EP2735695A1 - Downhole tool - Google Patents
Downhole tool Download PDFInfo
- Publication number
- EP2735695A1 EP2735695A1 EP12193847.6A EP12193847A EP2735695A1 EP 2735695 A1 EP2735695 A1 EP 2735695A1 EP 12193847 A EP12193847 A EP 12193847A EP 2735695 A1 EP2735695 A1 EP 2735695A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- tool
- downhole
- well
- downhole tool
- anode
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
- 229910052751 metal Inorganic materials 0.000 claims abstract description 46
- 239000002184 metal Substances 0.000 claims abstract description 46
- 239000002253 acid Substances 0.000 claims abstract description 45
- 238000000034 method Methods 0.000 claims abstract description 8
- 230000003628 erosive effect Effects 0.000 claims description 16
- 239000012530 fluid Substances 0.000 claims description 15
- 238000001514 detection method Methods 0.000 claims description 10
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 3
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 3
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 3
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 3
- 239000004411 aluminium Substances 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 229910052797 bismuth Inorganic materials 0.000 claims description 3
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 claims description 3
- 229910052749 magnesium Inorganic materials 0.000 claims description 3
- 239000011777 magnesium Substances 0.000 claims description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims description 3
- 239000011733 molybdenum Substances 0.000 claims description 3
- 229910052725 zinc Inorganic materials 0.000 claims description 3
- 239000011701 zinc Substances 0.000 claims description 3
- RYTYSMSQNNBZDP-UHFFFAOYSA-N cobalt copper Chemical compound [Co].[Cu] RYTYSMSQNNBZDP-UHFFFAOYSA-N 0.000 claims 1
- 239000003921 oil Substances 0.000 description 9
- 239000000463 material Substances 0.000 description 7
- 239000010405 anode material Substances 0.000 description 6
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 5
- 238000004891 communication Methods 0.000 description 5
- 239000007789 gas Substances 0.000 description 5
- 229910000041 hydrogen chloride Inorganic materials 0.000 description 5
- IXCSERBJSXMMFS-UHFFFAOYSA-N hydrogen chloride Substances Cl.Cl IXCSERBJSXMMFS-UHFFFAOYSA-N 0.000 description 5
- 239000010935 stainless steel Substances 0.000 description 5
- 229910001220 stainless steel Inorganic materials 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 3
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 3
- 239000000654 additive Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 2
- 238000010306 acid treatment Methods 0.000 description 2
- 150000007513 acids Chemical class 0.000 description 2
- 239000010941 cobalt Substances 0.000 description 2
- 229910017052 cobalt Inorganic materials 0.000 description 2
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 2
- 239000000470 constituent Substances 0.000 description 2
- 229910052802 copper Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 239000010779 crude oil Substances 0.000 description 2
- 239000003112 inhibitor Substances 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 230000000638 stimulation Effects 0.000 description 2
- 238000004873 anchoring Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000011010 flushing procedure Methods 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-M hydrogensulfate Chemical compound OS([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-M 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 239000011499 joint compound Substances 0.000 description 1
- 229910001092 metal group alloy Inorganic materials 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000004936 stimulating effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Images
Classifications
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B41/00—Equipment or details not covered by groups E21B15/00 - E21B40/00
- E21B41/02—Equipment or details not covered by groups E21B15/00 - E21B40/00 in situ inhibition of corrosion in boreholes or wells
-
- E—FIXED CONSTRUCTIONS
- E21—EARTH OR ROCK DRILLING; MINING
- E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
- E21B47/00—Survey of boreholes or wells
- E21B47/01—Devices for supporting measuring instruments on drill bits, pipes, rods or wirelines; Protecting measuring instruments in boreholes against heat, shock, pressure or the like
- E21B47/017—Protecting measuring instruments
Definitions
- the present invention relates to a downhole tool for performing an operation in an acid-containing well. Furthermore, the present invention relates to a downhole system comprising a downhole tool according to the invention and to a downhole operation method for operating the downhole tool according to the invention.
- Operations in a well are performed by means of different kinds of tools, and in some cases the well contains acid which complicates the operation since the acid environment is too harsh for the downhole tools used in performing the operations.
- operations in wells containing acid have to be performed after the well is flushed and the acid concentration has been brought down or tools have been entered for performing the operation. This flushing process is time-consuming and in some wells even impossible because circulation of fluid is not possible.
- a downhole tool for performing an operation in an acid-containing well comprising:
- the tool may be a driving tool which is self-propelling.
- the tool may be a wireline tool.
- the well may be a cased well or an openhole well.
- the tool may comprise a driving tool which is self-propelling.
- the driving tool may comprise wheels, each wheel being arranged on a wheel arm and being projectable from the tool housing.
- the sacrificial anode may be arranged in a first end or a second end of the tool housing.
- Said anode may be threadingly connected with one of the ends of the housing.
- the downhole tool may comprise several tool parts 1a, 1b and the anode may be arranged between two tool parts.
- the sacrificial anode may be an elongated element and may be arranged on an outer face of the tool housing.
- the anode may be shaped as a rod.
- the sacrificial anode may be arranged in a groove in the tool housing.
- the anode may be shaped as a mesh surrounding at least part of the tool housing.
- the first metal may be stainless steel.
- the second metal may comprise chrome, magnesium, bismuth, zinc, aluminium, molybdenum, cobalt, copper, or a combination thereof.
- the second metal may comprise additives or other constituents.
- the first metal may have an electrical potential between -0.32 and -0.40 V.
- the second metal may have an electrical potential between -0.82 and -0.60 V.
- the second metal may have an electrical potential which is at least -0.3 V lower than that of the first metal, preferably at least -0,40 V lower than that of the first metal, more preferably at least -0.5 V lower than that of the first metal.
- anode may be replaceably arranged in connection with the tool housing.
- the downhole tool as described above may further comprise a compartment, such as a magazine or cassette, of a plurality of anodes.
- Said compartment may comprise anodes of various metals.
- the downhole tool as described above may further comprise an erosion detection sensor for detection of erosion of the first metal of the tool housing.
- the downhole tool as described above may comprise a communication unit for receiving information from the sensor for detection of erosion of the first metal and communicating the information to surface.
- the sensor and the communication unit enable retraction of the downhole tool before the downhole tool is eroded to an extent that it cannot be reused.
- the sensor detects the thickness of the tool housing or another indication of the erosion of the tool housing, and the communication unit communicates the information to surface, e.g. only when the indicator is above a certain extent of erosion.
- the tool housing may be electrically connected with the sacrificial anode.
- the downhole tool as described above may further comprise a power supply for creating an electrical potential across the anode and the tool housing.
- the power supply may have a negative pole connected with the tool housing and a positive pole connected with the anode.
- the downhole tool may further comprise an acid detection sensor.
- the one or more anodes may cover at least 10% of a surface area of the tool housing.
- the downhole tool as described above may comprise several anodes arranged with at least one anode for each 10 metres of the downhole tool, preferably at least one anode for each 5 metres of the downhole tool, more preferably at least one anode for each 2 metres of the downhole tool, and even more preferably at least one anode for each 1 metre of the downhole tool.
- the downhole tool as described above may further comprise an operational tool section, such as a drill bit, an anchor tool, a stroking tool, a key tool, a release tool or a milling tool.
- an operational tool section such as a drill bit, an anchor tool, a stroking tool, a key tool, a release tool or a milling tool.
- the anodes may be arranged between the operation tool section and the tool housing.
- the driving tool may propel forward in the well at a velocity of at least 5 metres/hour.
- the present invention furthermore related to a downhole system comprising a downhole tool as described above and the well containing acidic fluid.
- the downhole system as described above may comprise several tools.
- anodes may be arranged between the tools.
- the acid may be HCl, H 2 S or H 2 SO 4 or any combination thereof.
- the downhole system as described above may further comprise tubing string, such as coiled tubing, connected with the downhole tool for supplying acid.
- tubing string such as coiled tubing
- the present invention also relates to a downhole operation method for operating the downhole tool as described above, comprising the steps of:
- the downhole operation method as described above may further comprise the step of cleaning the downhole tool before submerging the tool again.
- the anode may be replaced for another anode of a material which is different from that of the anode which is replaced.
- the downhole operation method as described above may further comprise the step of detecting which acid is present in the well.
- the downhole operation method may further comprise the step of measuring the erosion of the housing.
- Fig. 1 shows a downhole tool 1 submerged into a well 2 containing an acid-containing fluid 18.
- the downhole tool comprises a tool housing 3 made of a first metal and a sacrificial anode 4 made of a second metal.
- the anode 4 is arranged in connection with one first end 22 of the tool housing being the end furthest away from the top of the well.
- the second metal of the anode has a more negative electrochemical potential than the first metal of the tool housing.
- the acid When performing an operation in an acid-containing well, the acid erodes the metal tool housing to such an extent that the downhole tool cannot be reused for another operation.
- Downhole tools cannot be made in disposable materials, such as plastic, since the operations often require a significant amount of force.
- the tools have a robust design and are made of robust materials, such as stainless steel. The tools are therefore quite expensive to manufacture and hence being able to avoid discarding a tool after having performed one operation in an acid-containing well is very beneficial.
- the well may contain acid before the tool enters the well, or the tool may be used to perform the acid stimulation.
- Typical acids in an acid-containing well may be HCl (hydrogen chloride) which is typically injected into the well for performing a stimulation operation, or H 2 S (hydrogen sulphide) and H 2 SO 4 (hydrogen sulphate) which develop in the well.
- HCl hydrogen chloride
- H 2 S hydrogen sulphide
- H 2 SO 4 hydrogen sulphate
- the tool is a driving tool 5 which is self-propelling, meaning that the tool is able to propel itself forward in the well.
- the tool is connected with the top of the well via a wireline 24 and is thus a so-called wireline tool.
- the well is a cased well but may also be an openhole well.
- the driving tool comprises four wheels 6 and each wheel is arranged on a wheel arm 7 which is radially projectable from the tool housing 3, as shown also shown in Fig. 4 .
- a sacrificial anode is arranged in both the first end 22 and a second end 25 of the tool housing 3.
- the downhole tool comprises two tool parts 1a, 1b constituted by two operational tool sections being an anchor tool 20 and a key tool 21.
- the anchor tool has four radially projectable anchors 27 anchoring the tool in the longitudinal direction of the well so that the key tool can project its keys 28 and engage a sliding sleeve 29 for opening or closing the sleeve.
- a third anode is arranged between the anchor tool and the key tool, and the anodes are thus able to cover the entire tool surface so that the downhole tool is not eroded or etched and thus damaged.
- the downhole tool comprises another operational tool section, such as a drill bit, a stroking tool, a release tool or a milling tool.
- the anodes are detachable and are threadingly connected with the ends of the housing of the anchor tool and the ends of the housing of the key tool as shown in Fig. 2 .
- the anodes are designed as cylindrical modules also referred to as "subs" which can easily be connected to any tool by normal detachable connection means.
- the downhole tool comprises several sacrificial anodes 4.
- the anodes are shaped as elongated elements and are arranged on an outer face 8 of the tool housing of the driving tool 5.
- the anodes are shaped as solid rods, and the sacrificial anodes are arranged in a groove 9 in the tool housing as shown in Fig. 4 .
- the anode may also be shaped as a mesh 30 surrounding at least part of the outer surface 8 of the tool housing 3.
- the downhole tool 1 comprises a sensor unit 26 which e.g. comprises an acid detecting sensor 16, which is submerged into an openhole well 2 containing acid 18.
- the sensor unit 26 may also be another kind of sensor, such as a casing collar locator, a temperature measuring unit, a pressure measuring unit, a diagnostics related sensor or similar sensor unit.
- a driving unit such as a downhole tractor can be used to push the tool all the way into position in the well.
- the outer face of the tool is mostly made of the first metal which is a suitable stainless steel type.
- the anode is made of the second metal which may be chrome, magnesium, bismuth, zinc, aluminium, molybdenum, cobalt, copper, or a combination thereof.
- the sacrificial anode is designed to match a specific well, the condition of which depends on the acid and inhibitor content of the well in which the tool is to operate, and may therefore comprise any combination of suitable anode metals or metal alloys and even additives or other constituents for providing the most efficient sacrificial anode for the tool in that particular environment of the well.
- the second material may - apart from the suitable anode material - comprise additives or other kinds of metal. Even though the anode is very efficient, the tool may still be attacked by the acid, but the tool will be less damaged than if no sacrificial anode is used and not to such an extent that the tool cannot be reused for another operation.
- the first metal is substantially stainless steel or similar material and has an electrical potential between -0.32 and -0.40 V.
- the second metal has an electrical potential between -0.82 and -0.60 V.
- the second metal has an electrical potential which is at least -0.3 V lower than that of the first metal, preferably at least -0,40 V lower than that of the first metal, more preferably at least -0.5 V lower than that of the first metal.
- the tool of Fig. 1 comprises an erosion detection sensor 12 for continuously detecting if the first metal of the tool housing has been attacked by acid and thus has eroded.
- the erosion detection sensor 12 communicates with a communication unit 14 which communicates information from the erosion detection sensor 12 to the top of the well. By communicating erosion information to an operator at the top of the well, the operator is able to retract the downhole tool before the tool is eroded to an extent that the tool cannot be reused.
- the erosion detection sensor 12 detects the thickness of the tool housing, e.g. by means of magnetic sensor or an ultrasonic sensor, or by another indication of the erosion of the tool housing.
- the communication unit 14 communicates the information to surface, e.g.
- the used anodes may be replaced by new anodes of the same material or anodes of another anode material.
- the anode is replaceably arranged in connection with the tool housing, e.g. as rods in grooves or as detachable components or subs.
- the downhole tool may further comprise a compartment 11, such as a magazine or cassette, of a plurality of anodes, said compartment 11 being illustrated by dotted lines in Fig. 3 .
- the compartment may comprise anodes of various metals, so that instead of having to retract the tool from the well in order to replace the anodes, the replacement may occur downhole just by releasing the used anodes and collecting new anodes from the compartment.
- the anodes in the compartment may be used to push the used anodes radially outwards, and the used anodes just drop to the bottom of the well.
- the tool housing is electrically connected with the sacrificial anode, and the downhole tool may further comprise a power supply 15 for creating an electrical potential across the anode and the tool housing as shown in Fig. 2 .
- the power supply 15 has a negative pole connected with the tool housing and a positive pole connected with the anode.
- the one or more anodes cover(s), in some embodiments, at least 10% of a surface area of the tool housing.
- the amount of anode material depends on a variety of factors, such as acid type, acid concentration, period of time the tool is submerged, temperature and pressure, anode material, surface area of the anode and surface area of the tool.
- the optimal design of the anode, choice of anode material and arrangement of the anodes must be determined from operation to operation, but if the acid turns out to be more aggressive than expected, more anodes can easily be connected with the ends of the tool housing in the required number.
- the anodes are arranged so that they are able to cover the entire tool housing which is at least one anode for each 10 metres of the downhole tool, preferably at least one anode for each 5 metres of the downhole tool, more preferably at least one anode for each 2 metres of the downhole tool, and even more preferably at least one anode for each 1 meter of the downhole tool.
- the invention further relates to a downhole system 100 comprising the downhole tool and the well containing acidic fluid 18, where the system may comprise several tools or operational tools.
- the acid is typically HCl or H 2 SO4, where HCl is particularly aggressive.
- the acid is typically used for stimulating the well by injecting acid under high pressure into the well opposite the production zones.
- the injection of acid may be performed by inserting a tubing string 19, such as coiled tubing or similar pipe or tubing, at the top 23 of the well.
- the tubing string 19 may be connected with the downhole tool, such as a driving tool arranged in front of the tubing for dragging the tubing even further down the well as shown in Fig. 6 .
- the tubing When the tubing is positioned in the well, acid 18 is supplied down the tubing 19 and injected through openings in the end of the tubing close to the driving tool.
- the acid is supplied while the tubing and thus the driving tool is retracted slowly from the well.
- the housing 8 of the driving tool is subjected to the acid, since the tool is retracted through the well which was just treated with acid.
- the anode 4 may thus be advantageously arranged in the end facing the tubing string 19.
- the propelling means which in this embodiment are the wheels on the projectable wheel arms, may be retracted into the body of the tool while performing the acid treatment.
- the downhole operation is initiated by connecting an anode with the tool housing before submerging the tool into the well for performing an operation downhole. Then the downhole tool is retracted from the well and the sacrificial anode is replaced, and then the downhole tool may be submerged again and is ready to perform another operation in the same well or another well. Before submerging the tool again, the downhole tool may also be cleaned, e.g. flushed. The tool may detect what kind of acid is present in the well in order to insert the most suitable anode for protecting the tool.
- a stroking tool is a tool providing an axial force.
- the stroking tool comprises an electrical motor for driving a pump.
- the pump pumps fluid into a piston housing to move a piston acting therein.
- the piston is arranged on the stroker shaft.
- the pump may pump fluid into the piston housing on one side and simultaneously suck fluid out on the other side of the piston.
- fluid or well fluid any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc.
- gas is meant any kind of gas composition present in a well, completion, or open hole
- oil is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc.
- Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.
- a casing any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.
- the driving unit may be a downhole tractor with projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing.
- a downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.
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- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- Mining & Mineral Resources (AREA)
- Physics & Mathematics (AREA)
- Environmental & Geological Engineering (AREA)
- Fluid Mechanics (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)
Abstract
The present invention relates to a downhole tool for performing an operation in an acid-containing well, comprising a tool housing of a first metal, a sacrificial anode made of a second metal and arranged in connection with the tool housing, the second metal having a more negative electrochemical potential than the first metal. Furthermore, the present invention relates to a downhole system comprising a downhole tool according to the invention and to a downhole operation method for operating the downhole tool according to the invention, comprising the steps of connecting an anode with the tool housing, submerging the tool into the well for performing an operation downhole, retracting the downhole tool from the well, replacing the sacrificial anode, and submerging the downhole tool for performing another operation in the same well or another well.
Description
- The present invention relates to a downhole tool for performing an operation in an acid-containing well. Furthermore, the present invention relates to a downhole system comprising a downhole tool according to the invention and to a downhole operation method for operating the downhole tool according to the invention.
- Operations in a well are performed by means of different kinds of tools, and in some cases the well contains acid which complicates the operation since the acid environment is too harsh for the downhole tools used in performing the operations. Thus, operations in wells containing acid have to be performed after the well is flushed and the acid concentration has been brought down or tools have been entered for performing the operation. This flushing process is time-consuming and in some wells even impossible because circulation of fluid is not possible.
- Another way is to use coiled tubing. However, transportation of coiled tubing equipment normally takes approximately 14 days which results in the well being prevented from producing in the meantime.
- It is an object of the present invention to wholly or partly overcome the above disadvantages and drawbacks of the prior art. More specifically, it is an object to provide an improved downhole system capable of performing the operation without using the coiled tubing equipment for performing operations in closed acid-containing wells.
- The above objects, together with numerous other objects, advantages, and features, which will become evident from the below description, are accomplished by a solution in accordance with the present invention by a downhole tool for performing an operation in an acid-containing well, comprising:
- a tool housing of a first metal, and
- a sacrificial anode made of a second metal and arranged in connection with the tool housing, the second metal having a more negative electrochemical potential than the first metal.
- When entering an acid-containing well with a downhole tool, the acid erodes the metal tool housing to such an extent that the downhole tool cannot be reused for another operation and is often simply discarded. Downhole tools are made as reusable tools since the operations often require a significant amount of force, and the downhole tools thus have a robust design and are made of robust materials, such as stainless steel, and they are therefore quite expensive to manufacture. However, operations requiring this kind of force and thus robust tools may still need to be performed in wells containing aggressive acids, and by arranging a sacrificial anode in connection with the tool housing, such operations in acid environment may be performed without having to compromise the tool itself.
- In one embodiment, the tool may be a driving tool which is self-propelling.
- In another embodiment, the tool may be a wireline tool.
- Also, the well may be a cased well or an openhole well.
- Moreover, the tool may comprise a driving tool which is self-propelling.
- Further, the driving tool may comprise wheels, each wheel being arranged on a wheel arm and being projectable from the tool housing.
- In an embodiment, the sacrificial anode may be arranged in a first end or a second end of the tool housing.
- Said anode may be threadingly connected with one of the ends of the housing.
- The downhole tool may comprise
several tool parts - Furthermore, the sacrificial anode may be an elongated element and may be arranged on an outer face of the tool housing.
- Also, the anode may be shaped as a rod.
- In an embodiment, the sacrificial anode may be arranged in a groove in the tool housing.
- Moreover, the anode may be shaped as a mesh surrounding at least part of the tool housing.
- The first metal may be stainless steel.
- The second metal may comprise chrome, magnesium, bismuth, zinc, aluminium, molybdenum, cobalt, copper, or a combination thereof.
- Furthermore, the second metal may comprise additives or other constituents.
- In an embodiment, the first metal may have an electrical potential between -0.32 and -0.40 V.
- Also, the second metal may have an electrical potential between -0.82 and -0.60 V.
- Further, the second metal may have an electrical potential which is at least -0.3 V lower than that of the first metal, preferably at least -0,40 V lower than that of the first metal, more preferably at least -0.5 V lower than that of the first metal.
- Additionally, the anode may be replaceably arranged in connection with the tool housing.
- Several anodes may be connected with each other.
- The downhole tool as described above may further comprise a compartment, such as a magazine or cassette, of a plurality of anodes.
- Said compartment may comprise anodes of various metals.
- Additionally, the downhole tool as described above may further comprise an erosion detection sensor for detection of erosion of the first metal of the tool housing.
- Moreover, the downhole tool as described above may comprise a communication unit for receiving information from the sensor for detection of erosion of the first metal and communicating the information to surface.
- The sensor and the communication unit enable retraction of the downhole tool before the downhole tool is eroded to an extent that it cannot be reused. The sensor detects the thickness of the tool housing or another indication of the erosion of the tool housing, and the communication unit communicates the information to surface, e.g. only when the indicator is above a certain extent of erosion.
- In an embodiment, the tool housing may be electrically connected with the sacrificial anode.
- Also, the downhole tool as described above may further comprise a power supply for creating an electrical potential across the anode and the tool housing.
- The power supply may have a negative pole connected with the tool housing and a positive pole connected with the anode.
- Furthermore, the downhole tool may further comprise an acid detection sensor.
- In an embodiment, the one or more anodes may cover at least 10% of a surface area of the tool housing.
- Moreover, the downhole tool as described above may comprise several anodes arranged with at least one anode for each 10 metres of the downhole tool, preferably at least one anode for each 5 metres of the downhole tool, more preferably at least one anode for each 2 metres of the downhole tool, and even more preferably at least one anode for each 1 metre of the downhole tool.
- In addition, the downhole tool as described above may further comprise an operational tool section, such as a drill bit, an anchor tool, a stroking tool, a key tool, a release tool or a milling tool.
- The anodes may be arranged between the operation tool section and the tool housing.
- Further, the driving tool may propel forward in the well at a velocity of at least 5 metres/hour.
- The present invention furthermore related to a downhole system comprising a downhole tool as described above and the well containing acidic fluid.
- The downhole system as described above may comprise several tools.
- In an embodiment, anodes may be arranged between the tools.
- The acid may be HCl, H2S or H2SO4 or any combination thereof.
- Also, the downhole system as described above may further comprise tubing string, such as coiled tubing, connected with the downhole tool for supplying acid.
- The present invention also relates to a downhole operation method for operating the downhole tool as described above, comprising the steps of:
- connecting an anode with the tool housing,
- submerging the tool into the well for performing an operation downhole,
- retracting the downhole tool from the well,
- replacing the sacrificial anode, and
- submerging the downhole tool for performing another operation in the same well or another well.
- Further, the downhole operation method as described above may further comprise the step of cleaning the downhole tool before submerging the tool again.
- In the step of replacing the anode, the anode may be replaced for another anode of a material which is different from that of the anode which is replaced.
- Moreover, the downhole operation method as described above may further comprise the step of detecting which acid is present in the well.
- Finally, the downhole operation method may further comprise the step of measuring the erosion of the housing.
- The invention and its many advantages will be described in more detail below with reference to the accompanying schematic drawings, which for the purpose of illustration show some non-limiting embodiments and in which
-
Fig. 1 shows a cross-sectional view of a well in which a downhole tool according to the present invention is submerged, -
Fig. 2 shows another embodiment of the downhole tool comprising anodes in both ends, -
Fig. 3 shows yet another embodiment of the downhole tool comprising rod anodes arranged outside the tool housing, -
Fig. 4 shows the downhole tool ofFig. 3 seen from one end, -
Fig. 5 shows a downhole tool having mesh anode, and -
Fig. 6 shows a downhole system according to the invention. - All the figures are highly schematic and not necessarily to scale, and they show only those parts which are necessary in order to elucidate the invention, other parts being omitted or merely suggested.
-
Fig. 1 shows adownhole tool 1 submerged into a well 2 containing an acid-containingfluid 18. The downhole tool comprises atool housing 3 made of a first metal and asacrificial anode 4 made of a second metal. Theanode 4 is arranged in connection with onefirst end 22 of the tool housing being the end furthest away from the top of the well. In order to prevent erosion or etching of the tool housing when submerged in the acid-containingfluid 18, the second metal of the anode has a more negative electrochemical potential than the first metal of the tool housing. - When performing an operation in an acid-containing well, the acid erodes the metal tool housing to such an extent that the downhole tool cannot be reused for another operation. Downhole tools cannot be made in disposable materials, such as plastic, since the operations often require a significant amount of force. Thus the tools have a robust design and are made of robust materials, such as stainless steel. The tools are therefore quite expensive to manufacture and hence being able to avoid discarding a tool after having performed one operation in an acid-containing well is very beneficial. The well may contain acid before the tool enters the well, or the tool may be used to perform the acid stimulation. By arranging a sacrificial anode in connection with the tool housing, the anode material is eroded or sacrificed in favour of the metal of the tool itself, and thus operations in the acid environment may be performed without having to compromise the tool itself. Typical acids in an acid-containing well may be HCl (hydrogen chloride) which is typically injected into the well for performing a stimulation operation, or H2S (hydrogen sulphide) and H2SO4 (hydrogen sulphate) which develop in the well. Furthermore, inhibitors are added to the fluid in the well for protecting for example the metal casing, and the sacrificial anode therefore has to be designed to match the specific well in which the tool is to operate.
- In
Fig. 1 , the tool is adriving tool 5 which is self-propelling, meaning that the tool is able to propel itself forward in the well. The tool is connected with the top of the well via awireline 24 and is thus a so-called wireline tool. The well is a cased well but may also be an openhole well. The driving tool comprises fourwheels 6 and each wheel is arranged on awheel arm 7 which is radially projectable from thetool housing 3, as shown also shown inFig. 4 . - In
Fig. 2 , a sacrificial anode is arranged in both thefirst end 22 and asecond end 25 of thetool housing 3. The downhole tool comprises twotool parts anchor tool 20 and akey tool 21. The anchor tool has four radiallyprojectable anchors 27 anchoring the tool in the longitudinal direction of the well so that the key tool can project itskeys 28 and engage a slidingsleeve 29 for opening or closing the sleeve. A third anode is arranged between the anchor tool and the key tool, and the anodes are thus able to cover the entire tool surface so that the downhole tool is not eroded or etched and thus damaged. In another embodiment, the downhole tool comprises another operational tool section, such as a drill bit, a stroking tool, a release tool or a milling tool. - The anodes are detachable and are threadingly connected with the ends of the housing of the anchor tool and the ends of the housing of the key tool as shown in
Fig. 2 . The anodes are designed as cylindrical modules also referred to as "subs" which can easily be connected to any tool by normal detachable connection means. - In
Fig. 3 , the downhole tool comprises severalsacrificial anodes 4. The anodes are shaped as elongated elements and are arranged on anouter face 8 of the tool housing of thedriving tool 5. The anodes are shaped as solid rods, and the sacrificial anodes are arranged in agroove 9 in the tool housing as shown inFig. 4 . - As shown in
Fig. 5 , the anode may also be shaped as amesh 30 surrounding at least part of theouter surface 8 of thetool housing 3. InFig. 5 , thedownhole tool 1 comprises asensor unit 26 which e.g. comprises anacid detecting sensor 16, which is submerged into an openhole well 2 containingacid 18. Thesensor unit 26 may also be another kind of sensor, such as a casing collar locator, a temperature measuring unit, a pressure measuring unit, a diagnostics related sensor or similar sensor unit. In the event that the tool is not submergible all the way into the casing, a driving unit such as a downhole tractor can be used to push the tool all the way into position in the well. - The outer face of the tool is mostly made of the first metal which is a suitable stainless steel type. The anode is made of the second metal which may be chrome, magnesium, bismuth, zinc, aluminium, molybdenum, cobalt, copper, or a combination thereof. The sacrificial anode is designed to match a specific well, the condition of which depends on the acid and inhibitor content of the well in which the tool is to operate, and may therefore comprise any combination of suitable anode metals or metal alloys and even additives or other constituents for providing the most efficient sacrificial anode for the tool in that particular environment of the well. The second material may - apart from the suitable anode material - comprise additives or other kinds of metal. Even though the anode is very efficient, the tool may still be attacked by the acid, but the tool will be less damaged than if no sacrificial anode is used and not to such an extent that the tool cannot be reused for another operation.
- The first metal is substantially stainless steel or similar material and has an electrical potential between -0.32 and -0.40 V. The second metal has an electrical potential between -0.82 and -0.60 V. Thus, the second metal has an electrical potential which is at least -0.3 V lower than that of the first metal, preferably at least -0,40 V lower than that of the first metal, more preferably at least -0.5 V lower than that of the first metal.
- The tool of
Fig. 1 comprises anerosion detection sensor 12 for continuously detecting if the first metal of the tool housing has been attacked by acid and thus has eroded. Theerosion detection sensor 12 communicates with acommunication unit 14 which communicates information from theerosion detection sensor 12 to the top of the well. By communicating erosion information to an operator at the top of the well, the operator is able to retract the downhole tool before the tool is eroded to an extent that the tool cannot be reused. Theerosion detection sensor 12 detects the thickness of the tool housing, e.g. by means of magnetic sensor or an ultrasonic sensor, or by another indication of the erosion of the tool housing. Thecommunication unit 14 communicates the information to surface, e.g. when the indicator is above a certain amount of erosion so that the downhole tool may be retracted from the well before the tool is damaged too much. After retracting the tool from the well, the used anodes may be replaced by new anodes of the same material or anodes of another anode material. - As mentioned, the anode is replaceably arranged in connection with the tool housing, e.g. as rods in grooves or as detachable components or subs. The downhole tool may further comprise a
compartment 11, such as a magazine or cassette, of a plurality of anodes, saidcompartment 11 being illustrated by dotted lines inFig. 3 . The compartment may comprise anodes of various metals, so that instead of having to retract the tool from the well in order to replace the anodes, the replacement may occur downhole just by releasing the used anodes and collecting new anodes from the compartment. The anodes in the compartment may be used to push the used anodes radially outwards, and the used anodes just drop to the bottom of the well. - The tool housing is electrically connected with the sacrificial anode, and the downhole tool may further comprise a
power supply 15 for creating an electrical potential across the anode and the tool housing as shown inFig. 2 . Thus, thepower supply 15 has a negative pole connected with the tool housing and a positive pole connected with the anode. - In order to protect the downhole tool, the one or more anodes cover(s), in some embodiments, at least 10% of a surface area of the tool housing. The amount of anode material depends on a variety of factors, such as acid type, acid concentration, period of time the tool is submerged, temperature and pressure, anode material, surface area of the anode and surface area of the tool. The optimal design of the anode, choice of anode material and arrangement of the anodes must be determined from operation to operation, but if the acid turns out to be more aggressive than expected, more anodes can easily be connected with the ends of the tool housing in the required number.
- The anodes are arranged so that they are able to cover the entire tool housing which is at least one anode for each 10 metres of the downhole tool, preferably at least one anode for each 5 metres of the downhole tool, more preferably at least one anode for each 2 metres of the downhole tool, and even more preferably at least one anode for each 1 meter of the downhole tool.
- The invention further relates to a
downhole system 100 comprising the downhole tool and the well containingacidic fluid 18, where the system may comprise several tools or operational tools. The acid is typically HCl or H2SO4, where HCl is particularly aggressive. The acid is typically used for stimulating the well by injecting acid under high pressure into the well opposite the production zones. The injection of acid may be performed by inserting atubing string 19, such as coiled tubing or similar pipe or tubing, at the top 23 of the well. Thetubing string 19 may be connected with the downhole tool, such as a driving tool arranged in front of the tubing for dragging the tubing even further down the well as shown inFig. 6 . When the tubing is positioned in the well,acid 18 is supplied down thetubing 19 and injected through openings in the end of the tubing close to the driving tool. The acid is supplied while the tubing and thus the driving tool is retracted slowly from the well. During the acid treatment, thehousing 8 of the driving tool is subjected to the acid, since the tool is retracted through the well which was just treated with acid. Theanode 4 may thus be advantageously arranged in the end facing thetubing string 19. To further protect the tool, the propelling means, which in this embodiment are the wheels on the projectable wheel arms, may be retracted into the body of the tool while performing the acid treatment. - The downhole operation is initiated by connecting an anode with the tool housing before submerging the tool into the well for performing an operation downhole. Then the downhole tool is retracted from the well and the sacrificial anode is replaced, and then the downhole tool may be submerged again and is ready to perform another operation in the same well or another well. Before submerging the tool again, the downhole tool may also be cleaned, e.g. flushed. The tool may detect what kind of acid is present in the well in order to insert the most suitable anode for protecting the tool.
- A stroking tool is a tool providing an axial force. The stroking tool comprises an electrical motor for driving a pump. The pump pumps fluid into a piston housing to move a piston acting therein. The piston is arranged on the stroker shaft. The pump may pump fluid into the piston housing on one side and simultaneously suck fluid out on the other side of the piston.
- By fluid or well fluid is meant any kind of fluid that may be present in oil or gas wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is meant any kind of gas composition present in a well, completion, or open hole, and by oil is meant any kind of oil composition, such as crude oil, an oil-containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.
- By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.
- The driving unit may be a downhole tractor with projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.
- Although the invention has been described in the above in connection with preferred embodiments of the invention, it will be evident for a person skilled in the art that several modifications are conceivable without departing from the invention as defined by the following claims.
Claims (15)
- A downhole tool (1) for performing an operation in an acid-containing well (2), comprising:- a tool housing (3) of a first metal, and- a sacrificial anode (4) made of a second metal and arranged in connection with the tool housing, the second metal having a more negative electrochemical potential than the first metal.
- A downhole tool according to claim 1, wherein the tool is a driving tool (5) which is self-propelling.
- A downhole tool according to claim 2, wherein the driving tool comprises wheels (6), each wheel being arranged on a wheel arm (7) and being projectable from the tool housing.
- A downhole tool according to any of the preceding claims, wherein the sacrificial anode is arranged in a first end (22) or a second end (25) of the tool housing.
- A downhole tool according to any of the preceding claims, wherein the sacrificial anode is an elongated element and is arranged on an outer face (8) of the tool housing.
- A downhole tool according to any of the preceding claims, wherein the sacrificial anode is arranged in a groove (9) in the tool housing.
- A downhole tool according to any of the preceding claims, wherein the anode is shaped as a mesh surrounding at least part of the tool housing.
- A downhole tool according to any of the preceding claims, wherein the second metal comprises chrome, magnesium, bismuth, zinc, aluminium, molybdenum, cobalt copper, or a combination thereof.
- A downhole tool according to any of the preceding claims, wherein the anode is replaceably arranged in connection with the tool housing.
- A downhole tool according to any of the preceding claims, further comprising a compartment (11), such as a magazine or cassette, of a plurality of anodes.
- A downhole tool according to any of the preceding claims, further comprising an erosion detection sensor (12) for detection of erosion of the first metal of the tool housing.
- A downhole system comprising a downhole tool according to any of the preceding claims, and the well containing acidic fluid (18).
- A downhole system according to claim 12, wherein the system comprises several tools.
- A downhole system according to claim 12 or 13, further comprising tubing string (19), such as coiled tubing, connected with the downhole tool for supplying acid.
- A downhole operation method for operating the downhole tool according to any of claims 1-11, comprising the steps of:- connecting an anode with the tool housing,- submerging the tool into the well for performing an operation downhole,- retracting the downhole tool from the well,- replacing the sacrificial anode, and- submerging the downhole tool for performing another operation in the same well or another well.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12193847.6A EP2735695A1 (en) | 2012-11-22 | 2012-11-22 | Downhole tool |
PCT/EP2013/074443 WO2014079961A1 (en) | 2012-11-22 | 2013-11-22 | Downhole tool |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12193847.6A EP2735695A1 (en) | 2012-11-22 | 2012-11-22 | Downhole tool |
Publications (1)
Publication Number | Publication Date |
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EP2735695A1 true EP2735695A1 (en) | 2014-05-28 |
Family
ID=47263123
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP12193847.6A Withdrawn EP2735695A1 (en) | 2012-11-22 | 2012-11-22 | Downhole tool |
Country Status (2)
Country | Link |
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EP (1) | EP2735695A1 (en) |
WO (1) | WO2014079961A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
RU2667166C1 (en) * | 2014-12-15 | 2018-09-17 | Бейкер Хьюз Инкорпорейтед | System and method of management of electric drill tools and sensors for flexible pipes |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN105526958A (en) * | 2016-02-01 | 2016-04-27 | 西安科技大学 | Boring photoelectric probe support |
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US4211625A (en) * | 1978-09-11 | 1980-07-08 | Borg-Warner Corporation | Impressed current cathodic protection system for submersible downhole pumping assembly |
US4496013A (en) * | 1982-08-23 | 1985-01-29 | Smith International, Inc. | Prevention of cone seal failures in rock bits |
US4624329A (en) * | 1984-02-15 | 1986-11-25 | Varel Manufacturing Company | Rotating cutter drill set |
US6331242B1 (en) * | 1999-12-06 | 2001-12-18 | United States Pipe And Foundry Company, Inc. | Anodic encasement corrosion protection system for underground storage tanks, and metallic components thereof |
US20110315444A1 (en) * | 2010-06-25 | 2011-12-29 | Baker Hughes Incorporated | Apparatus and Methods for Corrosion Protection of Downhole Tools |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
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DZ3387A1 (en) * | 2000-07-18 | 2002-01-24 | Exxonmobil Upstream Res Co | PROCESS FOR TREATING MULTIPLE INTERVALS IN A WELLBORE |
-
2012
- 2012-11-22 EP EP12193847.6A patent/EP2735695A1/en not_active Withdrawn
-
2013
- 2013-11-22 WO PCT/EP2013/074443 patent/WO2014079961A1/en active Application Filing
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
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US4211625A (en) * | 1978-09-11 | 1980-07-08 | Borg-Warner Corporation | Impressed current cathodic protection system for submersible downhole pumping assembly |
US4496013A (en) * | 1982-08-23 | 1985-01-29 | Smith International, Inc. | Prevention of cone seal failures in rock bits |
US4624329A (en) * | 1984-02-15 | 1986-11-25 | Varel Manufacturing Company | Rotating cutter drill set |
US6331242B1 (en) * | 1999-12-06 | 2001-12-18 | United States Pipe And Foundry Company, Inc. | Anodic encasement corrosion protection system for underground storage tanks, and metallic components thereof |
US20110315444A1 (en) * | 2010-06-25 | 2011-12-29 | Baker Hughes Incorporated | Apparatus and Methods for Corrosion Protection of Downhole Tools |
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RU2667166C1 (en) * | 2014-12-15 | 2018-09-17 | Бейкер Хьюз Инкорпорейтед | System and method of management of electric drill tools and sensors for flexible pipes |
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