermined geographic spot adjacent the rig 150.

[0023] The target location 100 is the location at the sea surface where the vessel 1 10 is "parked". However, for a variety of reasons, the vessel 110 is not actually anchored and resides over a body of water 190. Thus, the vessel 110 does not tend to remain stationary, particularly during periods of harsh weather. Therefore, thrusters of the vessel 110 are utilized to continuously re-direct the vessel 100 back toward the target location 100 whenever it begins to drift away from the location 100. As shown, in Fig. 1, the target location 100 is aligned with the center of the vessel 100 and thruster action is not required at the moment depicted. However, as shown in Fig. 2, a bit of drift has occurred and there will be some need for thruster action as guided by the unique dynamic positioning techniques detailed herein.

[0024] Continuing with reference to Fig. 1, the vessel 110 is shown tethered to the rig 150 by a hose 125 that is used to deliver, in a non-limited example, a slurry for a stimulation application in a well 180. As discussed below, the hose 125 may be lightweight and need not be rated to excessive pressures. For example, the hose 125 may be rated to manage up to about 5,000 PSI. The rig 150 includes a host of operational equipment 175 and a crane 155 to aid in attaining the hose 125 from the vessel 110. However, once the hose 125 is secured as shown, keeping the vessel 110 near the target location 100 helps to avoid collision with the rig 150, which could be damaging to the rig 150 or the vessel 110 even at relatively slow speeds due to the massive tonnage of both bodies. By the same token, keeping the vessel 1 10 near the target locations 100 also helps to avoid breaking the hose 125 should the vessel tend to drift further away from the rig 150.

[0025] While a conventional hose may be about 100 meters in length with the vessel 110 positioned about 25 meters from the rig 150, for the embodiment shown, a hose length of about 150-300 meters may be utilized with the vessel positioned at about 75-250 meters from the rig 150. This is made practical where the hose 125 is sufficiently light in construction when combined with the dynamic positioning techniques detailed below. In one embodiment, the hose 125 is a steel reinforced lightweight polymer hose that may safely move further away from (127) or closer to (129) the rig 150 over a distance (D) that exceeds 75 meters. This degree of latitude is not available where the vessel 110 is positioned closer to the rig 150 and utilizes a substantially shorter hose 125. Indeed, when the vessel is positioned at 25 meters out, the safe zone in which the vessel 110 may be allowed to move should not exceed more than 5-10 meters. Thus, extremely high powered immediately responsive thruster control is necessary at all times.

[0026] As with any vessel serviced offshore operation at a rig 150, time is spent 1) securing the hose 125 to the rig 150 (which may be upwards of an hour), 2) running operations (perhaps 1-5 days in stimulation operations) and 3) returning the hose 125 to the vessel 1 10 (perhaps another hour). Weather may have a significant impact on any of the phases of the operation. However, the dynamic positioning techniques detailed below make the odds of weather significantly affecting the longest of these phases (e.g. 2) running operations) dramatically less likely due to the above noted latitude afforded to the hose 125 and vessel 110 location. That is, without undue concern over the vessel 110 colliding with the rig 150 that is 25 meters away or a need for an immediate high power responsive thrust in light of weather conditions, operations may run more continuously and/or on days previously not considered available for operating as detailed below. In fact, as detailed further below, weather related concerns over the third phase (e.g. 3) returning the hose), may also be minimized. Thus, only the initial phase of securing the hose may still be based largely on weather conditions. Fortunately, however, unlike phases 2 and 3, an operator can always pick when to start a job. Therefore, this is much more minimal of a concern.

[0027] Once secured to the rig 150, the hose 125 may be used to deliver, for example, slurry for the stimulation application. More specifically, the slurry may be pumped through a tubular within a riser 140, eventually reaching the well 180. The well 180 itself may traverse thousands of feet through a formation 195 below a seabed 197 eventually reaching a production region that is targeted by the slurry for the stimulation. In the embodiment shown, the operation is carried out with reliance on a semi-submersible version of a rig 150 with the riser 140 as indicated. Accordingly, a host of tendons 130 are secured to anchors 135 embedded below the seabed 197 to immobilize the rig 150. Of course, however, a variety of different equipment and rig architectures may be employed.

[0028] Referring now to Fig. 2, a top view of the vessel 110 of Fig. 1 is shown employing the dynamic positioning system to remain within a predetermined region 200. The target location 100 is the center point of the predetermined region 200 with the region 200 defined in light of the amount of acceptable drift or latitude. For example, as noted above, in one embodiment, there may be an acceptable 75 meters of safe zone from the target location 100. In such an embodiment, a radius of 50 meters from the target location may be used to establish the area of the predetermined region 200. [0029] With the predetermined region 200 established, it is apparent in Fig. 2, that the region is further divided into separate zones 250, 275 about the target location 100. For example, a first low power response zone 250 is defined with a perimeter immediately about the target location 100 with the next outer region being a second moderate power response zone 275. In an embodiment where the entire predetermined region 200 includes a radius of 50 meters, the low power response zone 250 may have about a 30 foot radius with the remainder of the region 200 constituting the moderate power response zone.

[0030] As the terms imply, the response zones 250, 275 are characterized by the power applied to thrusters of the vessel 110 in directing it back to the target location 100 in circumstances where it has drifted away. In the specific example shown in Fig. 2, GPS information acquired by the system indicates that the vessel 110 has indeed drifted somewhat away from the target location 100 but is still in the low power zone 250. Thus, low power is employed by thrusters of the vessel 1 10 in order to direct it back toward the target location 100 (see arrow 201). Of course, in cases where low power thruster application has failed to be sufficient and the vessel 110 has drifted outside of the low power zone 250 and into the moderate power zone 275, an application of moderate power to the thrusters would kick in. By the same token, if the vessel 110 makes it entirely outside of both zones 250, 275 and the entire region 200, high power will kick in for the thrusters of the vessel 110 in an attempt to return it back toward the target location. Because the engines operate in a redundant fashion, the high power level is actually set to about 45% with lower power levels set for the moderate and low levels.

[0031] Recall that the vessel 110 is likely over 75 meters away from the rig 150 of Fig. 1. Thus, a greater amount of drift may be tolerable. This means that it is now practical to use GPS coordinates to designate sizable separate zones 250, 275 with different responsive power levels applied to thrusters of the vessel 110. So, for example, the benefit of a low power response, say about 15% power being applied across much, if not a majority of the region 200 is also practical. Indeed, depending on the time of the year and weather-related issues, this level of power may be all that is necessary the majority of the time. Thus, a tremendous power and fuel savings may be realized. That is, energy savings should be expected under this type of protocol in contrast to a conventional method of simply automatically running thrusters at 45% every time a vessel designated at 25 meters from a rig moves 5-10 meters in one direction or another. This energy savings combined with the widened latitude as described above may ultimately translate into significantly more days that the vessel 110 may safely be operated. That is, as detailed further below, weather related issues affecting operation may be considerably reduced.

[0032] Referring now to Fig. 3, a top view of potential vessel positions adjacent the offshore rig 150 are shown. Specifically, conventional vessel positions 110' closer to the rig 150 are shown in contrast to vessel positions 110 enabled by the dynamic positioning system described above. From this vantage point, additional orientational advantages are apparent. For example, the closer vessel positions 110' afford about 90° of flexibility in orientational movement for a vessel. Any greater degree of orientational movement than that depicted results in the vessel tethered to a point on the rig 150 in a manner that leaves the vessel close to parallel with the rig 150 and not actually an intended 25 meter distance away (see 350). However, the vessel positions 110 supported by the dynamic positioning system described above may be afforded closer to 180° of positional flexibility. For example, with the vessel 110 at about a 100 meter distance from the rig 150 (see 300), the vessel 1 10 is able to occupy about any position adjacent the rig 150 so long as it remains to a given side of the rig 150. The limitation to the given side to avoid allowing the hose to contact or wrap around a portion of the rig 150.

[0033] Referring now to Fig. 4A, a chart 450 is shown plotting occurrences of significant wave heights in a zone around the offshore rig 150 that encompasses the predetermined region 200 of Fig. 2. The chart 450 also encompasses more conventional regions for vessel location (e.g. within 25 meters of the rig 150). Illustrated as dots and provided a plotted direction (e.g. N, S, E, W), the potentially pertinent significant wave heights are positioned on the chart 450 according to wave height (e.g. as opposed to actual geographic location or distance from the rig 150). Specifically note the indications of 1-5 on the chart 450 denoting wave heights in meters.

[0034] With such a plot of wave heights taken over a year or more, a weather pattern or "wave height pattern" may be established. So, for example, on days where significant wave heights are to be expected, operations with the vessel at the rig 150 may be avoided. However, with the availability of the dynamic positioning system detailed herein, that which constitutes a wave height significant enough to halt operations may be adjusted. For example, a conventional significant wave height 425 may include any wave height that is over 2.5 meters. However, where dynamic positioning as described above is utilized, an adjusted significant wave height 400 of 3.5 meters may be established. An example of the amount of added working days available to a vessel employing such dynamic positioning is reflected at the chart 475 and table 490 of Fig. 4B.

[0035] Referring now to Fig. 4B, a chart 475 and table 490 are shown which illustrate potentially increased productive vessel time for rig operations due to the dynamic positioning system in spite of Fig. 4A wave heights. For example, the table 490 reflects conventional significant wave heights at 2.5 meters for a vessel that does not employ dynamic positioning as described herein. For such a vessel, the percent of time waiting on weather (WOW%) in which the vessel is unavailable for operations ranges from a little over 7% in July and moves up to over 85% in January. Stated another way, in the summer, the vessel may sometimes be available to the rig for almost 93% of the time (July) but only available for a little under 15% in the more extreme weather of January, in the northern hemisphere. However, if the adjusted significant wave height of 3.5 meters is utilized due to the dynamic positioning system, these numbers may change dramatically in favor of vessel availability over the same periods of time. Specifically, in the example depicted, the percentage of time available (e.g. working %) for the adjusted significant wave height vessel is over 40% in January and over 99% in July.

[0036] The same comparative information is depicted at the chart 475 of Fig. 4B where the differences in what constitutes significant wave height are illustrated. Specifically, the percentage of vessel time available for a conventional significant wave height 427 is plotted over a year. The same is true for an adjusted significant wave height 401 over the same year. The differences are quite significant.

[0037] For a given year, the improvement in vessel availability due to the dynamic positioning system may be quite dramatic. In the particular example shown here, an increase in vessel availability of over 40% is realized when the conventional significant wave height is exchanged for the adjusted significant wave height made possible by the dynamic positioning system. Of course, this example scenario presumes a harsher weather environment such as in the North Sea where dynamic positioning may be of greater benefit. However, even in milder climates, periods of extreme weather may be predicted and an adjusted significant wave height may still be of substantial benefit.

[0038] Referring now to Fig. 5 A, with added reference to Fig. 1, a side view of an embodiment of a remotely actuatable release device 500 is shown. The device 500 is configured for securing a hose 125 from the vessel 110 to the rig 150 and for releasing the hose back. Specifically, the device 500 is suspended from the crane 155 to secure the hose 125 at the outset of operations. However, the device 500 is also equipped with a lanyard 550 that may be remotely shifted upward to release the hose 125 at the end of operations. This may be done through pneumatic, hydraulic or other appropriate actuation within the device 500. Regardless, as suggested above, this capability means that weather conditions may play a reduced role in returning the hose 125 back to the vessel 110. In fact, the vessel 110 need not return to immediately adjacent the rig 150. For example, during poor weather, the vessel 110 may remain in place as the lanyard 550 is remotely actuated and the hose 125 dropped in the water. The vessel 110 may then move away from the rig 150 while simultaneously spooling the hose 125 back in. In one embodiment, a floatation device may be secured to or incorporated with the hose 125 near the end or at various locations to ensure that the hose does not sink far enough to become tangled or encumbered with any subsea equipment or components.

[0039] Referring now to Fig. 5B, another overview of the rig 150 serviced by the vessel 110 with the intervening hose 125 is shown. In this embodiment, a laterally movable weight 501 for centering of the hose 125 and controlling its amount of slack between the vessel 110 and the rig 150. That is, given that the hose 125 for a dynamic positioning system is likely to be lighter and longer along with the greater amount of vessel position latitude that is afforded, the opportunity for the hose 125 to be loose and become tangled in a vessel propeller or other equipment component may be increased. However, by placing a movable weight on the hose 125 it will sink to a centered location thereon, pulling the hose 125 taught in both directions. Thus, the likelihood of lose hose 125 becoming tangled in equipment components may be reduced if not eliminated.

[0040] Referring now to Fig. 6, a flow-chart summarizing an embodiment of employing a dynamic vessel positioning system is shown. Utilizing the system involves establishing a target sea surface location for a vessel adjacent an offshore rig as indicated at 620. A first response zone may then be established about the target location (see 630) as well as a second response zone about the first zone (640). Of course, in some embodiments further zones may be established concentrically in this same fashion to dictate additional different thruster power responses as described above and here. That is, as indicated at 650, dynamic positioning thrusters of the vessel may be operated at a first power level when the vessel is in the first response zone and at a higher level when the vessel drifts further away and into the second zone (see 670).

[0041] In the meantime, an application fluid may be supplied to the rig over a hose from the vessel as noted at 660. Thus, an application in a well below the rig may be supported as noted at 680. From the vessel standpoint, weather related delays, challenges and energy costs may all be minimized due to use of the dynamic positioning technique. Furthermore, at the completion of the application, the hose may be remotely released as indicated at 690, further minimizing weather related or other challenges.

[0042] Embodiments described above allow for effective thruster responses that don't impose a significant risk of utilizing more than 45% power. This remains true even during worsening weather conditions. In fact, vessels employing the described dynamic positioning system and techniques may be employed a greater percentage of the time regardless of weather. Once more, from a fuel standpoint, the dynamic positioning system directs the thruster response in such a way as to significantly curb costs.

[0043] The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. For example, while stimulation fluids and applications are detailed hereinabove, these are only exemplary. Applications utilizing well service fluids directed at scale removing, acidizing, wax dissolving treatments and others may be supported by a rig that is serviced by a vessel as described herein. So long as a fluid is pumped from a at least one non- stationary vessel to another location at a well, the dynamic positioning techniques detailed herein may be beneficial. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope.

Claims

CLAIMS We Claim:

1. A method of dynamic positioning of a vessel adjacent an offshore structure, the method comprising:

setting a target sea surface location for a vessel adjacent an offshore structure; establishing a first response zone perimeter about the target location;

establishing a second response zone perimeter about the first response zone;

positioning the vessel at the target location in the first zone;

operating dynamic positioning thrusters of the vessel at first power level to direct the vessel to the target location when straying therefrom in the first zone; and

operating the thrusters at a second power level greater than the first power level to direct the vessel to the target location when straying into the second zone.

2. The method of claim 1 further comprising operating the thrusters at a third power level greater than the second power level to direct the vessel to the target location when straying outside of the first and the second zones.

3. The method of claim 2 wherein the third power level is at about 45% power capacity of the vessel.

4. The method of claim 1 wherein the target location is at the center of the first and second zones.

5. The method of claim 1 further comprising delivering an application fluid to the structure over a hose from the vessel.

6. The method of claim 5 further comprising performing an application in a well below the structure with the application fluid.

7. The method of claim 6 wherein the application is a stimulation application and the fluid is a stimulation fluid.

8. The method of claim 6 further comprising remotely releasing the hose from the structure after the performing of the application.

9. The method of claim 8 further comprising:

moving the vessel away from the structure; and

spooling the hose onto the vessel during the moving.

10. The method of claim 1 further comprising:

setting a significant wave height limit for the vessel at 3.5 meters; and

classifying the vessel as available for the positioning at the target location during any period determined to be below the significant wave height limit.

11. An system comprising:

an offshore rig raised over a sea surface; a vessel for positioning at a target location a predetermined distance from the rig at the sea surface, the location within a first response zone, the first response zone within a second response zone, the vessel having dynamic positioning capability incorporated therein; and

a hose for delivering an application fluid from the vessel to the offshore rig, the dynamic positioning capability to direct thrusters of the vessel at different power levels depending on the response zone occupied by the vessel.

12. The system of claim 1 1 wherein the predetermined distance is at least about 75 meters.

13. The system of claim 11 wherein the hose is at least about 150 meters in length.

14. The system of claim 11 further comprising:

a crane supported by the rig; and

a remotely actuatable release device supported by the crane to release the hose from the rig after the delivering of the application fluid.

15. The system of claim 11 wherein the hose is equipped with a floatation device.

16. The system of claim 1 1 wherein the vessel has a flexibility in orientation relative the rig that is greater than 90°.

17. The system of claim 1 1 further comprising a laterally movable weight secured to the hose to enhance taughtness thereof between the vessel and the rig.

18. The system of claim 11 wherein the hose is rated at less than about 5,000 PSI and comprised of a steel reinforced polymer.

19. A method of safely maintaining a vessel near a target location adjacent a rig for supporting an application in a well below the rig, the method comprising:

establishing a first zone about the target location and a second zone about the first; and

operating thrusters of the vessel at different power levels depending on whether the vessel is in the first or second zone;

20. The method of claim 19 further comprising:

securing a hose to the rig from the vessel;

supplying an application fluid to the rig from the vessel during the supporting of the application; and

remotely releasing the hose from the rig after the supplying of the application fluid.