Downhole casing auger for removal of paraffin from oil and gas wells

Abstract

An apparatus and method for removing paraffin from a casing in a borehole of an oil / gas well without using pressure from the well. The apparatus may include a shaft with a plurality of flights wound around the shaft in a spiral pattern. The apparatus may include a coupling on one end for attachment to a drilling string. The method may include lowering the apparatus into the casing down to a paraffin cake lodged in the borehole. The apparatus may be used dislodge paraffin using the flights to cut the paraffin, an end of the apparatus, impact the paraffin, or both. Then the dislodged paraffin may be collected on the flights and lifted out of the casing for disposal.

Description

BACKGROUND OF THE DISCLOSURE1. Field of the Disclosure

[0001] This disclosure relates to the field of downhole tools associated with production maintenance of oil and gas wells in earth formations, especially to remove accumulations of paraffins from within casings.2. DESCRIPTION OF THE RELATED ART

[0002] A frequent problem in oil and gas wells is the build-up of undesirable material in the casing that creates that annular space around the tubing. One particularly difficult undesirable material is paraffin, which is a byproduct of producing crude oil and accumulates in the well over time as “heavier” molecular chains of hydrocarbons separate during production. Paraffin can exist in multitude of forms. It can have a consistency within the well as a thick soup, a sticky-moldable mess like children's clay, or a solid chunk of wax, such as a room temperature stable wax candle found in households. Paraffin accumulation in oil wells is the most common reason for decreased oil and gas production and can be extremely costly and time consuming to remove.

[0003] Paraffin accumulation in oil wells causes numerous problems, including, but not limited to, decreased oil production, decreased gas production, pressure buildup downhole beneath the paraffin “cake” layer, and a plugged casing. Plugging the casing means that pumped in hot fresh water is blocked and cannot be used to treat the paraffin or eliminate salt issues downhole. This accumulation can be extremely expensive to remove. Paraffin accumulation downhole can cause well inflow to cease if the pressure buildup behind the paraffin cake increases to match the formation pressure.

[0004] Traditionally, paraffin has been removed by “knifing” or “hot-oiling”. Both of these methods have major downsides when it comes to operating oil and gas wells. Knifing involved inserting a sharp tool in the wellbore and using it to cut out chunks of hard paraffin. Knifing is a long and arduous process that can take weeks to complete depending on the extent of the problem.

[0005] Hot-oiling is an alternative technique whereby oil is heated above the melting temperature of paraffin and then pumped into the well to melt the paraffin deposit so that the deposit can be removed. Hot oiling is a quick fix that is costly, dangerous to operators (two pressurized propane tanks next to open burners and a well that can flow natural gas at any moment presents a high risk of explosion), and may harm the formation. The addition of hot oil may also cause the lighter and heavier hydrocarbons in the deposit to separate and cause the remaining paraffin cake to become significantly harder.

[0006] Even if the paraffin cake is unplugged due to hot oiling, the super-heated paraffin now needs to be raised to the surface by running it through the downhole pump at the bottom of the well, where the paraffin may solidify enough to clog up the pump's intake and shut the well down again.

[0007] The hot oiling process can be performed with water instead of oil, but this suffers from many of the same problems. Additionally, water is limited by its boiling temperature as to how much heat can be contained therein for melting of the downhole paraffin, though the water has a higher heat capacity that many oils.

[0008] While paraffin accumulation has been a long standing problem in the oil and gas industry, it has grown worse over time due to declines in reservoir pressure. As a formation is worked and pressure declines, there is less pressure to force paraffin to the surface unaided. Further, repeated hot-oiling sometimes damage wellbores and further increase the cost of removal. This weighs heavily against the economics of running the well.

[0009] Several augers designs, such as U.S. Pat. No. 3,044,552 have been developed to clear paraffin from tubing; however, all of these solutions require the well to be flowing under its own pressure and do not address paraffin deposits between the tubing and the casing. Tools like these are not suitable for old or neglected wells that have marginal reservoir pressure levels.

[0010] Chinese Pat. No. 21215728U requires a free flowing well or external gas source to “push” a plunger in the well in order to remove the paraffin.

[0011] U.S. Pat. No. 2,453,199 requires a well to be actively pumping in order to operate as it uses a helical scraper tool combined with a sucker rod.

[0012] Similarly, U.S. Pat. No. 6,182,754 requires a helical scraper attached to a sucker rod that moves up and down in the tubing of the well.

[0013] Therefore, what is needed is an apparatus for removing paraffin from inside the wellbore that does not require mere stabbing of the paraffin cake and fishing out pieces or melting it and passing the melted paraffin through a downhole pump. What is needed is an apparatus that can cut and lift the paraffin out of the wellbore, particularly solid or dense paraffin, when the well is not flowing and in a quick and efficient manner that does not damage the formation or downhole equipment.BRIEF SUMMARY OF THE DISCLOSURE

[0014] In aspects, the present disclosure is related to maintenance of oil and gas wells. Specifically, the present disclosure is related to removal of accumulated paraffin deposits down hole.

[0015] One embodiment according to the present disclosure includes an apparatus for removing paraffin, the apparatus that includes a longitudinal member having a first end and second end and configured for insertion in a casing of a borehole; a plurality of flights welded around the outer surface of the longitudinal member in a spiral pattern; and a coupler in mechanical communication with the second end configured to attach the apparatus to a drilling string. The longitudinal member may be solid or tubular. A piercer may be disposed on the first end of the longitudinal member. When the longitudinal member is tubular, the piercer may include one or more openings with passages that allow fluid pumped through the longitudinal member to be released by the piercer. The longitudinal member may have one or more openings in its surface disposed proximate to the first end, one or more openings in its surface disposed between a pair of the flights, or both. The longitudinal member may be made of steel. The plurality of flights may be continuous formed from a continuous piece of metal or discontinuous formed from multiple pieces of metal.

[0016] Another embodiment according to the present disclosure includes a method for removing paraffin from a casing of a borehole for an oil / gas well including the steps of: inserting an apparatus in the casing of the borehole down to contact with a paraffin cake, where the apparatus includes: a longitudinal member having a first end and second end and configured for insertion in a casing of a borehole; a plurality of flights welded around the outer surface of the longitudinal member in a spiral pattern; and a coupler in mechanical communication with the second end configured to attach the apparatus to a drilling string; rotating the apparatus to cut and dislodge paraffin from the paraffin cake with the plurality of flights; and lifting the apparatus with the dislodged paraffin to the surface. The method may also include a step of removing a production tubing from the casing prior to inserting the apparatus. The method may also include a step of impacting the paraffin cake with the apparatus. The method may also include a step of injecting a fluid into the paraffin cake through the apparatus, wherein the fluid is selected to loosen, melt, or dissolve the paraffin cake. The method may also include a step of removing the dislodged paraffin from the apparatus.

[0017] Examples of the more important features of the disclosure have been summarized rather broadly in order that the detailed description thereof that follows may be better understood and in order that the contributions they represent to the art may be appreciated. There are, of course, additional features of the disclosure that will be described hereinafter and which will form the subject of the claims appended hereto.BRIEF DESCRIPTION OF THE DRAWINGS

[0018] A better understanding of the present disclosure can be obtained with the following detailed descriptions of the various disclosed embodiments in the drawings, which are given by way of illustration only, and thus are not limiting the present disclosure, and wherein:

[0019] FIG. 1A is a diagram of a casing auger configured to remove paraffin from a casing in a borehole according to one embodiment of the present disclosure;

[0020] FIG. 1B is a three dimensional diagram of the casing auger of FIG. 1A according to one embodiment of the present disclosure;

[0021] FIG. 2 is a diagram of the casing auger of FIG. 1A disposed in a borehole according to one embodiment of the present disclosure;

[0022] FIG. 3A is a diagram a section of a borehole casing with a plug of paraffin cake surrounding a segment of tubing according to one embodiment of the present disclosure;

[0023] FIG. 3B is a diagram of the borehole section of FIG. 3A after removal of the tubing according to one embodiment of the present disclosure;

[0024] FIG. 3C is a diagram of the borehole section of FIG. 3A after insertion of the casing auger of FIG. 1 above the paraffin cake according to one embodiment of the present disclosure;

[0025] FIG. 3D is a diagram of the borehole section of FIG. 3A after penetration of the paraffin cake by the casing auger according to one embodiment of the present disclosure;

[0026] FIG. 3E is a diagram of the borehole section of FIG. 3A after removal of the casing auger of FIG. 1 from the paraffin cake and during removal of the paraffin wax up the borehole according to one embodiment of the present disclosure; and

[0027] FIG. 4A is a diagram of an alternative casing auger with a piercer configured to remove paraffin from a casing in a borehole according to one embodiment of the present disclosure;

[0028] FIG. 4B is a three dimensional diagram of the alternative casing auger of FIG. 4A according to one embodiment of the present disclosure;

[0029] FIG. 4C is a diagram of an alternative casing auger with a piercer and openings proximate to the bottom for injection of fluids and configured to remove paraffin from a casing in a borehole according to one embodiment of the present disclosure;

[0030] FIG. 4D is a three dimensional diagram of the alternative casing auger of FIG. 4C according to one embodiment of the present disclosure;

[0031] FIG. 4E is a diagram of an alternative casing auger with a piercer and openings between the some of the flights configured to remove paraffin from a casing in a borehole according to one embodiment of the present disclosure;

[0032] FIG. 4F is a three dimensional diagram of the alternative casing auger of FIG. 4E according to one embodiment of the present disclosure; and

[0033] FIG. 5 is a flow chart of an exemplary method for removing paraffin using the casing auger of FIG. 1 according to one embodiment of the present disclosure.DETAILED DESCRIPTION OF THE DISCLOSURE

[0034] In aspects, the present disclosure is related to maintaining an oil and gas well. Specifically, the present disclosure is related to removing accumulated debris in an oil or gas well, especially accumulations of paraffin within the casing.

[0035] The present invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments with the understanding that the present invention is to be considered an exemplification of the principles and is not intended to limit the present invention to that illustrated and described herein.

[0036] This invention presents an apparatus and method for breaking up and removing accumulated paraffin in a borehole. The apparatus can be operated in a borehole when the well is not flowing. This is a common situation when the paraffin has accumulated sufficiently to form a cake or plug that blocks the flow of oil or gas up the borehole. The thickness and density of the paraffin can trap pressurized oil and / or gas beneath the plug. This pressurized oil and / or gas presents a potentially dangerous situation, since the pressure at the surface may be a fraction of the pressure beneath the paraffin cake.

[0037] FIG. 1A shows a diagram of a casing auger apparatus 100 for removing paraffin from casing inside boreholes. The apparatus 100 includes a longitudinal member 110 with a longitudinal axis 120 that acts as a central shaft and attachment point. The longitudinal member 110 may be tubular or solid. In some embodiments, the longitudinal member 110 may be, but is not limited to, 2.375-inch J-55 EUE 3rd tubing. The longitudinal tubing 110 may be selected such that it may be attached to the end of a standard tubing string for a particular well as would be understood by a person of ordinary skill in the art. The longitudinal member 110 may have a first end 160 and a second end 170. A plurality of flights 130 may be disposed in a helical arrangement continuously around the longitudinal member 110 and between the first side 160 and the second side 170. A coupler 180 may be attached to the second side 170 to provide an attachment point for a drilling string. The flights 130 may not extend all the way to the first end 160, which leaves a portion of the longitudinal member 110 to penetrate the paraffin cake 250, dislodge a portion of the paraffin, and force dislodged paraffin onto the flights 130 when the apparatus 100 is rotated. In some embodiments, the flights 130 are made from one continuous piece of material that spirals around the longitudinal member 110. However, it is contemplated that some embodiments may have sets of flights 130 where each set is longitudinally separated from the other and is made from its own continuous piece of material that spirals around the longitudinal member 110. The flights 130 are dimensioned to have sufficient strength to cut paraffin and to support the weight of that paraffin when the apparatus 100 is lifted out of the borehole. The flights 130 may be dimensioned to have a width 150 perpendicular to the longitudinal axis 120 such that the outer edges 135 of the flights 130 are substantially the same as the width of the casing in the borehole where the apparatus 100 is to be inserted. The flights 130 may be welded onto the longitudinal member 110. In some embodiments, the flights 130 may have a thickness 145 of around 0.25 inches (0.64 cm). In some embodiments, the flights 130 may be made of steel. In some embodiments, the apparatus 100 may be dimensioned to have a horizontal width 150 (relative to the longitudinal axis 120 of the apparatus 100) of around 4.50 inches (11.43 cm); however, this is width is illustrative and exemplary only, as the apparatus 100 may be selected with a specific horizontal width 150 dependent on dimensions of the casing 220 in which it will be used as would be understood by a person of ordinary skill in the art. In some embodiments, the horizontal width 150 may be about 0.10 inches (0.25 cm) to 0.30 inches (0.76 cm) smaller than the inner diameter of the casing 220 to avoid or reduce impacts with the wall of the casing 220 during operations. In some embodiments, the flights 130 may have an angle 190 relative to the perpendicular of the longitudinal axis 120 of around 42 degrees. The flights 130 may have a longitudinal separation 140 of around 4 inches (10.2 cm). The dimensions of the apparatus may be varied to accommodate different dimensions of casing.

[0038] FIG. 1B shows a 3-dimensional diagram of the casing auger apparatus 100. The flights 130 are shown having a width 155 from the outer surface of the longitudinal member 110 to the outer edge 135. In some embodiments, the apparatus 100 may have flights 130 with a horizontal width of 4.5 inches (11.4 cm) and a tolerance of + / −0.125 inches (0.32 cm) (outer diameter), with longitudinal separation of 4.0 inches (10.2 cm) and a tolerance of + / −0.125 inches (0.32 cm) surrounding 2.375 inch (6.0 cm) EUE J-55 tubing with a tolerance of 0.0625 inches (0.16 cm). In some embodiments, the longitudinal member 110 may be 14 feet and 3 inches (4.34 meters) in length.

[0039] FIG. 2 shows a system 200 that includes the apparatus 100 inserted in a borehole 210 with a casing 220 that is inside an earth formation 230 beneath the earth's surface 240. The casing 220 is plugged by a mass of paraffin (paraffin cake 250). Beneath the paraffin cake 250 is a pressurized portion 260 of the borehole 210. The flow of oil or gas 270 is shown entering the pressurized portion 260 from the formation 230. The flow 270 applies pressure to the paraffin cake 250 from below. The apparatus 100 is shown disposed in the casing 220 and connected to a drilling string 280. The drilling string 280 is in mechanical communication with one or more motors and controls 290 that are designed to rotate the drilling string 280.

[0040] FIGS. 3A-3E show the operation of the casing auger apparatus 100. FIG. 3A shows a diagram of the casing 220 in the borehole 210 with production tubing 310 inside. The production tubing 310 is surrounded by the paraffin cake 250, which is disposed above the pressurized portion 260.

[0041] FIG. 3B shows a diagram of the casing 220 after the tubing 310 has been removed. The removal of the tubing 310 may leave behind a tunnel 320 in the paraffin cake 250. Depending on the viscosity, density, and hardness of the paraffin cake 250, the tunnel 320 may persist or collapse.

[0042] FIG. 3C shows a diagram of the casing 220 with the casing auger apparatus 100 inserted. The figure shows that the tunnel 320 has collapsed to reform a solid or semisolid paraffin cake 250; however, this is exemplary and illustrative only, as the apparatus 100 may operate if the tunnel 320 remains present in the paraffin cake 250.

[0043] FIG. 3D shows a diagram of the casing 220 when the apparatus 100 had contacted the paraffin cake 250. The apparatus 100 is designed such that rotation will cause the flights 130 to cut into the paraffin cake 250. The amount of paraffin cake 250 separated by the flights 130 increases as the apparatus 100 bores deeper through the paraffin cake 250.

[0044] FIG. 3E shows a diagram of the apparatus 100 begin raised up in the casing 220. The paraffin cake 250 is separated into remaining paraffin cake 330 in the casing 220 and dislodged paraffin 340 on the flights 130. If the paraffin cake 250 is sufficiently reduced in size, the remaining paraffin cake 330 will be unable to withstand the pressure in the pressurized portion 260, and the remaining paraffin cake 330 may be propelled up the borehole 210 by said pressure.

[0045] FIGS. 4A-4B show diagrams of the apparatus 400, which includes the elements for the apparatus 100 and a piercer 410 attached to the first end 160. The piercer 410 may be cone-shaped; however, this is illustrative and exemplary only, as the piercer 410 may be any suitable shape for penetrating the hard paraffin as would be understood by a person of ordinary skill in the art. In some embodiments, the piercer 410 may have a point 420 for penetrating paraffin and one or more openings 430 for pumping fluids from the surface 140 into the paraffin cake 250. The fluids may include, but are not limited to, one or more of hot water and solvents.

[0046] FIGS. 4C-4D show alternative apparatus 440 that includes the elements of the apparatus 400 and also include one or more lateral openings 450 in the longitudinal member 110. In FIG. 4C, lateral openings 450 may be disposed below the flights 130 and proximate to the first end 160 to allow fluids to be pumped from the surface and directed into the paraffin cake 250. FIG. 4D shows a 3-dimensional diagram of the apparatus 440.

[0047] FIGS. 4E-4F show alternative apparatus 460 that includes the elements of the apparatus 400 and also include one or more lateral openings 470 in the longitudinal member 110. In FIG. 4E, lateral openings 470 may be disposed between the flights 130 to allow fluids to be pumped from the surface and directed into the paraffin cake 250. FIG. 4F shows a 3-dimensional diagram of the apparatus 460.

[0048] It is also contemplated that some embodiments may include both the lateral openings 450 near the first end 160 and the lateral openings 470 between the some or all of the flights 130. It is also contemplated that the piercer 410 may be optional in the apparatus 440 and the apparatus 460. In some embodiments, the lateral openings 470 may be used to disperse fluid to remove dislodged paraffin from one or more of the flights 130.

[0049] FIG. 5 shows a flow chart of a method 500 for removing paraffin using the apparatus 100 or the apparatus 400. In step 510, the production tubing 310 (if present) may be removed from the borehole 210. In step 520, the apparatus 100 or the apparatus 400 may be inserted into the casing 220 and lowered toward the paraffin cake 250. In step 530, the apparatus 100 or the apparatus 400 may be used to impact the paraffin cake 250 to break up part of the upper portion until the lowest flight 130 can engage the paraffin cake. Step 530 is optional and may be used when the paraffin cake is dense or hard. In step 540, the apparatus 100 or the apparatus 400 is rotated so the flights 130 cut into the paraffin cake 250 and dislodged paraffin 340 accumulates on the flights 130. In step 550, fluid may be pumped through the longitudinal member 110 and out the first end 160 and / or the piercer 410 to loosen, melt, or dissolve paraffin if the apparatus 100 becomes stuck in the paraffin cake 250. This step may also include pumping fluid out of the optional one or more openings 450 and / or the optional one or more openings 470. Step 550 may be optional and can be performed before, during, or after the step 540. In step 560, the apparatus 100 may be lifted up the casing 220 to the surface 140 taking the dislodged paraffin 340 with it. In step 570, the dislodged paraffin 340 may be cleaned from the apparatus 100 at the surface 140. In step 580, a determination is made if the process should be repeated if sufficient remaining paraffin cake 330 is plugging the well, and then the process repeated starting with step 520.

[0050] While embodiments in the present disclosure have been described in some detail, according to the preferred embodiments illustrated above, it is not meant to be limiting to modifications such as would be obvious to those skilled in the art.

[0051] The foregoing disclosure and description of the disclosure are illustrative and explanatory thereof, and various changes in the details of the illustrated apparatus and system, and the construction and the method of operation may be made without departing from the spirit of the disclosure.

Claims

1. An apparatus for removing paraffin, the apparatus comprising:a longitudinal member having a first end and second end and configured for insertion in a casing of a borehole;a plurality of flights welded around the outer surface of the longitudinal member in a spiral pattern, wherein each of the plurality of flights have a width that extends substantially to an inner surface of the casing; anda coupler in mechanical communication with the second end configured to attach the apparatus to a drilling string.

2. The apparatus of claim 1, wherein the longitudinal member is tubular.

3. The apparatus of claim 2, further comprising a piercer disposed on the first end of the longitudinal member.

4. The apparatus of claim 3, wherein the piercer comprises one or more openings configured to allow fluid pumped through the longitudinal member to be released by the piercer.

5. The apparatus of claim 2, wherein the longitudinal member has one or more openings in its surface disposed proximate to the first end.

6. The apparatus of claim 2, wherein the longitudinal member has one or more openings in its surface disposed between two of the plurality of flights.

7. The apparatus of claim 1, wherein the longitudinal member is made of steel.

8. The apparatus of claim 1, wherein the plurality of flights are formed from a continuous piece of metal.

9. A method for removing paraffin from a casing of a borehole for an oil / gas well comprising the steps of:inserting an apparatus in the casing of the borehole down to contact with a paraffin cake, where the apparatus comprises:a longitudinal member having a first end and second end and configured for insertion in the casing of the borehole;a plurality of flights welded around the outer surface of the longitudinal member in a spiral pattern that extends from the longitudinal member substantially to an inner surface of the casing; anda coupler in mechanical communication with the second end configured to attach the apparatus to a drilling string;rotating the apparatus to cut and dislodge paraffin from the paraffin cake with the plurality of flights; andlifting the apparatus with the dislodged paraffin to the surface.

10. The method of claim 9, further comprising the step of:removing a production tubing from the casing prior to inserting the apparatus.

11. The method of claim 9, further comprising the step of:impacting the paraffin cake with the apparatus.

12. The method of claim 9, wherein the longitudinal member is tubular and further comprising the step of:injecting a fluid into the paraffin cake through the apparatus, wherein the fluid is selected to loosen, melt, or dissolve the paraffin cake.

13. The method of claim 9, further comprising the step of:removing the dislodged paraffin from the apparatus.

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