NO328755B1

NO328755B1 - Drilling mud mixture and use of cross-linked vinyl aromatic acrylic polymer in such

Info

Publication number: NO328755B1
Application number: NO19982881A
Authority: NO
Inventors: Patrick Andre Roger Freche
Original assignee: Eliokem Sas
Priority date: 1997-06-24
Filing date: 1998-06-19
Publication date: 2010-05-03
Also published as: NO982881L; NO982881D0

Abstract

Boreslamblanding omfattende (I) en organisk fase som inneholder en tverrbundet vinylaromatisk/akryl-polymer som et fluidtapsreduserende middel, (2) minst ett fast fyllstoff, (3) en vannfase og (4) baritt. Boreslam i form av en invertert emulsjon som er fri for mineralolje og hovedsakelig fri for sterkt hydrofile basiske materialer valgt blant alkalimetallhydroksider og aminer som er valgt blant dietanolamin og trietanolamin, bestående hovedsakelig av (A) en kontinuerlig oljefase sammensatt hovedsakelig av minst en monokarboksylsyreester av en C--monokarboksylsyre som er alifatisk mettet, (B) en dispergert, vandig fase, (C) minst en emulgator, (D) minst et vektøkende middel, (E) et fluidtaps-additiv, hvilket fluidtapsadditiv er en tverrbundet vinylaromatisk/akryl-polymer, og (F) en svakt alkalisk alkalireserve-bestanddel bestående av kalk i en mengde ikke over 4 g/1 boreslam. De tverrbundne vinylaromatisk/akryl-polymerer kan også anvendes i rent oljebaserte boreslamformuleringer.Drilling mud composition comprising (I) an organic phase containing a crosslinked vinyl aromatic / acrylic polymer as a fluid loss reducing agent, (2) at least one solid filler, (3) an aqueous phase and (4) barite. Drilling mud in the form of an invert emulsion free of mineral oil and substantially free of highly hydrophilic basic materials selected from alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, consisting essentially of (A) a continuous oil phase composed mainly of at least one monocarboxylic acid ester of C - monocarboxylic acid which is aliphatic saturated, (B) a dispersed aqueous phase, (C) at least one emulsifier, (D) at least one weight gain agent, (E) a fluid loss additive, which fluid loss additive is a crosslinked vinyl aromatic / acrylic polymer, and (F) a weakly alkaline alkali reserve component consisting of lime in an amount not exceeding 4 g / l drilling mud. The crosslinked vinyl aromatic / acrylic polymers can also be used in pure oil-based drilling mud formulations.

Description

Område for oppfinnelsen Field of the invention

Denne oppfinnelse er innen området for boreslam anvendt ved boring av oljebrønner, gassbrønner, geotermiske brønner og tilsvarende brønner, og nærmere bestemt et forbedret fluidtapsregulerende middel. This invention is in the area of drilling mud used in the drilling of oil wells, gas wells, geothermal wells and similar wells, and more specifically an improved fluid loss control agent.

Bakgrunn for oppfinnelsen Background for the invention

Det er kjent at borevæsker for boring nedover i fjell og for å bringe opp steinkaks, er svakt forrykkede, vannbaserte væskesystemer. Oljebaserte systemer er i praksis blitt brukt i økende grad, særlig ved boring til havs eller ved inntrengning i vannfølsomme lag. It is known that drilling fluids for drilling down into mountains and for bringing up cuttings are slightly displaced, water-based fluid systems. In practice, oil-based systems have been used to an increasing extent, particularly when drilling offshore or when penetrating water-sensitive layers.

Oljebaserte borevæsker blir vanligvis anvendt i form av såkalte inverterte emulsjonsslam som består av et trefasesystem, nemlig olje, vann og finfordelte, faste stoffer. Slike emulsjoner er av typen vann/olje-emulsjon. For eksempel er den vandige fase til stede i den kontinuerlige fase som en heterogen, fin dispersjon. Det er til stede en hel rekke med tilsetningsstoffer, innbefattende særlig emulgatorer og emulgator-systemer, vektøkningsmidler, fluidtapsadditiver, alkalireserver og viskositets-regulerende midler, for å stabilisere systemet som helhet og for å oppnå de ønskede bruksegenskaper. Fullstendige, detaljerte opplysninger kan finnes f.eks. i artikkelen av P. A. Boyd et al. kalt "New Base Oil Used in Low-Toxicity Oil Muds" i Journal of Petroleum Technology, 1985, s. 137-142, og i artikkelen av R. B. Bennett kalt "New Drilling Fluid Technology - Mineral Oil Mud" i Journal of Petroleum Technology, 1984, 975-981, og litteraturen angitt der. Oil-based drilling fluids are usually used in the form of so-called inverted emulsion mud, which consists of a three-phase system, namely oil, water and finely divided solids. Such emulsions are of the water/oil emulsion type. For example, the aqueous phase is present in the continuous phase as a heterogeneous fine dispersion. A whole range of additives are present, including in particular emulsifiers and emulsifier systems, weight gainers, fluid loss additives, alkali reserves and viscosity-regulating agents, to stabilize the system as a whole and to achieve the desired performance properties. Complete, detailed information can be found, e.g. in the article by P. A. Boyd et al. called "New Base Oil Used in Low-Toxicity Oil Muds" in the Journal of Petroleum Technology, 1985, pp. 137-142, and in the article by R. B. Bennett called "New Drilling Fluid Technology - Mineral Oil Mud" in the Journal of Petroleum Technology, 1984, 975-981, and the literature cited therein.

Den fluidtapsregulerende egenskap er også viktig i forbindelse med borevæsker. Borevæsker (særlig boreslam) er velkjente. Disse er fylte væsker som også må ha svært presise egenskaper når det gjelder reologi og densitet. Bortsett fra smøring av borkroneenden og bortføring av kaks til overflaten, så har boreslam en sentral funksjon av hydrostatisk natur, i særdeleshet med sikte på å hindre naturgass i å stige opp til overflaten, hvilket ville gi opphav til en katastrofal "utblåsing". The fluid loss regulating property is also important in connection with drilling fluids. Drilling fluids (especially drilling mud) are well known. These are filled liquids that must also have very precise properties in terms of rheology and density. Apart from lubricating the bit end and carrying cuttings to the surface, drilling mud has a central function of a hydrostatic nature, in particular with the aim of preventing natural gas from rising to the surface, which would give rise to a catastrophic "blowout".

Virkningen av det fluidtapsregulerende middel er å forsinke, forhindre eller i det minste begrense så mye som mulig fluidtap som kan forårsakes av bore-væsken under boreoperasjonen. Det er vanlig å anvende aminbehandlede lignitt- og asfalten-derivater som fluidtapsregulerende midler. Uheldigvis har disse materialer dårlig stabilitet ved høy temperatur og dårlig bestandighet mot skjærpåkjenning. The effect of the fluid loss control agent is to delay, prevent or at least limit as much as possible fluid loss that can be caused by the drilling fluid during the drilling operation. It is common to use amine-treated lignite and asphaltene derivatives as fluid loss control agents. Unfortunately, these materials have poor stability at high temperature and poor resistance to shear stress.

Sammenfatning av oppfinnelsen Summary of the Invention

Denne oppfinnelse er basert på den uventede erkjennelse at tverrbundne vinylaromat-akryl-polymerer kan anvendes som fluidtaps-additiver i boreslamblandinger. Ved å benytte tverrbundne vinylaromat-akryl-polymerer i boreslamblandinger, kan det oppnås kraftig forbedret høytemperaturstabilitet og forbedret skj ærbestandighet. This invention is based on the unexpected realization that cross-linked vinyl aromatic acrylic polymers can be used as fluid loss additives in drilling mud mixtures. By using cross-linked vinyl aromatic acrylic polymers in drilling mud mixtures, greatly improved high temperature stability and improved shear resistance can be achieved.

Med denne oppfinnelse tilveiebringes en boreslamblanding som er kjennetegnet ved at den omfatter (1) en organisk fase som inneholder som et fluidtapsreduserende middel, en tverrbundet vinylaromat-akryl-polymer hvor arkylmonomeren er valgt blant alkylakrylat, alkylmetakrylat og blandinger av disse, (2) minst ett fast fyllstoff, (3) en vannfase og (4) baritt. With this invention, a drilling mud mixture is provided which is characterized in that it comprises (1) an organic phase which contains, as a fluid loss reducing agent, a cross-linked vinyl aromatic acrylic polymer where the alkyl monomer is selected from among alkyl acrylate, alkyl methacrylate and mixtures thereof, (2) at least one solid filler, (3) an aqueous phase and (4) barite.

Med den foreliggende oppfinnelse tilveiebringes også anvendelse av en tverrbundet vinylaromat-akryl-polymer hvor akrylmonomeren er valgt blant alkylakrylat, alkylmetakrylat og blandinger av disse, som et fluidtapsreduserende middel i boreslamblandinger ifølge oppfinnelsen, og i boreslam i form av invertert emulsjon, hvor boreslammet i form av en invertert emulsjon er fritt for mineralolje og hovedsakelig fritt for sterkt hydrofile basiske materialer valgt blant alkalimetallhydroksider, og aminer valgt blant dietanolamin og trietanolamin, hvor boreslammet i form av en invertert emulsjon er særegent ved at det hovedsakelig består av (A) en kontinuerlig oljefase sammensatt hovedsakelig av minst én monokarboksylsyreester av en C2.\ 2-monokarboksylsyre som inneholder fra 12 til 16 karbonatomer og som er alifatisk mettet, (B) en dispergert vannfase, (C) minst én emulgator, (D) minst ett vektmiddel, (E) et fluidtapsadditiv, og (F) en svakt alkalisk alkalireservebestanddel bestående av kalk i en mengde som ikke overskrider ca. 4 gram pr. liter av boreslammet. The present invention also provides the use of a cross-linked vinyl aromatic acrylic polymer where the acrylic monomer is selected from among alkyl acrylate, alkyl methacrylate and mixtures thereof, as a fluid loss reducing agent in drilling mud mixtures according to the invention, and in drilling mud in the form of inverted emulsion, where the drilling mud in the form of an inverted emulsion is free of mineral oil and mainly free of strongly hydrophilic basic materials selected from alkali metal hydroxides, and amines selected from diethanolamine and triethanolamine, where the drilling mud in the form of an inverted emulsion is distinctive in that it mainly consists of (A) a continuous oil phase composed essentially of at least one monocarboxylic acid ester of a C2.\2-monocarboxylic acid containing from 12 to 16 carbon atoms and which is aliphatically saturated, (B) a dispersed aqueous phase, (C) at least one emulsifier, (D) at least one weighting agent, (E ) a fluid loss additive, and (F) a weakly alkaline alkali reserve component consisting of lime i an amount that does not exceed approx. 4 grams per liters of the drilling mud.

I slike boreslamblandinger i form av invertert emulsjon kan den tverrbundne vinylaromat-akryl-polymer virke både som fluidtapsadditiv og som et fortykningsmiddel. In such drilling mud mixtures in the form of inverted emulsion, the cross-linked vinyl aromatic acrylic polymer can act both as a fluid loss additive and as a thickening agent.

De tverrbundne vinylaromat-akryl-polymerene kan også anvendes i rene oljebaserte borslamformuleringer. The cross-linked vinyl aromatic acrylic polymers can also be used in pure oil-based drilling mud formulations.

Den tverrbundne vinylaromat-akryl-polymer er i små andeler svært effektiv som et fluidtapsregulerende additiv. Således er det konkurransedyktig med konvensjonelle aminbehandlede lignitt- og asfalten-derivater. Uten å ville være bundet til noen teori, antas at den tverrbundne aromatisk/akryl-polymer er effektiv fordi det mikrogelede produkt er godt disperget gjennom hele væsken. Det skal gjøres oppmerksom på at mikrogelen har en partikkelstørrelse som ligger innen området fra ca. 0,1 um til ca. 1 um. The cross-linked vinyl aromatic acrylic polymer is, in small proportions, very effective as a fluid loss control additive. Thus, it is competitive with conventional amine-treated lignite and asphaltene derivatives. Without wishing to be bound by any theory, it is believed that the crosslinked aromatic/acrylic polymer is effective because the microgelled product is well dispersed throughout the liquid. It should be noted that the microgel has a particle size that lies within the range from approx. 0.1 µm to approx. 1 µm.

Nærmere beskrivelse av oppfinnelsen Detailed description of the invention

De tverrbundne vinylaromat-akryl-polymerer som anvendes som fluidtapsadditiv i boreslamblandingen ifølge oppfinnelsen, er fremstilt ved emulsjonspolymerisasjon. Disse tverrbundne polymerer er typisk kopolymerer av minst én vinylaromatisk monomer og minst én akrylmonomer. En liten mengde av minst ett tverrbindingsmiddel, så som divinylbenzen eller etylenglykoldimetakrylat, vil også være innbefattet. Generelt kan det anvendes enhver vinylaromatisk monomer som vil polymerisere i friradikal-emulsjonssystemer. Slike vinylaromatiske monomerer inneholder typisk fra 8 til 20 karbonatomer. Vanligvis vil den vinylaromatiske monomer inneholde fra 8 til 14 karbonatomer. Noen representative eksempler på vinylaromatiske monomerer som kan benyttes, innbefatter styren, 1-vinylnaftalen, 2-vinylnaftalen, 3-metylstyren, 4-metylstyren, 4-propylstyren, t-butylstyren, 4-syklo-heksylstyren, 4-dodecylstyren, 2-etyl-4-benzylstyren, 4-(fenylbutyl)-styren og divinylbenzen. Styren og 4-metylstyren er vanligvis foretrukket som den vinylaromatiske monomer, med 4-vinylstyren som den mest foretrukne. The cross-linked vinyl aromatic acrylic polymers used as fluid loss additive in the drilling mud mixture according to the invention are produced by emulsion polymerization. These crosslinked polymers are typically copolymers of at least one vinyl aromatic monomer and at least one acrylic monomer. A small amount of at least one cross-linking agent, such as divinylbenzene or ethylene glycol dimethacrylate, will also be included. In general, any vinyl aromatic monomer that will polymerize in free radical emulsion systems can be used. Such vinyl aromatic monomers typically contain from 8 to 20 carbon atoms. Typically, the vinyl aromatic monomer will contain from 8 to 14 carbon atoms. Some representative examples of vinyl aromatic monomers that may be used include styrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 3-methylstyrene, 4-methylstyrene, 4-propylstyrene, t-butylstyrene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl -4-benzylstyrene, 4-(phenylbutyl)styrene and divinylbenzene. Styrene and 4-methylstyrene are usually preferred as the vinyl aromatic monomer, with 4-vinylstyrene being the most preferred.

Den anvendte akrylmonomer vil typisk være en alkylakrylatmonomer eller en alkylmetakrylatmonomer, eller en blanding av begge. Alkylakrylat-monomerene som kan anvendes, har generelt strukturformelen: The acrylic monomer used will typically be an alkyl acrylate monomer or an alkyl methacrylate monomer, or a mixture of both. The alkyl acrylate monomers that can be used generally have the structural formula:

hvor R representerer en alkylgruppe som inneholder fra 1 til 10 karbonatomer. Alkyl-gruppen i slike alkylakrylatmonomerer inneholder fortrinnsvis fra 2 til 8 karbonatomer, med alkylgrupper som inneholder 4 karbonatomer som de mest foretrukne. I henhold til dette er foretrukne alkylakrylatmonomerer etylakrylat, propylakrylat, butylakrylat, pentylakrylat, heksylakrylat og 2-etylheksylakrylat, med 2-etylheksylakrylat som den mest foretrukne. Alkylgruppene i slike alkylakrylatmonomerer kan være rettkjedede eller forgrenede. Således kan det benyttes normal-propylakrylat, isopropylakrylat, normal-butylakrylat eller tertiær-butylakrylat. En særlig foretrukket monomer er 2-etylheksylakrylat. Alkylmetakrylatmonomerene som kan anvendes, har vanligvis alkylgrupper som inneholder fra 1 til 20 karbonatomer. Alkylmetakrylat-monomeren vil fortrinnsvis ha en alkylgruppe som inneholder fra 2 til 12 karbonatomer. Noen representative eksempler på alkylmetakrylatmonomerer som kan anvendes, innbefatter metylmetakrylat, butylmetakrylat, 2-etylheksylmetakrylat, laurylmetakrylat og isobutylmetakrylat. where R represents an alkyl group containing from 1 to 10 carbon atoms. The alkyl group in such alkyl acrylate monomers preferably contains from 2 to 8 carbon atoms, with alkyl groups containing 4 carbon atoms being the most preferred. Accordingly, preferred alkyl acrylate monomers are ethyl acrylate, propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate and 2-ethylhexyl acrylate, with 2-ethylhexyl acrylate being the most preferred. The alkyl groups in such alkyl acrylate monomers can be straight-chain or branched. Thus, normal propyl acrylate, isopropyl acrylate, normal butyl acrylate or tertiary butyl acrylate can be used. A particularly preferred monomer is 2-ethylhexyl acrylate. The alkyl methacrylate monomers which can be used usually have alkyl groups containing from 1 to 20 carbon atoms. The alkyl methacrylate monomer will preferably have an alkyl group containing from 2 to 12 carbon atoms. Some representative examples of alkyl methacrylate monomers that may be used include methyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate and isobutyl methacrylate.

Den tverrbundne vinylaromat-akryl-polymer vil typisk inneholde repeterende enheter hvor inntil 99,99 vekt% er dannet av vinylaromatisk monomer, inntil 99,99 vekt% er dannet av akrylmonomer og fra 0,01 til 5 vekt% er dannet av tverrbindingsmiddel. Imidlertid er det vanligvis foretrukket at den tverrbundne vinylaromat-akryl-polymer inneholder minst noen repeterende enheter som er dannet av en vinylaromatisk monomer og noen repeterende enheter som er dannet av en akrylmonomer. Den tverrbundne vinylaromat-akryl-polymer vil fortrinnsvis inneholde repeterende enheter hvor 25-70 vekt% er dannet av den vinylaromatiske monomer, 25-70 vekt% av akrylmonomeren og 0,01-5 vekt% av tverrbindingsmidlet. En svært foretrukket tverrbundet vinylaromat-akryl-polymer omfatter repeterende enheter hvor 39,5-60 vekt% er dannet av den vinylaromatiske monomer, 39,5-60 vekt% av akrylmonomeren og 0,1-0,5 vekt% av tverrbindingsmidlet. The crosslinked vinyl aromatic acrylic polymer will typically contain repeating units where up to 99.99% by weight is formed by vinyl aromatic monomer, up to 99.99% by weight is formed by acrylic monomer and from 0.01 to 5% by weight is formed by crosslinking agent. However, it is generally preferred that the crosslinked vinyl aromatic acrylic polymer contains at least some repeating units formed from a vinyl aromatic monomer and some repeating units formed from an acrylic monomer. The crosslinked vinyl aromatic acrylic polymer will preferably contain repeating units where 25-70% by weight are formed by the vinyl aromatic monomer, 25-70% by weight of the acrylic monomer and 0.01-5% by weight of the crosslinking agent. A highly preferred crosslinked vinyl aromatic acrylic polymer comprises repeating units where 39.5-60% by weight is formed by the vinyl aromatic monomer, 39.5-60% by weight of the acrylic monomer and 0.1-0.5% by weight of the crosslinking agent.

De tverrbundne vinylaromat-akryl-polymerer kan ifølge oppfinnelsen anvendes som fluidtapsreduserende middel ved fremstilling av boreslamblandinger som omfatter (1) en organisk fase, hvor den organiske fase inneholder den tverrbundne vinylaromat-akryl-polymer som det fluidtapsreduserende middel, (2) minst ett fast fyllstoff, (3) en vannfase og (4) baritt. Den organiske fase i slike boreslamformuleringer vil typisk omfatte fra 85 til 98,5 vekt% av en olje, fra 1 til 10 vekt% av en emulgator og fra 0,5 til 5 vekt% av den tverrbundne vinylaromat-akryl-polymer. Den organiske fase i slike boreslamformuleringer vil mer typisk omfatte fra 90 til 96 vekt% av en olje, fra 3 til 7 vekt% av en emulgator og fra 1 til 3 vekt% av den tverrbundne vinylaromat-akryl-polymer. Oljen vil typisk være en esterolje, en parafinisk olje eller gassolje, eller en annen type olje. According to the invention, the cross-linked vinyl aromatic acrylic polymers can be used as a fluid loss reducing agent in the production of drilling mud mixtures comprising (1) an organic phase, where the organic phase contains the cross-linked vinyl aromatic acrylic polymer as the fluid loss reducing agent, (2) at least one solid filler, (3) an aqueous phase and (4) barite. The organic phase in such drilling mud formulations will typically comprise from 85 to 98.5% by weight of an oil, from 1 to 10% by weight of an emulsifier and from 0.5 to 5% by weight of the crosslinked vinyl aromatic acrylic polymer. The organic phase in such drilling mud formulations will more typically comprise from 90 to 96% by weight of an oil, from 3 to 7% by weight of an emulsifier and from 1 to 3% by weight of the crosslinked vinyl aromatic acrylic polymer. The oil will typically be an ester oil, a paraffinic oil or gas oil, or another type of oil.

Det faste fyllstoff vil typisk være en organoleire eller en blanding av en organoleire og kalsiumhydroksid. For eksempel er det vanligvis foretrukket å anvende som fast fyllstoff en blanding som inneholder fra 55 til 80 vekt% kalsiumhydroksid og fra 20 til 45 vekt% organoleire. Det er typisk mer foretrukket å anvende som fast fyllstoff en blanding som inneholder fra 65 til 70 vekt% kalsiumhydroksid og fra 30 til 35 vekt% organoleire. The solid filler will typically be an organoclay or a mixture of an organoclay and calcium hydroxide. For example, it is usually preferred to use as solid filler a mixture containing from 55 to 80% by weight calcium hydroxide and from 20 to 45% by weight organoclay. It is typically more preferred to use as solid filler a mixture containing from 65 to 70% by weight calcium hydroxide and from 30 to 35% by weight organoclay.

Vannfasen vil typisk være en saltlakeløsning som inneholder minst 10 vekt% av et uorganisk salt, så som kalsiumklorid. Det er foretrukket at vannfasen er en vandig oppløsning som inneholder fra 12 til 16 vekt% kalsiumklorid. The water phase will typically be a brine solution containing at least 10% by weight of an inorganic salt, such as calcium chloride. It is preferred that the water phase is an aqueous solution containing from 12 to 16% by weight of calcium chloride.

Boreslammet vil typisk inneholde fra 28 til 68 vekt% av den organiske fase, fra 0,25 til 2 vekt% av det faste fyllstoff, fra 10 til 30 vekt% av vannfasen og fra 20 til 40 vekt% baritt (BaS04). Fortrinnsvis inneholder boreslammet typisk fra 44 til 45 vekt% av den organiske fase, fra 0,5 til 1 vekt% av det faste fyllstoff, fra 14 til 20 vekt% av vannfasen og fra 30 til 35 vekt% baritt. The drilling mud will typically contain from 28 to 68% by weight of the organic phase, from 0.25 to 2% by weight of the solid filler, from 10 to 30% by weight of the water phase and from 20 to 40% by weight of barite (BaSO4). Preferably, the drilling mud typically contains from 44 to 45% by weight of the organic phase, from 0.5 to 1% by weight of the solid filler, from 14 to 20% by weight of the water phase and from 30 to 35% by weight of barite.

De tverrbundne vinylaromat-akrylat-polymerer anvendt ifølge denne oppfinnelsen, kan også anvendes ved fremstilling av esterolje-baserte boreslamformuleringer av typen beskrevet i patentskriftet US 5.252.554, og i boreslam i form av en invertert emulsjon som er fri for mineralolje og hovedsakelig fri for høyt hydrofile basiske materialer valgt blant alkalimetallhydroksider og aminer valgt blant dietanolamin og trietanolamin, bestående hovedsakelig av (A) en kontinuerlig oljefase sammensatt hovedsakelig av minst én monokarboksylsyreester av en C2.i2-monokar-boksylsyre inneholdende fra 12 til 16 karbonatomer og som er alifatisk mettet, (B) en dispergert, vandig fase, (C) minst én emulgator, (D) minst ett vektøkningsmiddel, (E) et fluidtaps-additiv og (F) en svakt alkalisk alkalireservebestanddel bestående av kalkstein i en mengde som ikke overskrider ca. 4 gram pr. liter av boreslammet. I slike boreslamblandinger i form av invertert emulsjon kan den tverrbundne vinylaromat-akryl-polymer virke både som fluidtapsadditiv og som et fortykningsmiddel. The cross-linked vinyl aromatic acrylate polymers used according to this invention can also be used in the production of ester oil-based drilling mud formulations of the type described in patent document US 5,252,554, and in drilling mud in the form of an inverted emulsion which is free of mineral oil and mainly free of highly hydrophilic basic materials selected from alkali metal hydroxides and amines selected from diethanolamine and triethanolamine, consisting essentially of (A) a continuous oil phase composed essentially of at least one monocarboxylic acid ester of a C2.i2 monocarboxylic acid containing from 12 to 16 carbon atoms and which is aliphatically saturated , (B) a dispersed, aqueous phase, (C) at least one emulsifier, (D) at least one weight increasing agent, (E) a fluid loss additive and (F) a weakly alkaline alkali reserve component consisting of limestone in an amount not exceeding approx. 4 grams per liters of the drilling mud. In such drilling mud mixtures in the form of inverted emulsion, the cross-linked vinyl aromatic acrylic polymer can act both as a fluid loss additive and as a thickening agent.

I slike ester-baserte boreslamformuleringer vil den svakt alkaliske alkalireservebestanddel fortrinnsvis inneholde fra 2 til 3,6 g/l med kalk. Det er også foretrukket at monokarboksylsyren i bestanddel (A) er fremstilt av kokosnøttolje, palmeolje eller babussuolje. Den dispergerte vandige fase vil typisk inneholde kalsiumklorid og/eller kaliumklorid som et oppløst salt, og den vandige fase vil være til stede i boreslamformuleringen i en mengde fra 5 til 45 vekt%. Slike boreslamformuleringer vil fortrinnsvis inneholde fra 5 til 25 vekt% av den dispergerte vandige fase. Minst én monokarboksylsyreester i bestanddel (A) vil typisk ha et hellepunkt under ca. -10 °C og et flammepunkt over ca. 100 °C. Minst én monokarboksylsyreester i bestanddel (A) vil fortrinnsvis ha et hellepunkt under ca. -15 °C og et flammepunkt over ca. 160 °C. In such ester-based drilling mud formulations, the weakly alkaline alkali reserve component will preferably contain from 2 to 3.6 g/l of lime. It is also preferred that the monocarboxylic acid in component (A) is produced from coconut oil, palm oil or babussu oil. The dispersed aqueous phase will typically contain calcium chloride and/or potassium chloride as a dissolved salt, and the aqueous phase will be present in the drilling mud formulation in an amount from 5 to 45% by weight. Such drilling mud formulations will preferably contain from 5 to 25% by weight of the dispersed aqueous phase. At least one monocarboxylic acid ester in component (A) will typically have a pour point below approx. -10 °C and a flash point above approx. 100 °C. At least one monocarboxylic acid ester in component (A) will preferably have a pour point below approx. -15 °C and a flash point above approx. 160 °C.

Denne oppfinnelse er belyst med følgende eksempler som er tatt med i den hensikt å belyse oppfinnelsen. Så sant annet ikke er spesifikt angitt, er alle deler og prosenter basert på vekt. This invention is illustrated with the following examples which have been included for the purpose of illustrating the invention. Unless otherwise specifically stated, all parts and percentages are by weight.

Eksempler 1- 6 Examples 1-6

I dette forsøk ble en serie boreslamformuleringer fremstilt ved å anvende forskjellige tverrbundne vinylaromat-akryl-polymerer. Eksempel 1 ble utført som et sammenligningsforsøk ved at ikke noe fluidtapsadditiv var tilsatt. I eksempel 2 ble det som fluidtapsadditiv benyttet polymeren "Pliolite AC-5" (2-propensyre, 2-metyl-, 2-metylpropylester, polymer med etenylbenzen og 2-etylheksyl-2-propenoat). I eksempel 3 ble det som fluidtapsadditiv benyttet polymeren "Pliolite AC3H" (2-propensyre, 2-etylheksylester, polymer med l-etenyl-3-metylbenzen og l-etenyl-4-metyl-benzen). 1 eksempel 4 ble det som fluidtapsadditiv benyttet polymeren "Plioway ECT" In this experiment, a series of drilling mud formulations were prepared using different crosslinked vinyl aromatic acrylic polymers. Example 1 was carried out as a comparative trial in that no fluid loss additive was added. In example 2, the polymer "Pliolite AC-5" (2-propenoic acid, 2-methyl-, 2-methylpropyl ester, polymer with ethenylbenzene and 2-ethylhexyl-2-propenoate) was used as fluid loss additive. In example 3, the polymer "Pliolite AC3H" (2-propenoic acid, 2-ethylhexyl ester, polymer with l-ethenyl-3-methylbenzene and l-ethenyl-4-methylbenzene) was used as fluid loss additive. 1 example 4, the polymer "Plioway ECT" was used as fluid loss additive

(2-propensyre, 2-metyl-, 1,2-etandiylester, polymer med l-etenyl-4-metylbenzen, 2-etylheksyl-2-propenoat og 2-metylpropyl-2-metyl-2-propenoat). I eksempel 5 ble det (2-propenoic acid, 2-methyl-, 1,2-ethanediyl ester, polymer with 1-ethenyl-4-methylbenzene, 2-ethylhexyl-2-propenoate and 2-methylpropyl-2-methyl-2-propenoate). In example 5 it became

som fluidtapsadditiv benyttet polymeren "Plioway Ultra G20" (2-propensyre, 2-metyl-, 1,2-etandiylester, polymer med l-(l,l-dimetyletyl)-4-etenyl-benzen, l-etenyl-4-metyl-benzen, 2-etylheksyl-2-propenoat og 2-metylpropyl-2-metyl-2-propenoat). Eksempel 6 ble også utført som et sammenligningsforsøk ved å anvende som fluidtapsadditiv et as fluid loss additive used the polymer "Plioway Ultra G20" (2-propenoic acid, 2-methyl-, 1,2-ethanediyl ester, polymer with 1-(1,1-dimethylethyl)-4-ethenyl-benzene, 1-ethenyl-4-methyl -benzene, 2-ethylhexyl-2-propenoate and 2-methylpropyl-2-methyl-2-propenoate). Example 6 was also carried out as a comparison experiment by using as fluid loss additive et

konvensjonelt, aminbehandlet lignitt. conventional, amine-treated lignite.

Boreslamformuleringene ble tilberedt ved å fremstille en organisk fase som inneholdt 190 g esterolje, 10 g emulgator og 4,2 g av fluidkontrolladditivet. Faste fyllstoffer ble fremstilt ved å blande 2 g kalsiumhydroksid og 1 g organoleire. Den benyttede vannfase var en 14% vandig oppløsning av kalsiumklorid. Boreslamformuleringer ble fremstilt ved å blande 204,2 g av de organiske faser, 3 g av de faste fyllstoffer, 71 g av vannfasene og 138 g baritt. The drilling mud formulations were prepared by preparing an organic phase containing 190 g of ester oil, 10 g of emulsifier and 4.2 g of the fluid control additive. Solid fillers were prepared by mixing 2 g of calcium hydroxide and 1 g of organoclay. The water phase used was a 14% aqueous solution of calcium chloride. Drilling mud formulations were prepared by mixing 204.2 g of the organic phases, 3 g of the solid fillers, 71 g of the aqueous phases and 138 g of barite.

Boreslammenes fluidtapsegenskaper ble deretter bestemt ved 120 °C ved å benytte den standardiserte HTHP/API- filtreringsmetoden. Boreslammene ble varmrullet ved 120 °C i 16 timer for å bestemme fluidtap etter aldring. Boreslamformuleringenes fluidtapskarakteristika før (opprinnelig) og etter aldring er rapportert i tabell 1. The fluid loss characteristics of the drilling muds were then determined at 120 °C using the standardized HTHP/API filtration method. The drilling muds were hot rolled at 120°C for 16 hours to determine fluid loss after ageing. The fluid loss characteristics of the drilling mud formulations before (initial) and after aging are reported in Table 1.

Som det kan ses av tabell 1, så hadde boreslamformuleringene fremstilt ved å anvende tverrbundet vinylaromat-akryl-polymerer som fluidtapsadditiver (eksempler 2-5) mye bedre fluidtapsegenskaper etter aldring enn begge sammen-ligningsprøver (eksempler 1 og 6). Før aldring var fluidtapsegenskapene sammenlign-bare med, eller bedre enn, boreslammet fremstilt ved å anvende det aminbehandlede lignitt, og mye bedre enn sammenligningsprøven fremstilt uten å anvende noe fluidtapsadditiv. Dette eksempel viser således at de tverrbundne vinylaromat-akryl-polymerer virker meget bra som fluidtapsadditiver i boreslamformuleringer. As can be seen from Table 1, the drilling mud formulations prepared using cross-linked vinyl aromatic acrylic polymers as fluid loss additives (Examples 2-5) had much better fluid loss properties after aging than both comparative samples (Examples 1 and 6). Before aging, the fluid loss properties were comparable to, or better than, the drilling mud prepared using the amine-treated lignite, and much better than the control sample prepared without using any fluid loss additive. This example thus shows that the cross-linked vinyl aromatic acrylic polymers work very well as fluid loss additives in drilling mud formulations.

Eksempler 7- 12 Examples 7-12

I dette forsøk ble en serie boreslamformuleringer fremstilt ved å anvende forskjellige tverrbundne vinylaromat-akryl-polymerer. Eksempel 7 ble utført som et sammenligningsforsøk ved at ikke noe fluidtapsadditiv var tilsatt. I eksempel 8 ble det som fluidtapsadditiv benyttet polymeren "Pliolite AC-5" (2-propensyre, 2-metyl-, 2-metylpropylester, polymer med etenylbenzen og 2-etylheksyl-2-propenoat). I eksempel 9 ble det som fluidtapsadditiv benyttet polymeren "Pliolite AC3H" (2-propensyre, 2-etylheksylester, polymer med l-etenyl-3-metylbenzen og l-etenyl-4-metylbenzen). I eksempel 10 ble det som fluidtapsadditiv benyttet polymeren "Plioway ECT" (2-propensyre, 2-metyl-, 1,2-etandiylester, polymer med l-etenyl-4-metyl-benzen, 2-etylheksyl-2-propenoat og 2-metylpropyl-2-metyl-2-propenoat). I eksempel 11 ble det som fluidtapsadditiv benyttet polymeren "Plioway Ultra G20" (2-propensyre, 2-metyl-, 1,2-etandiylester, polymer med l-(l,l-dimetyletyl)-4-etenyl-benzen, l-etenyl-4-metylbenzen, 2-etylheksyl-2-propenoat og 2-metylpropyl-2-metyl-2-propenoat). Eksempel 12 ble også utført som et sammenligningsforsøk ved å anvende som fluidtapsadditiv et konvensjonelt aminbehandlet lignitt. In this experiment, a series of drilling mud formulations were prepared using different crosslinked vinyl aromatic acrylic polymers. Example 7 was carried out as a comparative test in that no fluid loss additive was added. In example 8, the polymer "Pliolite AC-5" (2-propenoic acid, 2-methyl-, 2-methylpropyl ester, polymer with ethenylbenzene and 2-ethylhexyl-2-propenoate) was used as fluid loss additive. In example 9, the polymer "Pliolite AC3H" (2-propenoic acid, 2-ethylhexyl ester, polymer with l-ethenyl-3-methylbenzene and l-ethenyl-4-methylbenzene) was used as fluid loss additive. In example 10, the polymer "Plioway ECT" (2-propenoic acid, 2-methyl-, 1,2-ethanediyl ester, polymer with 1-ethenyl-4-methyl-benzene, 2-ethylhexyl-2-propenoate and 2 -methylpropyl-2-methyl-2-propenoate). In example 11, the polymer "Plioway Ultra G20" (2-propenoic acid, 2-methyl-, 1,2-ethanediyl ester, polymer with l-(1,1-dimethylethyl)-4-ethenyl-benzene, l- ethenyl-4-methylbenzene, 2-ethylhexyl-2-propenoate and 2-methylpropyl-2-methyl-2-propenoate). Example 12 was also carried out as a comparison experiment by using as fluid loss additive a conventional amine-treated lignite.

Boreslamformuleringene ble tilberedt ved å fremstille en organisk fase som inneholdt 184 g isomeriserte a-olefiner, 7,4 g emulgator og 4,2 g av fluidkontrolladditivet. Faste fyllstoffer ble fremstilt ved å blande 2 g kalsiumhydroksid og 2 g organoleire. Den benyttede vannfase var en 14 % vandig oppløsning av kalsiumklorid. Boreslamformuleringer ble fremstilt ved å blande 195,6 g av de organiske faser, 4 g av de faste fyllstoffer, 81 g av vannfasene og 138 g baritt. The drilling mud formulations were prepared by preparing an organic phase containing 184 g of isomerized α-olefins, 7.4 g of emulsifier and 4.2 g of the fluid control additive. Solid fillers were prepared by mixing 2 g of calcium hydroxide and 2 g of organoclay. The water phase used was a 14% aqueous solution of calcium chloride. Drilling mud formulations were prepared by mixing 195.6 g of the organic phases, 4 g of the solid fillers, 81 g of the aqueous phases and 138 g of barite.

Boreslammenes fluidtapsegenskaper ble deretter bestemt ved 150 °C ved å benytte den standardiserte HTHP/API- filtreringsmetoden. Boreslammene ble varmrullet ved 150 °C i 16 timer for å bestemme fluidtap etter aldring. Boreslamformuleringenes fluidtapskarakteristika før (opprinnelig) og etter aldring, er rapportert i tabell 2. The fluid loss characteristics of the drilling muds were then determined at 150 °C using the standardized HTHP/API filtration method. The drilling muds were hot rolled at 150°C for 16 hours to determine fluid loss after ageing. The fluid loss characteristics of the drilling mud formulations before (initial) and after ageing, are reported in Table 2.

Som det kan ses av tabell 2, så hadde boreslamformuleringene fremstilt ved å anvende tverrbundet vinylaromat-akryl-polymerer som fluidtapsadditiver (eksempler 8-11) mye bedre fluidtapsegenskaper etter aldring enn begge sammen-ligningsprøver (eksempler 7 og 12). Dette eksempel viser således at de tverrbundne vinylaromat-akryl-polymerer virker meget bra som fluidtapsadditiver i boreslamformuleringer. As can be seen from Table 2, the drilling mud formulations prepared using cross-linked vinyl aromatic acrylic polymers as fluid loss additives (Examples 8-11) had much better fluid loss properties after aging than both comparative samples (Examples 7 and 12). This example thus shows that the cross-linked vinyl aromatic acrylic polymers work very well as fluid loss additives in drilling mud formulations.

Claims

1. Drilling mud mixture, characterized in that it includes

(1) an organic phase containing as a fluid loss reducing agent, a cross-linked vinyl aromatic acrylic polymer where the alkyl monomer is selected from alkyl acrylate, alkyl methacrylate and mixtures thereof, (2) at least one solid filler, (3) an aqueous phase and (4) barite.

2. Drilling mud mixture according to claim 1, where it comprises from 28 to 68% by weight of the organic phase, from 0.25 to 2% by weight of the solid filler, from 10 to 30% by weight of the water phase and from 20 to 40% by weight of barite .

3. Drilling mud mixture according to claim 2, where the organic phase comprises from 85 to 98.5% by weight of an ester oil, from 1 to 10% by weight of an emulsifier and from 0.5 to 5% by weight of crosslinked vinyl aromatic acrylic polymer.

4. Drilling mud mixture according to claim 3, where the water phase is a salt solution containing an inorganic salt.

5. Drilling mud mixture according to claim 4, where the water phase contains at least 10% by weight of an inorganic salt.

6. Drilling mud mixture according to claim 5, where the inorganic salt is calcium chloride.

7. Drilling mud mixture according to claim 1, where the cross-linked vinyl aromatic acrylic polymer is 2-propenoic acid 2-methyl-2-methylpropyl ester, polymer with ethenylbenzene and 2-ethylhexyl-2-propenoate.

8. Drilling mud mixture according to claim 1, where the cross-linked vinyl aromatic acrylic polymer is 2-propenoic acid, 2-ethylhexyl ester, polymer with 1-ethenyl-3-methylbenzene and 1-ethenyl-4-methylbenzene.

9. Drilling mud mixture according to claim 1, where the cross-linked vinyl aromatic acrylic polymer is 2-propenoic acid, 2-methyl-, 1,2-ethanediyl ester, polymer with 1-ethenyl-4-methyl-benzene, 2-ethylhexyl-2-propenoate and 2-methylpropyl-2-methyl-2-propenoate.

10. Drilling mud mixture according to claim 1, where the cross-linked vinyl aromatic acrylic polymer is 2-propenoic acid, 2-methyl-1,2-ethanediyl ester, polymer with l-(1,1-dimethylethyl)-4-ethenyl-benzene, l- ethenyl-4-methylbenzene, 2-ethylhexyl-2-propenoate and 2-methylpropyl-2-methyl-2-propenoate.

11. Drilling mud mixture according to claim 1, where the cross-linked vinylaromatic-acrylic polymer comprises repeating units of which from 0 to 99.99% by weight are formed of vinylaromatic monomer, from 0 to 99.99% by weight of an acrylic monomer and from 0.01 to 5% by weight of a cross-linking agent.

12. Drilling mud mixture according to claim 1, where the crosslinked vinylaromatic-acrylic polymer comprises repeating units of which from 25 to 70% by weight are formed of vinylaromatic monomer, from 25 to 70% by weight of an acrylic monomer and from 0.01 to 5% by weight of a cross-linking agent.

13. Drilling mud mixture according to claim 1, wherein the crosslinked vinylaromatic-acrylic polymer comprises repeating units of which from 39.5 to 60% by weight are formed by vinylaromatic monomer, from 39.5 to 60% by weight of an acrylic monomer and from 0.1 to 5% by weight of a cross-linking agent.

14. Drilling mud mixture according to claim 13, where the vinyl aromatic monomer is styrene.

15. Drilling mud mixture according to claim 13, where the cross-linking agent is divinylbenzene.

16. Drilling mud mixture according to claim 13, where the cross-linking agent is ethylene glycol dimethacrylate.

17. Drilling mud mixture according to claim 1, where the organic phase contains an ester oil.

18. Drilling mud mixture according to claim 1, where the organic phase contains an isomerized α-olefin.

19. Use of a cross-linked vinyl aromatic acrylic polymer where the acrylic monomer is selected from among alkyl acrylate, alkyl methacrylate and mixtures thereof, as a fluid loss reducing agent in drilling mud mixtures according to claims 1-18, and in drilling mud in the form of inverted emulsion, where the drilling mud in the form of an inverted emulsion is free of mineral oil and mainly free of strongly hydrophilic basic materials selected from alkali metal hydroxides, and amines selected from diethanolamine and triethanolamine, where the drilling mud in the form of an inverted emulsion is characterized by the fact that it mainly consists of (A) a continuous oil phase composed of essentially of at least one monocarboxylic acid ester of a C2-12 monocarboxylic acid containing from 12 to 16 carbon atoms and which is aliphatically saturated, (B) a dispersed aqueous phase, (C) at least one emulsifier, (D) at least one weighting agent, (E) a fluid loss additive , and (F) a weakly alkaline alkali reserve component consisting of lime in an amount not exceeding approx. 4 grams per liters of the drilling mud.