PREVENTING FOULING OF CRUDE OIL EQUIPMENT

Abstract

A uniform oleophobic or oleo- and hydrophobic film is applied to equipment used in the petroleum industry. The methods can be applied to new equipment or equipment pulled from service, with the application process being performed in a controlled environment or the field. Applicator tools for efficient delivery and application of cleaners, solvents, and films used in the coating process are also described.

Claims

1) A method of preventing organic and inorganic fouling of crude oil equipment, comprising: a) physically cleaning a crude oil contacting surface of a piece of crude oil equipment to remove solid material, oxidation and/or paraffin deposits; b) degreasing and/or washing said crude oil contacting surface; c) rinsing and drying said crude oil contacting surface; d) activating said crude oil contacting surface by applying an activating agent to expose or produce oxide and/or hydroxyl moieties; e) rinsing and drying said activated surface; f) coating said dried activated surface with a self-assembled monolayer (SAM) solution comprising one or more organic molecules and a solvent, each organic molecule having a head and a tail, wherein said head forms a covalent bond with said oxide and/or hydroxyl moieties and said tail is both oleophobic and hydrophobic; g) drying said coated surface to produce an oil and water repelling surface; and h) using said crude oil equipment in the production, transport or processing of crude oil, wherein less organic and inorganic fouling of said oil and water repelling surface occurs than would occur in a similar item of crude oil equipment that was not treated by said method.

2) The method of claim 1, wherein said physically cleaning uses a high pressure water spray.

3) The method of claim 1, wherein said degreasing uses a caustic solution.

4) The method of claim 1, wherein said washing uses a surfactant or detergent.

5) The method of claim 1, wherein said rinsing and drying uses an alcohol and optionally heat.

6) The method of claim 1, wherein said activating agent is an aqueous solution containing hydroxide ions.

7) The method of claim 1, wherein said SAM solution comprises: ##STR00008## where A is an oxygen radical or a chemical bond; n is 1 to 20; Y is H, F, C.sub.nF.sub.2n+1, C.sub.nH.sub.2n+1; Z is H or F; b is 0 to 50; m is 0 to 50; p is 1 to 20; and X is a group selected from carboxylic acid, a sulfonic acid, a phosphoric acid, a phosphinic acid and a phosphonic acid.

8) The method of claim 1, wherein said SAM solution comprises alcohol or glycol and ##STR00009## wherein Y is H, F, C.sub.nF.sub.2n+1 or C.sub.nH.sub.2n+1.

9) The method of claim 1, wherein said SAM solution is about 50-52% ethanol, about 2-3% 2 propanol and about 2-3% methanol, the remainder comprising one or both of 2-(difluoromethoxymethyl)-1,1,1,2,3,3,3-heptafluoropropane or 4-methoxy-1,1,1,2,2,3,3,4,4-nona-fluorobutan).

10) A method of preventing organic and inorganic fouling of crude oil equipment, comprising: a) cleaning a crude oil contacting surface (“surface”) of a piece of crude oil equipment with a high pressure water wash to remove solids; b) degreasing said surface with an aqueous alkaline degreaser that is optionally heated; c) washing said surface with an aqueous surfactant or detergent that is optionally heated; d) activating said surface with an aqueous solution of a base; e) rinsing and drying said surface with an alcohol and optionally with heat; f) applying a self-assembled monolayer (SAM) or a self-assembled monolayer of phosphonate (SAMP) product to said surface after said cleaning, degreasing, washing, activating and rinsing and drying steps; and g) optionally repeating said application 3 times to ensure complete coverage.

11) The method of claim 10, wherein: a) said degreaser comprises NaOH, KOH, ethylene glycol, monobutyl ether, ethoxylated alcohols, sulfonic acid, or salts thereof; or b) said surfactant or detergent comprises ADBAC Quat, DDBSA, or sodium metasilicate; or c) said alcohol comprises methanol, ethanol, propanol, isopropanol, or butanol; or d) said aqueous solution of a base comprises KOH, NaOH, ammonia, sodium bicarbonate, pyridine, or methylamine, or e) combinations thereof.

12) A method of inhibiting organic and inorganic deposition on crude oil equipment, comprising: a) cleaning a crude oil contacting metal surface of a crude oil equipment with heat, detergent, caustic solution, mechanically or combinations thereof to remove contamination, oxidation and/or paraffin deposits; b) applying methanol to said cleaned surface and drying said surface; c) activating said dried surface with a hydroxide ion containing solution, wherein said activated surface has free and exposed oxide and/or hydroxyl moieties; d) drying said activated surface; e) coating said dried activated surface by applying a SAM solution comprising an alcohol and at least one molecule having and a head and a tail; i) said head for covalently bonding with said oxide and/or hydroxyl moieties on said surface and selected from the group consisting of a phosphinic acid, a phosphonic acid, sulphonic acid, phosphoric acid, carboxylic acid; and ii) said tail being both oleophobic and hydrophobic and selected from the group consisting of perfluorinated hydrocarbon backbone; f) drying said coated surface; and g) deploying said oil equipment so that said coated surface contacts crude oil, wherein organic and inorganic fouling is reduced as compared to a similar item of oil equipment not treated with said method.

13) The method of claim 12, wherein said SAM solution comprises alcohol and ##STR00010## where A is an oxygen radical or a chemical bond; n is 1 to 20; Y is H, F, C.sub.nF.sub.2n+1, C.sub.nH.sub.2n+1; Z is H or F; b is 0 to 50; m is 0 to 50; p is 1 to 20; and X is a group selected from carboxylic acid, a sulfonic acid, a phosphoric acid, a phosphinic acid and a phosphonic acid.

14) The method of claim 12, wherein said SAM solution comprises alcohol and ##STR00011## wherein Y is H, F, or C.sub.nF.sub.2n+1

15) The method of claim 12, wherein said SAM solution is about 50-52% ethanol, about 2-3% 2 propanol and about 2-3% methanol, the remainder comprising one or both of 2-(difluoromethoxymethyl)-1,1,1,2,3,3,3-heptafluoropropane or 4-methoxy-1,1,1,2,2,3,3,4,4-nona-fluorobutan).

16) The method of claim 12, wherein said coating step is performed by filling said crude oil equipment with said SAM solution.

17) The method of claim 12, wherein said coating step is performed by spraying said crude oil contacting surface with SAM solution.

18) The method of claim 12, wherein said coating step is performed by wiping said crude oil contacting surface with SAM solution.

19) The method of claim 12, wherein said coating step is performed by immersing said crude oil equipment in SAM solution.

20) An apparatus, comprising a piece of crude oil equipment having an oil and water repelling surface intended to contact crude oil, said crude oil equipment made by the method of claim 1 or 10 or 12.

21) A method of preventing organic and inorganic fouling of oil equipment, comprising: a) activating an oil contacting surface of an item of oil equipment by applying an activating agent to expose or produce oxide and/or hydroxyl moieties using a rotating brush soaked in said activating agent; b) rinsing and drying said activated surface; c) coating said dried activated surface with a self-assembled monolayer (SAM) solution using a rotating brush soaked in said SAM solution, said SAM solution comprising one or more organic molecules and a solvent, each organic molecule having a head and a tail, wherein said head forms a covalent bond with said oxide and/or hydroxyl moieties and said tail is both oleophobic and hydrophobic; and, d) drying said coated surface to produce an oil and water repelling surface; and e) using said item of oil equipment in the production, transport or processing of crude oil, wherein less organic and inorganic fouling of said oil and water repelling surface occurs than would occur in a similar item of oil equipment that was not treated by said method.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0079] FIG. 1. Paraffin or wax deposits inside used oil well tubulars.

[0080] FIG. 2A. SAM of an oleophobic organic material attached to a metal surface.

[0081] FIG. 2B shows a schematic for a SAMP from Aculon.

[0082] FIG. 2C displays other organic molecules for use in the SAM of an oleophobic material.

[0083] FIG. 3A-C. Schematic of application tools.

[0084] FIG. 4. One embodiment of the general preparation method for surface of a substrate in contact with crude oil.

[0085] FIG. 5A is a basic sediment and water (BS&W) probe reading at Location 1 using an uncoated BS&W probe and a BS&W probe reading using a probe that has been coated with an oleophobic and hydrophobic monolayer.

[0086] FIG. 5B is a BS&W probe reading at Location 2 using an uncoated BS&W probe and a BS&W probe reading using a probe that has been coated with an oleophobic and hydrophobic monolayer.

[0087] FIG. 6 displays pictures taken at Location 1. FIG. 6A presents an uncoated BS&W probe with paraffin deposition, FIG. 6B shows bottom of a coated probe after 3 months use, and FIG. 6C shows top of a coated probe after 3 months use.

[0088] FIG. 7 displays pictures taken at Location 2. FIG. 7A shows an uncoated BS&W probe with paraffin deposition, FIG. 7B presents bottom of coated probe after 3 months use, and FIG. 7C shows top of coated probe after 3 months use.

[0089] FIG. 8A displays the readings for a coated, previously in-service BS&W probe installed at Location 3.

[0090] FIG. 8B displays the readings for a coated, previously in-service BS&W probe installed at Location 4.

[0091] FIG. 9A displays data for Coriolis Meter 1.

[0092] FIG. 9B displays the meter factors for one of the coated Coriolis flow meters. The blue line is the first application on the new meter that was installed March 2018. The orange line is the meter factor readings on the previously in service meter that was cleaned, activated and SAM applied.

DETAILED DESCRIPTION

[0093] The present disclosure provides a novel method of applying an oleophobic and hydrophobic monolayer to surfaces of petroleum equipment that come into contact with crude oil, and method using such oleophobic and hydrophobic surface coatings in oil production and usage. Applicator tools to aid in even distribution of the solutions used during the application process to various shaped and sized equipment are also described, as well as oil equipment with such coatings.

[0094] The substrates treated using the described methods can be any piece of equipment or pipeline that comes into contact with crude oil, including production tubing, pipelines, turbine meters, Coriolis meters, magnetic flow meters, down hole pumps, check valves, valves, pigs, heat exchangers, basic sediment and water (BS&W) probes, storage tanks, and the like.

[0095] In some embodiments, the substrate is preferably stainless or carbon steel as the surface of these materials can be activated using the methods presently described, allowing the head groups on the SAMs to form covalent bonds with oxides on the activated surface of the steel. However, non-metallic substrates can also be treated. Such is the case for steel substrates like instruments and meters that have an epoxy and phenolic resins coating.

[0096] No significant changes are required for non-metallics that contain oxide and/or hydroxyl groups. Epoxy coatings can/have been used as to facilitate/promote SAM formation. Information on SAMs on epoxy coatings can be found in US20060166000.

[0097] Applying the solvents and/or oleophobic monolayer onto a substrate surface with a wipe is not enough to fully and uniformly coat the surface for equipment with bends, small openings, long lengths, or intricate geometries. As such, tools were designed to both ensure even distribution of the solvents, solutions, and monolayer of oleophobic product on all desired surfaces, and to address the various geometries of the substrates. The novel applicator tools described herein have been designed to be used with substrates having large lengths, sharp bends, small diameter openings, and/or surfaces requiring 360° applications (including allowing for straight, curved, notched, or bent surfaces). Further, the designs of the tools facilitate an even distribution of the monolayer material, negating the need for an added step to remove excess material or residue from the treated surfaces.

[0098] The novel applicator tools are shown in FIG. 3A-C. The tool in FIG. 3A is suitable for use in tubing, pipes, pumps, and the like wherein a small amount of flexibility in spray direction is needed to traverse gentle light bends, spray behind shoulders, and the like. It comprises a hand pump 301, fluidly coupled to a product reservoir 303, fluidly coupled to a rigid lance 305. Of course, the hand pump can be replaced with a separate or integral electronic pump, as suitable for the job at hand, in which case the reservoir location may be appropriately adjusted. The pump details are known in the art and are not illustrated herein for simplicity.

[0099] The lance is in the range of 10-40 feet long, as needed for access to pipe joints, with an internal diameter of about ⅜-⅝ inches. A flexible lance or whipstock 309 is fluidly connected to the rigid lance via a coupling 307 that allows the whip stock to rotate freely with respect to the lance. The whip has a nozzle 311 at its tip, and preferably the tips are either interchangeable or adjustable for different spray patterns, or both.

[0100] FIG. 3B shows a hybrid spray/wipe applicator tool, with a hand drill 313 providing for rotation of the tool detachably attached to a solid lance 315 tipped with a fibrous wipe 317. We used a cotton, 20 gauge, shotgun cleaner in our prototype device. This tool is dipped in the SAM solution, inserted into a pipe and rotated through the length of the pipe. The pipe is then dried, and can then be installed in oilfield equipment.

[0101] If desired, tool features of FIGS. 3A and 3B can be combined, such that the pump fluidly dispenses solution down a hollow lance, which can also be rotated.

[0102] FIG. 3C shows an embodiment that can travel through significant bends in equipment, having a hand pump 319 and pressure indicator 320 fluidly connected to product reservoir 321. Rotary coupler 323 provides a rotatable and fluidic connection to a flexible lance 325 of length about 10-40 feet, although other sizes may be suitable depending on the application. The lance has an internal diameter of ⅜ to ⅝, but other sizes are possible. The lance is provided with an end piece, called a distribution fitting or tip 331, that has holes in its surface, allowing egress of the SAM. The distribution fitting also has a wicking material (327 and 329), e.g., a fibrous material or fine bristles, for holding the SAM and conveying it to the inner surface of e.g., a piping. While the distribution fitting could be integral with the lance, it is more convenient to have a separate and exchangeable piece so that different tips can be used with the same base unit, e.g., when the wicking material degrades or when a different size is needed.

[0103] To prevent the affixation of e.g., paraffins and scale, films with dual oleophobic and hydrophobic character are preferably applied to the surface that contacts oil. Any oleophobic/hydrophobic composition that can form a strong, self-assembled monolayer that is covalently bonded to a metal contact surface can be used in the present methods. As the name implies, SAMs are monolayers of organic molecules that spontaneously form an ordered structure on a surface of a substrate, with the molecules interacting with a surface through the ‘head’ group of the organic molecule. The ‘tail’ group of the organic molecule is tailored to modify the surface properties of substrate, such as to produce an oleophobic/hydrophobic surface as required in the present disclosure. An optional spacer may be present between the head and tail groups.

[0104] Previous use of SAMs have been problematic because the interaction between the head group and the surface was not necessarily strong, with most SAMs relying on weak van der Waals forces between the organic molecules and the surface of the substrate. This weak interaction is problematic as the formed monolayer has poor durability and lacks application longevity. Thus, the presently used organic molecules have a head group that contains at least one linker atom that must form a covalent bond with the surface of the substrate to permanently change the molecular characteristics of substrate and reduce the need for reapplication.

[0105] A variety of head groups can be used on the organic molecules in the film, depending on the material of the substrate being treated. Most oil and gas equipment are stainless steel or carbon steel, which can be activated as described below to have oxide and/or hydroxyl groups on their surfaces. Thus, the head groups must be capable of forming a covalent bond with the oxides and/or hydroxyl groups.

[0106] Exemplary head groups for bonding with surface oxides/hydroxyls include alcohols, carboxylic acids, silanes, sulfonic acids, phosphinic acids and phosphonic acids. In some embodiments, phosphonic acids are preferred as they are capable of polydentate attachment to the oxides on passive stainless and carbon steel, and have hydrolytically robust binding.

[0107] For other surfaces such as epoxy and phenolic resins, US20060166000 describes a number of suitable binding groups, such as organophosphorus compounds, which binds directly to the substrate via a phosphorus-oxygen bond.

[0108] The tail of the organic molecules in the SAM imparts the new surface characteristics of the coated substrates, i.e. the ability to repel crude oil, and by extension, repel paraffin precipitates and are generally of a highly polar nature. The tail of the organic molecules is preferably hydrocarbon based, although other moieties, including fluorinated groups, can be included in the backbone of the chain. For example, the tail can have a mixture of fluoro substituted hydrocarbons and hydrocarbons containing ethylenically unsaturated groups or oxyethylene groups.

[0109] Exemplary SAMs for use in the present methods can be found in U.S. Pat. Nos. 8,524,367, 8,524,367 and 8,236,426, each incorporated by reference in its entirety for all purposes.

[0110] For example, U.S. Pat. No. 8,524,367 teaches organometallic films comprising a polymeric metal oxide with alkoxide and hydroxyl ligands and halide ligands, preferably where the metal is selected from Ti, Zr, La, Hf, Ta and W. Exemplary compounds include:

##STR00003##

[0111] To provide a hydrophobic aspect to the SAM, the organo acid or derivative thereof is preferably a perfluorinated oligomer of structure:

R.sub.f—(CH.sub.2).sub.p—X  (2) [0112] where R.sub.f is a perfluorinated alkyl group or a perfluorinated alkylene ether group and p is 2 to 4, preferably 2.

[0113] Examples of perfluoroalkyl groups include:

##STR00004##

[0114] U.S. Pat. No. 8,236,426 teaches fluorinated material having the following structures:

##STR00005## [0115] X is:

##STR00006## [0116] wherein Y is H, F, C.sub.nH.sub.2n+1 or C.sub.nF.sub.2n+1.

[0117] U.S. Pat. No. 8,178,004 teaches a hydrophobic coating comprising (a) a perfluorinated acid capable of forming a self-assembled monolayer on the metal substrate, (b) a surfactant, (c) an organic solvent, and (d) water. Examples include:

##STR00007##

[0118] The thickness of the monolayer film is one molecule thick. Depending on the size of the tail, the monolayer can have thickness between about 1 and about 100 nm. Preferably, the monolayer is about 1-10 nm thick, the most preferred 2-4 nm.

[0119] To achieve a surface conducive to covalent bonding with the heads of the oleophobic/hydrophobic layer, novel methods of treating the substrate were developed. While the methods will vary depending on if the substrate has been in service and needs extensive cleaning, the general steps, shown in FIG. 4, are:

[0120] Clean surface debris and deposits, if needed.

[0121] Create a water wet surface;

[0122] Activate the surface; and,

[0123] Apply SAM solution to form SAM.

[0124] The application methods can be applied to both new or in-service substrates. For new pieces of equipment, the cleaning step can be skipped unless the new piece has a coating or other surface contaminant that needs to be removed before applying SAM solution. Otherwise, the first step (101) is to clean the substrate to remove surface contaminants.

[0125] For equipment that has already been in use, the cleaning step is especially important because debris and paraffin will likely already have collected on the surface. As such, thermal, chemical, or mechanical methods can be applied to remove deposited paraffin, followed by methods using soaps or detergents to clean additional debris. Alternatively, hot water (about 180° F.) with a paraffin dispersant can be circulated through the substrate to remove the paraffin before using soaps or detergents to clean the substrate. For new substrates, a simple cleaning with soaps or detergents may be all that is needed to remove dirt or other contaminants.

[0126] Any method of cleaning the metal substrates can be used, including thermal treatments to break down oil buildup, mechanical cleaning such as Ceria polish (or other polishing compound), pigging, scraping and the like, applying high pressure liquids to dislodge debris or deposits, and/or using of detergents and/or soaps. Excellent cleaning methods include hot caustic treatments (e.g., Aculon 907 (a heated caustic dip) or 905 (a room temperature caustic cleaner)), plasma cleaning, corona discharge or piranha bath (H.sub.2SO.sub.4/H.sub.2O.sub.2). However, some of these may be impractical for oil field use.

[0127] We used nonylphenol ethoxylates, sodium metasilicate and sodium percarbonate to preclean the metal surfaces before treatment with the SAM. These can leave films, however we used very dilute solutions of <100 mM, <50 mM, <10 mM, and <1 mM to avoid film deposition.

[0128] The second step (102) is to create a water wet surface on the substrate using a solvent such as methanol. Wetting steps are generally done before applying the SAMs to improve bonding. What is meant by ‘water wet surface’ is that aqueous liquids can directly contact the substrates surface which allow the SAM to form the monolayer. If the surface is ‘oil wet’ there would be a barrier preventing surface contact with aqueous solutions.

[0129] The third step (103) is to ‘activate’ the surface of the substrate to allow for application of a uniform monolayer surface. Any solution that reacts with the substrate to form or expose oxide or hydroxyl moieties on the surface of the substrate can be used. The presence of the oxide or hydroxyl moieties activates the surface and improves bonding of the SAMs in the next step. Exemplary solutions include caustic solutions such as KOH/NaOH, detergents or both. Acids cannot be used on metal because of the solubility of metal oxides in low pH solutions, which would tend to remove the desired functionality and create a less active surface.

[0130] The fourth step (104) in the application process applies the SAM to the activated surface only, wherein head group, typically phosphate-based, on the oleophobic/hydrophobic molecules forms a covalent bond with the oxide or hydroxyl moieties. The SAMs will not, however, be able to form covalent bonds with surfaces of the substrate that were not activated during the third step. Thus, the judicious choice of treatment surfaces can lower costs associated with wasted SAM material and removal of SAMs from undesired locations on the substrate.

[0131] An advantage of the application process and applicator tools specific to the process is the ability to coat a substrate surface in or near the field of use. This allows for substrates already in use in the field to be pulled from service, cleaned, activated, coated with the SAM, and placed back on-line without having to transport the substrate to a different location. As the SAM is covalently attached, service calls for the treated equipment are expected to decrease exponentially.

[0132] Once treated, the equipment can be put on-line and in-use, wherein the crude oil can continue to be produced, transported, measured and/or tested, or treated. As the present methods do not act by interference with the precipitation of paraffin, the treated substrates can be still used with other methods of paraffin control as required by other operations. However, the SAM of oleophobic and hydrophobic material is all that is needed to prevent deposition on the treated surface.

[0133] The present invention is exemplified with respect to BS&W probes, Coriolis flow meters, and hairpin heat exchangers. However, this is exemplary only, and the invention can be broadly applied to other equipment used in the petroleum industry, such as blowcase level bridals, level switches, chokes, valves, tuning forks, piping, tanks, and the like.

EXAMPLES

[0134] The following examples are included to demonstrate embodiments of the appended claims. These examples are intended to be illustrative only, and not to unduly limit the scope of the appended claims. Those of skill in the art should appreciate that many changes can be made in the specific embodiments which are disclosed and still obtain a like or similar result without departing from the spirit and scope of the disclosure herein. In no way should the following examples be read to limit, or to define, the scope of the appended claims.

[0135] Substrates: The substrates selected for the examples included both new and in-service equipment for use in various areas of the petroleum industry. The new equipment was cleaned to remove oils and/or surface contaminants, whereas the in-service equipment underwent a series of physical deposit removal methods.

[0136] Surface testing: The surface properties of the coated equipment were measured pre- and post-treatment with Dyne pens to evaluate the success of the application of the SAM oleophobic and hydrophobic monolayer. Briefly, when the Dyne level test pen is applied to the surface, the liquid from the pen will either form a continuous film on the surface or pull back into small droplets. If the Dyne test fluid remains as a film for 3 seconds, the substrate will have a minimum surface energy of that ink value, expressed in mN/m (Dynes). Should the Dyne test liquid reticulate or draw back into droplets in less than 1 second then the surface energy of the substrate is lower than that of the liquid itself. The exact surface energy (Dyne level) can be determined by applying a range of increasing or decreasing values of Dyne test pens and finding the break point. If the break point cannot be determined based on the range of pens available, it can only be determined that the surface energy is greater than or less than the test range.

[0137] In the present proof of concept work, reduction in the surface energy between pre- and post-treatment indicated that the SAM application was successful for the tested area. Our experiments are described in more detail next.

BS&W Probes

[0138] BS&W probes frequently experience paraffin deposition, which is only discovered by inaccurate readings that are greater than the actual BS&W content, i.e., a drift in the signal. Once a drift in the signal is noticed, the system is shut down and the BS&W probes are removed for cleaning, with oil production being temporarily diverted to tanks. Thus, BS&W probes were ideal for conducting a proof-of-concept trial as they are easily monitored for signal drift, i.e., paraffin deposition.

[0139] The general SAM application method described herein was first performed on two new BS&W probes in a laboratory setting. New probes were used to remove residual paraffin interference as a variable from the trial results, and a laboratory setting was used to eliminate poor application of SAM as a variable and to monitor the performance of the SAM layer post-application.

[0140] Cleaning. The internal parts of the probes were cleaned with a detergent to remove oils and/or surface contaminants. No thermal or mechanical cleaning was required because the probes were new.

[0141] Surface wettability. The cleaned surfaces were wiped with pure methanol and allowed to dry.

[0142] Surface Activation. To activate the internal surfaces, the surfaces were wiped with a caustic solution Aculon 907 caustic solution and allowed to dry. Aculon 907 contains a mixture of ethanol (50-52%), 2-(difluoromethoxymethyl)-1,1,1,2,3,3,3-heptafluoropropane and 4-methoxy-1,1,1,2,2,3,3,4,4-nonafluorobutan) (43-46%), 2 propanol (2-3%) and methanol (2-3%).

[0143] Film application. Two different SAM linking techniques were used to evaluate which, if either, was most persistent. One was a SAM, the other was a sol-gel process that does not covalently bond to the substrate.

[0144] The ability of the SAM to coat the inner surface of the BS&W probes to repel paraffin in crude oil was tested at two different trial locations. The trial locations were selected by reviewing the frequency of BS&W cleaning due to paraffin deposition. Each trial location had three work orders requesting paraffin removal over a three-month period, indicating that paraffin was a significant issue in that reservoir.

[0145] FIGS. 5A and 5B display the readings for locations 1 and 2 respectively, before a coated BS&W probe was installed and after the installation. Before a coated probe was used, both locations experienced drifts (1) in readings every 2-3 months. This resulted in the systems being shut down so that each probe could be removed and cleaned of paraffin deposits before being returned to service. Since the installation of a probe coated by the methods described above (2), neither location has experienced a drift in readings for over a period of a year. Thus, the film was considered to have significantly mitigated paraffin deposition on the probes (at least 4× improvement).

[0146] Both coated probes were also proactively pulled within three months of service for visual inspections. FIG. 6 displays pictures of the initial uncoated BS&W probe (6A), and the bottom (6B) and top (6C) of the coated probe after three months of service for location 1. The internal inspection of the BS&W probes showed that there were paraffin deposits at the top of the probe where the coated probe interfaced with the uncoated pipe. This is due to the pipe not having an oleophobic and hydrophobic layer to repel paraffin deposits. The SAM coated probe itself was largely free of paraffin deposition, as seen in 5B. Similar results were seen with location 2, shown in FIG. 7A-C.

[0147] Thus, this trial proved that the new BS&W probes could be coated effectively with an oleophobic and hydrophobic monolayer to mitigate paraffin deposition for period of at least a year, and quite possibly 2 years or more. The trial was then expanded to include in-service BS&W probes that were coated in the field.

[0148] Six in-service BS&W probes were pulled from service. All six probes required significant cleaning to prepare the phenolic interior surface to receive the film application. The procedure for applying the film to the previously in-service probes in the field was as follows:

[0149] Cleaning. As much paraffin as possible was physically removed from each probe. Then, the probes were soaked in a detergent solution comprising sodium metasilicate and sodium percarbonate for 12 hours. After soaking, hot water (˜180° F.) with a paraffin dispersant was circulated through each probe to remove any remaining paraffin or other contaminant.

[0150] Surface wettability. Once cleaned, the internal parts of the probes were filled and soaked with an aromatic solvent for about 1 hour before the solvent was drained. Then, the internal parts were filled with methanol, but not soaked. The methanol was drained, and the internal parts were allowed to dry.

[0151] Surface Activation. To activate the internal surfaces, the surfaces were wiped with a caustic solution of NaOH and allowed to dry.

[0152] Film application. The oleophobic and hydrophobic SAM was applied with a “fill” application by filling the internals parts of the probe with the SAM solution in for 15 minutes. For the “fill” application, a blind flange was place on one side of the probe. The probe was filled with the SAM and carrier, and a blind flange was place on the other side of the probe to seal the probe. The probe was then allowed to soak for about 15 minutes with periodic agitation. The probe was opened and the SAM/carrier solution was recaptured for additional applications. The pieces were allowed to dry, allowing the SAM to bond to the activated surfaces of the internal parts.

[0153] FIG. 8A displays the readings for one of the probes installed at Location 3 on Jun. 6, 2018. The location was selected due to high BS&W readings related to paraffin deposition in the probe. The BS&W readings for this location consistently remained <1% since the probe was installed. The well has been producing to tanks since Aug. 17, 2018 and therefore no readings have been recorded since that date.

[0154] FIG. 8B displays the readings for a second probe that was installed at Location 4 on Jul. 12, 2018, wherein previous high BS&W readings were caused by paraffin deposition. Since the installation of the coated probe, there was one event for high BS&W that occurred on Sep. 24, 2018. The event was confirmed to be due to actual water content, however, and not drift resulting from paraffin deposition.

[0155] These coated probes are still early in the life of the trial, but the initial results are extremely promising. It is clear that the field application of the SAM was successful, and that the SAM is mitigating paraffin deposition within the probes. Indeed, time between servicing for fouling can be increased at least 4-fold, and likely 4-5-fold, and possibly 6, 8, or even 10 fold.

[0156] The initial results also make clear that the process is economically efficient, as interventions to clean the BS&W probes have not been needed since the equipment was coated. The primary economic driver for coating BS&W probe was the elimination of system intervention. When the probes experience paraffin deposition, the probes require cleaning and/or removal from the system for a new probe. Based on the cost evaluation of the application of an oleophobic and hydrophobic SAM versus the cost of intervention, eliminating a single intervention per year would be a break even or slightly better return. However, as paraffin deposition is quite frequent in BS&W probes, the results indicate that multiple interventions may be eliminated. Thus, this method can be used to coat new probes as well as retro-actively coat in-service probes at problematic locations.

Coriolis Flow Meters

[0157] Coriolis flow meters are another important piece of petroleum equipment that frequently experience paraffin deposition, which results in meter factor corrections due to measurement error.

[0158] Specifically, Coriolis flow meters work on the principle that the inertia created by fluid flowing through an oscillating tube causes the tube to twist in proportion to mass flowrate. Many Coriolis flow meters have two tubes that are made to vibrate in opposition to each other by means of a magnetic coil. Sensors in the form of magnet and coil assemblies are mounted on the inlet and the outlet of both flow tubes. Under no-flow conditions, the inlet and outlet waves are in phase with each other. When fluid is moving through the tubes, the tubes twist in proportion to mass flowrate. The amount of this twist is detected by the inlet and outlet sensors, based on a phase shift (time difference) that occurs in the waves formed by the two sensors. The mass flowrate is derived from the difference in phase shift in the waves formed by the inlet and outlet sensors.

[0159] Paraffin deposition reduces the cross-sectional area of the tubes and thus increases the velocity of the fluid. As such, an adjustment is made to the meter factor to account for the error in the measurement. Specifically, increases to the meter factor occur following the monthly proving cycle because of paraffin deposits to correct oil metered versus actual. For every 10-point change (10 points=0.0010) in meter factor, there is a 100 bbls change per 100,000 bbls metered. For this reason, mitigating paraffin deposition is critical for more consistent meter factors and accurate measurements.

[0160] As before, the SAM application methods were tested on a new Coriolis flow meter. The internal surfaces of the meter are stainless steel, which has a uniform passive oxide layer. However, due to the geometry of the meter, custom applicator tools were created to deliver cleaners, solvents and filming products through a delivery tube and wick to the surface. The applicator used for the Coriolis flow meter is shown in FIG. 3C.

[0161] The trial location for the coated Coriolis flow meters was a LACT skid that had two 8″ Coriolis flow meters for metering outgoing oil to Company 1 and two 8″ Coriolis flow meters for metering outgoing oil to Company 2. As such, four new 8″ Coriolis flow meters were obtained for the present test.

[0162] Cleaning. The internal parts of the flow meters were cleaned with a detergent (as described above) to remove oils and/or surface contaminants. No thermal or mechanical cleaning was required because the flow meters were new.

[0163] Surface wettability. The cleaned surfaces were wiped with methanol and allowed to dry.

[0164] Surface Activation. To activate the internal surfaces, the surfaces were wiped with a caustic solution (as described above) and allowed to dry.

[0165] Film application. The same SAM solution as described above was applied via a wipe application with the specially designed applicator shown in FIG. 3C to achieve 360° coverage through the bends.

[0166] The surface properties of the Coriolis flow meters were measured pre- and post-treatment with Dyne pens to evaluate the success of the application. The pre-treatment test marks ranged from 38-56 d/cm, and post treatment marks ranged from 30-42 d/cm. The reduction in surface energy indicated by the Dyne pens indicate that the film application was successful.

[0167] The meter factors for one of the coated meters are displayed in FIG. 9A. The meter factors for the coated meter are highlighted in the shaded box. The values of the meter factors have smoothed out significantly by single digit points (1 point=0.0001) where double digit point changes in the past have been common. The oleophobic and hydrophobic coating has maintained consistent readings to date. Unexpectedly, higher meter factor changes due to cooler weather have not been experienced since the coated meter was installed. This in itself is a significant improvement over uncoated meter.

[0168] The primary economic driver for the Coriolis flow meter application was the accuracy of the metered oil and accounting for all oil that flows through the LACT skid. Treatment and remediation cost were negligible and were not considered. It was found that the oleophobic and hydrophobic SAM application mitigated excessive paraffin deposition and mitigated large changes in meter factors. Based on the past experience with meter factor trends and the performance to date, the application of an oleophobic and hydrophobic monolayer to Coriolis flow meter is economically viable.

Hairpin Heat Exchanger

[0169] Hairpin heat exchangers used in stabilizers were the next piece of equipment coated with oleophobic and hydrophobic SAMs. These hairpin heat exchangers experience paraffin deposition on the tube side where the stabilized condensate approaches 100° F. Paraffin deposition reduces heat exchange efficiency and increase differential pressure across the system. As such, mitigating paraffin deposition in the hairpin heat exchangers maintains heat exchange efficiency and pressure drop across the system which increases processing efficiency and reliability.

[0170] The heat exchanger used in this example was previously in-service and had significant paraffin deposition that required cleaning of the exchanger with a pressure washer and flex lance. The exchanger tubes are constructed of carbon steel and a process had to be developed to produce the proper surface properties to achieve a uniform film. A hybrid spray/wipe application was used for the final SAM application step, where the product was distributed to the surface of the tubes and wiped on with a swab attached to a rotating flex lance shown in FIG. 3B. The overall application process is below:

[0171] Cleaning. To properly clean and prepare the surface of the heat exchanger tubes, applicator tools with flexible lances and flex spray tips were designed to achieve an even distribution of detergents, solvents and caustic. The paraffin in the tubes within the heat exchanger were physically removed with a pressure washer. The tubes were then sprayed with a paraffin dispersant using the flex spray tip in FIG. 3A, and allowed to soak for about 2 hours. The exchange tube where then scrubbed using a stainless-steel brush tip applied to the rotating flex lance of the tool in FIG. 3B.

[0172] Because the tubes are constructed of carbon steel, the surface flash rusted following the pressure washing and detergent soak. As loose surface rust would result in a poor surface condition to apply the film, the tubes were scrubbed clean of loose surface rust prior to surface preparation and film application.

[0173] Surface wettability. The cleaned surfaces were wiped with methanol and allowed to dry.

[0174] Surface Activation. To activate the internal surfaces, the surfaces were wiped with a caustic solution and allowed to dry.

[0175] SAM application. For the SAM application step, a hybrid spray/wipe tool with a swab attached to a rotating flex lance (shown in FIG. 3B) was used to distribute and wipe the film on the activated surfaces of the tubes.

[0176] The quality of the SAM application was assessed near the tube sheet. It was found that the internal surface of the tube was accessible and that greater than 90% of the surface area was successfully coated. However, it was difficult to assess the SAM through the entire length of the tubes. Our results were qualitative based on dyne pen readings at the time of SAM application, but have since been evaluated and the results confirm a mostly complete SAM coating.

[0177] The results of the tests performed herein indicate that surface modification treatment with an oleophobic and hydrophobic SAM layer is an effective method of mitigating paraffin deposition. The method is cost effective because it reduces costs associated with current methods of stopping systems to pulled untreated parts. Finally, the application methods are easily adaptable to field-based environments, which means the coatings can be added to both new and used equipment. However, it is significantly easier, efficient and cost effective to apply the treatment steps and film to new equipment as there is no need to remove deposits during a cleaning step.

[0178] Additionally, the selected petroleum equipment that was coated and evaluated during the above trials were varied enough that the methods are expected to be applicable to even more equipment, such as blowcase level bridals, level switches, chokes, tuning forks, piping, and the like.

[0179] As such, any piece of equipment that comes into contact with crude is capable of being treated with an oleophobic and hydrophobic SAM to avoid the initial affixation of paraffin, asphaltenes, scale, salts etc. deposits. The application tools described herein can be used to apply a uniform monolayer to any size or shaped piece of equipment such that a permanent change is made in the molecular characteristics of the contact surface through a covalent bond between the contact surface and the SAM layer. This results in improved reliability of equipment, piping, sensors and devices, as well as providing improved operational and maintenance personnel safety.

[0180] The following references are incorporated by reference in their entirety.

[0181] U.S. Pat. No. 8,178,004, Hanson, “Compositions for providing hydrophobic layers to metallic substrates,” Aculon, Inc. (2009).

[0182] U.S. Pat. No. 8,236,426, Hanson & Bruner, “Inorganic substrates with hydrophobic surface layers,” Aculon, Inc. (2011).

[0183] U.S. Pat. No. 8,524,367, Hanson, “Organometallic films, methods for applying organometallic films to substrates and substrates coated with such films,” Aculon, Inc. (2012).

[0184] U.S. Pat. No. 8,658,258, Hanson, “Plasma treatment of substrates prior to the formation a self-assembled monolayer,” Aculon, Inc. (2010).

[0185] US20180142170, Drees, et al., “Methods of applying multi-bonded SAMPS to equipment and products and apparatus comprising SAM surfaces,” Electrolab, Inc. (2018). See also all related material US20170130145, US20170130146, US2014237800 (U.S. Pat. No. 9,476,754), US2017292081 (U.S. Ser. No. 10/059,892), US2017292082 (U.S. Ser. No. 10/150,924), US2016348014 (U.S. Pat. No. 9,688,926), US2017029725, US2017029726, US2017029727, US2017029728, and US2017029729.