METHOD AND SYSTEM FOR REDUCING FRICTION IN RADIAL DRILLING AND JET DRILLING OPERATIONS

Abstract

Disclosed is a method for reducing friction in a radial drilling application. The method involves coating the interior of a deflector shoe with at least one lubricant. Lubrication of the deflector shoe can be accomplished by applying a dry lubricant to the interior of the deflector shoe, allowing the dry lubricant to harden, and applying a wet lubricant over the hardened dry lubricant. The interior surface of the deflector shoe may be roughened prior to application of the lubricant. The method can further include coating a hose and/or a jet nozzle, and passing the hose and/or jet nozzle through the coated interior of the deflector shoe. The method can further include coating components of a milling cutter, and passing the components of the milling cutter through the coated interior of the deflector shoe. An apparatus for reducing friction in a radial drilling application is also disclosed.

Claims

1. A method for reducing friction in a radial drilling application, the method comprising: coating the interior of a deflector shoe with at least one lubricant.

2. The method of claim 1, further comprising the step of: applying a wet lubricant to a wellbore and the interior of the deflector shoe, the wet lubricant comprising a liquid mixed with a friction reducer.

3. The method of claim 1, the step of coating comprising: applying a dry lubricant on the interior of the deflector shoe; hardening the applied dry lubricant; and applying a wet lubricant over the hardened dry lubricant.

4. The method of claim 1, further comprising: coating a hose with at least one lubricant; and passing the hose through the coated interior of the deflector shoe.

5. The method of claim 1, further comprising: coating a jet nozzle with at least one lubricant; and passing jet nozzle through the coated interior of the deflector shoe.

6. The method of claim 1, further comprising: coating components of a milling cutter with at least one lubricant; and passing the components of the milling cutter through the coated interior of the deflector shoe.

7. The method of claim 1, the at least one lubricant being selected from a group consisting of: tire shine, flouropolymer coatings, tungsten disulfide coating, polytetrafluoroethylene, molybdenum disulfide, graphite, silicone, epoxy and Never Seez?.

8. The method of claim 1, further comprising the step of: roughening the interior of the deflector shoe prior to the step of coating.

9. The method of claim 8, the step of roughening comprising sanding the interior of the deflector shoe with sandpaper.

10. A method for reducing friction in a radial drilling application, the method comprising: roughening an interior of a deflector shoe; coating the interior of the deflector shoe with at least one lubricant; passing a hose through the coated interior of the deflector shoe; and applying a wet lubricant to the deflector shoe during the step of passing.

11. The method of claim 10, wherein the at least one lubricant applied to the deflector shoe comprises a hardened dry lubricant with a wet lubricant layer over the hardened dry lubricant.

12. The method of claim 10, further comprising the step of: coating an exterior of the hose with at least one lubricant prior to the step of passing.

13. The method of claim 10, further comprising the step of: coating a jet nozzle with at least one lubricant; and passing jet nozzle through the coated interior of the deflector shoe.

14. The method of claim 10, further comprising the step of: coating components of a milling cutter with at least one lubricant; and passing the components of the milling cutter through the coated interior of the deflector shoe.

15. The method of claim 10, the at least one lubricant being selected from a group consisting of: tire shine, fluoropolymer coatings, tungsten disulfide coating, polytetrafluoroethylene, molybdenum disulfide, graphite, silicone, epoxy and Never Seez?.

16. The method of claim 10, wherein the step of applying a wet lubricant is continuous during a drilling process, wherein the wet lubricant is a liquid mixed with a friction reducer.

17. An apparatus for reducing friction in a radial drilling application, the apparatus comprising: a deflector shoe having an interior surface; at least one lubricant applied to the interior surface of the deflector shoe.

18. The apparatus of claim 17, wherein the interior surface of the deflector shoe is roughened prior to application of the lubricant.

19. The apparatus of claim 17, said at least one lubricant comprising a hardened dry lubricant with a wet lubricant layer over the hardened dry lubricant.

20. The apparatus of claim 17, the at least one lubricant being selected from a group consisting of: tire shine, fluoropolymer coatings, tungsten disulfide coating, polytetrafluoroethylene, molybdenum disulfide, graphite, silicone, epoxy and Never Seez?.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0036] FIG. 1 is a schematic illustration showing a prior art indexing deflector assembly having a deflector shoe.

[0037] FIG. 2 is a schematic illustration of a jet drilling process illustrating a jet nozzle passed through a deflector shoe.

[0038] FIG. 3 is an example of the prior art thumper nozzle subassembly as used in radial jet drilling operations.

[0039] FIG. 4 illustrates the method and system of the present invention.

[0040] FIG. 5 shows Graph 1, wherein tests results show that as the inner pressure of the hose increases, the force required to pull the hose through the shoe increases.

[0041] FIG. 6 shows Graph 2 wherein test results illustrate how the force required changes depending on different coating of the hose.

[0042] FIG. 7 shows Graph 3, wherein test results are provided when the hose is coated with Never Seez?.

[0043] FIGS. 8A and 8B illustrate, at a microscopic level, the interface between the surfaces of the hose and the deflector shoe.

[0044] FIG. 8C illustrates the interface between the surfaces of the hose and deflector shoe when the surfaces have been lubricated and the deflector shoe surface has been roughened.

DETAILED DESCRIPTION OF THE INVENTION

[0045] Referring to FIG. 4, there is shown an illustration of the system and method of the present invention. A deflector shoe 52 is associated with the casing 62 of a wellbore. The deflector shoe 52 has an interior through which a flexible hose 54 is moved. The flexible hose 54 has a jet nozzle 64 at an end thereof. FIG. 4 also illustrates work tubing 53 having a coil tubing 56 therein. This is connected by connector 58 to the flexible hose 54. Also illustrated in FIG. 4 is a centralizer 60 which serves to position the deflector shoe within the casing 62.

[0046] The interior of the deflector shoe 52 is provided with a lubricant coating 70. As can be seen in FIG. 4, the lubricant coating 70 is provided on the interior surface of the deflecting shoe 52, and is importantly provided at contact surfaces between the flexible hose 54, jet nozzle 64 and the interior of the deflector shoe 52. The lubricant coating 70 can include be wet lubricant or a dry lubricant, or a combination of the two.

[0047] In the case of a wet lubricant, the lubricant coating 70 can be applied manually by a worker onsite or in the field. In the case of a dry lubricant, the lubricant coating is preferably sprayed or otherwise manually applied on the interior of the deflector shoe 52.

[0048] As used herein, the term wet lubricant can be any lubricant which remains in a wet, liquid or non-hardened state. For example, wet lubricants include less viscous lubricants such as water, and relatively highly viscous liquids such as those having a grease or paste consistency. Wet lubricants can also be combinations of wet lubricants, such as water or other liquid having a friction reducer introduced into the water. The friction reducer can be a polyacrylamide-based polymer.

[0049] The term dry lubricant includes those lubricants which harden by heat treatment or by the nature of the lubricant. In the hardened state, these dry lubricants result in a surface having a lower coefficient of friction than the bare metal of the deflector shoe or other equipment. The dry lubricant can be applied to the equipment, and heat-treated or otherwise allowed to harden before introduction into the wellbore, resulting in the lubricant remaining on the equipment during operations.

[0050] In the present invention, the flexible hose 54 and jet 64 may also be coated with the same or another lubricant coating so as to further reduce friction between the components. It is also within the concept of the present invention that the components of a milling cutter can be coated with a lubricant before passing through the lubricated deflector shoe 52.

[0051] In a preferred embodiment of the present invention, both the wellbore (casing 62) and drilling equipment (i.e. the flexible hose 54, jet 64 and the milling cutter) are lubricated. A wet lubricant is applied to the drilling hole from the surface. The wet lubricant applied to the drilling hole is preferably a liquid (brines or water, for example) containing powders, and is applied continuously during drilling operations. The wet lubricant may also include a friction reducer added to the liquid treatment fluid, which is continuously pumped into the wellbore.

[0052] In an embodiment, the dry lubricant is applied to the drilling equipment and deflector shoe, ensuring full coverage of the surfaces. Either epoxy-based and spray coated lubricants can be applied. Once the dry lubricant is hardened, a wet lubricant (such as a grease-type lubricant) is preferably applied over the hardened dry lubricant. This additional coating of lubricant was found to result in the lubricants remaining on the equipment for a longer period of time.

[0053] A number of different commercially available lubricants may be utilized in the system and method of the present invention, including tire shine, fluoropolymer coatings, tungsten disulfide coating, polytetrafluoroethylene, molybdenum disulfide, graphite, silicone, epoxy and Never Seez?. Commercially-available lubricants may also be modified by adding substances so as to increase lubricity.

[0054] Tire shine is a range of products which use specialized polymer technology to create a gloss finish on the tire surface. Such polymer compounds are formulated to not only make tires look good (due to the gloss finish) but also to protect them from harmful UV rays, grime and other contaminants picked up on road surfaces. Typically, tire shine is a silicon-based lubricant.

[0055] The Never-Seez? product line (by BOSTIK) covers a range of anti-seize compounds to meet a wide range of anti-seize, anti-galling, and lubrication applications. Special greases are entrained with specific particulates (predominantly metallic) to protect parts even in high-temperature, high-pressure and corrosive environments, allowing parts to work longer with less wear. Not all compounds are appropriate to every application. The Never-Seez? lubricant is known to contain graphite, copper flake, aluminum powder and zinc oxide.

[0056] Experimentation by the inventors found that treatment with lubricants at the contact surfaces between the hose and the deflector shoe helped greatly decrease the force required to pull the hose through the deflector shoe. This, in turn, decreased the required propulsion force needed from the nozzle to pull the hose and the required flow rate to the nozzle itself. It was discovered that with the maximum force required to pull a 5600 p.s.i. pressurized hose through the deflector shoe reduced by 65%, from 25 lbft for the dry hose to 8 lbft for a tire shine or oil coated hose through a Never Seez? coated shoe

[0057] Experiments utilizing a combination of wet lubricants were conducted by the inventors, and are detailed below. First, a pull through shoe test was conducted. Specifically, this tested the force required to pull a pressurized hose through a shoe having different surface conditions. This test was performed to analyze how much force was required to pull a hose through a deflector shoe by varying the magnitude of the pressure with different surface conditions. The hose was laid between two steel deflector shoe pieces. The hose was pulled out at continuous rate and the maximum required force was recorded. The test was conducted with various hose conditions (1) dry hose, (2) hose wet with water, (3) dry hose through shoe pieces coated with commercially-available lubricant, and (4) oily hose through shoe pieces coated with commercially-available lubricant. A commercially-available hose was utilized. In this test, the commercially-available lubricant was Never Seez?.

[0058] The results of the tests are shown in Graph 1 (see FIG. 5). Graph 1 illustrates that as the inner pressure of the hose increases, the force required to pull the hose through the shoe increases. The maximum applied hose pressure was 5600 p.s.i. However, by lubricating the surface of the hose, the required pull force decreases about 50% from a dry hose to an oily hose and a shoe coated with commercially-available lubricant.

[0059] By reducing the friction on the hose, effectively more force can be transmitted. Further experiments were conducted with different coatings. The Graph 2 (see FIG. 6) illustrates three additional conditions, namely (5) tire shine-coated hose through deflector shoe, (6) tire shine/oil coated hose through deflector shoe, and (7) tire shine/oil coated hose through Never Seez? coated shoe. It was discovered that the maximum required force to pull a 5600 p.s.i. hose through the deflector shoe drops from 8.4 lbft for tires for condition (7), namely tire shine/oil coated hose through Never Seez? coated could shoe.

[0060] Coating the hose with Never Seez? also resulted in differences in the average force required to pull a hose through the deflector shoe, as is illustrated in Graph 3 (see FIG. 7).

[0061] The experiments detailed above were conducted using a wet lubricant, which can be manually applied. Further experimentation shows that a dry lubricant would also be likely to adhere to the interior of the deflector shoe over time, maintaining a reduced friction. These dry lubricants may be sprayed on or otherwise manually applied and allowed to dry and/or heat treated, and can also be used for longer periods of time. The inventors expect similar or better results from the dry lubricant in terms of differences in pulling force.

[0062] The present invention may also include a step of roughening of the surface of the deflector shoe 52, or in the case of an apparatus or system, providing a roughened deflector shoe 62. FIG. 8A illustrates, at a microscopic level, the interface between the metallic surface 80 of the deflector shoe 62 and the irregular surface 82 of the rubber hose. FIG. 8B illustrates the interface when the hose is tensioned and pressurized. In FIG. 8B, it can be seen how the flattened hose surface 82 abuts the metallic surface 80, which may generate vacuum between the surfaces and induces higher drag. The vacuum is generated between points of contact between the hose and the metallic surface 80. Higher drag may also be caused by increased area of contact between surfaces

[0063] As a solution to this problem, in the present invention, the originally smooth and shiny metallic surface of the deflector shoe may be roughened prior to installation and coating with the lubricant. The roughening can be accomplished in a number of ways, including sanding with various grades of sandpaper. The roughened surface 80 may be created by dimpling the surface in another manner.

[0064] The resulting roughened surface 80 is illustrated in FIG. 8C. As can be seen, the effect of the roughened surface 80 is to create channels to release air or fluid, and thus the vacuum. This was found to reduce drag on the hose. The wet and/or dry lubricants applied to the stiff hose reduces deformation, while the wet lubricant applied to the wellbore further reduces hose deformation and friction between the surfaces. The roughened surface 80 also results in an enhanced application and retention of the lubricant.

[0065] The method and system of the present invention allows for greatly reduced friction between drilling components and the deflector shoe. This, in turn, increases the useful life of the components associated with these operations. Additionally, the reduced friction allows for a reduction in the power requirements of equipment used to run the tools in the drilling operations, contributing to a reduction in costs association with these operations.

[0066] The foregoing disclosure and description of the invention is illustrative and explanatory thereof. Various changes in the details of the illustrated construction can be made is the scope of the present invention without departing from the true spirit of the invention.