Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
  • C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
  • C09K8/467—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement containing additives for specific purposes
  • C09K8/487—Fluid loss control additives; Additives for reducing or preventing circulation loss
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/14—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing calcium sulfate cements
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F293/00—Macromolecular compounds obtained by polymerisation on to a macromolecule having groups capable of inducing the formation of new polymer chains bound exclusively at one or both ends of the starting macromolecule
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/02—Well-drilling compositions
  • C09K8/03—Specific additives for general use in well-drilling compositions
  • C09K8/035—Organic additives
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
  • C09K8/504—Compositions based on water or polar solvents
  • C09K8/506—Compositions based on water or polar solvents containing organic compounds
  • C09K8/508—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/50—Compositions for plastering borehole walls, i.e. compositions for temporary consolidation of borehole walls
  • C09K8/504—Compositions based on water or polar solvents
  • C09K8/506—Compositions based on water or polar solvents containing organic compounds
  • C09K8/508—Compositions based on water or polar solvents containing organic compounds macromolecular compounds
  • C09K8/5083—Compositions based on water or polar solvents containing organic compounds macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/0045—Polymers chosen for their physico-chemical characteristics
  • C04B2103/0059—Graft (co-)polymers
  • C04B2103/006—Comb polymers
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/0045—Polymers chosen for their physico-chemical characteristics
  • C04B2103/0061—Block (co-)polymers
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
  • C04B2103/46—Water-loss or fluid-loss reducers, hygroscopic or hydrophilic agents, water retention agents

Definitions

• the present invention relates to the field of oil extraction. More specifically, it relates to agents providing an effect of controlling fluid loss in fluids injected under pressure into subterranean formations.
• subterranean formation In the field of oil extraction, numerous stages are carried out by injecting fluids under pressure within subterranean formations.
• subterranean formation is understood in its broadest sense and includes both a rock containing hydrocarbons, in particular oil, and the various rock layers traversed in order to access this oil-bearing rock and to ensure the extraction of the hydrocarbons.
• rock is used to denote any type of constituent material of a solid subterranean formation, whether or not the material constituting it is strictly speaking a rock.
• oil-bearing rock is employed here as synonym for “oil-bearing reservoir” and denotes any subterranean formation containing hydrocarbons, in particular oil, whatever the nature of the material containing these hydrocarbons (rock or sand, for example).
• Mention may in particular be made, among the fluids injected under pressure into subterranean formations, of the various fluids for completion and workover of the wells, in particular drilling fluids, whether they are used to access the oil-bearing rock or else to drill the reservoir itself (drill-in), or else fracturing fluids, or alternatively completion fluids, control or workover fluids or annular fluids or packer fluids.
• oil cement grouts which are employed for the cementing of the annulus of oil wells according to a method well-known per se, for example described in Le Forage [Drilling] by J. P Nguyen (Editions Technip 1993). These oil cement grouts are injected under pressure within a metal casing introduced into the drilling hole of the oil wells, then rise again, under the effect of the pressure, via the “annulus” space located between the casing and the drilling hole, and then set and harden in this annulus, thus ensuring the stability of the well during drilling.
• the fluid loss can in addition result in excessively rapid setting of the cement, before the space of the annulus is cemented, which can, inter alia, weaken the structure of the well and harm its leaktightness.
• fluid loss control agents For the purpose of inhibiting the phenomenon of fluid loss, a number of additives have been described which make it possible to limit (indeed even in some cases completely prevent) the escape of the liquid present in the fluid toward the rock with which it comes into contact.
• These additives known as “fluid loss control agents”, generally make it possible to obtain, in parallel, an effect of control of the migration of gases, namely isolation of the fluid with respect to the gases present in the rock (gases which it is advisable to prevent from penetrating into the fluid, in particular in the case of cement grouts, these gases having a tendency to weaken the cement during setting).
• fluid loss control agents of the abovementioned type have been provided, which include in particular cellulose derivatives (for example hydroxyethylcellulose) or alternatively AMPS-based copolymers, such as those described, for example, in U.S. Pat. No. 4,632,186 or U.S. Pat. No. 4,515,635.
• cellulose derivatives for example hydroxyethylcellulose
• AMPS-based copolymers such as those described, for example, in U.S. Pat. No. 4,632,186 or U.S. Pat. No. 4,515,635.
• These additives are not always fully suitable for providing, in practice, effective limitation of fluid loss.
• the presence of other additives can inhibit the effect of the agents employed for providing control of fluid loss.
• the abovementioned fluid loss control agents generally experience a deterioration in their properties.
• An aim of the present invention is to provide novel fluid loss control agents for fluids injected under pressure into subterranean formations which are well-suited in practice.
• the present invention proposes to use specific copolymers, which are capable of providing a fluid loss control effect when they are employed with particles, with which they combine, it being possible for these particles to be particles present within the subterranean formation; and/or cement particles in the case of a fluid employed in cementing; and/or particles injected within subterranean formations with the copolymers.
• a subject matter of the present invention is the use, as fluid loss control agent in a fluid (F) injected under pressure into a subterranean formation,
• a block polymer (P) comprising at least three blocks, including:
• a block polymer (P) of use according to the invention can be a triblock copolymer of (A)-(B)-(A) or (B)-(A)-(B) type.
• It can also be a polymer of star type, comprising chains (“arms” or “branches”) bonded together around a central atom or, more generally, a more complex molecular structure acting as “core”, to which the branches are covalently bonded.
• the polymer (P) is typically of the following type:
• a star polymer comprising at least one branch of type (A) and at least two branches of type (B); or
• a polymer of star type comprising at least two branches of type (A) and at least one branch of type (B).
• a block polymer (P) of use according to the invention can be a copolymer of comb type, with side chains carried by a linear chain (backbone), for example:
• the specific polymers employed in the context of the present invention due to the presence of the specific blocks of type (A) and (B), turn out to provide a particularly efficient effect of control of the fluid: the presence of the short blocks of type (A) provides anchoring of the polymer to the particles and the presence of the long blocks of type (B), which are large in size and soluble, schematically provides an effect of local increase in the viscosity of the fluid (F) around the particles.
• the short block (A) of a polymer (P) of use according to the invention comprises:
• the strong interactions between particles and polymers make it possible, if need be, to employ the polymer (P) in the presence of additives which are normally harmful to the effectiveness of the fluid loss control agents.
• the polymers (P) as employed according to the invention can be employed in the majority of the formulations of fluids intended to be injected into oil-bearing rocks, in particular oil cement grouts comprising additives of dispersant or set retarder type, as well as in drilling fluids and fracturing fluids.
• the injected fluid (F) comprises the polymer (P) but does not comprise solid particles (p), and it encounters said particles (p) within the subterranean formation subsequent to its injection.
• the association between particles and polymers then takes place in situ.
• a fluid can, for example, be injected during a drilling operation, and the rock cuttings formed during the drilling then perform the role of the particles (p) in situ.
• the injected fluid (F) comprises, before the injection, at least a portion and generally all of the particles (p) combined with the polymer (P), it being understood that it can optionally encounter other particles (p) within the subterranean formation.
• the subject matter of the present invention is certain specific block polymers which can be used according to the invention, which have been developed by the inventors specifically for this application.
• Another subject matter of the invention is the fluids for injection under pressure within an oil-bearing rock or a drilling well comprising these specific block polymers, and also the blends for the preparation of these fluids comprising these polymers in combination with particles (p).
• fluid is understood to mean, within the meaning of the description, any homogeneous or non-homogeneous medium comprising a liquid or viscous vector which optionally transports a liquid or gelled dispersed phase and/or solid particles, said medium being overall pumpable by means of the devices for injection under pressure used in the application under consideration.
• liquid or viscous vector of the fluid (F) is understood to mean the fluid itself, or else the solvent, in the case where the fluid comprises dissolved compounds, and/or the continuous phase, in the case where the fluid comprises dispersed elements (droplets of liquid or gelled dispersed phase, solid particles, and the like).
• the nature of the fluid (F) and of the long block (B) of the polymers (P) used according to the present invention can vary to a fairly large extent, subject to the compatibility of the liquid or viscous vector of the fluid (F) and of the long block (B).
• the long blocks of type (B) of the polymers of use according to the invention are specifically soluble in the fluid (F).
• the long block (B), taken in isolation, can be dissolved in the liquid or viscous vector of the fluid (F).
• the long block (B) is soluble at 25° C. and at 1% by weight in the liquid or viscous vector of the fluid (F).
• the notion of “solubility at 25° C.” implies only that it is possible to obtain a more or less viscous, indeed even gelled, solution which, at 25° C., does not result in precipitation. This notion does not exclude the possibility of the dissolution of the block (B) involving prior heating to more than 25° C. in order to obtain this solution.
• the notion of “solubility at 25° C.” implies the possibility of forming a solution which does not precipitate at 25° C. and not the possibility of forming, at 25° C., a solution which does not precipitate.
• the long block (B) it is preferable for the long block (B) to develop the fewest possible interactions, indeed even no interactions at all, with the particles (p). Furthermore, it is preferable for the long block (B) of the polymers (P) of use according to the invention to develop fewer interactions with the particles than the short block (A).
• the blocks of type (A) and the block (B) have distinct compositions within one and the same polymer. This is understood to mean that:
• the long block (B) preferably has a weight-average molecular weight of at least 20000 g/mol, this weight-average molecular weight preferably being at least 50000 g/mol, indeed even at least 100000 g/mol.
• the weight-average molecular weight of the long block (B) is greater than or equal to 250000 g/mol, indeed even greater than or equal to 500000 g/mol, for example greater than 1000000 g/mol.
• the fluid (F) is an aqueous fluid.
• aqueous is understood here to mean that the fluid comprises water as liquid or viscous vector, either as sole constituent of the liquid or viscous vector or in combination with other water-soluble solvents.
• the water advantageously remains the predominant solvent within the liquid or viscous vector, advantageously present in a proportion of at least 50% by weight, indeed even of at least 75% by weight, with respect to the total weight of the solvents in the liquid or viscous vector.
• the block (B) is advantageously a block of hydrophilic nature.
• block of hydrophilic nature is understood here to mean a polymer block which, in the isolated state, is soluble in pure water in a proportion of 1% by weight at 25° C. (it being possible for the dissolution to optionally involve heating), forming a more or less viscous, indeed even gelled, solution but without formation of precipitate at 25° C.
• the blocks of type (B) of hydrophilic nature employed when the fluid (F) is an aqueous fluid are at least predominantly composed of monomer units selected from the group consisting of the monomer units U1 to U5 defined below, and the mixtures of these monomer units:
• polymer or polymer block at least predominantly composed of monomer units ‘x’ denotes a homopolymer or copolymer (block) resulting from the polymerization of a mixture of monomers, including monomers ‘x’, this homopolymer or copolymer (block) comprising less than 25 mol %, preferably less than 15 mol % and more advantageously still less than 10 mol % of monomer units other than the units ‘x’.
• polymer or polymer block essentially composed of monomer units ‘x’ for its part denotes, within the meaning of the present description, a homopolymer or copolymer (block) at least predominantly composed of monomer units ‘x’ of the abovementioned type, more specifically comprising less than 5 mol %, preferably less than 2 mol % and more advantageously still less than 1 mol % of monomer units other than the units ‘x’.
• the block (B) of hydrophilic nature employed when the fluid (F) is an aqueous fluid can comprise hydrophobic monomers in small proportions, typically in a proportion of at least 0.05%, in particularly at least 0.1%, indeed even at least 0.5%, if appropriate; this content of hydrophobic monomers preferably remaining below 10%, for example below 5%, in particular below 3%, indeed even 2%, these percentages being expressed by weight with respect to the total weight of monomer units in the block (B).
• hydrophobic monomers of this type can typically (but nonlimitingly) be chosen from alkyl acrylates (such as methyl acrylate), styrene, alkyl methacrylates and/or vinyl acetate.
• the long block (B) present in the polymers employed according to the present invention furthermore has a weight sufficiently great to provide the desired effect of controlling fluid loss.
• the block (B) typically has a weight-average molecular weight of greater than 100000 g/mol, preferably of greater than 150000 g/mol, for example of greater than 200000 g/mol, in particular of greater than 250000 g/mol, this being the case in particular when the block (B) is of one of the abovementioned types.
• this weight-average molecular weight generally remains below 3000000 g/mol (and typically between 150000 and 2000000 g/mol) but higher weights can be envisaged in the absolute, except in the specific case of a fluid (F) used in the context of a cementing operation, where it is preferable for the weight-average molecular weight of the long block (B) to remain below 1000000 g/mol and advantageously below 800000 g/mol.
• the block (B) has a weight-average molecular weight of between 10000 and 100000 g/mol, preferably of at least 20000 g/mol, for example of at least 25000 g/mol, it being possible for this weight-average molecular weight to be typically less than 90000, for example less than 75000, indeed even less than 50000.
• An estimation of the weight-average molecular weight of the long block (B) can be measured by size exclusion chromatography and measurement of weight using external calibration with polyethylene oxide standards (relative SEC), which results in a slightly increased value of the weight-average molecular weight denoted in the present description by Mw(relative SEC).
• This Mw(relative SEC) is typically measured under the following conditions:
• the Mw(relative SEC) of the long block (B) of the polymers (P) of use according to the invention is generally greater than or equal to 125000 g/mol, preferably greater than or equal to 150000 g/mol, this Mw(relative SEC) typically being between 200000 and 2500000 g/mol, in particular between 250000 and 2000000 g/mol. According to a more specific embodiment, it can be less than 125000 g/mol, for example between 12500 and 100000 g/mol.
• the Mw(relative SEC) of the long block (B) of the polymers (P) is typically (but nonlimitingly) between 25000 and 900000 g/mol, for example between 250000 and 900000 g/mol.
• the Mw(relative SEC) of the polymer (P) is measured, which, as a result of the low weight of the block (A), also represents a fairly good approximation, inflated, of the weight-average molecular weight of the block (B).
• the Mw(relative SEC) of the polymer (P) is generally greater than or equal to 15000 g/mol, and for example greater than or equal to 150000 g/mol, preferably greater than or equal to 200000 g/mol, for example greater than or equal to 300000 g/mol, in particular greater than or equal to 400000 g/mol, this Mw(relative SEC) of the polymer (P) typically being between 200000 g/mol and 2500000 g/mol, in particular between 250000 g/mol and 2000000 g/mol. It is more particularly between 25000 and 900000 g/mol, for example between 250000 g/mol and 800000 g/mol, in the case of a fluid (F) used in the context of a cementing operation.
• particle within the meaning under which it is employed in the present description is not confined to that of individual particles. It more generally denotes solid entities which can be dispersed within a fluid, in the form of objects (individual particles, aggregates, and the like) for which all the dimensions are less than 5 mm, preferably less than 2 mm, for example less than 1 mm.
• the nature of the particles (p) and of the short block (A) of the polymers (P) used according to the present invention can vary to a fairly large extent, provided that the block (A) interacts with the particles (p) and results in an immobilization, preferably irreversible, of the polymer (P) on the surface of the particles (p).
• the block (A) generally comprises monomer units carrying groups which develop, with the particles (p), stronger interactions than the long block (B).
• the particles (p) are inorganic particles introduced within the fluid (F) or with which the fluid (F) comes into contact subsequent to its injection. These particles (p) are then typically cement, calcium carbonate, clay, baryte, silica, sand or carbon black particles.
• the block (A) is preferably at least predominantly (and preferably essentially, indeed even exclusively) composed of monomer units chosen from the preferred groups defined hereinafter, to be adjusted on an individual basis as a function of the nature of the particles (p):
• the short block (A) present in the polymers employed according to the present invention generally has a weight-average molecular weight between 500 and 30000 g/mol, for example between 1000 and 25000 g/mol, this being the case in particular when the block (A) is of one of the abovementioned types.
• the short block (A) is a poly(acrylic acid) homopolymer block with a weight-average molecular weight ranging from 1000 to 20000 g/mol.
• the weight-average molecular weight of the short block (A) can in particular be measured by gel permeation chromatography, followed by a multi-angle light scattering analysis (GPC-MALS).
• the polymers of use according to the present invention are specific polymers which comprise at least three blocks, one of which has a very different size from the other two, including a large-sized block (B).
• the polymers (P) of triblock or star type can typically be prepared by controlled radical polymerization, which makes it possible to finely control the size of the blocks.
• the polymers of comb type can also be obtained by controlled radical polymerization or else by postgrafting of polymers, themselves advantageously obtained by controlled radical polymerization, for example under the conditions defined below.
• the controlled radical polymerization technique is a technique well known per se which makes it possible, using a control agent for the polymerization, to obtain polymers of controlled weights and in particular block polymers, both the architecture and the size of each of the blocks of which can be controlled.
• Controlled radical polymerization processes which are highly suitable for the synthesis of the polymers (P) of use according to the invention are the “RAFT” or “MADIX” processes, which typically employ a reversible addition-fragmentation transfer process employing control agents (also known as reversible transfer agents), for example of xanthate type (compounds carrying —SC ⁇ SO— functional groups). Mention may in particular be made, as examples of such processes, of those described in WO 96/30421, WO 98/01478, WO 99/35178, WO 98/58974, WO 00/75207, WO 01/42312, WO 99/35177, WO 99/31144, FR 2 794 464 or WO 02/26836.
• Triblock polymers (P) of use according to the invention can thus be prepared according to a process comprising the following stages:
• the size of the polymer block being formed is controlled by the monomer/control agent molar ratio corresponding to the initial amount of monomers with respect to the amount of control agent: schematically, all the chains grow starting from each of the control agents present and the monomers are homogeneously distributed over all the growing chains. For this reason, the monomer/control agent molar ratio dictates the degree of polymerization of the block synthesized in each of the stages and thus makes it possible to define the theoretical number-average molecular weight expected for each of the blocks.
• the monomer/control agent molar ratios in stages (E1) and (E2) are chosen so that:
• the theoretical number-average molecular weight of the block (B) is between 70000 and 5000000 g/mol, preferably between 80000 and 3000000 g/mol, in particular between 90000 and 2000000 g/mol.
• this theoretical number-average molecular weight of the block (B) is more preferably between 90000 and 1000000 g/mol, advantageously between 100000 and 500000 g/mol.
• the block (B) can advantageously be prepared in stage (E2) by bringing into contact:
• This polymerization technique makes it possible to access large-sized blocks (B).
• the synthesis of the block (B) can be carried out under the polymerization conditions described in the application WO 2012/042167.
• the block (B) when the block (B) is hydrophilic, the block (B) can be synthesized by bringing into contact, within an aqueous medium (M) in which the block (B) formed is not soluble:
• the conditions to be employed in the abovementioned polymerization stages can be those typically employed in controlled radical polymerizations.
• stage (E) of the process of the invention use may be made, in stage (E) of the process of the invention, of any source of free radicals known per se.
• any source of free radicals known per se.
• one of the following initiators may be concerned:
• hydrogen peroxides such as: tert-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyoctoate, t-butyl peroxyneodecanoate, t-butyl peroxyisobutyrate, lauroyl peroxide, t-amyl peroxypivalate, t-butyl peroxypivalate, dicumyl peroxide, benzoyl peroxide, potassium persulfate or ammonium persulfate,
• azo compounds such as: 2,2′-azobis(isobutyronitrile), 2,2′-azobis(2-butanenitrile), 4,4′-azobis(4-pentanoic acid), 1,1′-azobis(cyclohexanecarbonitrile), 2-(t-butylazo)-2-cyanopropane, 2,2′-azobis[2-methyl-N-(1,1)-bis(hydroxymethyl)-2-hydroxyethyl]propionamide, 2,2′-azobis(2-methyl-N-hydroxyethyl]propionamide, 2,2′-azobis(N,N′-dimethyleneisobutyramidine) dichloride, 2,2′-azobis(2-amidinopropane) dichloride, 2,2′-azobis(N,N′-dimethyleneisobutyramide), 2,2′-azobis(2-methyl-N-[1 ,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide), 2,2′-azobis(2-methyl-N-
• redox systems comprising combinations, such as:
• alkali metal persulfates in combination with an arylphosphinic acid, such as benzenephosphonic acid and the like, and reducing sugars.
• an arylphosphinic acid such as benzenephosphonic acid and the like
• a radical initiator of redox type which exhibits the advantage of not requiring heating of the reaction medium (no thermal initiation), which makes it possible to manage even better the exothermicity of the reaction.
• the source of free radicals which is employed can typically be chosen from the redox initiators conventionally used in radical polymerization, typically not requiring heating for their thermal initiation. It is typically a mixture of at least one oxidizing agent with at least one reducing agent.
• the oxidizing agent present in the redox system is preferably a water-soluble agent.
• This oxidizing agent can, for example, be chosen from peroxides, such as: hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxyacetate, t-butyl peroxybenzoate, t-butyl peroxyoctoate, t-butyl peroxyneodecanoate, t-butyl peroxyisobutyrate, lauroyl peroxide, t-amyl peroxypivalate, t-butyl peroxypivalate, dicumyl peroxide, benzoyl peroxide, sodium persulfate, potassium persulfate, ammonium persulfate or also potassium bromate.
• peroxides such as: hydrogen peroxide, tert-butyl hydroperoxide, cumene hydroperoxide, t-butyl peroxy
• the reducing agent present in the redox system is also preferably a water-soluble agent.
• This reducing agent can typically be chosen from sodium formaldehyde sulfoxylate (in particular in its dihydrate form, known under the name Rongalit, or in the form of an anhydride), ascorbic acid, erythorbic acid, sulfites, bisulfites or metasulfites (in particular alkali metal sulfites, bisulfites or metasulfites), nitrilotrispropionamides, and tertiary amines and ethanolamines (which are preferably water-soluble).
• Possible redox systems comprise combinations, such as:
• An advantageous redox system comprises (and preferably consists of), for example, the combination of ammonium persulfate and sodium formaldehyde sulfoxylate.
• reaction medium of stage (E) it proves to be preferable for the reaction medium of stage (E) to be devoid of copper.
• a copper-complexing agent such as EDTA.
• control agent employed in the stages for the synthesis of the blocks (A) and (B) can, for its part, vary to a large extent.
• control agent used is a compound carrying a thiocarbonylthio —S(C ⁇ S)— group.
• the control agent can carry several thiocarbonylthio groups.
• control agent employed in stage (E2) is a living polymer resulting from stage (E1).
• control agent of stage (E1) can be envisaged as resulting from a preliminary stage (E0) in which the radical polymerization was carried out of a composition comprising:
• control agent suitable for the synthesis of the polymer (P) of use according to the invention advantageously corresponds to the formula (A) below:
• the R 1 or Z groups when they are substituted, can be substituted by optionally substituted phenyl groups, optionally substituted aromatic groups, saturated or unsaturated carbocycles, saturated or unsaturated heterocycles, or groups selected from the following: alkoxycarbonyl or aryloxycarbonyl (—COOR), carboxyl (—COOH), acyloxy (—O 2 CR), carbamoyl (—CONR 2 ), cyano (—CN), alkylcarbonyl, alkylarylcarbonyl, arylcarbonyl, arylalkylcarbonyl, phthalimido, maleimido, succinimido, amidino, guanidimo, hydroxyl (—OH), amino (—NR 2 ), halogen, perfluoroalkyl C n F 2n+1 , allyl, epoxy, alkoxy (—OR), S-alkyl, S-aryl, groups exhibiting a hydrophilic or ionic nature, such as alkali metal
• R 1 is a substituted or unsubstituted, preferably substituted, alkyl group.
• the optionally substituted alkyl, acyl, aryl, aralkyl or alkynyl groups generally exhibit from 1 to 20 carbon atoms, preferably from 1 to 12 and more preferably from 1 to 9 carbon atoms. They can be linear or branched. They can also be substituted by oxygen atoms, in particular in the form of esters, sulfur atoms or nitrogen atoms.
• the alkyne groups are radicals generally of 2 to 10 carbon atoms; they exhibit at least one acetylenic unsaturation, such as the acetylenyl radical.
• the acyl group is a radical generally exhibiting from 1 to 20 carbon atoms with a carbonyl group.
• R 1 or Z is a polymer chain
• this polymer chain can result from a radical or ionic polymerization or from a polycondensation.
• control agents xanthates, trithiocarbonates, dithiocarbamates or dithiocarbazates.
• control agent Use is advantageously made, as control agent, of compounds carrying a xanthate —S(C ⁇ S)O— functional group, for example carrying an O-ethyl xanthate functional group of formula —S(C ⁇ S)OCH 2 CH 3 , such as, for example, O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate of formula (CH 3 CH(CO 2 CH 3 ))S(C ⁇ S)OEt.
• the comb polymers according to the invention can typically be obtained by copolymerizing, by the radical route, preferably controlled radical route, ethylenically unsaturated monomers in the presence of macromonomers carrying a block of type (A) or (B), which results in the formation of a monomer chain carrying side blocks of type (A) or (B).
• a control agent for the radical polymerization typically an agent comprising a thiocarbonylthio —S(C ⁇ S)— group of the abovementioned type.
• (meth)acrylic acid monomers as monomer m A and (methoxy)polyethylene glycol ((M)PEG) macromonomers carried on a (meth)acrylic acid CH 3 O—(C 2 H 4 O) n —OC(O)(CH 3 )C ⁇ CH 2 , whereby a comb polymer is obtained, the side chains of which are (M)PEGs.
• the weight-average molecular weight of each of these (M)PEG side chains is greater than 5000 g/mol, more preferably greater than 10000 g/mol (for example between 10000 g/mol and 50000 g/mol) and more preferably still greater than 20000 g/mol.
• comb polymers according to the invention can be synthesized by post-grafting polymer chains with grafts carrying blocks of type (A) and/or (B) and a grafting group, according to any method known per se.
• grafts carrying blocks of type (A) and/or (B) and a grafting group according to any method known per se.
• the polymers of use according to the invention can be employed in virtually all of the fluids used in oil extraction and potentially subject to fluid loss.
• the fluid (F) is an oil cement grout which comprises the polymer (P) as additive.
• the polymer (P) combined with the particles present in the cement, provides the effect of control of fluid loss during the cementing.
• the fluid (F) is a drilling fluid or a fracturing fluid which comprises the polymer (P) combined with particles (p).
• the particles (p) are then generally introduced jointly with the polymer into the fluid (F) before the injection of the fluid.
• the polymer then generally provides stabilization of the dispersion of the particles in the fluid (F) by keeping at least a portion of the particles (p) in suspension in the fluid.
• concentrations of polymer and particles to be employed in these various fluids can be adjusted individually as a function of the application targeted and of the rheology desired.
• the synthesis was carried out at the laboratory scale in a glass reactor equipped with a mechanical stirrer, with a system for heating/cooling and for effective regulation of temperature and with a system for reflux/condensation of the vapours.
• O-ethyl S-(1-(methoxycarbonyl)ethyl) xanthate (Rhodixan A1) of formula (CH 3 CH(CO 2 CH 3 ))S(C ⁇ S)OEt was used as MADIX transfer agent.
• polyacrylic acid functionalized by the xanthate group was synthesized with a number-average molecular weight targeted at 1000 g/mol.
• solution A A solution of monomers (solution A) is prepared by weighing respectively 55.68 g of AMPS (50% by weight solution), 48.16 g of DMAM and 63.934 g of demineralized water.
• the vessel heel is degassed for 30 minutes and heated to 40° C.
• reaction medium When the reaction medium reaches the temperature of 40° C., 1.34 g of ammonium persulfate (APS) (5% by weight solution) and 0.21 g of sodium formaldehydesulfoxylate (NaFS) (0.25% by weight solution) are added. 167.77 g of the solution A are then introduced into the reaction medium at a flow rate of 1.40 ml/min for 2 h. At the same time, 5.15 g of 0.25% by weight NaFS solution are also added over a period of time of 2 h.
• APS ammonium persulfate
• NaFS sodium formaldehydesulfoxylate
• the triblock polymer was used to prepare oil cement grouts having the following formulation:
• the fluid loss control agent is mixed with the liquid additives and with the municipal water before incorporation of the cement.
• the grout obtained was conditioned at 88° C. for 20 minutes in an atmospheric consistometer (model 1250 supplied by Chandler Engineering Inc.), prestabilized at this temperature, which makes it possible to simulate the conditions experienced by the cement grout during descent in a well.
• the fluid loss control performance was determined by a static filtration at 88° C. in a double-ended cell with a capacity of 175 ml equipped with a 325 mesh ⁇ 60 mesh metal screen (supplied by Ofite Inc., reference 170-45).
• the fluid loss volume collected is 27.6 ml, which corresponds to a reasonable API volume of 55 ml.

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