CA1245435A - Method for controlled introduction of reagent into a liquid - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A method is provided for the controlled introduction of a reagent into a liquid, preferably a reagent peremeable substantially hydrocarbon liquid, which method comprises the steps of:
(a) placing as in a geological crude oil reservoir solid polymeric bodies, each body comprising a reagent permeable polymeric matrix containing a substantially water insoluble reagent such as at least one of a wax crystal modifier, demulsi-fier, scale inhibitor, corrosion inhibitor, biocide, ashless dispersant, antioxidant and mixtures thereof in said liquid (includes both crude and refined hydrocarbon liquids); and, (b) leaching out said reagent from said bodies at a controlled and predetermined rate into said liquid

Description

1 - .

-1 Field of the Invention

2 This invention relates to a method useful for3 introduction of an additive into a substantially hydro-4 carbon liquid. More particularly this invention relates to a method of utilizing a bead containing an additive 6 which is leachable therefrom to introduce the additive in 7 useful amounts into the liquid hydrocarbon.
8 Back~rQund of the Invention 9 The recovery of oil and gas from underground geological formations is of great importan.ce in modern 11 society which uses vast amounts of fossil fuels for its 12 essential energy. The individual well produotivity 13 declines over a period of time because of a number of 14 factors including changes in reservoir fluid charac-teristics, depletion of reservoir energy, decreasing16 permeability of the formation to the oil, the gradual 17 dissipation of the expanding pressure transient, contami-18 nation of the well bore, reduced permeability of the oil 19 ~hrough the region immediat ly surrounding the well bore and reduction of the internal diameter of the well pipeO
21 The response to the declining productivity was 22 the development of numerous techniques which has become 23 collectively known as well workover and stimulation. The 24 concept of fracturing or formation breakdown has been recognized to play 8 very impcrtant role in the applica-26 tion of these oil production enhancement techniques 27 including stimulation, acidizing, water injection and 28 cementing of the formation.
29 Hydraulic fracturing has found wide usage as a well stimulation procedure for creating deep-penetrating 31 fractures (both horizontal and vertical) that provide high 32 capacity channels for flow from deep within the producing 33 formation to the well as well as for overcoming damaged .

~L2~LS~35 1 matrix permeability surrounding a wellbore. In order to 2 produce gas or liquids from a well at a higher rate

3 following a hydraulic fracturing treatment, the reservoir

4 must contain enough fluids in place and the formation must not have regions of severe permeability reduction partic-6 ularly in regions adjacent to the well. Early experi-7 mental work in shallow wells demonstrated that a 8 hydraulically formed fracture tend~ to heal - that is, to 9 lose its fluid carrying capacity after the parting lû pressure is released - unless the fracture is propped 11 Typical propping agents for retaining the integrity of the 12 fractures are nutshells, plastic beads, aluminum spacers, 13 glass beads, sand and urea prills.
14 Proppants thus provide a means for meeting the obje~tive of the fracturing which i~ to increase the well 16 production by preventing collapse of the formation and 17 resultant decrease in fluid permeability.
18 Another cause of declining well production is 19 caused by paraffin deposition from the crude oil onto the inner walls of the production tubing and equipment.
21 Paraffin is a reservoir produced group of 22 straight-chain alkanes that contain more than 1~ to more 23 than 80 carbon atoms. The melting point of the paraffin 24- increases as the size of the molecule increases. Paraffin is deposited in the form of crystalline solids which may 26 collect on the i-nterior of the tubing and flswlines, 27 slowly choking off eroduction. ParaFfin deposits have 28 also caused the breaking oF pump rods. In some cases, 29 paraffin deposits have caused plugging ~f formations during stimulation treatments. Paraffin has also been 31 blamed For the difFiculty in pumping crude oil at cool 32 temperatures.
33 One method of handling paraffin deposition is to 34 mechanically remove the paraffin. There are several mechanical methods for removing deposited paraffin from 36 tubing, flowlines and pipelines which include rod 37 scrapers, free-floating pistons, etc. The major advantage 1 of mechanically removing paraffin is that positive 2 cleaning is assured, however, it is limited due to time 3 and equipment involved, custly and has the danger and 4 difficulty inherent in retrieving tools lost in the hole S during the cleaning operationO
6 Other methods of cleaning include:
7 t1) thermal methods, using bottomhole heaters, 8 circulation of hot oil, water or steam, and heat-9 liberating chemicals; and, chemical including the use of paraffin solvents, dispersants and detergents and crystal 11 modifiers whereby the latter prevents paraffin deposition 12 by disrupting the nucleation, agglomeration and/or 13 deposition of the paraffin crystals environment. At 14 present the chemical reagent is injected into the desired location but it can be difficult to supply it uniformly to 16 the optimum location, for instance in the permeable 9' oil 17 bearing, mineral formation. Also it is necessary tc 18 -inject the reagent continuously or repeatedly since it is 19 soluble-in the produced fluid and so is rapidly removed from thP point of injection 21 As indicated it is known to introduce reagents 22 downhole during fra~turing and other well stimulation 23 processes. Traditionally this is done by torcing a solu-24 tion of the reagent down the hole and into the form2tion, whereupon it becomes absorbed onto the formation and is 26 released slowly from it. Unfortunately the rate of 27 release is variable and generally is quite fast.
28 It is known to force beads of ethylene-vinyl 29 acetate copolymers into the formation, `but they are generally too large to get into the fractures ~ormed in 31 the formation and smaller beads would dissolve too 32 rapidly. Also the beads are rather soft.
33 Another approach to overcoming the paraffin 34 deposition in the recovery of crude oil is by adding to the oil a polymer having pendant polar and non-polar 36 moieties, such as a partially hydrolyzed ethylene-vinyl 37 acetate copolymer, whereby the deposition of wax from the .

3~ .

1 oil is inhibited (see U.S. Patent 3,693,720 wherein the 2 inhibitor is added to the crude petroleum oil before the 3 temperature of said oil decreases to a wax-deposition 4 temperature).
It is known from British Patent Specification 6 1,290,5~4 to inhibit scale formation downhole by supplying 7 downhole a solid linear carboxylic polymer having low 8 molecular weight and in which the carboxylic groups are 9 neutralized by an alkaline earth or other insolubilizing cation to an extent such that the polymer has a controlled 11 low solubility in water. It is stated in that specifica 12 tion that water soluble scale inhibitors may also be 13 supplied downhole with the substantially insoluble 14 polymer.
It is an object of this invention to provide a 16 method for using an article to enhance the p-roduction of 17 hydrocarbons from geological reservoirs, more particularly 18 from fractured formations.
19 It has been an additional object to devise a method for providing controlled release of a reagent 21 downhole, in a pipeline, in other oil-containing environ-22 ments or fluids.
23 5~ b~ n 24 It has been discovered that it is possible to introduce an additive reagent into a substantially hydro-26 carbon liquid by placing solid polymeric bodies each 27 comprising a polymeric matrix containing a substantially 28 water insoluble reagent such as a wax crystal modifier, 29 demulsifier, scale inhibitor, corrosion inhibitor, biocide, ashless dispersant, antioxidant and.mixtures 31 thereof in the liquid These bodies are, in use, 32 positioned at a location where it is desired to release 33 the reagent into the substantially hydrocarbon fluid and, 34 upon contact with fluid in this location, active reagent is released into the fluid.

~ _ 5 ~ S~35 Thus, in accordance with this invention there is provlded a method for releasing a treating reagent in a liquid hydrocarbon stream which comprises:
(a) placlng in sald stream a plurality of porous, substantlally wax free, plastic particles havlng a softening point above 60C and being chemicslly resistant to sald hydrocarbon stream, said particles containing a treatin8 reagent in the pores thereof, said reagent being insoluble in water and in said particles and being leachable on contact wlth the hydrocsrbon stream; and (b) flowing the hydrocarbon stream past said particles whereby said reagent ls leached from the pores thereoE, and whereby said partlcles retain their structural inte~ritY-The object of this invention has been realized in speciflc form by amethod for recovering crude oil from an underground geologicsl formation comprising the steps of:
(a) depositing solid porous polymeric particles containing in the ~ores thereof a substantially water-insoluble, well treating reagent downhole in the oil producing region of the formation in an amount sufflcient to alter the reactive properties of said crude oil, said rea~ent being insoluble in said polymeric particles and sald partlcles belng substantially wax-frea and 2C structurally stable at formation condltions;
tb) flowing said crude oil to the earth's surface through said bodles in a continuous manner thereby leaching sald reagent lnto sald crude oll; and (c) recovering said oll modlfied by the presence of an active amount of said reagent.

Detalled Descriptlon of the Invention The sub~ect matter of thls lnvention is embodied ~n a method for the controlled introductlon of a reagent into a substantlally hydrocarbon liquid, which method comprlses the steps of: placlng as by means of a stimulation or workover fluid or in a porous device solid polymerie bodies, if desired in a damp and water-wetted state, each body comprising a polymeric matrlx containing a substantially water lnsoluble reagent such as at least one wax ~rystal modlfler, demulslfier, scale inhibitor, 1 corrosion inhibitor, biocide, ashless dispersant, anti-2 oxidant or mixtures thereof in the substantially hydro-3 carbon liquid which liquid includes a crude oil such as is 4 obtained from an underground reservoir or from shale or tar sands and refined hydrocarbon liquids including 6 lubricating oils, gasolines and petrochemical byproducts;
7 and, leaching out said reagent From said bodies at a 8 controlled and predetermined rate, for example at a rate g in which fifty percent of the reagent is leached from the 10 body in 3 months to 3 years, into said liquid.
11 Each of the solid polymeric bodies may consist 12 solely of a pDlymeric matrix containing the reagent or may 13 contain a region, generally an outer region, of polymeric 14 material having a lower rate of reagent permeation than 15 that of the interior region and substantially free of 16 reagent. The polymer of such an outer shell may be of the 17 same material as the matrix or may be diffelent, and will 18 be selerted having regard to the release properties 19 required from the polymeric bodies. Matrix containing 20 reagent may be of uniform composition throughout its body 21 or its composition may vary, for instance having a 22- different polymer composition in i~s outermost portions 23 from its core portion. By appropriate selection of the 24 polymeric materials for forming the bodies and the 25 distribution of reagent within the bodies it is possible 26 to control the rate and duration of release of r`eagent 27 into the fluid while retaining the phys-ical (structural) 28 integrity of the polymeric matrix 29 It is this polymeric propert~ of reagent 30 permeativity which makes possible the transfer of the 31 reagent from the body into the substantially hydrocarbon 32 liquid in contact with the surface of the body. During 33 and after the leaching of the reagent from the reagent 34 permeative matrix of the body, the polymeric matrix 35 retains its structural integrity which is in marked 36 contrast to the approach taught in Egypt. ~. Pharm. Sci., 37 19 No. 1-4, pages 143-62, 1930 in an article by A. Kassem 3~
--7~
l et al entitled Formulation and Evaluation of Cnntrolled 2 Dissolution Phenobarbitone Macromolecular Products 3 Employing In Situ Suspension Poly~erization With Methyl-4 methacrylate wherein the reagent coatPd beads w.ere compressed into a body which upon.reagent dissolution into 6 the body fluids broke down the body into its component 7 beads thus fully destroying the structural integrity of -8 the compressed body.
9 The polymeric bodies are preferably paIticles.
The particle size is generally at least 10 microns ~nd ll preferably at least 50, and usually at least 100, microns 12 since small particles can be difficult to handle and to ` 13 position permanently in their desired ~nvironment. The 14 particle size is generally less than 2 mm and preferably 15 .less than 1 mm, since large particles also may be diffi-16 cult to position in their desired environment. Best 17 results are generally--obtained with a particle size of 18 from 50 microns to 1 mm. The particles may have irregular .- -l9 shape and sizes,.for instance as a result of having been 20 made by crushing, but preferably the particles are of 21 substantially spherical or other uniform shape.
- 22 When being used in fracturing~-the.~particles 23 preferably have a size and hardness and/or resistance to 24 fIow such that they can be`used in sand packing and will not be significantly degraded by the sand. The particle 26 size distribution will be selectsd so that a pack of 27 controlled permeability to fluid flow is formed and su~h 28 that th-e particles have a controlled leach rate as set 29 forth earlier.
The reagent must be substantially water 31 i.nsoluble, and so must partition into an organic phase of 32 substantially water-insoluble polymerizable monomer or 33 monomer mixture in preference to a water phase. The 34 reagent may be in its active form or it may be in a blocked water-insoluble form from which an ac~ive form may 36 be released during use and that may be water soluble.

, ~2~
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The reagent may be dissolved in the polymeric 2 matrix but preferably at least some, and generally 3 substantially all, of the reagent is dispersed in the 4 matrix. The softening point of the reagent should be above ambient temperatures encountered in use.
6 The reagent may be any active reagent that is 7 usefully administered to and is soluble in refined or 8 crude oil, or that is any b]ocked reagent that is water 9 insoluble but which, upon contact with water or oil, will lO release a water soluble or water insoluble reagent that i8 ll useful in the substantially hydrocarbon fluid. The 12 reagents are usefully selected from wax crystal modifiers, 13 demulsifiers, scale inhibitors, corrosion inhibitors, 14 biocides, dispersants, antioxidants and mixtures thereof.
15 (a) Wax Crystal Modifiers 16 These reagents, usefully introduced in at least a wax 17 deposit inhibiting amount to the refined and crucle oil, 18 are represented by oil-soluble polymers having pendant 19 polar and non-polar moieties and oil-soluble polymeric 20 materials having long linear side chains. The oil-soluble 21 copolymers ha~ing pendant polar and non-polar moieties are 22 -represented by the -formula 23 [1~CH2CHR~m~CH2CHX~p~CH~CllY ~ ff ]q 24 ~herein X is a non-polar moiety, Y is a polar moiety, R is 25 hydrogen, an alkyl, aryl7 aralkyl~ or alkaryl moiety, m is 26 1.5-3, n is 0.1-0.87 p is 0.01-0.5, m/(m+nlp) is 27 0.65-0.97, p/(n+p) is 0.1-0.853 q is 2 to 500, and the 28 molecular weight ~w of said polymer is 500-100,000.
29 The above polymer may typically`be a polymer 30 having a molecular weight Mw of 500~100,000, p~eferably 31 1,000-10,000, commonly 1,500-4,000, say 2,003, and 32 characterized by a long straight backbone chain on which 33 there may be pendant moieties X and Y.
34 Xn the above copolymer, the moiety 35 ~ CH2CHR ) m may be derived from an alpha~olefin 36 includir,g ethylene, propylene, butene-19 styrene, 37 3-phenyl~ propene, octene-1, etc Preferred alpha-.

S~3~ii 1 olefins may be the C2-C30 alpha-oleFins and most preferred 2 is ethylene. When the alpha olefin is propylene, the 3 formula -~-CH2CHR ) m may be 4 C~l3 6 ~--CH2 C~ m 7 in which R is -CH3. When the alphQ oleFin is ethylene, 8 the formula may be -~- CH2-CH2-~- mL The carbon 9 atoms may bear insert substituents (i.eO in place of the 13 hydrogen atoms) including alkyl7 cycloalkyl, aryl, 11 alkaryl, aralkyl, etc., moieties.
12 In the above copolymer, the moiety 13 ( CH2CHX-~ n may be derived from an alpha~olefin 14 which bears non-polar moiety X. The non-polar X moiety 15 may be characterized by the fact that it does not contain . .
16 a hydrogen atom active in the Zerewitinoff test for active 17 hydrogen~ Typically, the non-polar moiety will conta-in 18 atoms of carbon, nitrogen, sulphur, phosphorous, boron~
19 oxygen, etc. The polar moiety Y ~y be a moie~y con-20 taining carbon, oxygen, sulphur, nitrogen, phosphorous 21 boron or their congeners. The Y moiety contains a hydro-22 gen atom-which is capable of participating-in hydrogen 23 bonding. A typically useful wax crystal modifier is a 24 partially hydrolyzed ethylene vinyl acetate copolymer 25 having a molecular weight hw of 1,500-4,000. For a more 26 complete description of these copolymers reference should 27 be made to U.5. Patent 3,693,720.

Another class or wax crystal modifiers are the 31 oil-soluble polymeric materials having long linear side 32 chains as descriobed in U.S. Patent 3,854,893 and include 33 condensation polymers of dicarboxylic acid or anhydride, 34 polyol and monocarboxylic acid; addition polymers of 35 unsaturated esters, or long chain alpha monoolefins, or 36 -copolymers of said olefins with said unsaturated ester;
37 polystyr2ne acylated with long rhain fatty acids; and, .
L~ , .

~Z45~3~ -l mixtures thereof. Particularly useful are the copolymers 2 of C1g to C46 olefin with a C4 to C44 straight chain 3 alcohol per molar proportion of said dicarboxylic acid.
4 Representative of these particularly useful copolymers are the esters formed by reaction between the resction product 6 of an olefin and maleic anhydride with a long chain 7 (typically C16-C2g) aliphatic alcohol, and most preferably 8 the reagent i9 the behenyl ester of alkenyl succinic 9 anhydride having a molecular weight of from 3000 to 10,000 formed by polymerizing a C22-C2g alpha-olefin with maleic ll anhydride.
12 Other wax crystal modifiers known for use as 13 pour point depressants are represented by: low molecular 14 weight C16-24 alkyl acrylates and copolymers with 4-vinyl 15 pyridine, acrylamide, maleic acid, or dimethylaminoethyl 16 acrylate; copolymers of alkyl fumarate and vinyl acetate;
17 copolymers of ethylene or other olefins with vinyl alky-18 late (such as acetate, ~tearate or laurate); and, copoly-19 mers of alpha-olefins with maleic anhydride or other 20 dicarboxylic group, for instance to form alkenyl succinic 21 anhydride and the reaction products of such materials with 22 long chain epoxides and long chain alcohols. - -23 (b) Demulsifiers 24 These reagents which san be introduced into a fractured subterranean oil bearing formation in accordance with this 26 invention are usefully introduced to inhibit emulsifica-27 tion of the crude oil with formation water, water flood 28 injection water and/or water introduced by such processes 29 as steam stimulation. These oil-soluble reagents include 30 polyoxyalkylene ether and polyalkylene surfactants formed 31 from the alkoxylation of hydrocarbon soluble alkyl 32 phenols, phenolic resins, alcohols~ glycols, amines, 33 organic acids, carbohydrates, mercaptans9 and partial 34 esters of polybasic acids.
(c) Scale Inhibitors 36 Since scale inhibitors are water soluble each is intro-37 duced into a fractured subterranean formation in accor-s~

1 dance with this invention as the reagent in a blocked form 2 such that the reagent upon contact with water, as by 3 leaching from the polymeric matrix, is converted into a 4 water soluble active form, e~g. as a result of hydrolysis

5 or ion exchange. Suitable blocked forms are fatty acid

6 esters and salts.

7 Typical examples of blocked scale inhibitors are

8 the salts formed by the resction of hydrophobic amines

9 with low molecular weight polycarboxylic acids or poly-

10 ph'osphonic acids, e.g. a tri(C6-C10 alkyl) ammonium salt

11 of: polyacrylic acid having a ~w of from 1,000 to

12 5,0ûO; or dihexylene triamino pentak'is methylene phos-

13 phonic acid. It is believed that the latter reagent also

14 has activity as a corrosion inhibitor.

15 (d) Corrosion Inhibitors and Biocides ~ .

16 Useful reagents which have the property of corrosion

17 inhibition and/or biocidal activity include both oil-

18 soluble and water-soluble materials~ 'The latter must be

19 incorporated into the polymeric matrix in blocked form.
Typical examples of oil soluble corrosion 21 inhibitors and/ùr biocides are amines, diamines, fatty 22 amines, polyamines,-alkoxylated amines,-hydrogenated fatty 23 amines, amides, fatty acid amides, imidazolines, and 24 trimer acids.
Typical examples of water soluble corrosion 26 inhibitors and/or biocides are quaternary amines and 27 quaternized imidazolines each of which can be indivi~ually 28 blocked'by reaction with oleophilic fatty acids to form 29 water insoluble salts whereby it becomes useful in the 30 present invention~

~24~43~

1 The reagents may also be materials of value in ~ fuels and lubricating oils, for instance ashless disper-3 sants or antioxidants. A filter bed through which such 4 fluids or oils pass may contain or consist of the parti-5 cles containing such reagents.
6 (e) As~less Dispersants 7 As used herein, the terminology "ashless dispersant" is 8 intended to describe the now well-known class of non-9 metal containing oil-soluble polymeric additives or the 10 acyl derivatives of relatively high molecular weight 11 carboxylic acids which are capable of dispersing contami-12 nants and the like in hydrocarbons such as lubricating 13 oils. The carboxylic acids may be mono- or polycarboxylic 14 acids and are generally characterized by substantially 15 hydrocarbon constituents containing an average of 50 to 16 250 aliphatic carbon atoms.
17 A preferred class of ashless dispersants are the 18 nitrogen-containing dispersant additives which include 19 mineral- oil-soluble salts, amides and esters made from

20 high molecular weight mono- and dicarboxylic acids (and

21 where they exi~t the corresponding acid anhydrides) and

22 various amines of nitrogen-contsining mat~rials having

23 amino ni~rogen or heterocyclic nitrogen and at lea~t one

24 amido or hydroxy group capable of salt7 amide, imide or

25 ester formation. Usually, these dispersants are made by

26 condensing a mono_carboxylic acid or a dicarboxylic acid

27 or anhydride, preferably a succinic acid producing

28 material such as alkenyl succinic anhydride~ with an amine

29 or alkylene polyamine. Usually, the molar`ratio of acid

30 or anhydride to amine is between 1:1 to 5:1.

31 Primarily because of its ready availability and

32 low cost, the hydrocarbon portion of the mono-, or

33 dicarboxylic aeid or anhydride is preferably derived from

34 a polymer of a C2 to C5 monoolefin, said polymer mono-

35 olefin generally having between 50 and 250 carbon atoms. A

36 particularly preFerred polymer is polyisobutylene.

-13~
1 Polyalkyleneamines are ususlly used to make the 2 non metal-containing dispersant. These polyalkyleneamines 3 include diethylenetriamine, tetraethylenepentamine, 4 dipropylenetriamine, octaethylenenonamine, and tetra-5 propylenepentamine. Highly useful mixtures of alkylene 6 polyamines approximating tetraethylene pentamine are 7 commercially availaole.
8 Representative dispersants are Formed by 9 reacting about one molar amount of an oil-soluble poly 10 isobutenyl succinic anhydrid~3 with from about one to about 11 two molar amounts of tetraethylene pentamine or with from 12 about 0.5 to 1 moles of a:polyol, e~g. pentaerythritol.
13 It is possible to modify the ashless dispersants 14 generally by the addition of metals such as boron in order 15 to enhance the dispersancy of the additive.
16 (9) Antioxidants 17 As used herein, antioxidants are oil-soluble oxidation 18 inhibitors and generally represented by-the additives for 19 lubrioating oils which include phenols, amines, sul-20 phuri ed phenols, alkyl phenothiazines, and zinc dihydro=
21 carbyl phosphorodithioates, e.g. ~inc di-n-propyl 22-dithiophosphate. - -23 Polymeric Body 24 The polymeric matrix is rbagent permeative and preferably 25 has a so~tening point as measured by a temperature~graded 26 hot bar of above 30DC and most preferably is above 60C, 27 often up to 120~C. The combination of the reagent and the 28 polymeric matrix must be such that the reagent is released 29 into surrounding fluid at the desired time and rate either 30 as a result of the fluid permeating through the ~atrix to 31 dissolve the reagent or as a result of the reagent 32 permeating through the matrix to dissolve into the Fluid, 33 or both.
34 The polymer of the matrix is preferably formed 35 mainly of acrylio alkyl ester or styrene or acrylonitrile 36 or a mixture thereof. Suitable acrylic esters are alkyl

37 acrylates and methacrylates where the alkyl group contains ~245'~3~ii l from 1 to 6 and preferably 1 to 3 carbon atoms. The ester 2 is preferably a methacrylate and the preferred ester is 3 methyl methacrylate. The polymer is preferably formed 4 mainly of methyl methacrylate or a blend of methyl 5 methacrylate and styrene. Small amounts of other poly-6 merizable monomers, for instance up to 40~, generally 7 below 20~ by weight and preferably below 10~ by weight, 8 may be included provided they do not deleteriously affect 9 the properties of the polymer. Other suitable monomers lO include hydroxyalkyl acrylates and methacrylates, maleate ll esters, vinyl esters, dialkylaminoalkylacrylates and 12 methacrylates and cross-linking monomers such as glycol 13 dimethacrylate. It is particularly preferred to include 14 carboxylic monomers such as acrylic or methacrylic a~id 15 which are useful in modification of the rate of reagent 16 permeation From the polymeric body when these monomers are 17 incorporated into the monomer mixture, they tend to 18 migrate toward the outer layers of the polymeri~ing body l9 due to their hydrophilic nature relative to the reagents.
20 The result is a body having a lower rat~ of reagent 21 permeation through its outer region than that of the 22 interior region. This approach provides a means of 23 controlling the leach rate of the reagent from the body 24 The amount of reagent is generally at least 5~
25 by weight of -the total body in order to maximize the 26 amount of reagent introduced into the desired location. It 27 can be difficult to produce bodies containing very high 28 amounts of reagent and so the amount is generally not more 29 than 50~, and usually not more than 30~1 by weight of the 30 total body. The preferred reagent amount is usually 10 to 31 30~ by weight of the total body.
32 The invention has ~idely diverse applications 33 since it makes possible a controlled release of reagent 34 into liquids in a uniform manner and over extended time 35 periods. It makes possible the release of certain 36 reagents from previously non- or difficulty accessible and ~;24~3S
-15~-1 diverse points such as in an oil bearing mineral formation 2 one or more miles underground and in the flow path of a 3 circulating engine lubricant.
4 This invention provides a method for the 5 controlled introduction of a reagent into a liquid which 6 method comprises the steps ol^:
7 (a) placing solid bodies, each body comprising a reagent 8 permeable polymeric matrix containing at least one 9 reagent preferably a s~!bstantially water insoluble reagent in a liquid, generally flowin9, substantially 11 hydrocarbon fluid; and 12 (b) leaching out said resgent from said bodies at a 13 controlled and predetermined rate into said liquid 14 fluid, said fluid preferably containing oil.
In a preferred manner the invention proviqes a 16 method of recovering a crude petroleum oil containing waxy 17 components, from a reservoir wherein the oil is at a 18 temperature above its wax deposition temperature which 19 comprises:
20 a. passing a portion of said crude petroleum oil from 21 said reservoir to a first central collection point, 22 i.e. the well bore;
23 b. passing said oil from said first central collection 24 point to a second collection point~ i.e. the well head at a temperature below the wax deposition 26 temperature of said oil whereby the temperature of 27 said oil decreases and passes through a wax-28 deposition temperature at which the waxy components 29 begin to precipitate and to deposit on~surfaces with which said oil comes in contact as it passes to said 31 second collection point;
32 c. collecting said crude petroleum oil at said second 33 collection point; and9 34 d. adding to said portion of crude petroleum oil before it passes to said first central collection point a 36 wax-deposition inhibiting amount of a wax crystal 37 modifier reagent by flowing said portion through a ' ~5435 -16~-1 particulate grid of proppant and solid polymeric 2 bodies each body comprising a polymeric matrix 3 containing a substantially water-insoluble w~x 4 deposition inhibitor reagent, ~aid reagent optirnally the bshenyl half ester of a C24-C2g alkenyl succinic 6 anhydride polymer and contained in said matrix in an 7 amount ranging from 5 to 50 weight percent of the 8 total weight of said body.
9 The method of making the bodies of polymeric 10 matrix containing sub tantially water-insoluble reagent 11 involves forming a dispersion in an aqueous medium of 12 particles of reagent and Iiquid polymerizablè material and 13 polymerizing the polymerizable material while maintaining 14 the particles dispersed in the medium. The polymerization results in the formation of a suspension of polymer beads 16 each containing reagent. The beads may be filtered or 17 otherwise separated from the aqueous medium. They may be 18 wsshed and dried but for introduction by means of an 19 aqueous-fluid or into an aqueous fluid the beads are best 20 left in a damp and water-wetted state..
21 The aqueous medium will generally include a 22 polymeric stabilizer suitable for suspension polymeriza-23 tion. This is often a hydrophilic polymer that is 24 swellable in, and usually soluble in~ the aqueous medium.
25 The hydrophilic dispersing stabilizer may be a naturally 26 occurring or modified naturally occurring polyme~, such as 27 a hydroxyethyl cellulose, or a synthetic water soluble 28 polymer, ~or instance polyvinyl alcohol or polyethylene 29 oxide but preferably is a synthetic carboxylic acid 30 containing polymer, most preferably polyacrylic acid 31 having a molecular weight in the range 1 million to 1û
32 million. The amount is generally 0.2 to 5~D weight of the 33 waterO
34 In order to obtain uniform and fine distribution 35 of the reagent in the polymeric matrix, it is necessary 36 for the reagent to be monomer-wetting rather than water-37 wetting anà preferably the reagent is in liquid form .

~2~L5~3S

l during polymerization of the matrix. It could be intro-2 duced as a solution in toluene or other suitable organic 3 solvent but this would have the disadvantage of incor-4 porating solvent in the matrix. Preferably therefore the reagent is one that dissolves into the polymerizable 6 material, if necessary as a result of being heated, For 7 instance it may be insoluble in the polymerizable material 8 at ambient temperatures but may become soluble upon 9 heating to a temperature between 50 and 80C, in which event the dispersion of the particles of reagent and ll liquid polymerizable material is formed at such a 12 temperature. The elevate'd temperatUEe may be such that 13 the ~eagent is then truly molten or may be such as to 14 promote solubility of the reagent in the polymerizable material.
16 Preferably a homogeneous b'lend is formed of the 17 reagent and the monomer--or monomers, di~persed into the 18 aqueous medium by stirring and polymerization is initiated 19 by using an oil soluble thermal initiator.
The following are examples of the i'nvention.

- - -22 The behenyl half ester of- a C24-C2B alkenyl 23 succinic anhydride polymer produced generally according to 24 the procedure set forth '~or preparation of Polymer ~
disclosed in United States Patent 3,8~547893 was supplied 26 as a solution in toluene7 and this solvent was evaporated' 27 to leave 3 waxy solid. This wax, i.e. the reagent, was 28 insoluble in methyl methacrylate monomers at temperatures - 29 up to 50C. A monomer solution containing t~e wax reagent was formed of 85 9 methyl methacrylate, 5 9 methacrylic 31 acid and 10 9 of the wax by heating all to 65C, at which 32 temperature the wax dissolved into the monomers. The 33 resultant solution was then dispersed in 2ûO g water 34 containing 3 9 polyacrylic acid (molecular weigh'c about 2 million) as a dispersing stabilizer of the monomer drop-36 lets during polymerization in a one litre enclosed vessel 37 provided with a stirrer for controlled agitation of the . .

1~4~

l contents within the vessel. Under constant agitation 1 9 z of azodiisobutyronitrile as the polymerization inhibitor 3 was added. Suspension polymerizat;on was continued with 4 constant agitation for two hours after which time the product within the vessel consisted of a suspension of 6 small polymeric beads in the aqueous medium. Thes0 beads 7 ~ere separated from the aqueous medium~ washed and draed 8 to give free flowing beads of from 0.~ to 1 mm in diameter g with 10~ by weight of the waxy ester polymer reagent lû dispersed in the polymeric matrix.
ll Since the behenyl ester wax reagent is very l2 soluble in hexane, to demonstrate the retardation of l3 solubility by the invention the produced beads were l4 stirred in hexane st 35C and the amount of wax released recorded. The following results were obtained.
16 ~ of Total Wax ReleasedTime Hours 17 at }5C

l9 42 2 22 - - - - 5~ -- 5 23 EXAMPLE ~
24 When the above process was repeated using 10 9 25 wax reagent (as above described), 5 9 acrylic acid, 5 9 26 methacrylic acid and 80 9 methyl methacrylate followed by 27 neutralization with sodium hydroxide dispersion, the beads 28 have a shell containing a high proportion of sodium poly 29 acrylate and have slower release propertie~ compsred to 30 the release properties of the beads of Example 1 when the 31 polymerizate dispersion was similarly neutralized~ In 32 particular, after 5 hours at 35DC in hexane as in Example 33 1, only 25~ of the wax was released from the pDlymerio 34 bodies.

S~3~ .

2 To produce a polymeric body according to this 3 invention containing.a leachable scale inhibitor, the 4 polymerization mixture will be 859 of methyl methacrylate, 59 methacrylic acid and 109 tri(C6-C10 alkyl) ammonium 6 salt of a poly(acrylic acid) having a Mw of 1,000 to 7 5,000. The polymerization mixture is to be polymerized 8 under the conditions of Example 1.
g EXAMPLE 4 In order to produce the polymeric bodies 11 according to this invention containing a leachable 12 corrosion inhibitor reagent, the procedure of Example 3 is 13 to be Followed except that the 59 of methacrylic acid is 14 replaced with 59 of dimethylaminoethy-l acrylate, the 109 of the ammonium salt is replaced with 109 of the equimolar 16 reaction product of tall oil fatty acid and diethylene 17 triamine and the anionic dispersing stabili~er is changed 18 to 39 of the methyl ch.loride quaternary salt o~ poly 19 (di-methylaminoacrylate) of about 1 million Mw~

21 In order to produce a polymeric body according 22 to this invention containing a leachable demulsi~ier 9 the.
23 procedure of Example 3 is followed except that the 24 following monom~r mixtùre is used: 659 methyl 25 methacrylate, 209 styrene9 59 methacrylic acid and 109 of 26 an oxyalkylated phenol formaldehyde resin of 2000 Mw 27 where the weight ration of ethylene oxide to propylene 28 oxide tD resin is about û..5:0~5:1.5.

In order to produce a polymeric body ~ccording 31 to this invention containing a leachable ashless 32 dispersant, the procedure of Example 1 is followed except 33 that the wax is replaced with the equimolar reaction 34 product of polyisobutenyl succinic anhydride having a ~w 35 of about 900 and pentacrythritol.

3~

l EXAMPLE 7 2 The effectiveness of the present invention in 3 the inhibition of wax deposition from a crude oil was 4 shown by comparison of the product of Example 1 with a 5 solution of the reagent of Example 1 on a crude oil (in 6 which the aforesaid reagent has shown measurable W8X
7 deposition inhibiting activity) using the following 8 procedure. 0.03 weight parts o~ active ingredient was g introduced into 100 weight parts of crude petroleum oil.
lO Th0 resultant mixture was placed within a test cell con-ll taininQ a preweiyhed, removable standard water chilled 12 deposition steel plate, a stirrer thermometer, and an 13 electrical heater. The test cell was placed in an 14 insulated bath together with an identical reference cell 15 containing the reagent solution treated base crude oil.
16 The temperature of the oils in both cells was maintained 17 at 2 to 5.5C. above the known cloud point temperature of 18 the oil (as determined by ASTM ~-97-57). The test was l9 continued for 6 hours and then each deposition plate was 20 removed, and weighed. The amount of wax deposit on each 21 plate was for measurable activity the same.

23 The polymeric bodies of the present invention 24 can be used to inhibit paraffin deposition from waxy crude 25 oils by placing them downhole with the proppant sand 26 during the course of a fracturing operation;
27 To effect the placement of the particles of the 28 invention a fracturing operation is carried out as 2~ follows. A fracturing fluid is prepared b~ gelling a 2Z
30 solution of potassium chloride ~ith hydroxy propyl guar 31 cross linked with a transition metal complex. As the 32 fluid is pumped downhole 8 lbs/100D gals of 20-40 mesh 33 sand mixed with 5~ of the beads of the invention are added 34 to serve as a proppant in the fractures formed in the 35 producing formation. Pump pressure is increased above the 36 fracture gradient of the rock formation and the fluid 37 carries the proppant mixture into the fractures. The well , S~3'~, -1 is then shut in for 24 hours to allow the guar gel to 2 degrade to a low viscosity solution. The well i5 allowed 3 to flow back and the fracturing fluid is recovered leaving 4 the proppant mixture of sand and polymer bead-like bodies 5 behind.
6 As the produced oil flows through the proppant 7 pack past the polymeric bodies the wax deposition 8 inhibitor slowly leaches out and deposition is inhibited 9 in the well bore and the flcw lines as the oil cools and 10 production is maintained at a high level without wax 11 blockage~

13 The polymeric bodies of Example-3 can be used to 14 prevent scale deposition from produced fluids by placing 15 them downhole with the other solids used in gravel packing 16 a well to prevent the production of loose unconsolidated 17 sand. -18 To eFfect the placement of the`bodies of Example19 3 a graYel packing operation is performed with a carrier 20 fluid and the proper mechanical equipment to place the 21 packing solids at the specific producing zone. A screen 22 or slotted liner is placed in front of the packing to hold 23 it and thereby the formation in place. The carrier fluid 24 may be salt water, crude oIl, diesel or acid fluids. These 25 fluids must be filtered to less than 2 microns. The 26 viscosity and density of the fluid depends on the specific 27 well being treated.
28 An example might be to use a carrier fluid that 29 is 2~ potassium chloride gelled with hydroet~yl cellulose.
30 The beads of Example 3 are mixed with packing gravel and 31 sand to make à slurry containing about 20~ by weight of 32 the bead. The slurry is then placed at the producing zone 33 by using one of the accepted techniques.
34 As the produced fluid flows through the gravel 35 pack containing about 10~ of the bodies, the scale 36 inhibitor slowly leaches out and deposition is inhibited 37 in the well bore, flowline and other associated equipment.

4~ .
~22-2 The particulate bodies of Example 4 can be used 3 to prevent corrosion of the metal equipment by the 4 produced fluids by placing the beads downhole in a 5 replacea~le cartridge packed with the bead-like bodies.
6 The cartridge cou:Ld be designed to snap lock in the downhole tubing so it can be periodically replaced 8 when all the corrosion inhibitor is leached out of the g beads by the produced fluids passing through the 10 cartridge. The length of service can be controlled by the 11 leach out rate of the bead and by the size of the bead 12 packed cartridge.
13 As the produced fluid flows through the 14 cartridge containing the beads the corrosion inhibitor 15 slowly leaches out and inhibits corrosion of well tubing 16 or casing, flowline and associated equipment ~ .~ ~ , 18- The bodies of Example 5 can be used to i.nhibit 19 emulsification of the crude oil formation water, water-20 flood injection water snd/or water introduced by stimula-21 tion/workover. processes by placing them downhole with the .. 22. prop.pant sand during.the course of a fractur.ing operation.. ..
23 To effect the placement of the bodies, a 24 fracturing operation is carried out as described in the -25 inhibition of paraffin deposition Example 8 26. As the produced fluid flows through the proppant 27 psck past the bodies? demulsifier would slowly leach out 28 to inhibit emulsion formation during production 29 operations~ -31 The use of the polymeric bodies containing an 32 ashless dispersant to extend the operational life of a 33 lubricating oil for internal combustion engines is easily 34 realized. One need only to introduce the product of 35 Example 6 into a lubricating oil filter container as by 36 opening the container ? pouring the bodies into the volume 37 not occup.ied by the filter and reclosing the container~

.

5~;~5 1 All that remains is to position the packed filter modified 2 for use according to this invention in the lubricating oil 3 flow circuit of the engine.
4 As used herein ~ by weight is based on the total 5 weight of the body, polymer composition9 water or bead9 6 respectively.

Claims (18)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR PRIVILEGE
IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A method for releasing a treating reagent in a liquid hydrocarbon stream which comprises:
(a) placing in said stream a plurality of porous, substantially wax free, plastic particles having a softening point above 60°C and being chemically resistant to said hydrocarbon stream, said particles containing a treating reagent in the pores thereof, said reagent being insoluble in water and in said particles and being leachable on contact with the hydrocarbon stream; and (b) flowing the hydrocarbon stream past said particles whereby said reagent is leached from the pores thereof, and whereby said particles retain their structural integrity.

2. A method according to claim 1, wherein said liquid hydrocarbon is substantially crude oil.

3. A method according to claim 1 wherein said liquid hydrocarbon is substantially refined oil.

4. A method according to claim 3 wherein said oil is a lubricating oil.

5. A method according to claim 1 wherein said reagent is a wax crystal modifier, demulsifier, scale inhibitor, corrosion inhibitor, biocide, ashless dispersant, anti-oxidant and mixtures thereof.

6. A method according to claim 1 wherein the placing of said bodies is by means of an aqueous stimulation fluid.

7. A method according to claim 1 wherein the placing of said bodies is by means of a workover fluid.

8. A method according to claim 1 wherein the placing of said particles is by means of a cartridge packing with said bodies.

9. A method according to claim 1 wherein the placing of said particles is by means of a packed filter.

10. A method according to claim 6 wherein said fluid is aqueous and said bodies are introduced into said fluid in a damp and water-wetted state.

11. A method for recovering crude oil from an underground geological formation comprising the steps of:
(a) depositing solid porous polymeric particles containing in the pores thereof a substantially water-insoluble, well treating reagent downhole in the oil producing region of the formation in an amount sufficient to alter the reactive properties of said crude oil, said reagent being insoluble in said polymeric particles and said particles being substantially wax-free and structurally stable at formation conditions;
(b) flowing said crude oil to the earth's surface through said bodies in a continuous manner thereby leaching said reagent into said crude oil; and (c) recovering said oil modified by the presence of an active amount of said reagent.

12. A method according to claim 1 wherein said reagent is the behenyl half ester of a C24-C28 alkenyl succinic anhydride polymer and contained in said matrix in an amount ranging from 5 to 50 weight percent of the total weight of said body.

13. A method as defined in claim 1 wherein the pores in said particles are substantially uniformly distributed therein.

14. A method as defined in claim 13 wherein the particles containing reagent are prepared by suspension polymerizing a monomer with the reagent dissolved therein to form the polymer with the reagent dispersed therein, forming pores therein.

15. A method as defined in claim 13 wherein the plastic is selected from acrylic alkyl ester, styrene, and acryolnitrile polymers or mixtures thereof.

16. A method as defined in claim 13 wherein the plastic is selected from alkyl acrylates and methacrylates wherein the alkyl group contains from 1 to 6 carbon atoms.

17. A method as defined in claim 14 wherein the reagent in the particles resulting from the suspension polymerization is from 5 to 50 volume percent of the particle.

18. A method as defined in claim 1 wherein the reagent is soluble in the hdyrocarbon stream.