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| ==Reasons for fishing== | | ==Reasons for fishing== |
| + | <gallery mode=packed heights=400px widths=400px> |
| + | fishing_fig1.png|{{figure number|1}}Differential sticking. ©Exploration Logging<ref name=ExplorationLogging>Exploration Logging, Inc., 1979, Field geologists training guide—an introduction to oilfield geology, mudlogging, and formation evaluation: Sacramento, CA, p. 4-52 to 4-57.</ref> |
| + | file:fishing_fig2.png|{{figure number|2}}Key seating. © Short;<ref name=Short1981>Short, J. A., 1981, Fishing and casing repair: Tulsa, OK, PennWellBooks, 365p.</ref> courtesy of PennWell Books. |
| + | </gallery> |
| | | |
| ''Fishing'' (in the oilfield sense) refers to the recovery of unwanted material left in the wellbore. Numerous situations can occur that require fishing: | | ''Fishing'' (in the oilfield sense) refers to the recovery of unwanted material left in the wellbore. Numerous situations can occur that require fishing: |
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| * Items dropped into the hole from the rig floor. | | * Items dropped into the hole from the rig floor. |
| * Failure of surface equipment, especially pumps, which allows the hole to cave in and stick the drill string. | | * Failure of surface equipment, especially pumps, which allows the hole to cave in and stick the drill string. |
− | * Differential sticking to a permeable formation (Figure 1). | + | * Differential sticking to a permeable formation ([[:file:fishing_fig1.png|Figure 1]]). |
− | * Key seating, where a slot is worn into the wall of the well (Figure 2). | + | * Key seating, where a slot is worn into the wall of the well ([[:file:fishing_fig2.png|Figure 2]]). |
| * Twist-offs resulting from a stuck drill string being rotated until the pipe shears above the sticking point. | | * Twist-offs resulting from a stuck drill string being rotated until the pipe shears above the sticking point. |
| * Loss of portions of downhole equipment, such as stabilizer fragments and bit cones. | | * Loss of portions of downhole equipment, such as stabilizer fragments and bit cones. |
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| * Pulling the drill string apart when trying to free stuck pipe. | | * Pulling the drill string apart when trying to free stuck pipe. |
| * Bridging off by swelling formations or a collapsed hole. | | * Bridging off by swelling formations or a collapsed hole. |
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− | [[file:fishing_fig1.png|thumb|{{figure number|1}}Differential sticking. Copyright: Exploration Logging, 1979.]]
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− |
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− | [[file:fishing_fig2.png|thumb|{{figure number|2}}Key seating. Copyright: Short, 1981; courtesy of PennWell Books.]]
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| When material is left in the hole due to these or other factors, a decision must be made whether to try to recover the material, to sidetrack around the original material, to abandon the well, or to attempt to complete in a shallower zone. Because all but the first of these options are costly, and the last is often undesirable, an attempt to recover the fish is almost always made. | | When material is left in the hole due to these or other factors, a decision must be made whether to try to recover the material, to sidetrack around the original material, to abandon the well, or to attempt to complete in a shallower zone. Because all but the first of these options are costly, and the last is often undesirable, an attempt to recover the fish is almost always made. |
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| ==Types of fishing tools== | | ==Types of fishing tools== |
| + | <gallery mode=packed heights=200px widths=200px> |
| + | file:fishing_fig3.png|{{figure number|3}}Magnet. |
| + | file:fishing_fig4.png|{{figure number|4}}Junk basket. |
| + | file:fishing_fig5.png|{{figure number|5}}Poor boy junk basket. © Exploration Logging, 1979. |
| + | file:fishing_fig6.png|{{figure number|6}}Core type basket. |
| + | file:fishing_fig7.png|{{figure number|7}}(a) Tapered mill, (b) Flat mill. |
| + | file:fishing_fig8.png|{{figure number|8}}Washover pipe. |
| + | file:fishing_fig9.png|{{figure number|9}}Overshot. |
| + | file:fishing_fig10.png|{{figure number|10}}Pipe spear. |
| + | file:fishing_fig11.png|{{figure number|11}}Wireline spear. |
| + | </gallery> |
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| Many specialized tools have been developed to address specific types of recoveries. In general, fishing tools fall into two categories: those used to recover small items (junk) and those used to recover larger items such as drill pipe. | | Many specialized tools have been developed to address specific types of recoveries. In general, fishing tools fall into two categories: those used to recover small items (junk) and those used to recover larger items such as drill pipe. |
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| ====Magnet==== | | ====Magnet==== |
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− | A magnet is used to recover small metal pieces from the hole, such as bit cones (Figure 3). | + | A magnet is used to recover small metal pieces from the hole, such as bit cones ([[:file:fishing_fig3.png|Figure 3]]). |
− | | |
− | [[file:fishing_fig3.png|thumb|{{figure number|3}}Magnet.]] | |
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| ====Junk or boot basket==== | | ====Junk or boot basket==== |
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− | A “junk” or “boot” basket is run just above the bit and catches small pieces of junk thrown up by turbulence. It is often part of the BHA, and it is almost always run before a core barrel or diamond bit to prevent damage (Figure 4). | + | A “junk” or “boot” basket is run just above the bit and catches small pieces of junk thrown up by turbulence. It is often part of the BHA, and it is almost always run before a core barrel or diamond bit to prevent damage ([[:file:fishing_fig4.png|Figure 4]]). |
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− | [[file:fishing_fig4.png|thumb|{{figure number|4}}Junk basket.]] | |
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| ====Poor boy junk basket==== | | ====Poor boy junk basket==== |
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− | Often made at the wellsite, a “poor boy” junk basket consists of a small section of casing with beveled “fingers” cut into the end. The basket is lowered on the drill string where it cuts a small core. More weight is applied to the tool, bending the fingers in and snaring the core containing the junk (Figure 5). | + | Often made at the wellsite, a “poor boy” junk basket consists of a small section of casing with beveled “fingers” cut into the end. The basket is lowered on the drill string where it cuts a small core. More weight is applied to the tool, bending the fingers in and snaring the core containing the junk ([[:file:fishing_fig5.png|Figure 5]]). |
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− | [[file:fishing_fig5.png|thumb|{{figure number|5}}Poor boy junk basket. Copyright: Exploration Logging, 1979.]] | |
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| ====Core type basket==== | | ====Core type basket==== |
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− | A core type basket consists of a barrel with a mill shoe and two sets of internal catchers. The basket is slowly rotated onto the junk in the hole where it cuts a small core. The catchers hold the core while the tool is retrieved (Figure 6). | + | A core type basket consists of a barrel with a mill shoe and two sets of internal catchers. The basket is slowly rotated onto the junk in the hole where it cuts a small core. The catchers hold the core while the tool is retrieved ([[:file:fishing_fig6.png|Figure 6]]). |
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− | [[file:fishing_fig6.png|thumb|{{figure number|6}}Core type basket.]] | |
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| ===Tools commonly used to retrieve drill pipe and logging tools=== | | ===Tools commonly used to retrieve drill pipe and logging tools=== |
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| ====Mill==== | | ====Mill==== |
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− | Before some fish can be recovered, it is necessary to “dress” the top, that is, to grind the uneven top to a shape that the fishing tool can grasp, or to clear and open the inside of the fish. To do this, either a flat or a tapered mill bit is used (Figure 7). The mill bit has tungsten carbide abrasive surfaces that can trim the fish to the desired shape. | + | Before some fish can be recovered, it is necessary to “dress” the top, that is, to grind the uneven top to a shape that the fishing tool can grasp, or to clear and open the inside of the fish. To do this, either a flat or a tapered mill bit is used ([[:file:fishing_fig7.png|Figure 7]]). The mill bit has tungsten carbide abrasive surfaces that can trim the fish to the desired shape. |
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− | [[file:fishing_fig7.png|thumb|{{figure number|7}}(a) Tapered mill, (b) Flat mill.]]
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| ====Washover==== | | ====Washover==== |
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− | Washover equipment consists of casing with a cutting shoe. It is run over the fish to clear away debris before the fishing tool is run (Figure 8). Washing over is often done to free key-seated or differentially stuck pipe. | + | Washover equipment consists of casing with a cutting shoe. It is run over the fish to clear away debris before the fishing tool is run ([[:file:fishing_fig8.png|Figure 8]]). Washing over is often done to free key-seated or differentially stuck pipe. |
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− | [[file:fishing_fig8.png|thumb|{{figure number|8}}Washover pipe.]]
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| ====Overshot==== | | ====Overshot==== |
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− | The most common and widely used tool, the overshot consists of a large diameter, open mouth pipe with a tapered tap or die, or, more commonly, with a set of slips that grab the outside of the fish when the assembly is lifted and prevent its release (Figure 9). | + | The most common and widely used tool, the overshot consists of a large diameter, open mouth pipe with a tapered tap or die, or, more commonly, with a set of slips that grab the outside of the fish when the assembly is lifted and prevent its release ([[:file:fishing_fig9.png|Figure 9]]). |
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− | [[file:fishing_fig9.png|thumb|{{figure number|9}}Overshot.]] | |
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| ====Pipe spear==== | | ====Pipe spear==== |
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− | Like an overshot, a pipe spear is used to recover large tubulars, but it instead attaches to the inside of the fish via a set of slips that are extended after the spear is inserted (Figure 10). | + | Like an overshot, a pipe spear is used to recover large tubulars, but it instead attaches to the inside of the fish via a set of slips that are extended after the spear is inserted ([[:file:fishing_fig10.png|Figure 10]]). |
− | | |
− | [[file:fishing_fig10.png|thumb|{{figure number|10}}Pipe spear.]] | |
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| ====Wireline spear==== | | ====Wireline spear==== |
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− | A wireline spear is a simple spear with barbs used to hook parted wireline (Figure 11). | + | A wireline spear is a simple spear with barbs used to hook parted wireline ([[:file:fishing_fig11.png|Figure 11]]). |
− | | |
− | [[file:fishing_fig11.png|thumb|{{figure number|11}}Wireline spear.]] | |
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| ==Freeing stuck pipe== | | ==Freeing stuck pipe== |
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| * [[Core orientation]] | | * [[Core orientation]] |
| * [[Mudlogging: Gas extraction and monitoring]] | | * [[Mudlogging: Gas extraction and monitoring]] |
| + | |
| + | ==References== |
| + | {{reflist}} |
| | | |
| ==External links== | | ==External links== |
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| [[Category:Wellsite methods]] | | [[Category:Wellsite methods]] |
| + | [[Category:Methods in Exploration 10]] |