The present invention relates to a paraffin inhibitor composition comprising a) an acrylic copolymer formed from an alkyl methacrylate and methacrylic acid monomers, and b) a solvent. The paraffin inhibitor composition as described herein provides utility in hydrocarbon oils and may be especially useful as a paraffin inhibitor, pour point depressant or cold flow improver, in hydrocarbon based crude oils, fuel oils, or lubricant oils.

Hydrocarbon oil flow problems are generally associated with the naturally occurring paraffins in crude oils which present many problems for the oil industry; assessing and dealing with such problems is termed flow assurance, particularly in relation to crude oil. Flow assurance challenges in both production and transportation of crude oils include wax deposition, flow problems and gelling, and these are most evident in subsea and deep water operations. In addition, flow assurance problems continue to be evident in refined hydrocarbon oils, particularly when used as fuel oils or lubricant oils, where the removal of particularly problematic paraffinic constituents in the oil may not be complete post refining.

Additives including those which function as paraffin inhibitors, pour point depressants, wax inhibitors and cold flow improvers are typically added to hydrocarbon oils to assist in ensuring or maintaining desirable flow properties, and this is at the heart of flow assurance. The present invention provides a functional paraffin inhibitor, but also in some embodiments provides additional functional properties meaning that less additives may be required to ensure that a particular hydrocarbon oil maintains its flow during its processing, transport, storage, or intended use.

Paraffins present in crude oil may crystallise upon a reduction of temperature, or upon increase in paraffin content, forming a three-dimensional structure comprising needles and/or flakes of paraffin wax. This crystallisation of otherwise dispersed paraffins results in reduction of oil flow, which causes associated problems in terms of processing (pumping, flow maintenance, removal) production in the field, transport and storage prior to refining, and even treatment and refining of the removed crude oil product. “Plugging” of production and refinement process equipment is a problem that can result in a large amount of down time, and additives such as paraffin inhibitors are actively sought to add to crude oils to mitigate this problem.

Crude oil may contain large fractions of paraffins, the exact type and proportion of these paraffins varies from source location, i.e. paraffinic content can vary in crude oil on a well by well basis. There is a high level of paraffin variability observed in different crude oil production sites and processes, for example, shale derived oil is known to be high in paraffin content. Some crude oil types are known to have particular difficulty in maintenance of flow assurance during oil extraction due to paraffin content, whereas crude oil from alternative geographical locations may have lower levels of paraffin content, and as such experience no flow assurance problem arising from the presence of paraffin content. Due to the varied nature and content of paraffins experienced in the field, new and improved paraffin inhibitors, or paraffin inhibitors “tuned” to suit the particular paraffin type and content of a particular extraction or source location, are required.

Inhibition of paraffins is also important for use of hydrocarbon oils, post extraction. In applications such as engine lubricants, or other areas where circulation of the oil across a range of temperatures is likely, problems with paraffin crystallisation may occur when a lower than anticipated temperature occurs or where a large range of temperatures are encountered during normal use of the hydrocarbon oil.

A pour point depressant is an additive which assists in maintaining flow of a hydrocarbon oil, typically a crude oil, at a suboptimal temperature. All crude oils/hydrocarbon products have their own particular pour point, a temperature below which their flow is impeded; this may or may not be due to the presence of paraffin crystallisation, as described above, and as such although a paraffin inhibitor may provide a pour point depressant function (where an oils pour point is largely dependent upon paraffin content) it is not necessarily the case that a pour point depressant can act as a paraffin inhibitor. As such, both of these functions may be provided by a single additive for a given crude oil/hydrocarbon oil, but it may also be the case that two additives are required to achieve both paraffin inhibition and a desirable pour point depression.

Alternative polymer and copolymer materials to those described herein provide commercially available paraffin inhibitors and pour point dispersants. However, there still remains a need for improved paraffin inhibitors, which are effective in a large number of crude oils (including those with high paraffin content), across a large range of paraffin types, and which may also provide a pour point depressant function, removing the need for additional additives. In addition, wax inhibitors which have a relatively simple method of manufacturing, ensuring a highly uniform products, and reproducible result would be beneficial, since a large degree of variability can arise in production of polymer, and particularly co-polymer products.

As used herein, the terms ‘for example,’ ‘for instance,’ ‘such as,’ ‘including,’ or similar such terms are intended to introduce examples that further clarify more general subject matter. Unless otherwise specified, these examples are not meant to be limiting in any fashion.

All parts and percentages are given by weight unless otherwise stated. All tests and physical properties have been determined at atmospheric pressure and room temperature (i.e. about 20 °C), unless otherwise stated herein, or unless otherwise stated in the referenced test methods and procedures.

It will be understood that, when describing the number of carbon atoms in a substituent group or compound (e.g. C1 to C6), the number refers to the total number of carbon atoms present in the substituent group or compound, including any present in any branched groups.

In this specification, the term molecular weight refers to a weight average molecular weight where necessary, e.g. when used with regard to a polymeric species, unless otherwise specified.

According to the present invention there is provided a paraffin inhibitor composition comprising a) an acrylic copolymer formed from an alkyl methacrylate monomer and an methacrylic acid monomer, and b) a solvent, wherein the copolymer comprises no more than 20 weight % methacrylic acid based on the total weight of the copolymer.

In accordance with an alternative embodiment of the present invention there is provided a method of manufacturing the paraffin inhibitor composition as described herein.

There is also provided a hydrocarbon oil treatment formulation comprising the paraffin inhibitor composition as described herein.

Additionally, there is provided a method of inhibiting paraffin crystallisation in a hydrocarbon oil by addition of a paraffin inhibitor composition as described herein. As such, in accordance with one embodiment of the present invention there is provided a paraffin inhibitor composition comprising a) an acrylic copolymer formed from an alkyl methacrylate monomer and an methacrylic acid monomer, and b) a solvent, wherein the copolymer comprises no more than 20 weight % methacrylic acid.

The paraffin inhibitor acrylic copolymer may be formed from an alkyl methacrylate monomer having an alkyl chain which is saturated or unsaturated. However, the paraffin inhibitor acrylic copolymer is preferably formed from an alkyl methacrylate monomer having an alkyl chain which is saturated. Additionally, the alkyl methacrylate alkyl chain may be linear or branched, although preferably the alkyl chain is linear.

Alkyl methacrylate monomers having alkyl carbon chain lengths of C22 and above are difficult to react to form the copolymer of interest. Carbon chain lengths below C12 have been found to provide copolymers which do not function as paraffin inhibitors, although it is possible that some short chain alkyls may have an effect in some specific hydrocarbon oils. As such, most suitably, the alkyl chain of the alkyl methacrylate monomer has a carbon chain length of C12 to C22. In particular the alkyl methacrylate monomer preferably has an alkyl carbon chain length of C14 to C20, more preferably C16 to C18, and most preferably the alkyl methacrylic monomer alkyl carbon chain length is C18.

Suitably the alkyl methacrylate monomer may be selected from the following examples: cetyl methacrylate, myristyl methacrylate, pentadecyl methacrylate, stearyl methacrylate, nonadecyl methacrylate, arachidyl methacrylate, and behenyl methacrylate. Most preferably the alkyl methacrylate is stearyl methacrylate.

Suitably, the alkyl methacrylate monomer may be derived from a natural source i.e. is organic, or it may be synthetic. Preferably the alkyl methacrylate monomer is synthetic.

The paraffin inhibitor acrylic copolymer is formed from a methacrylic acid monomer, and the copolymer comprises no more than 20 weight % (wt%) of said methacrylic acid, based on the total weight of the copolymer. Methacrylic acid is a short (C4) carboxylic acid, and is often abbreviated, and referred herein to, as MAA. It is essential that the MAA not be present in the acrylic copolymer at a level above 20 wt% due to undesirable copolymer gelling above this 20 wt% inclusion level. In particular, it has been found that when MAA is present at a level of approximately 40 wt% a solid acrylic copolymer is formed, and this is unsuitable for use as a paraffin inhibitor in hydrocarbon oils, whether that is crude oils or post refined oils, in accordance with the present invention. Preferably, the acrylic copolymer comprises between 8 wt% and 20 wt% MAA, more preferably between 8wt% and 18wt%, and most preferably between 10 wt% and 15 wt%; this provides a good balance between the activity of the copolymer as a paraffin inhibitor and physical properties suited to the intended end use.

Preferably the paraffin inhibitor acrylic copolymer comprises at least 80 wt% alkyl methacrylate, based on the total weight of the copolymer, more preferably between 92 wt% and 80 wt%, even more preferably between 92 wt% and 82 wt%, and most preferably between 90 wt% and 85 wt%.

Preferably the present described acrylic copolymer consists exclusively of MAA as its minor constituent and alkyl methacrylate as its major constituent.

Preferably the acrylic copolymer of the present paraffin inhibitor is devoid of crosslinking - crosslinking is disadvantageous due to the increase in gelling observed when crosslinking is present.

Preferably the acrylic copolymer of the paraffin inhibitor once formed, has a molecular weight of between 20,000 and 60,0000. Preferably the molecular weight is between 20,000 and 45,0000, and more preferably between 20,000 and 35,000, as the relatively lower molecular weight copolymers have desirable improved viscosity profiles.

Additionally, or alternatively, the acrylic copolymer of the paraffin inhibitor has a polydispersity index (PDI) of between 2 and 3. PDI of a polymer is calculated as the ratio of weight average by number average molecular weight.

Additionally, or alternatively, the paraffin inhibitor composition is liquid at 4 °C. More especially, it is intended that the paraffin inhibitor composition of the present invention is suitable for use in crude oil processing and extraction processes at the seabed; the operating temperature at seabed is around 5 °C.

Additionally, or alternatively, the paraffin inhibitor composition has a pour point of less than 0 °C, preferably less than minus 2 °C, more preferably less than minus 4 °C, and in some embodiments has a pour point of at least minus 6 °C. Such low pour point properties enable the paraffin inhibitor to be particular suited to use in seabed processing sites, and also to be suitable for use in refined hydrocarbon oil products which are exposed to low temperatures, such as engine oils in cold temperature weather regions.

The present paraffin inhibitor composition comprises b) a solvent. The solvent acts as a carrier or diluent for the acrylic copolymer as described above. Preferably the solvent is an organic solvent, and more preferably the solvent is a hydrocarbon solvent. Suitable hydrocarbon solvents include mineral oils or may contain paraffinic, natphthenic and aromatic constituents in various proportions. Hydrocarbon solvents containing paraffinic constituents are particularly preferred. Suitable hydrocarbon solvents include, as particularly preferred examples, Isopar M (a C13-C14 Iso-paraffin based solvent containing <0.01 wt% aromatics) and Solvesso 150 ND (an aromatic solvent), both ex. ExxonMobil. In addition, environmental concerns may render some otherwise suitable solvents undesirable, for example, xylene. Paraffinic based solvents offer the best balance between copolymer activity levels obtainable and environmental and user handling concerns.

The type of solvent b) selected is a limiting factor on the amount of active acrylic copolymer a) which may be provided in the total paraffin inhibitor composition. However, suitably, the paraffin inhibitor comprises between 20 wt% to 55 wt% acrylic copolymer. Preferably the paraffin inhibitor comprises between 25 wt% to 50 wt% acrylic copolymer, more preferably the paraffin inhibitor comprises between 30 wt% to 45 wt% acrylic copolymer. The preferred solvents, as described above, allow for the incorporation of the highest levels of incorporation of active acrylic copolymer whilst avoiding environmental concerns and gelling of the paraffin inhibitor composition rendering it unsuitable for its intended end use.

The copolymers of the present invention are not soluble in water or short chain alcohols such as ethanol. As such, these materials are not suitable as solvents in the presently described paraffin inhibitor composition. More especially, preferable the paraffin inhibitor composition of the present invention is water free.

Additionally, or alternatively, there is provided a method of manufacturing a paraffin inhibitor composition as described above. The method of manufacturing the paraffin inhibitor comprising a) an acrylic copolymer formed from an alkyl methacrylate monomer and a methacrylic acid (MAA) monomer, and b) a solvent, wherein the copolymer comprises no more than 20 weight % methacrylic acid, comprises the following steps: a) polymerising the alkyl methacrylate and MAA monomers to provide the acrylic copolymer, and b) providing the solvent.

The preferable embodiments relating to the alkyl methacrylate, MAA and solvent as described above in relation to the individual constituents of the paraffin inhibitor composition apply equally to the individual constituents utilised in the method described herein below.

The polymerisation of step a) is performed necessarily in a reaction vessel. As such the method includes the pre-step of i) providing a reaction vessel.

Preferably the polymerisation of the monomers at step a) is performed in the solvent of step b), such that the provision of the solvent is performed prior to step a). However, it is envisaged that the polymerisation step a) may be performed in an alternative solution, and the solvent provided at a later stage, i.e. after copolymer formation in an alternative solution and subsequent removal of the alternative solution. However, preferably, the method includes i) providing a reaction vessel, subsequently b) providing the solvent to the reaction vessel, and subsequently c) polymerising the alkyl methacrylate and MAA monomers to provide the acrylic copolymer within the reaction vessel.

Suitably the method is performed in a batch wise manner. As such, once the acrylic copolymer is formed it may be removed from the reaction vessel for (optional) post processing and use, and the method repeated utilising the reaction vessel.

Suitably the reaction vessel is purged prior to commencing the polymerisation. The purge is performed by providing an inert atmosphere of nitrogen. The purge removes any oxygen present in the reaction vessel which may adversely affect the polymerisation reaction. Preferably the purge is performed prior to introduction of any of the monomers to be reacted in the polymerisation step a), but after provision of the solvent (or less preferably an alternative solution) to the reaction vessel.

The polymerisation step may be performed at any polymerisation temperature above the auto-initiation temperature of the monomer. Alternatively, and advantageously, the polymerisation step is performed in the presence of a polymerisation initiator at a polymerisation temperature in the range of 60 °C to 105 °C, preferably 80 °C to 95 °C; this allows for a more controlled polymerisation reaction to occur. As such, optionally (although preferably), a polymerisation initiator is provided to the reaction vessel. The initiator may be provided in an amount in the range of 1 wt% to 5 wt%, and preferably the initiator is provided in an amount in the range of 2 wt% to 4 wt%, based on the total weight of the monomers. Preferably the polymerisation initiator is a thermal initiator. Suitable polymerisation initiators are known to the skilled person and include Azo initiators and organic peroxides such as benzoyl peroxide (BPO). However, Azo-initiators are preferred including 2,2'-Azobisisobutyronitrile (AIBN) and 2,2’-Azodi(2-methylbutyronitrile) (AMBN), and AMBN is particularly preferred in the present method. As alluded to above, the amount of initiator provided effects the molecular weight of the final reaction product co polymer; higher levels of initiator inclusion provide lower molecular weight copolymers and these will have an associated lower viscosity which may be beneficial for product handling and use, i.e. the copolymer will be readily pourable at room temperature. A good balance between suitable molecular weight and viscosity is achieved when the initiator is provided in the preferred range of 2 % - 4 %.

Suitably, the initiator may be introduced to the reaction vessel simultaneously with one, or alternatively both, of the monomers. Such simultaneous introduction is conveniently achieved via dissolving the initiator into the bulk monomer. Most preferably the initiator is dissolved in the MAA monomer.

Advantageously the polymerisation initiator may be provided in more than one aliquot. Preferably the polymerisation initiator is provided in two aliquots, and more preferably in three aliquots. More especially, one aliquot of the polymerisation initiator may be introduced to the reaction vessel prior to the introduction of either of the monomers, a further aliquot may be introduced simultaneously with one or both monomers as described above, and a further aliquot may be introduced subsequently to the polymerisation monomers i.e. after monomer feeds into the reaction vessel are complete. Addition of at least one aliquot of polymer initiator prior to introduction of the copolymer monomers is particularly preferred, since this allows for the greatest degree of control of the molecular weight of the acrylic copolymer reaction product as described above, in particular, most preferably an aliquot of the polymerisation initiator is dissolved in the solvent (or alternatively but less preferably dissolved in alternative solution) and provided to the reaction vessel prior to introduction of any polymerisation monomer; this may be introduced prior to the purge of the reaction vessel prior to commencing the polymerisation step a). Preferably, when one aliquot of the polymerisation initiator is introduced to the reaction vessel prior to the introduction of either of the monomers between 40% and 50% of the total initiator amount is introduced to the reaction vessel.

Additionally, preferably a portion of the alkyl methacrylate is provided to the reaction vessel prior to polymerisation step a), that is to say that an amount of this monomer is pre-charged into the reaction vessel prior to introduction of the MAA. Preferably up to 20 % of the total amount of alkyl methacrylate to be reacted is pre-charged into the reaction vessel. Providing an initial portion of the alkyl methacrylate in this way is desirable due to the relative reactivity of the two monomers; methacrylic acid being more reactive. Pre-charging the less reactive monomer (preferably a portion thereof) to the reaction vessel allows for better incorporation of the alkyl methacrylate into the final acrylic copolymer and acts to prevent ‘blocks’ of one monomer type occurring in the final acrylic copolymer backbone; this provides a better quality product.

Optional post processing steps may also be utilised after the polymerisation step (and prior to providing the solvent where the polymerisation is performed in an alternative solution). Such post processing steps may include removal or reduction of residual monomers, and/or filtering to remove undesirable reaction particulates.

In accordance with a further embodiment of the present invention there is also provided a hydrocarbon oil treatment formulation comprising the paraffin inhibitor composition as described above.

Preferably the paraffin inhibitor composition as described above is suitable to be used as a hydrocarbon oil treatment formulation in the absence of any additional constituents. That is, the hydrocarbon treatment formulation consists of the paraffin inhibitor composition as described above exclusively. However, alternatively, the hydrocarbon treatment formulation may comprise additional additives.

Suitable additional additives may be selected from one or more of the following: additional paraffin inhibitors, additional pour point depressants, additional solvents, asphaltene inhibitors, dispersants, corrosion inhibitors, antioxidants, biocides, lubricants, defoamers, and viscosity modifiers.

More especially, in some preferred embodiments the hydrocarbon oil treatment formulation comprises an additional paraffin inhibitor. Additional paraffin inhibitors may be selected from one or more of the following: acrylic polymers or acrylic copolymers, alkyl acrylate copolymers, alkyl acrylate vinylpyridine copolymers, ethylene vinyl acetate copolymers, maleic anhydride ester copolymers, branched polyethylenes, naphthalene, anthracene, microcrystalline wax and asphaltenes. Preferably, the additional paraffin inhibitors may be an acrylic polymer or acrylic copolymer, More especially, the one or more additional paraffin inhibitor may preferably be effective for inhibition of paraffins of a differing carbon chain length to those on which the presently described active acrylic copolymer are effective for. As will be appreciated from the examples provided below, the presently described paraffin inhibitor compositions are particularly effective for inhibition of paraffins having carbon chain lengths of C20 to C35, and in particular C25 to C31 . Therefore, the inclusion of an additional paraffin inhibitor being particularly effective for inhibition of paraffins having carbon lengths above C30, particularly above C31 may be advantageous, particularly for use in some crude oils, and the acrylic polymer FlowSolve ™ 140 ex. Croda is particularly suitable. More especially, as will be appreciated from the examples, the presence of a paraffin inhibitor composition according to the present invention appears to provide a “boost” to the effectiveness of the acrylic polymer additional paraffin inhibitors effect on the longer carbon chain paraffins, as such the utilisation of the present paraffin inhibitor composition is believed to achieve a synergistic effect on paraffin inhibition when used in combination with an additional paraffin inhibitor effective for paraffins having carbon chains above C30.

Suitable additional solvents may be selected from one or more of the following: water, brine, alcohols (including isopropanol, methanol and ethanol), ketones, heavy aromatic naptha, toluene, glycols (including ethylene glycol, ethylene glycol monobutyl ether (EGMBE), diethylene glycol monoethyl ether), xylene, isobutanol, and heptane.

Suitable asphaltene inhibitors may be selected from one or more of the following: organic sulphonic acids, organic sulfonates, organic sulfonated resins, polyolefin esters, polyolefin imides, polyolefin amides, alkenyl/vinyl pyrrolidone copolymers, salts of alkyl succinates, sorbitan monooleate, and polyisobutylene succinic anhydride, and functionalised derivatives thereof.

Suitable dispersants may be selected from one or more of the following: dodecyl benzene sulfonate, oxyalkylated alkylphenols, and oxyalkylated alkylpnenolic resins.

Suitable corrosion inhibitors may be selected from one or more of the following: alkyl, hydroxyalkyl, alkylaryl, arylalkyl or arylamine quaternary salts; mono or polycyclic aromatic amine salts; imidazoline derivatives; mono-, di- or trialkyl or alkylaryl phosphate esters; phosphate esters of hydroxylamines; phosphate esters of polyols; and monomeric or oligomeric fatty acids.

Additionally, in accordance with an alternative embodiment of the present invention, there is provided a method of inhibiting paraffin crystallisation in a hydrocarbon oil by addition of a paraffin inhibitor composition as described herein. Preferably, the hydrocarbon oil is a crude oil, fuel oil or lubricant oil, although it will be appreciated that other hydrocarbon oil based products may benefit from the addition of a paraffin inhibitor composition according to the present invention.

The paraffin inhibitor composition may be added to the hydrocarbon oil as described above, or it may be added as a constituent part of a hydrocarbon oil treatment formulation as described above. In either case the paraffin inhibitor composition must be added to the hydrocarbon oil in a suitable amount to be effective at inhibiting paraffin crystallisation.

Suitably the paraffin inhibitor composition is added to the hydrocarbon oil in an effective amount. Preferably the amount of paraffin inhibitor composition added will be in an amount in the range of 1 ppm to 1000 ppm, preferably 100 ppm to 500 ppm. Additionally, or alternatively, it is preferred that where the paraffin inhibitor composition of the present invention is used in conjunction with an additional paraffin inhibitor, as described above, then the total amount of all paraffin inhibitors used in the method may be between 2 ppm and 5000 ppm, and more preferably between 100 ppm and 2000 ppm.

In some particularly preferred embodiments, the present method is particularly suited to inhibiting paraffin crystallisation of paraffins having a carbon chain length of C20 to C35, and in particular a carbon chain length of C25 to C31 .

Use of the present paraffin inhibitor composition, as described above, to prevent or reduce paraffin crystallisation in a hydrocarbon oil is contemplated.

The present invention will now be described with reference to the following non-limiting examples.

Examples Example 1 - Preparation of Copolymer A

An example stearyl methacrylic copolymer paraffin inhibitor composition in accordance with the present invention, denoted as Copolymer A, was prepared in accordance with the following preparation method. Generally, Copolymer A was prepared via polymerisation of stearyl methacrylate (SMA) and methacrylic acid (MAA), utilising the thermal polymerisation initiator AMBN, in the solvent Isopar G (an iso-paraffinic hydrocarbon solvent ex. ExxonMobil). Isopar G is a suitable solvent for preparation of the acrylic copolymer and is also suitable as a constituent of the final paraffin inhibitor composition for its intended use. Table 1 , below, shows each of the reaction phases and the components within each phase.

Table 1 : Reaction composition for each phase

The preparation method is based on a 1 litre scale solution polymerisation with continuous feed of monomer. A flange flask was employed as the reaction vessel and fitted with a stirrer for mixing, a nitrogen sparge, condenser and a gear pump.

The reaction vessel is purged with nitrogen, and an inert nitrogen atmosphere established before the solvent is added and subsequently the reaction vessel is de-gassed to remove any oxygen introduced with a nitrogen sparge. The contents of the reaction vessel are then heated to 85 °C and an aliquot of the polymerisation initiator, AMBN, and a 20 wt% portion of the SMA (based on total weight of SMA to be added) are provided to the reactor.

A further aliquot of the AMBN is dissolved in the MAA monomer. The MAA containing AMBN, and the remaining SMA monomers are then fed into the reaction vessel; in this case the feeds are added over a time of 180 minutes to ensure good mixing and a final homogenous copolymer is achieved. The reaction vessel contents are maintained at a temperature of between 83 °C and 85 °C throughout the monomer addition.

Once addition of the monomers is complete, a further aliquot of the thermal initiator is added to the reaction vessel, and the reaction vessel contents are allowed to polymerise for a further 1 -2 hours at 90 °C to provide the final copolymer product and facilitate residual monomer reductions.

Activity determination is performed by calculating the final solids content of the reaction products and, if desired this activity/solids content may be adjusted with further addition of the solvent, here Isopar G, to provide the final level required for end use. In this example Copolymer A had an activity of 27.5 % and was not adjusted by further addition of the solvent.

Once the copolymer product has been formed, and the necessary activity level has been confirmed, the contents of the reaction vessel are then cooled to approximately 40 °C for convenience of handling and transferred to a product container through a filter mesh to remove any reaction particulates that may have formed. The resultant copolymer in solvent product, i.e. Copolymer A, is a ready to use paraffin inhibitor product, although it may be formulated into a more complex hydrocarbon oil treatment formulation by the inclusion of additional additives or additional and/or alternative solvents.

In this example, 20 wt% of the total SMA is preloaded into the reaction vessel, to allow for better incorporation of the stearyl methacrylate into the final co-polymer, as this prevents ‘blocks’ of one monomer type occurring in the co-polymer backbone.

Seven (7) further paraffin inhibitor composition sample materials were prepared, in accordance with the method described above, save for the variations detailed in Table 2; details of Copolymer A are included for ease of reference.

In Table 2:

Viscosity is measured at 25 °C on a Brookfield viscometer and expressed in centipoise (cP), Mw is molecular wight by weight average,

Mn is molecular weight by number average, and,

PDI is polydispersity index.

Table 2: Copolymer A variant samples

Of these Copolymer A variants five samples were chosen to cover a range of actives, monomer feed times and viscosity for further testing (in addition to Copolymer A) as described below.

Example 3 - Preparation of Copolymer B

Paraffin inhibitor composition sample material Copolymer B was prepared in accordance with the method described above for sample Copolymer A, except that the solvent selected was Isopar M (ex. ExxonMobil), and the final activity/solids content of this copolymer was 25%. The final reaction product was suitable to be used as a final paraffin inhibitor product.

Isopar G has a flash point of 42 °C and may have associated safety, storage and transport problems. As such, in this example Isopar G was replaced by Isopar M as the paraffin inhibitor solvent. Isopar M is a similar solvent but with a flash point of 78 °C. Isopar M and Isopar G have the same CAS number: 64742-47-8.

Example 4 - Preparation of Copolymer A in Alternative Solvents

Four further samples were produced, in accordance with the method described above for Example 1 , Copolymer A , save for the variations detailed in Table 3, below. The solvent LPA 170 (ex. Sasol) is a mixture of hydrotreated isoparaffins and naphthenics. The solvent Solvesso 150 ND is an aromatic solvent (ex. ExxonMobil).

Table 3: Summary of samples prepared with alternative solvents and initiator

CPA 9 provided the product with the most desirable physical properties; it is a stearyl methacrylate-methacrylic acid copolymer, initiated with AMBN, at 40 % activity in Solvesso 150 ND. CPA 9 had a kinematic viscosity at 40 °C - 147.31 mm ² /s, density - 0.8985 g/cm ² and a flash point of >61 °C (142 °F) by ASTM D-93. It has also been shown to be liquid at desirable concentrations to a temperature below -20 °C, which is desirable for subsea or other cold temperature application environments.

Testing of Samples

Pour Point i) Product Pour Point

Copolymer A was tested for product pour point (PP) on an ISL MPP 5Gs Analyser, with measurements made according to ASTM D97.

The product pour point of sample Copolymer A was -6 °C; this is lower than 4 °C, meaning that the material is suitable for use in sub-sea environments and other cold temperature applications. ii) Pour Point Performance in Hydrocarbon Oil

Two crude oils were treated with treatment of Copolymer A to evaluate how well the composition depressed the pour point of each of these crude oils. Crude oil 1 is a crude oil from a well in India with a distribution of high hydrocarbon chain lengths. Crude oil 2 is a crude oil from Alberta, Canada which has a distribution of shorter hydrocarbon chain lengths. Thereafter, Crude oil 2 was treated with Copolymer B to evaluate how well this composition depressed the pour point of this crude oil. The solvent Isopar G was also tested to see if had any influence on pour point performance on its own. Pour point and change in pour point were tested in accordance with ASTM D5985 using a Pour Point Tester PPT 45150 ex. PSL Systemtechnick.

The pour point of the treated crude oil, and change in pour point, compared to the blank crude oil may be seen in Tables 4 and 5 below for Crude oil 1 and 2 respectively. It can be seen that the solvent, Isopar G, on its own showed no performance as a pour point depressant.

Table 4: Pour point performance in Crude oil 1

Table 5: Pour point performance in Crude oil 2

Testing of Example 2 - Variants on Copolymer A iii) Pour Point Performance in Hydrocarbon Oil

Change in pour point (D PP) was measured for some of the composition variants of Copolymer A, as prepared above. These variants were tested in Crude oil 2 in accordance with ASTM D5985.

The test results showed that changing the parameters of the reaction process did not affect the pour point depressant performance of the composition variant samples and all samples gave good performance in the crude oil, as shown in Table 6 below. Table 6 also includes data points for Copolymer A and Copolymer B for ease of reference.

Table 6: Pour point performance in Crude oil 2 iv) Pour Point Performance in Hydrocarbon Oil at 25 % Activity Level To achieve 25 % actives the following samples were diluted as detailed in Table 7 below. 270 mI of these 25 % active samples were then added individually to the crude oil to achieve a solution containing 1000 ppm active material to be tested.

As the alternative sample CPA 1 had an activity level below 25 % the amount added to the crude oil was increased to achieve a solution containing 1000 ppm of active material to be tested, as detailed in Table 8 below.

15 Table 8: Volume of sample added to achieve 1000 ppm solution

Table 9, below, shows the results for pour point testing in Crude oil 2. All samples tested provided a good performance at this 1000 ppm treat rate.

Table 9: PPD performance in Crude oil 2 v) Pour Point Performance in Model Wax Solutions

Since crude oil samples vary depending on extraction site, samples of model wax solutions were prepared to better understand the performance of some of the paraffin inhibitor composition sample materials prepared above. To ensure consistency between tests a main stock of 500 g of model wax solution was created. Model wax solutions were made by placing 50 g of the wax of interest in a glass jar and adding 450 g dodecane, to create a 10 % wax dodecane mixture. This mixture was then shaken and placed in an oven at 40 °C, except for in the case of Kerawax 422 and Kerawax 1301 when the mixture was placed in the oven at 60 °C to ensure the wax had melted, due to the higher melting range of these products. This shaking and heating procedure resulted in a homogenous 10 % wax solution.

Table 10, below, lists the wax products utilised in the model wax solutions. The Kerawax products are ex Kerax Limited, and Paraffin Wax (PHC5254) is ex. PothHille.

Table 10: Paraffin waxes used to make model wax solutions

Pour point testing was carried out in the model wax solutions in accordance with ATSM D5985. More especially, 50g of model wax solution to be tested was weighed into a glass jar and heated to ensure it was fully homogenous then 1000 ppm of paraffin inhibitor (with respect to actives), was added and the mixture shaken before running the test in the pour point machine, (Pour Point Tester PPT 45150 ex. PSL Systemtechnik GmbH).

FlowSolve 140 (ex. Croda) a commercially available wax inhibitor product and sample material Copolymer B were initially tested.

The pour point of each of the model wax solutions (blank) and as treated with 1000 ppm active content of FlowSolve 140 or Copolymer B are shown in Table 11 below. The pour points of the model wax solutions, along with the reduction in pour point after addition of the additive, are provided in Table 11 in order of increasing melting point of the blank model wax solution. Each of the materials tested have different effects on the wax solutions. Table 11 : Pour point values for wax solutions, blank and treated with 1000 ppm sample

As can be seen from the data in Table 11 FlowSolve 140 showed good pour point depression for model wax solutions Kerawax 422 and Kerawax 1301 ; these model wax solutions have the highest melting points and also the longest chain lengths as determined using gas chromatography (described below). Copolymer B, in the alternative, shows good pour point depression in model wax solutions Kerawax 2203 and PHC5254; these model wax solutions have lower melting points and shorter chain lengths as determined using gas chromatography (described below). Similarly, comparing sample CPA 9 as described above and FlowSolve 140 showed that the two samples also performed differently in different wax environments. In this test the wax environments included the model wax solutions (10 % in dodecane) as described above, in addition to the Crude oil 2 sample. The test data is shown in Table 12 below. Based on the paraffin distribution in the model wax system described above (as determined using gas chromatography) FlowSolve 140 was seen to work best in wax systems containing C30 to C40 carbon chains as the longest wax chains above a critical concentration, compared to CPA 9 which was seen to work best in wax systems containing C27 to C31 as the longest wax chain lengths, above a critical concentration. More especially, sample CPA 9 acts as a good pour point depressant in the model wax solution of PHC5254.

Video Microscopy Studies

In order to gain an understanding of how the samples interacted with the waxes the model wax solution PHC5254 (10 % in dodecane) was chosen to be studied under a video microscope as the samples tested herein showed some level of pour point depression in this model wax. Video images of the wax solutions as they cooled were taken, and these videos could provide still images of any crystals formed for visual assessment. i) Blank Wax Solution

The blank PHC5254 wax solution alone, i.e. untreated, had a pour point of 21 °C, with a freeze point of 18.2 °C. Video microscopy shows the first appearance of wax crystals to be around 21 .5 °C with quick growth of crystals which remain largely unchanged on further cooling. The wax crystals formed large flat structures of which only the edges were visible, due to the size of the crystals. Large wax crystal plates had formed by a temperature of 21 °C being reached. ii) Wax Solution Treated with FlowSolve 140

Treatment of the PHC5254 wax solution with the commercially available sample FlowSolve 140 reduced the pour point to 15 °C.

In this case, the video microscopy showed three stages of wax crystal growth. In the initial stage crystals appeared at 20 °C, however the crystals were very small, although they did cover the field of view, but at this temperature the crystals clearly had spaces between them. A second period of growth then began at 15.7 °C where long needle like crystal formations were seen, this was accompanied by formation of wider flatter structures which were present from around 14 °C. Below 20 °C where the initial crystal growth is seen there are many wax crystals present which are generally small. The fact that the crystals are small means that the pour point is reduced compared to the blank solution, as the crystals now do not form large plates which interlock. However, there is not much space between the crystals and this could explain why the pour point reduction is not as great as for some of the other samples tested herein, It is believed that as the wax crystals are close together they have the potential to interact with each other and this interaction leads to less fluidity in the solution. iii) Wax Solution Treated with Copolymer B

The greatest pour point reduction of PHC5254 wax solution, (a decrease of 18 °C), was seen when the wax solution was treated with sample Copolymer B, where a pour point of 3 °C was obtained.

In the microscopy video, wax crystals first appeared at 20 °C. Medium sized crystals were formed with space between them. The initial crystals that formed were most easily described as being “butterfly” shaped, however as time progressed these crystals appeared to link up with fractal-like columns reaching between them. The interrelationship of the crystal size and shape with the improved pour point reduction, observed for this sample in particular, is not yet understood.

Gas Chromatography Analysis of Model Waxes

The model waxes were diluted to a concentration of 0.5 wt% in dodecane and subject to gas chromatography analysis, the traces of which were compared to a standard provided by an external party. This allowed the wax carbon chain lengths present in the different wax samples to be identified. As alluded to above, the samples pour point performance was compared for each of the model waxes tested and the wax gas chromatography traces studied to see if it was possible to identify which wax carbon chain lengths the sample additives may be acting upon. i) Wax Interaction with FlowSolve 140

From the pour point data provided above it can be seen that the commercial sample, FlowSolve 140, performs well in model wax solutions Kerawax 422 and Kerawax 1301 , it shows minimal performance in model wax PHC5254 and no performance in model wax Kerawax 2245. Based on examination of the model wax gas chromatography analysis, FlowSolve 140 is thought to interact with waxes having carbon chain lengths of C30 to C40 and this is further described below.

The model wax solution of Kerawax 2245 has wax chain lengths ranging from C17 to C30, as identified by the gas chromatography analysis. FlowSolve 140 shows no pour point performance in this model wax solution, and so the wax chain lengths on which FlowSolve 140 is effective must not be present in this wax.

The model wax solution PFIC5254 has wax chains ranging from C20 to C33 as identified by gas chromatography analysis, and FlowSolve 140 shows only a limited performance in this model wax solution suggesting only a few wax chains are interacted with.

The model wax solution Kerawax 422 has wax chain lengths ranging from C21 to C39 as identified by gas chromatography analysis. FlowSolve 140 shows good performance in this model wax solution.

The model wax solution Kerawax 1301 has wax chain lengths ranging from C22 to C40 as identified by gas chromatography analysis. FlowSolve 140 shows good performance in this model wax solution.

Interaction by FlowSolve 140 with wax carbon chains lengths ranging from C30 to C40 explains the performance observed in each of the different model waxes.

FlowSolve 140 does not work in Kerawax 2245 as it does not contain carbon chain lengths above C30 and so FlowSolve 140 is unable to interact with this wax, therefore giving no performance. ii) Wax Interaction with Copolymer B

From the pour point data provided above it can be seen that sample Copolymer B performs well in model wax solution PHC5254. As such, it is believed that Copolymer B interacts with wax carbon chains lengths ranging from C27 to C31and this is further described below.

Without wishing to be bound by theory it is believed that the solubility limit of different wax carbon chain lengths is important in the performance of the sample additive to maintain the flowability of the wax environment at decreasing temperatures. It is believed that in many cases it is not the most abundant wax chain lengths in the wax environment that cause a problem with the pour point of a given solution, instead the problem is believed to be due to the higher chain length waxes being present above their limit of solubility. This theory is most easily explained with a simple diagram, shown in Figure 1 . In Figure 1 the solubility limit is indicated with the dotted line, and for the idealised sample shown on the left of Figure 1 there is very little high chain length wax above the solubility limit and so the presence of these high chain length waxes do not cause a problem. Flowever, for the idealised sample shown on the right of Figure 1 there is a larger amount of high chain length waxes above the solubility limit level. As the samples shown on the right cools these waxes crystallise out of solution first and cause a problem.

High chain waxes do High chain waxes are not cause a problem problematic

Figure 1 : Simple diagram showing solubility limit of waxes

The model wax Kerawax 422 shows no improved pour point depression when treated with Copolymer B. This performance result is thought to be due to a number of high carbon chains (C32 to C37) being above the wax environments solubility limit and therefore crystallising out and causing problems with gelling or solidification of the wax.

On the one hand, the best pour point performance is seen with addition of Copolymer B to model wax solution PFIC5254, which is due to sample Copolymer B interacting with the majority of wax carbon chain lengths present in that wax environment. On the other hand, there is lower performance observed with addition of sample Copolymer B to the model wax solution Kerawax 2245, even though this wax environment contains waxes with carbon chain lengths in the range C17 to C30 where the sample is believed to be effective. Flowever, in this wax environment, the wax carbon chain lengths in the range C27 to C30 are the highest chain lengths present, but they are not present in abundance and wax carbon chain lengths in the range C24 to C26 are likely to be more problematic due to their presence at levels above the wax environments solubility limit. As such, sample Copolymer B is not believed to be interacting with these lower carbon chain length waxes. As such, it is believed that Copolymer B interacts most effectively with wax carbon chains lengths ranging from C27 to C31 .

For sample Copolymer B interaction with wax is only seen in model wax solution PHC5254 as this is the only model wax which contains solely wax carbon chain lengths in the range of C27 to C31 above the wax environments solubility limit. Whilst Kerawax 422 and Kerawax 1301 contain carbon chains of this length they have chains longer than C31 above the solubility limit which will cause the wax to solidify. As such, sample Copolymer B is found to be an effective pour point depressant and wax inhibitor for wax environments where problematic (above the wax environments solubility limit) wax carbon chain lengths in the range of C27 to C31 are present. iii) Wax Interaction with Combination of FlowSolve 140 and Sample Copolymer B Two of the model wax solutions were treated with a combination of sample Copolymer B and commercially available sample FlowSolve 140, each at an inclusion rate of 500 ppm (of active content), giving a total sample additive treat rate of 1000 ppm (of active content). Pour point data for the combination of the two samples is shown alongside data for the individual samples for comparison is provided in Table 13 and Table 14 below. Table 13 shows the results in model wax solution PFIC5254. As described above, in this wax environment, little interaction was seen with FlowSolve 140 but a good pour point depression (of 18 °C), was seen for this wax when treated with sample Copolymer B. In this wax environment combining the two samples gave lower performance than when Copolymer B was used alone.

Table 13: Pour point data for model wax PFIC5254

Table 14 shows the results in model wax solution Kerawax 422. As described above, sample Copolymer B did not interact with this wax environment. However, in this case combining FlowSolve 140 with sample Copolymer B provides a synergistic effect resulting in a surprising pour point reduction of 21 °C.

Table 14: Pour point data for model wax Kerawax 422

As such, in can be seen that in wax environments where FlowSolve 140 provides a good performance, this performance if further enhanced by the presence of the sample Copolymer B; the presence of the sample is providing a synergistic effect. However, in a wax environment where sample Copolymer B provides a good performance, this performance is reduced by the presence of FlowSolve 140 (presumably due to the lower treatment rate of the effective sample additive). Therefore, interestingly, FlowSolve 140 has been found to be synergised by the presence of sample Copolymer B, however, sample Copolymer B is not synergised by the presence of FlowSolve 140.