Tool and method for forming a cavern for hydrocarbon production

Abstract

A tool for forming a cavity for hydrocarbon production includes a housing (242) having a cavity. A rotary actuator (250) is disposed in the cavity. A fluid distributor (220) has an inner chamber (224) for receiving an aqueous solution and one or more nozzles (230, 232) for dispensing the aqueous solution. The fluid distributor is coupled to the rotary actuator and can be rotated about a tool axis by the rotary actuator. One or more proximity sensors (260) are disposed at the periphery of the housing to measure a distance relative to the tool.

Description

Technical Field

[0001] The present disclosure generally relates to producing fluids from subterranean reservoirs. Background Art

[0002] Fluids are extracted from reservoirs in underground formations, usually by drilling a wellbore into the underground formation, establishing a flow path between the reservoir and the wellbore, and transporting the fluid from the reservoir to the ground through the wellbore. Typically, production tubing is disposed in the wellbore to transport the fluid to the ground. The production tubing may include a pump to help lift the fluid above the wellbore. The fluids extracted from hydrocarbon reservoirs may include natural gas, oil, and water. A common challenge in extracting fluids from hydrocarbon reservoirs through a wellbore is the ability to continuously lift a net volume of oil or gas (i.e., a volume in which water is not mixed with oil or gas) to the ground relatively inexpensively and without interfering with the fluid system. Summary of the invention

[0003] A method for hydrocarbon production includes forming a wellbore in a subterranean formation, placing a tool including a fluid distributor and at least one proximity sensor in the wellbore, positioning the fluid distributor at an initial depth in an end section of the wellbore, providing an acidic aqueous solution to the fluid distributor, and forming a cavity of a selected height in the end section of the wellbore using the tool. The cavity is formed by rotating the fluid distributor to distribute the acidic aqueous solution to a portion of the subterranean formation surrounding the fluid distributor, wherein the acidic aqueous solution dissolves rock material in the portion of the subterranean formation; measuring the distance between the tool and the portion of the subterranean formation surrounding the fluid distributor using the at least one proximity sensor; and adjusting the position of the fluid distributor to another depth in the end section of the wellbore if the measured distance is equal to or above a predetermined threshold. The tool may be lowered into the wellbore at the end of a coiled tubing. The acidic aqueous solution may be provided to the fluid distributor through the coiled tubing. The wellbore may be formed in a carbonate formation containing a hydrocarbon reservoir. The initial selected depth of the fluid distributor may be near the bottom of the wellbore. The position of the fluid distributor can be adjusted to another selected depth by lifting the fluid distributor to another selected depth in the end section of the wellbore. The formed cavern can have a cylindrical sidewall and a dome-shaped top wall. The tool can be removed from the wellbore after the cavern is formed, and the cavern can be filled with brine. A production tubing can be arranged in the wellbore. The production tubing can be connected to the cavern. The brine from the cavern can be discharged through the production tubing. When the brine is discharged from the cavern, fluid from the underground formation can flow into the cavern. The fluid from the underground formation can be stratified by gravity in the cavern. The method can include discharging the stratified fluid from the cavern through the production tubing. The brine and the stratified fluid can be discharged from the cavern through the production tubing by operating a pump arranged in the production tubing.

[0004] A tool for forming a cavern for hydrocarbon production, comprising a shell having a cavity, a rotary actuator disposed in the cavity, and a fluid distributor, the fluid distributor having an inner chamber for receiving an aqueous solution and at least one nozzle for distributing the aqueous solution. The fluid distributor is coupled to the rotary actuator and is rotatable around a tool axis by the rotary actuator. The tool comprises at least one proximity sensor disposed at the periphery of the shell to measure a distance relative to the tool. The at least one proximity sensor may be an ultrasonic sensor. The sensing direction of the at least one proximity sensor may be perpendicular to the tool axis. The sensing direction of the at least one proximity sensor may be inclined relative to the tool axis. The fluid distributor may comprise a plurality of nozzles for distributing the aqueous solution. At least one of the plurality of nozzles may have a straight shape, and at least another of the plurality of nozzles may have an angled shape. The tool may comprise a support tube coupled to the shell. The support tube may have a hole connected to the inner chamber fluid.

[0005] A system for forming a cavern comprises a wellbore passing through an underground formation, a coiled tubing supported by a reel, and a tool for forming a cavern, the tool being disposed in the wellbore at an end of the coiled tubing. The tool comprises a housing having a cavity, a rotary actuator disposed in the cavity, and a fluid distributor in fluid connection with the coiled tubing. The fluid distributor has an inner chamber for receiving a fluid from the coiled tubing and at least one nozzle for distributing the fluid. The fluid distributor is coupled to the rotary actuator and is rotatable about a tool axis by the rotary actuator. The tool comprises a fluid path between the inner chamber and the coiled tubing. The tool comprises at least one proximity sensor disposed at a periphery of the housing to measure a distance between the underground formation and the tool. The system may comprise a tank containing an acidic aqueous solution. The system may comprise a pump for transporting the acidic aqueous solution from the tank to the coiled tubing.

[0006] The above summary and the following detailed description are examples of the present invention and are intended to provide an overview or framework for understanding the nature of the claimed invention. The accompanying drawings are included to provide a further understanding of the present invention and are incorporated into and constitute a part of the specification. The accompanying drawings illustrate various embodiments of the present invention and together with the description serve to explain the principles and operation of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following is a description of the figures in the accompanying drawings. In the accompanying drawings, the same reference numerals identify similar elements or actions. The sizes and relative positions of the elements in the drawings are not necessarily drawn to scale. For example, the shapes and angles of various elements are not necessarily drawn to scale, and some of these elements may be arbitrarily enlarged and positioned to improve the readability of the drawings. In addition, the particular shapes of the drawn elements are not necessarily intended to convey any information about the actual shapes of these particular elements, but are merely selected for ease of identification in the drawings.

[0008] Figure 1 is a schematic diagram of a system including a cavern for producing hydrocarbons from a reservoir, according to one embodiment.

[0009] Figure 2 shows the reservoir fluid inflow Figure 1 The cave chamber.

[0010] Figure 3 Shows Figure 1 Stratification of reservoir fluids in the caverns.

[0011] Figure 4 is a front view of a tool for forming a cavity according to one embodiment.

[0012] Figure 5 According to one embodiment Figure 4 Vertical section through the tool shown.

[0013] Figure 6 According to another embodiment Figure 4 Vertical section through the tool shown.

[0014] Figure 7 is a schematic diagram of a system for forming a cavern for hydrocarbon production, according to one embodiment.

[0015] Figure 8 is used Figure 7 A flow chart of a method for forming a cavern by the system shown.

[0016] Fig. 9 It shows that according to Figure 8 Schematic diagram of the stages of the method for forming a cavern.

[0017] Fig.10 It shows that according to Figure 8 Schematic diagram of another stage of the method of forming a cavern.

[0018] Fig.11 It shows that according to Figure 8 Schematic diagram of the cavern formed by the method. DETAILED DESCRIPTION

[0019] In the following detailed description, certain specific details are set forth in order to provide a thorough understanding of the various embodiments and examples disclosed. However, those skilled in the relevant art will recognize that the embodiments and examples may be practiced without one or more of these specific details or with other methods, components, materials, etc. In other cases, well-known features or processes associated with hydrocarbon production systems are not shown or described in detail to avoid unnecessarily obscuring the description of the embodiments and examples. For the sake of consistency and simplicity, the same or similar reference characters may be used for the same or similar objects in multiple figures.

[0020] Figure 1 A system 100 for producing hydrocarbons according to an illustrative embodiment is shown. For illustrative purposes, underground formations 120, 122, 124 are shown below ground 126. Typically, there may be many layers of underground formations below ground 126. For illustrative purposes, formations 120, 122, 124 may be carbonate formations. In one example, formation 124 is a target reservoir containing hydrocarbons to be produced. System 100 includes a cavern 130 formed in formations 122, 124. Thus, at least a portion of cavern 130 is disposed in the target reservoir (formation 124). Cavern 130 has a cylindrical sidewall 132 and a dome-shaped top wall 134. Top wall 134 is connected to wellbore 110, which is connected to ground 126. Cavern 130 is in fluid communication with formation 124 and can receive reservoir fluid directly from formation 124. The cavern 130 may be initially filled with brine 136 to prevent the cavern 130 from collapsing and to equalize the pressure within the cavern 130 with the pressure in the formation 124 , thereby temporarily preventing reservoir fluids from flowing into the cavern 130 .

[0021] The system 100 includes a production tubing 140 disposed in the wellbore 110. The production tubing 140 extends into the cavern 130, thereby forming a flow conduit from the cavern 130 to the surface 126. The production tubing 140 may include an electric submersible pump (ESP) 142, which may be powered from the surface 126 by an electrical cable 144. A packer 146 may be arranged to seal an annulus 148 between the production tubing 140 and the wellbore 110 from the cavern 130. A packer 150 may be arranged in the annulus 148 and above the ESP 142. A casing 152 may be installed in the wellbore 110, and the annulus 148 may be formed between the production tubing 140 and the casing 152. The annulus 148 may be filled with brine 154. At the surface 126, fluid from the production tubing 140 may be received in a separator 170, which may then operate to separate the fluid into oil, water, and gas. The separated fluids may be transferred to corresponding flow lines 172, 174, 176.

[0022] A method of producing hydrocarbons using system 100 may include operating ESP 142 to gradually drain brine 136 from chamber 130. Figure 2 As shown, as the brine 136 is drained from the cavern 130, reservoir fluid 180 from the formation 124 will enter the cavern 130 and occupy the volume left by the drained brine 136. The reservoir fluid 180 can include any combination of oil, gas, and water. Gravity causes heavier fluids (such as water) to sink downward, while lighter fluids (such as oil and gas) float upward. Figure 3 Stratification of fluids in the cavern 130 due to gravity is shown. For purposes of illustration, the fluid 180a forming a first layer at the deepest depth within the cavern 130 may be water, the fluid 180b forming a second layer on top of the first layer may be oil, and the fluid 180c forming a third layer on top of the second layer may be gas. In this regard, the cavern 130 acts as a downhole separator disposed between the formation 124 (or target reservoir) and the wellbore 110. The production tubing 140 transports fluids from the upper volume of the cavern 130 to the separator 170 at the surface 126. This is a continuous process in which ( Figure 2 The reservoir fluid 180 enters the cavern 130 and is stratified by gravity ( Figure 3 180a, 180b, 180c), and then mined to the surface according to its position in the cavern 130.

[0023] In one embodiment, a method of producing hydrocarbons includes forming the cavern 130 prior to producing fluids from the cavern 130 . Figure 4 and Figure 5 One embodiment of a tool 200 for forming a cavity for hydrocarbon production is shown. Figure 4 In the embodiment, the tool 200 includes a support tube 210, a fluid distributor 220, and a rotating table 240. Figure 5In the embodiment, the tool 200 has a tool axis 202. The support tube 210 has an axial axis aligned with the tool axis 202. The support tube 210 has an axial bore 212 to deliver fluid to a fluid distributor 220. A connector 214 is provided at the end of the support tube 210 for connecting the tool 200 to a coiled tubing (not shown). The fluid distributor 220 has a container 222 having an inner chamber 224 to receive fluid from the support tube 210. The fluid distributor 220 has a tube 226 connected to the container 222 at one end and extending upward from the container 222. The tube 226 is axially aligned with the support tube 210. The tube 226 has a bore 228 that is fluidly connected to the inner chamber 224 and the bore 212 of the support tube 210, allowing fluid to flow from the support tube 210 into the inner chamber 224. The container 222 has a port 223 in which nozzles 230, 232 are mounted. The nozzles 230, 232 have orifices (not separately shown) that are fluidly connected to the interior chamber 224. The nozzles 230, 232 are used to provide a fluid flow directed outwardly from the fluid dispenser 220. The nozzles 230, 232 extend laterally from the container 222. Figure 4 and Figure 5 In the example shown, nozzle 230 is a straight nozzle and nozzle 232 is an angled nozzle. The staggered arrangement of the nozzles is Figure 4 and Figure 5 In general, any number of nozzles, any combination of straight and angled nozzles, and any arrangement of nozzles may be selected to achieve a desired fluid dispensing pattern from fluid dispenser 220 .

[0024] The rotary table 240 includes a housing 242, which may be generally cylindrical in shape. The housing 242 has an axial axis aligned with the tool axis 202. Within the housing 242 is a rotary actuator 250. In one example, the rotary actuator 250 is a hollow shaft motor. The hollow shaft motor has a hole running through the center of the motor. This allows the tube 226 of the fluid dispenser 220 to be assembled to the rotor of the motor. As the rotor rotates, the tube 226 will rotate, which will cause the fluid dispenser 220 to rotate as a whole. Figure 5In the example shown, the tube 226 is shown extending through the rotary actuator 250, and the support tube 210 is shown extending into the tube 226. In one example, the tube 226 rotates relative to the support tube 210. A dynamic seal 252 may be provided between the tubes 226, 210 to allow relative movement between the tubes 226, 210 while sealing between the tubes 226, 210. The support tube 210 may be attached to a cover 256, which is attached to the housing 242 so that the support tube 210 is coupled to the housing 242. In one example, the rotary actuator 250 may be electric. Electricity may be provided to the rotary actuator 250 by a cable 258 extending beside the support tube 210. Alternatively, the rotary actuator 250 may be hydraulically driven. For example, the hydraulic power for the rotary actuator 250 may come from the fluid movement from the tube 226 to the inner chamber 224.

[0025] In one embodiment, the proximity sensor 260 is disposed at the periphery 246 of the housing 242, i.e., the sensing surface 262 of the proximity sensor 260 is exposed at the periphery of the housing 242. The proximity sensor 260 can be used to measure the distance between the housing 242 and the surrounding objects (e.g., the surrounding formations). During the use of the tool 200, the proximity sensor 260 can measure parameters related to the radius of the cavity formed by the tool 200. The measurements made by the proximity sensor 260 can be used to make a decision about when to move the tool 200 to another depth in order to form another part of the cavity. In one embodiment, the proximity sensor 260 is an ultrasonic sensor. In one example, the ultrasonic sensor works by emitting an ultrasonic pulse and receiving the reflection of the pulse. The distance to the object can be determined from the time difference between the emitted pulse and the reflected pulse. In some cases, the cable 258 can provide power to the proximity sensor 260 (260'). The cable 258 can also be used as a medium for transmitting measurement data from the proximity sensor 260 to a control system at a surface location. The control system may include a processor that receives measurement data from the proximity sensor 260 and uses the measurement data to determine whether to adjust the position of the tool 200 during formation of a cavity using the tool 200 .

[0026] One or more proximity sensors 260 may be disposed on the periphery 246 of the housing 242 to sense the distance between the housing 242 and surrounding elements. Figure 5In the example shown, the sensing face 262 of the proximity sensor 260 is substantially parallel to the tool axis 202 (or the axial axis of the housing 242). This means that the sensing direction of the proximity sensor 260 is perpendicular to the tool axis 202. In this case, each proximity sensor 260 will measure the distance between the housing 242 and the portion of the formation surrounding the corresponding sensing face 262. In order to allow continuous monitoring of the etching of the formation at each position of the tool 200 in the wellbore, at least some of the nozzles (e.g., the angled nozzles 232) should be arranged to etch the portion of the formation that will surround the sensing face 262 of the proximity sensor 260. Alternatively, the proximity sensor can be arranged so that the sensing direction of the proximity sensor is directed toward the portion of the formation that will surround the container 222. This is in the example shown in FIG. Figure 6 260' is shown in FIG. Figure 6 In FIG. 2 , the sensing surface 262 ′ is inclined relative to the tool axis 202 (or the axial axis of the housing 242 ).

[0027] Figure 7 A system 300 is shown that can be used to form a cavern for hydrocarbon production. The system 300 includes a wellbore 330 that passes through underground formations 320, 322 below ground 324. For illustrative purposes, the formation 322 can be a hydrocarbon reservoir in which at least a portion of the cavern is to be formed. The wellbore 330 can be a vertical wellbore. The system 300 includes a tool 200 (according to the method of FIG. 20) disposed in the wellbore 330. Figures 4 to 6 ). The tool 200 is connected to the end of a coiled tubing 340 and is suspended in the wellbore 330 by the coiled tubing 340. The coiled tubing 340 is dispensed from a reel 342 at the surface 324. The coiled tubing 340 may be guided into the wellbore 330 through a tubing injector 344 and a wellhead 346. In one example, the coiled tubing 340 may be an electrical coiled tubing (also referred to as an eCoil). In this case, the coiled tubing 240 includes conductors (not shown separately) to transmit power. The conductors may also carry communication signals. When the coiled tubing 340 is connected to the tool 200, an electrical connection is established between the conductors in the coiled tubing 340 and the cable 258 carried by the tool 200. At the surface, the conductors in the coiled tubing 340 may be connected to a power and communication module (not shown), thereby allowing power to be delivered to and communication with components in the tool 200.

[0028] The system 300 includes a tank 350 containing an aqueous solution that will be used to etch the formation 322 to form a cavity. The system 300 includes a pump 352 to pump the aqueous solution from the tank 350 into the coiled tubing 340. The aqueous solution pumped into the coiled tubing 340 will flow into the support tube 210 of the tool 200 and the fluid distributor 220 of the tool 200, where the fluid can be ejected through the nozzles 230, 232 and directed to the surrounding formation 322. The injection speed can be controlled by the pressure of the aqueous solution supplied to the fluid distributor 220.

[0029] Figure 8 It shows the use of Figure 7 The system 300 is a flow chart of a method of forming a cavern for hydrocarbon production. Figure 7 and Figure 8 The method includes placing the tool 200 at the end of the coiled tubing 340 and lowering it into the wellbore 330 Figure 8 The tool 200 may be lowered into the wellbore 330 by operating the reel 342. The method includes positioning the fluid dispenser 200 at an initial depth in the end section 332 of the wellbore 330 ( Figure 8 In one embodiment, the initial depth is at the bottom of the wellbore 330. The method includes providing an acidic aqueous solution ( Figure 8 404 in). The acidic aqueous solution can be pumped from the tank 350 into the coiled tubing 340, which is fluidly connected to the fluid distributor 220. For etching of carbonate formations, the acidic aqueous solution can be an aqueous solution of an inorganic acid such as hydrochloric acid, hydrofluoric acid, nitric acid, and phosphoric acid.

[0030] The method includes forming a cavity of a selected height in an end section 332 of a wellbore 330. The cavity is formed in sections. To form the sections of the cavity, the method includes rotating a fluid distributor 220 to distribute an acidic aqueous solution to a portion of the formation 322 surrounding the fluid distributor 220 at the current depth of the fluid distributor 220 ( Figure 8 406 in the figure). Typically, the rotation of the fluid distributor 220 is continuous. In some cases, the rotation may be paused while the tool is being moved or while measuring the distance between the tool and the surrounding formation. As the fluid distributor 220 rotates, the acidic aqueous solution is provided to the fluid distributor 220 ( Figure 8 404 in the fluid distributor 220), thereby continuously supplying the acidic aqueous solution for distribution to the surrounding formation 322. The acidic aqueous solution in the inner chamber of the fluid distributor 220 is discharged through the nozzles 230, 232 of the fluid distributor 220 in the form of a jet (fluid stream) directed toward the surrounding formation 322. When the acidic aqueous solution contacts the formation, the acid will dissolve the rock material in the formation, thereby etching the formation (removing material from the formation).

[0031] Fig. 9 330. When the portion 310a of the cavity is formed at the selected depth, the method includes using the proximity sensor 260 carried by the tool 200 to measure the distance ( Figure 8 408 in ). The method includes determining whether the distance measured by the proximity sensor is less than a threshold value ( Figure 8 If the distance is less than the threshold, the method continues to distribute the acidic aqueous solution to the surrounding formation ( Figure 8 If the measured distance between the proximity sensor and the formation is at or above the threshold, the method includes moving the fluid distributor to another depth in the wellbore ( Figure 8 412 in ). For the purpose of illustration, Fig. 9 322. The distance d measured by the proximity sensor 260 is shown. Each proximity sensor 260 carried by the tool 200 can measure a certain distance d between the tool 200 and the surrounding formation 322. In one example, the decision to adjust the position of the fluid dispenser 200 ( Figure 8 410) can be based on individual outputs of the proximity sensors 260. For example, in the event that all proximity sensors 260 have reported a distance d at or above a predetermined threshold, a decision can be made to adjust the position of the fluid dispenser 220 to the next depth. Alternatively, the decision to adjust the position of the fluid dispenser 220 can be based on a combination of the outputs of the proximity sensors 260. For example, an average of the distances measured by the proximity sensors 260 can be taken. If the average is equal to or above a predetermined threshold, a decision can be made to adjust the position of the fluid dispenser 220.

[0032] In the illustrated example, the straight nozzle 230 forms a cylindrical portion 312a of the cavity portion 310a, and the angled nozzle 232 forms a dome-shaped portion 312b of the cavity portion 310a. The fluid dispenser 200 can be positioned at the next depth so that the straight nozzle 230 will etch the dome-shaped portion of the previous cavity portion, while the angled nozzle 232 will form another dome-shaped portion. The next position (from Fig. 9 shown in the position) Fig.10 At the new location, as the fluid dispenser 200 rotates, the fluid dispenser 200 will dispense the acidic aqueous solution, resulting in etching of the surrounding formation 322. During this etching, the distance between the tool 200 and the surrounding formation 322 will be measured to determine when to move the fluid dispenser 200 to form another portion of the cavity. Typically, the formation of the cavity begins at the bottom of the wellbore 300, and each movement of the tool 200 to a new depth includes, for example, moving the reel 342 ( Figure 7 Middle) to pull up the coiled tubing 340 ( Figure 7 ) to lift tool 200.

[0033] The method includes determining whether the chamber has reached a desired height ( Figure 8 The height of the cavern may be determined by the difference between the length of coiled tubing 340 disposed in the wellbore 330 when the fluid distributor 220 was positioned at the initial depth and the length of coiled tubing 340 disposed in the wellbore 330 at the current depth of the fluid distributor 220. If the cavern is not at the desired height, a process of forming a new portion of the cavern is performed ( Figure 8 406 to 412 in ). If the chamber is at the desired height, the method includes stopping the flow of the acidic aqueous solution to the fluid distributor 220 ( Figure 8 416 in). The angled nozzles 232 will allow the final dome shape to be formed at the top of the chamber. Another method of forming a dome shape at the top of the chamber without using the angled nozzles 232 is to orient the tool 200 at various angles when the chamber has reached the desired height so as to form a dome shape at the top of the chamber. Before stopping the flow of the acidic aqueous solution to the fluid distributor 220, if desired, a dome shape can be formed at the top of the chamber. After the desired height and shape of the chamber has been formed, the method includes stopping the rotation of the fluid distributor 220 and removing the tool 200 from the wellbore 330 ( Figure 8 418 of ). The method comprises filling the cavity with salt water ( Figure 8 420 in the above table). Fig.11 A cavern 310 having a desired height is shown formed in an end section 332 of a wellbore 330. The tool 200 has been pulled out of the wellbore 330, and the cavern 310 has been filled with brine 360. Although not shown, the portion of the wellbore 330 above the cavern 330 may also be filled with brine. Figures 7 to 11 The method of forming a cavity described can be used to form Figures 1 to 3 The cavern 130.

[0034] Although the present invention has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be designed which do not depart from the scope of the invention as described herein. Therefore, the scope of the present invention should be limited only by the appended claims.

Claims

1. A method for hydrocarbon production, the method comprising: forming a wellbore in a subterranean formation; placing a tool including a fluid dispenser and at least one proximity sensor in the wellbore; positioning the fluid distributor at an initial depth in an end section of the wellbore; providing an acidic aqueous solution to the fluid dispenser; and Using the tool to form a cavity of a selected height in the end section of the wellbore, the forming comprising: rotating the fluid distributor to distribute the acidic aqueous solution to a portion of the subterranean formation surrounding the fluid distributor, wherein the acidic aqueous solution dissolves rock material in the portion of the subterranean formation; measuring a distance between the tool and the portion of the subterranean formation surrounding the fluid dispenser using the at least one proximity sensor; If the measured distance is at or above a predetermined threshold, pulling the fluid dispenser to another depth in the end section of the wellbore; and The tool is removed from the wellbore and the chamber is filled with brine.

2. The method according to claim 1, wherein: Positioning a tool including a fluid dispenser and at least one proximity sensor in the wellbore includes lowering the tool into the wellbore at the end of a coiled tubing.

3. The method according to claim 1, wherein: Providing the acidic aqueous solution to the fluid distributor includes providing the acidic aqueous solution through coiled tubing.

4. The method according to claim 1, wherein: Positioning the fluid distributor at an initially selected depth in an end section of the wellbore includes positioning the fluid distributor near a bottom of the wellbore.

5. The method according to claim 1, wherein: The resulting chamber has cylindrical side walls and a dome-shaped top wall.

6. The method of claim 1 further comprising placing a production tubing in the wellbore and in fluid communication with the cavern.

7. The method of claim 6, further comprising draining the brine from the cavern through the production tubing, wherein: As the brine is drained from the cavern, fluid from the subterranean formation flows into the cavern.

8. The method according to claim 7, wherein: The fluid from the subterranean formation is stratified by gravity within the chamber, and the method further includes draining the stratified fluid from the chamber through the production tubing.

9. The method according to claim 8, wherein: Each of draining the brine from the cavern through the production tubing and draining the stratified fluid from the cavern through the production tubing includes operating a pump disposed in the production tubing.

10. The method according to any one of claims 1 to 9, wherein: Forming a wellbore in a subterranean formation includes forming the wellbore in a carbonate formation containing a hydrocarbon reservoir.

11. A system for forming a cavern, the system comprising: a wellbore, which penetrates underground formations; Coiled tubing, the coiled tubing being supported by a reel; A tool for forming a cavern, the tool being arranged in the wellbore and located at the end of the coiled tubing, the tool comprising: a housing having a cavity; a rotary actuator disposed in the cavity; a fluid distributor fluidly connected to the coiled tubing, the fluid distributor having an internal chamber for receiving fluid from the coiled tubing and at least one nozzle for dispensing the fluid, the fluid distributor being coupled to the rotary actuator and rotatable about the tool axis by the rotary actuator; a fluid path between the inner chamber and the coiled tubing; and at least one proximity sensor disposed at a periphery of the housing to measure a distance between the subterranean formation and the tool, and Brine is configured to fill the cavity after the tool forms the cavity and is removed from the wellbore.

12. The system of claim 11, further comprising a tank containing an acidic aqueous solution and a pump that transports the acidic aqueous solution from the tank to the coiled tubing.

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