Controllable-dissolution composite lubricating grease coating for dissolvable component of downhole tool

Abstract

The coating (10) is used to protect a dissolvable component of a downhole tool such that the dissolvable component can be deployed to a desired downhole location, work at high stresses of a fracturing operation, and effectively dissolve after completion of the fracturing operation. According to the invention, the performance of the existing lubricating grease is improved, so that the lubricating grease can realize the functions of polymers and metal coatings generally manufactured by complex factories. The coating (10) includes an activation layer (20), a first grease layer (30), and a second grease layer (50). The first grease layer (30) and the second grease layer (50) have different grease layer consistency ranges and thickness ranges. The coating (10) includes a non-uniform layer of grease manually applied in situ to effectively control degradation of the component substrate as a factory coating prefabricated on the component.

Description

[0001] Claiming priority

[0002] This application claims the benefit of the following nonprovisional applications, each of which is incorporated herein by reference in its entirety:

[0003] USN 18045769; Application date: October 11, 2022; Invention name: Composite grease coating for controlled dissolution of dissolvable components of downhole tools. Technical Field

[0004] The present invention relates to material compositions in the oil and gas industry. In particular, the present invention relates to a grease coating for a downhole tool formed of at least one dissolvable component. More particularly, the present invention relates to a composite grease coating for a dissolvable metal substrate of a bridge plug. Background Art

[0005] A bridge plug is a downhole tool used in oil and gas operations. In unconventional oil and gas production, soluble bridge plugs have replaced milled composite bridge plugs in downhole operations such as fracturing operations. After fracturing, the soluble bridge plug dissolves in the downhole fluid. Dissolvable bridge plugs include bridge plugs formed of all soluble components or bridge plugs formed of at least one soluble component to collapse and disengage the bridge plug from a set position in the borehole. The soluble component can be a soluble metal or a degradable polymer. Milling is no longer required to remove the composite bridge plug. Therefore, the operation time and cost of milling are saved.

[0006] Dissolvable bridge plugs, traditionally made from dissolvable magnesium alloy technology, have made a significant contribution to the "shale revolution" in the oil and gas industry. These dissolvable bridge plugs temporarily block the wellbore during hydraulic fracturing operations and then quickly "disappear" by dissolving in the produced fluids in the wellbore. During the operation, the degradable bridge plugs are required to maintain mechanical integrity under high stress during the hydraulic fracturing operation. After the hydraulic fracturing operation, the dissolvable bridge plugs need to be quickly removed without leaving large solid residues so that the well can be quickly put into actual production. It is important to prevent the downhole oil and hydraulic fracturing proppants from "encapsulating" the dissolvable magnesium alloy of the dissolvable bridge plug, as this will isolate the dissolvable magnesium alloy from the aqueous fluid downhole. It is reported that this "encapsulation" will isolate the dissolvable magnesium alloy from the water, thereby completely stopping the dissolution process of the dissolvable magnesium alloy, resulting in partial or permanent blockage of the well. On the one hand, the dissolution rate of the soluble magnesium alloy is required to be low so that the bridge plug can maintain reliable strength during operation, and on the other hand, the dissolution rate of the soluble magnesium alloy is required to be as high as possible after the hydraulic fracturing operation is completed. These conflicting requirements lead to two types of failures widely observed in the field, either "premature" decomposition or ultimately no dissolution at all. To solve this problem, known coatings are used, including delayed surface coatings or "temporary" coatings, such as polymer spray coatings.

[0007] In addition, the dissolution rate of soluble magnesium alloys is highly sensitive to downhole conditions, including well temperature and downhole fluid salinity. Due to stricter environmental regulations and the scarcity of fresh water resources, operators are required to use flow-back water and produced water for hydraulic fracturing operations. The salinity of these allowed fluids can fluctuate significantly between different wells, even at different stages of the same well. Therefore, each well, or even each hydraulic fracturing operation in a well, may require a specific bridge plug made of a specific grade of soluble magnesium alloy and a corresponding compatible polymer coating. For bridge plug manufacturers and oil well operators, it is a difficult and costly challenge to provide different numbers of bridge plugs and corresponding different coatings for a single well.

[0008] The challenge facing the oil and gas industry today is the control of the dissolution process of dissolvable components and the provision of all the different coatings for a single well. During deployment and operation, dissolvable components must not dissolve or degrade prematurely. Dissolvable components must retain the ability to dissolve as quickly and efficiently as possible for removal. Coatings are developed so that they do not dissolve or degrade until needed. Resin-based fluoropolymer coatings and fluoropolymer lubricants provide corrosion resistance during deployment, and these coatings are able to degrade so that rapid dissolution of the component can be triggered when the tool is removed. Electroless nickel coatings are also known. Electroless nickel coatings require their own triggering conditions to degrade before the dissolvable metal alloy of the component substrate degrades. Grease coatings are also known. Grease coatings include a base lubricant, a thickener, and additives. Different coatings can also be combined in layers to form a composite coating so that the properties of each layer can be triggered in a preset sequence.

[0009] There are various patents and publications in the field of multilayer coatings. The composition of each layer is carefully selected to obtain the desired physical properties. It is known that irregularities and porosity in the transition area between layers have a synergistic effect. The low viscosity layer washes off quickly, but the transition layer with irregularities and porosity between the low viscosity layer and the high viscosity layer lasts longer than the low viscosity layer. The low viscosity coating composition lasts longer than expected. See US Pat. No. 7,770,935 (Imai et al., Aug. 10, 2010), US Pat. No. 6,679,526 (Yamamoto et al., Jan. 20, 2004), US Pat. No. 2011 / 0084477 (Mallis et al., Apr. 14, 2011), US Pat. No. 9,752,710 (Goto et al., Sept. 5, 2017), US Pat. No. 8,276,946 (Kimoto et al., Oct. 2, 2012), and US Pat. No. 7,842,403 (Meyer Jr. et al., Nov. 30, 2010). There are inherent differences between the layers due to the different material compositions of the layers.

[0010] US Patent US7955694 (Hazel et al., June 7, 2011) describes a temporary top coating that can be washed off and fills the holes in the lower layer, thereby having a more permanent protective function. Russian Patent RU58059 (Astafiev et al., November 10, 2006) discloses a multilayer structure based on coatings of different relative hardness and thickness.

[0011] Existing coating compositions in the oil and gas industry are able to remain intact for a short period of time. However, some operations require delivery times in the wellbore of more than 8 hours. Delivery cycles and waiting times may also be extended at downhole locations within the wellbore. In addition, components that are dissolvable materials must remain reactive to trigger conditions in the prior art to achieve dissolution of the component. Bridge plugs or other components may require waiting for more than 30 days before they can be activated. The coating must protect the dissolution effectiveness of the material components of the dissolvable components. Coatings that last less than 4 hours will not prevent the dissolvable components from degrading due to premature exposure, resulting in the dissolution effectiveness of the dissolvable components not being protected during longer delivery cycles and extended waiting times. Existing coatings for downhole tools are not suitable for these longer delivery cycles and extended waiting times. Therefore, a different coating composition is needed.

[0012] Furthermore, known polymer coatings (including fluoropolymer coatings), electroless nickel coatings, and composite coatings containing polymers or electroless nickel must be prefabricated. These coatings require equipment and materials for curing or plating, which cannot be performed on-site at the wellbore location. Coated soluble metal alloy components must be manufactured in a specialized coating or fabrication facility equipped with appropriate equipment, supplies, and safety regulations. Fabrication facilities have only a selected inventory to choose from, and the inventory available on-site at the wellbore location is further limited. Furthermore, the prefabrication of known coatings and known composite coatings does not allow for field adjustments and modifications. Different types of soluble magnesium alloys and corresponding coatings must be ordered in advance. Even if the type of soluble magnesium alloy is appropriate, the corresponding coating may not be appropriate. Furthermore, shipping soluble magnesium alloys with coatings carries the additional risk of coating damage. A single scratch can result in premature disintegration of the bridge plug or at least a portion of the bridge plug, thereby creating a structural weakness. These structural weaknesses may make it impossible to perform hydraulic fracturing operations.

[0013] It is an object of the present invention to provide a composite coating that is capable of protecting dissolvable components from corrosion under wellbore conditions during a deployment period of 6-24 hours.

[0014] It is an object of the present invention to provide a composite coating that is capable of maintaining the effectiveness of dissolvable components degrading under wellbore conditions during operations.

[0015] It is an object of the present invention to provide a composite coating of a dissolvable component that can be controllably degraded to expose the dissolvable component.

[0016] Another object of the present invention is to provide a composite coating of a dissolvable component that degrades based on thickness and differential consistency between layers, ie, National Lubricating Grease Institute (NLGI) consistency.

[0017] Another object of the present invention is to provide a composite grease coating that can be applied in the field.

[0018] Another object of the present invention is to provide a composite grease coating with non-uniform bonding between layers suitable for field application.

[0019] Another object of the present invention is to provide a composite grease coating that is interchangeable with different dissolvable substrates of downhole tools.

[0020] These and other objects and advantages of the present invention are clearly set forth in the accompanying description, drawings and claims. Summary of the invention

[0021] Embodiments of the coating of the present invention protect the dissolvable components of the downhole tool during transportation and waiting in the wellbore. The coating covers the dissolvable downhole tool components. The coating includes an activation layer, a first grease layer, and a second grease layer. The coating of the present invention is a composite coating that improves the functionality of existing greases to be comparable to polymer and chemical nickel coatings. The present invention also allows non-uniform grease layers applied manually on site to control degradation of the component substrate as effectively as factory coatings prefabricated on the component.

[0022] The activation layer comprises an activation compound, which can be applied by spraying. The activation compound effectively bonds to the metal of the component substrate and the grease of the first grease layer. The activation layer thickness of the activation layer ranges from 10 to 500 μm. Since the activation layer 20 is applied on-site by field workers, the activation layer is non-uniform and may have activation layer cracks and activation layer pores.

[0023] The first grease layer has a first grease layer consistency range of NLGI 200-250 and a first grease layer thickness range of 100-1000 μm. The first grease layer comprises a first lubrication base, a first thickener and a first additive. The first lubrication base is chemically compatible with the activating compound of the activating layer. The lubrication base is also hydrophobic / waterproof to protect the metal of the component substrate from the effects of water-based downhole fluids. The first grease layer consistency range allows the first grease layer to maintain mechanical integrity even at high temperatures. The first thickener and first additive are also selected to be compatible with the first lubrication base to ensure that the first grease layer is firmly bonded to the activating layer and has mechanical integrity. Importantly, an embodiment of the first grease layer is non-uniformly bonded to the activating layer and is manually applied by field personnel. The first grease layer may have first grease layer cracks and first grease layer pores.

[0024] The second grease layer has a second grease layer consistency range of NLGI 280-320 and a second grease layer thickness range of greater than 500 μm. The second grease layer comprises a second lubrication base, a second thickener and a second additive. The second grease layer consistency range allows the second grease layer to form a transition zone. In addition, the second thickener and the second additive are selected to be compatible with the activation layer and the second lubrication base to form a transition zone. The second grease layer 50 is also non-uniformly bonded to the first grease layer and is also manually applied by field personnel. The second grease layer may have second grease layer cracks and second grease layer pores.

[0025] The first grease layer is located between the activation layer and the second grease layer to form a coating that is a composite coating of the present invention. There is a transition zone that allows the composite coating to remain in solution for 6-24 hours, thereby protecting the component substrate from dissolving too quickly during the 6-24 hours. The transition zone can include portions of the second grease layer that are located within cracks in the first grease layer and pores in the first grease layer. For the second grease layer, lack of uniformity is still not unacceptable. The non-uniform second grease layer is still effective and can therefore be applied in the field at the wellbore location in the field.

[0026] Embodiments of the present invention also include an activated transition zone. The activated transition zone includes a portion of the first grease layer located within the non-uniform activated layer.

[0027] Embodiments of the present invention also include methods of removing a downhole tool from a wellbore using the coating of the present invention. The method includes spraying an activating layer on a clean component substrate of the downhole tool at a wellbore location. The activating layer need not uniformly cover the component substrate. The method includes applying a first grease layer on the activating layer at the wellbore location. The first grease layer is non-uniformly bonded to the activating layer. Then, a second grease layer is applied on the first grease layer at the wellbore location. The second grease layer is also non-uniformly bonded to the first grease layer to form a composite coating on the component substrate.

[0028] The method also includes forming a transition zone with a first grease layer and a second grease layer, and deploying the component substrate with the composite coating to a downhole location. The composite coating can protect the component substrate from being dissolved for 6-24 hours. After the hydraulic fracturing operation, the method includes the step of dissolving the component substrate to remove the downhole tool from the wellbore. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic diagram of a coating embodiment of the present invention.

[0030] Figure 2a is a photographic illustration of a coating with only the second grease layer, showing early stage degradation.

[0031] Figure 2b is a photographic illustration of a coating with only the first grease layer, showing early stage degradation.

[0032] Figure 2c is a photographic representation of one embodiment of a coating of the present invention showing the protective effect on a dissolvable substrate after 6 hours.

[0033] Figure 3a is a photographic illustration and schematic diagram of a coating having a second grease layer thickness not within the scope of the present invention, showing early stage decomposition.

[0034] Figure 3b is a photographic illustration and schematic diagram of a coating of the present invention showing the protective effect on a dissolvable substrate after 6 hours.

[0035] Figure 3c is a photographic illustration and schematic diagram of a coating having a first grease layer thickness that is not within the scope of the present invention, showing early stage decomposition.

[0036] Figure 4 is a diagrammatic illustration of an embodiment of a prior art coating and a coating of the present invention. DETAILED DESCRIPTION

[0037] refer to Figure 1-Figure 4, the coating of the present invention protects the dissolvable components of the downhole tool during transportation and waiting time in the wellbore. The coating of the present invention is a composite coating that elevates the functionality of existing greases to that comparable to polymer and electroless nickel coatings. While existing coatings are neither able to provide hours of protection nor are too irregular to achieve consistent application, the composite coating of the present invention solves the problem of providing the appropriate number of dissolvable plugs with corresponding coatings for the varying needs of a single well through the special synergistic effect of two layers of grease. The non-uniformity of the grease layers of the present invention when applied in the field is no longer a difficult problem to overcome. The range of thicknesses and consistencies of the two grease layers transforms the non-uniformity of grease application in the field into a reliable and cost-effective solution that can provide a properly expanded inventory of dissolvable bridge plugs for any well.

[0038] In the present invention, the coating 10 covers the dissolvable downhole tool component. The coating 10 includes an activation layer 20, a first grease layer 30 and a second grease layer 50. More specifically, the coating 10 covers a component substrate 80, which can be a dissolvable metal substrate, including a dissolvable magnesium alloy. The coverage of the dissolvable metal substrate is non-uniform. The activation layer 20 is located between the component substrate 80 and the first grease layer 80.

[0039] An embodiment of the activation layer 20 comprises an activation compound 22. Grease does not adhere well to metal surfaces due to low polarity, resulting in problems such as poor wettability and low mechanical integrity. After cleaning the metal surface (e.g., the soluble metal substrate of the component substrate 80), the activation layer 20 is applied. The activation layer 20 can be applied by spraying. The activation compound 22 is selected to effectively combine with the metal of the component substrate 80 and the grease of the first grease layer 30. The activation compound 22 can be a polysiloxane, an epoxy resin, a polyacrylic acid, or other suitable composition. The activation layer 20 is bonded to the first grease layer 30 and is capable of bonding to the component substrate 80. The activation compound 22 can be stored in a small pressurized tank so as to be highly portable and easy to use by field workers at the wellbore site.

[0040] like Figure 1 As shown, the activation layer 20 has an activation layer thickness 24 ranging from 10 to 500 μm. Since the activation layer 20 is applied on-site by the on-site operator, the activation layer 20 is non-uniform and may have activation layer cracks 26 and activation layer pores 28.

[0041] Embodiments of the first grease layer 30 have a first grease layer consistency in the range of NLGI 200-250 and a first grease layer thickness 32 in the range of 100-1000 μm. The first grease layer 30 comprises a first lubricating matrix 34, a first thickener 36 and a first additive 38. The first lubricating matrix 34 is chemically compatible with the activating compound 22 of the activating layer 20, i.e., the first lubricating matrix 34 and the activating compound 22 have similar chemical properties. The first lubricating matrix 34 is also hydrophobic / waterproof to protect the metal of the component substrate 80 from the effects of water-based downhole fluids. The first lubricating matrix 34 is selected to be thermally and chemically stable under downhole conditions up to 175° C. and above. The first lubricating matrix 34 can be polysiloxane (including fluorosilicone), synthetic oil and petroleum oil, including polyaphaolefin (PAO) and polyol esters. In some embodiments, the first grease layer thickness ranges from 100 μm to 300 μm.

[0042] The first grease layer consistency range allows the first grease layer 30 to maintain mechanical integrity even at high temperatures. The first thickener 36 and the first additive 38 are also selected to be compatible with the first lubricating matrix 34 so that the first grease layer 30 is firmly bonded to the activation layer 20 and maintains mechanical integrity. During the deployment of the bridge plug and during hydraulic fracturing operations downhole, the first grease layer or a harder grease layer can withstand strong downhole fluid turbulence. Importantly, an embodiment of the first grease layer 30 is non-uniformly bonded to the activation layer 20. The first grease layer 30 is manually applied by a worker on site. The first grease layer 30 may have first grease layer cracks 40 and first grease layer pores 42, such as Figure 1 shown.

[0043] Embodiments of the second grease layer 50 have a second grease layer consistency range of NLGI 280-320 and a second grease layer thickness 52, the second grease layer thickness range is greater than 500 μm. The second grease layer 50 includes a second lubricating matrix 54, a second thickener 56, and a second additive 58. The second grease layer consistency range allows the second grease layer 50 to form a transition zone 70. The second thickener 56 and the second additive 58 are also selected to be compatible with the activation layer 20 and the second lubricating matrix 54 to form the transition zone 70. The second grease layer or the softer grease layer can effectively penetrate the non-uniform first grease layer 30. The second lubricating matrix 54 can be polysiloxane, synthetic oil, and petroleum. In some embodiments, the second grease layer thickness ranges from 500-2000 μm.

[0044] The second grease layer 50 is unevenly combined with the first grease layer 30. The second grease layer 50 is also manually applied by a worker on site. The second grease layer 50 may have second grease layer cracks 60 and second grease layer pores 62.

[0045] like Figure 1 As shown, the first grease layer 30 is located between the activation layer 20 and the second grease layer 50 to form the coating 10 as the composite coating 12 of the present invention. The first grease layer 30 and the second grease layer 50 form a transition zone 70 so that the composite coating can be maintained in the solution for 6-24 hours, which ensures that the component substrate 80 will not dissolve too quickly within 6-24 hours. The transition zone 70 includes a portion 64 of the second grease layer 30 located in the cracks 40 of the first grease layer and the pores 42 of the first grease layer, as shown in FIG. Figure 4 and Figure 3b As shown. Due to the second grease layer consistency range or its lower viscosity, the second grease layer is able to more effectively penetrate and plug the first grease layer cracks 40 and the first grease layer pores 42. Although most of the second grease layer or the "softer" grease can be relatively easily washed away by the strong flow downhole, during deployment, the transition zone 70 is still bonded to the portion 64 of the second grease layer 30. There is no obvious upper limit to the thickness of the second grease layer because the second grease layer consistency range allows even excess second grease layer 50 to be easily wiped off. In the present invention, the second grease layer thickness is related to the first grease layer thickness to form the transition zone 70, thereby providing 6-24 hours of protection to the component substrate 80. Similarly, the lack of uniformity for the second grease layer 50 is still not unacceptable. The non-uniform second grease layer 50 is still effective and can therefore be applied in the field at the wellbore location in the field.

[0046] exist Figure 1 and Figure 3b In some embodiments, the activation layer 20 and the first grease layer 30 form an activation transition zone 72. The activation transition zone includes the portion 44 of the first grease layer 30 located within the activation layer cracks 26 and the activation layer pores 28. The activation layer 20 applied by spraying is no longer necessarily uniform. Therefore, the composite coating 12 may include Figure 1 The activated layer 20, the activated transition zone 72, the first grease layer 30, the transition zone 70 and the second grease layer 50 are shown in FIG.

[0047] The present invention includes an embodiment of a method for removing a downhole tool from a wellbore. The method includes spraying an activating layer 20 onto a component substrate 80 of the downhole tool at a wellbore location. A step of cleaning the component substrate 80 may also be included, particularly when the component substrate 80 is a soluble metal substrate. At the site, the activating layer thickness ranges from 10-500 μm and does not need to uniformly cover the component substrate 80. The next step is to spray a first grease layer 30 onto the activating layer at the wellbore location. The first grease layer 30 is non-uniformly bonded to the activating layer 20. The next step of the method is to apply a second grease layer 50 onto the first grease layer at the wellbore location. The second grease layer 50 is non-uniformly bonded to the first grease layer 30 so as to form a composite coating 12 on the component substrate 80.

[0048] An embodiment of the method of the present invention includes forming a transition zone 70 using a first grease layer 30 and a second grease layer 50; deploying a component substrate 80 having a composite coating 12 to a downhole location; and protecting the component substrate 80 from being dissolved for 6-24 hours by the composite coating 12 on the component substrate 80. The first grease layer has a first grease layer consistency range of NLGI 200-250 and a first grease layer thickness, and the first grease layer thickness range is 100-1000 μm. The second grease layer has a second grease layer consistency range of NLGI 280-320 and a second grease layer thickness, and the second grease layer thickness range is greater than 500 μm. After the hydraulic fracturing operation, the method includes the step of dissolving the component substrate 80 to remove the downhole tool from the wellbore.

[0049] Figure 1 , Figure 2c and Figure 3b An embodiment of the method of the present invention is shown, including a first grease layer including first grease layer cracks 40 and first grease layer pores 42, and a transition zone 70 including a portion 64 of the second grease layer located within the first grease layer cracks 40 and the first grease layer pores 42. In these embodiments, the first grease layer thickness ranges from 100 μm to 300 μm, and the second grease layer thickness ranges from 500 μm to 2000 μm. The component substrate 80 includes a soluble metal substrate, so the step of protecting the component substrate 80 from being dissolved for 6-24 hours by the composite coating 12 on the component substrate 80 includes the step of removing at least a portion 14 of the composite coating 12 from the component substrate 80. The second grease layer 50, the first grease layer 30, and the activation layer 20 are non-uniform. Despite this non-uniformity, Figure 2c and Figure 3bStill, the protection step is shown. In some embodiments, the step of removing at least a portion of the composite coating includes removing at least a portion of the second grease layer 50 before removing at least a portion of the activation layer 20. Alternatively, the step of removing at least a portion of the composite coating includes removing at least a portion of the transition zone 70 before removing at least a portion of the activation layer 20.

[0050] Another embodiment of the method of the present invention includes that the activation layer 20 is non-uniform and has activation layer cracks 26 and activation layer pores 28. In the case where the component substrate 80 includes a dissolvable metal substrate, the method also includes the step of forming an activation transition zone 72 after the step of applying the first grease layer 30 to the activation layer 20 at the wellbore site. The activation transition zone 72 includes a portion 44 of the first grease layer 30 located within the activation layer cracks 26 and the activation layer pores 28. As part of the composite coating 12, at least a portion of the activation transition zone 72 can be removed during the step of protecting the component substrate 80.

[0051] Figure 4 The coating 10 and method of the present invention are further summarized. Figure 2a and Figure 2b The data supports Figure 2c The synergy effects reflected in Figure 2a , Figure 2b and Figure 2c In the present invention, the component substrate is a soluble magnesium alloy. Usually, in a 3% KCl solution at 140°C, this soluble magnesium alloy will be completely dissolved within 2 hours. Figure 2a A separate second grease layer or softer grease layer is shown and the results show that the part substrate is not protected after 6 hours. Figure 2b The first grease layer alone or a harder grease layer is shown and the results show that the part substrate is not protected after 6 hours. Figure 2c The coating 10 of the invention is shown. After 6 hours in a 3% KCl solution at 140°C the component substrate was intact. Individually, grease is not a suitable protective material, but in the composite coating of the invention, a specific combination of specific different greases is suitable.

[0052] This synergy itself is not the present invention, since synergy between two different layers is known in many prior arts, where even more complex multilayer structures and interactions exist. Figure 3a , Figure 3b and Figure 3cThis shows the key point of the present invention, because this synergistic effect may disappear. Not any two different greases will work. Nor can any two different greases be made to provide 6-24 hours of protection to the component substrate through conventional testing. For a first grease layer with a consistency range of NLGI 200-270 and a second grease layer with a consistency range of NLGI 280-320, Figure 3a The failure cases of the first and second grease layers are shown. After being placed in a 3% KCl solution at 140°C for 6 hours, the mass loss of the component substrate exceeded 5%. The thickness of the second grease layer was insufficient relative to the thickness of the first grease layer. Figure 3c Another failure case of the first grease layer and the second grease layer is shown. After 6 hours in a 3% KCl solution at 140°C, the mass loss of the component base material is about 10.3%. Adding a second layer of grease or a softer grease by itself does not solve this problem. There is an interaction between the first grease layer with a specific first grease layer consistency range of NLGI 200-270 and the second grease layer with a second grease layer consistency range of NLGI 280-320. Figure 3b It is demonstrated that for a first grease layer having a specific first grease layer consistency range of NLGI 200-270 and a second grease layer having a second grease layer consistency range of NLGI 280-320, the criticality of a first grease layer thickness range between 100-1000 μm and a second grease layer thickness range between 500-2000 μm.

[0053] The present invention provides a composite coating that protects dissolvable components during deployment and while awaiting hydraulic fracturing operations. The goal is to maintain protection time of 6-24 hours, which is consistent with the performance standards expected to be achieved by coatings in the prior art to control the dissolution of dissolvable components (i.e., bridge plugs or other downhole tool components containing soluble magnesium alloys). The present invention improves the performance of greases, which traditionally cannot meet the performance standards of polymer and electroless nickel coatings. The protection provided by a single grease is too short to last in downhole conditions.

[0054] Grease has also not been considered effective for controlling degradation of soluble components due to the non-uniform layers formed by the grease. In particular, the application of the grease is not uniform or smooth for field operators at the wellbore location. The lack of consistency and cracks and pores in the grease layer generally prevent consistent and reliable protection of the soluble components. The present invention further improves the field application effect of the grease layer. When there are specific thickness differences and consistency (National Lubricating Grease Institute (NLGI) consistency) differences between the layers, the non-uniform combination of layers consistent with the field application conditions becomes a functional advantage with special synergy.

[0055] The present invention has tremendous advantages because the previously non-uniform field application of unsuitable greases enables operators to supply a full inventory of different dissolvable components for multiple wells. Rather than providing multiple sets of different dissolvable components with different coatings for a single well, the present invention enables any set of different dissolvable components to have an adjustable coating on-site at the wellbore location, as required for each well. The first grease layer and the second grease layer of the present invention can be applied to any set of different dissolvable components. It is no longer necessary to pre-order large quantities of factory pre-coated dissolvable components. The present invention now allows dissolvable components to be coated on-site as needed, without the guesswork of whether a certain factory pre-coated dissolvable component is needed, or guessing how many factory pre-coated dissolvable components are needed.

[0056] The foregoing disclosure and description of the present invention are intended to be illustrative and explanatory thereof. Various changes may be made to the details of the structures, constructions, and methods shown without departing from the spirit of the present invention.

Claims

1. A coating for a dissolvable component of a downhole tool, include: an activating layer comprising an activating compound and having an activating layer thickness in the range of 10-500 μm; a first grease layer, wherein the consistency of the first grease layer is in the range of NLGI 200-270, the thickness of the first grease layer is in the range of 100-1000 μm, and the first grease layer is non-uniformly bonded to the activation layer; and A second grease layer, wherein the consistency of the second grease layer is in the range of NLGI 280-320, the thickness of the second grease layer is in the range of greater than 500 μm, the second grease layer is non-uniformly bonded to the first grease layer, the first grease layer is located between the activation layer and the second grease layer to form a composite coating, wherein the first grease layer and the second grease layer form a transition zone so that the composite coating can be maintained in the solution for between 6 hours and 24 hours.

2. The coating according to claim 1, in, The activating compound is selected from one of the group consisting of polysiloxane, epoxy resin and polyacrylic acid.

3. The coating according to claim 1, in, The activation layer is bonded to the first grease layer and is capable of bonding to a component substrate.

4. The coating according to claim 1, in, The active layer is non-homogeneous.

5. The coating according to claim 4, in, The active layer has active layer cracks and active layer pores.

6. The coating according to claim 1, in, The first grease layer comprises a first lubricating base, a first thickener and a first additive.

7. The coating according to claim 6, in, The first lubricating matrix is ​​selected from the group consisting of polysiloxane, synthetic oil and petroleum.

8. The coating according to claim 1, in, The thickness of the first grease layer is in the range of 100-300 μm.

9. The coating according to claim 1, in, The first grease layer has first grease layer cracks and first grease layer pores.

10. The coating according to claim 1, in, The second grease layer comprises a second lubricating base, a second thickener and a second additive.

11. The coating according to claim 10, in, The second lubricating matrix is ​​selected from the group consisting of polysiloxane, synthetic oil and petroleum.

12. The coating according to claim 8, in, The thickness of the second grease layer is in the range of 500-2000 μm.

13. The coating according to claim 9, in, The second grease layer has second grease layer cracks and second grease layer pores.

14. The coating according to claim 9, in, The transition zone includes portions of the second grease layer located within cracks in the first grease layer and pores in the first grease layer.

15. The coating according to claim 5, in, The activation layer and the first grease layer form an activation transition zone, and The activated transition zone includes the portion of the first grease layer located in the cracks of the activated layer and the pores of the activated layer, and the composite coating includes the activated layer, the activated transition zone, the first grease layer, the transition zone and the second grease layer.

16. A method for removing a downhole tool from a wellbore, the method The following steps are involved: spraying an activation layer on a component substrate of a downhole tool in situ at a wellbore location, the activation layer comprising an activation compound and having an activation layer thickness ranging from 10 to 500 μm; applying a first grease layer on the activation layer at the wellbore site, the first grease layer having a first grease layer consistency in the range of NLGI 200-270, a first grease layer thickness in the range of 100-1000 μm, and the first grease layer being non-uniformly bonded to the activation layer; applying a second grease layer to the first grease layer in situ at the wellbore location, the second grease layer having a second grease layer consistency in the range of NLGI 280-320, a second grease layer thickness in the range of greater than 500 μm, the second grease layer non-uniformly bonded to the first grease layer to form a composite coating on the component substrate; The first grease layer and the second grease layer form a transition zone; deploying the component substrate having the composite coating to a downhole location; The composite coating on the component substrate protects the component substrate from being dissolved within 6-24 hours; and The component substrate is dissolved to facilitate removal of the downhole tool from the wellbore.

17. The method according to claim 16, in, The first lubricating grease layer comprises first lubricating grease layer cracks and first lubricating grease layer pores, wherein the transition zone includes a portion of the second grease layer located within cracks in the first grease layer and pores in the first grease layer, Wherein, the thickness of the first grease layer ranges from 100 to 300 μm. Wherein, the thickness of the second grease layer ranges from 500 to 2000 μm. wherein the component substrate comprises a soluble metal substrate, and The step of protecting the component substrate by the composite coating on the component substrate so that it is not dissolved within 6-24 hours comprises the following steps: At least a portion of the composite coating is removed from the component substrate.

18. The method according to claim 17, in, The step of removing at least a portion of the composite coating comprises the following steps: At least a portion of the second grease layer is removed before removing at least a portion of the activation layer.

19. The method according to claim 18, in, The step of removing at least a portion of the composite coating comprises the following steps: At least a portion of the transition zone is removed prior to removing at least a portion of the active layer.

20. The method according to claim 16, in, The active layer is non-uniform and has active layer cracks and active layer pores, and Wherein the component substrate comprises a dissolvable metal substrate, the method further comprises the following steps: After the step of applying the first grease layer on the activation layer at the wellbore site, an activated transition zone is formed, the activated transition zone includes portions of the first grease layer located within the cracks of the activation layer and the pores of the activation layer, and the composite coating includes the activation layer, the activated transition zone, the first grease layer, the transition zone and the second grease layer.

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