Rheological agent, preparation methods and uses thereof

Abstract

The present invention relates to a method to prepare a rheological agent comprising the polymerization of the following monomers: (a) at least one styrene-based monomer, (b) at least one (meth)acrylate-based monomer or butadiene, and (c) optionally a copolymerisable surfactant containing an optionally substituted vinyl function and moieties derived from propylene oxide and/or ethylene oxide, optionally in the presence of a non polymerisable surfactant containing moieties derived from propylene oxide and/or ethylene oxide, and optionally in the presence of another surfactant, wherein at least the copolymerisable surfactant or the non polymerisable surfactant is present during the said polymerization, as well as a rheological agent obtainable by said method, an oil-based drilling fluid containing such a rheological agent, the use of such a rheological agent as a thixotropic agent in an oil-based drilling fluid and a method of drilling using an oil-based drilling fluid containing such a rheological agent.

Claims

1. An oil-based drilling fluid comprising a rheological agent, said rheological agent being obtained by a polymerization of monomers to form the rheological agent, the monomers consisting of: (a) styrene-based monomer(s) substituted on the phenyl moiety, wherein the styrene-based monomer(s) is chosen among meta-methyl-styrene, para-methyl-styrene, para-propyl-styrene, para-tert-butyl-styrene, para-cyclohexyl-styrene, para-dodecyl-styrene, 2-ethyl-4-benzyl-styrene, para-(phenylbutyl)-styrene, divinylbenzene and mixtures thereof, (b) optionally (meth)acrylate-based monomer(s) or butadiene, wherein the (meth)acrylate-based monomer(s) is chosen among ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, tert-butyl acrylate, pentyl acrylate, hexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, isobornyl methacrylate, isobornyl acrylate and mixtures thereof, (c) a copolymerisable surfactant having the following formula:
CHR′═CRL-(O—CHR.sup.7n—CHR.sup.8n).sub.n—X.sup.1 wherein: L represents a single bond or a linker, R and R′ represent, independently of each other, H or a (C.sub.1-C.sub.25)alkyl, n represents an integer of at least 1, each R.sup.7n and each R.sup.8n represent, independently of each other, a hydrogen atom or a methyl group but R.sup.7n and R.sup.8n cannot both represent a methyl group, and X.sup.1 represents an —O-(optionally substituted aryl), —O(C.sub.1-C.sub.25)alkyl, —O—(C.sub.1-C.sub.6)alkanediyl-SO.sub.3H, —OH, —S(O).sub.2(OH), —O—P(O)(OH).sub.2 group, or a salt thereof, and (d) optionally a crosslinking agent, said polymerization being performed in the presence of a non polymerisable surfactant, the non polymerisable surfactant has the following formula:
X.sup.3—(OCH.sub.2CH.sub.2).sub.q—X.sup.2 wherein: q represents an integer comprised between 1 and 60, X.sup.3 represents a (C.sub.8-C.sub.25)alkyl chain or an aryl optionally substituted with a (C.sub.1-C.sub.25)alkyl, and X.sup.2 represents an —OH, —S(O).sub.2(OH), —O—P(O)(OH).sub.2 or —O—S(O).sub.2(OH) group, or a salt thereof, and optionally in the presence of another surfactant.

2. The oil based drilling fluid according to claim 1, wherein the copolymerisable surfactant is chosen among anionic and non-ionic surfactants.

3. The oil based drilling fluid according to claim 1, wherein the styrene-based monomer(s) is chosen among para-tert-butyl-styrene (PTBS), para-methyl-styrene (PMS) and mixtures thereof.

4. The oil based drilling fluid according to claim 1, wherein monomer (b) is (meth)acrylate-based monomer(s) chosen among isobornyl methacrylate (IBOMA), isobornyl acrylate (IBOA), isobutyl methacrylate (IBMA), 2-ethylhexyl acrylate (2-EHA) and mixtures thereof.

5. The oil based drilling fluid according to claim 1, wherein the ratio by weight of monomer (a) to monomer (b) is comprised between 100:0 and 10:90.

6. The oil based drilling fluid according to claim 5, wherein the ratio by weight of monomer (a) to monomer (b) is comprised between 100:0 and 70:30.

7. The oil based drilling fluid according to claim 1, wherein: R and R′ represent, independently of each other, H or a (C.sub.1-C.sub.6)alkyl, and n represents an integer comprised between 3 and 120.

8. The oil based drilling fluid according to claim 1, wherein: X.sup.1 represents an —O-(optionally substituted aryl), —O(C.sub.1-C.sub.25)alkyl, —O—(C.sub.1-C.sub.6)alkanediyl-SO.sub.3H, —OH, —S(O).sub.2(OH), —O—P(O)(OH).sub.2 or —O—S(O).sub.2(OH) group, or a sodium, potassium or ammonium salt thereof, R and R′ represent, independently of each other, H, and n represents an integer comprised between 5 and 40.

9. The oil-based drilling fluid according to claim 1, wherein X.sup.1 represents an —O-(optionally substituted aryl), —O(C.sub.1-C.sub.25)alkyl, —O—(C.sub.1-C.sub.6)alkanediyl-SO.sub.3H, —OH, —S(O).sub.2(OH), —O—P(O)(OH).sub.2 or —O—S(O).sub.2(OH) group, or a sodium, potassium or ammonium salt thereof.

10. The oil based frilling fluid according to claim 1, wherein q represents an integer comprised between 3 and 20, and wherein X.sup.2 represents an —OH, —S(O).sub.2(OH), —O—P(O)(OH).sub.2 or —O—S(O).sub.2(OH) group, or a sodium, potassium or ammonium salt thereof.

11. The oil based drilling fluid according to claim 1, wherein the polymerization is carried out in the presence of a crosslinking agent.

12. The oil based drilling fluid according to claim 1, using 0.5 to 10 wt % relatively to the total weight of the rheological agent on a dry basis of the combination of the copolymerisable surfactant and the non polymerisable surfactant.

13. The oil based drilling fluid according to claim 10, wherein the oil-based drilling fluid contains 0.1 to 10 ppb (0.285 to 28.5 kg/m.sup.3) of the rheological agent.

Description

EXAMPLES

(1) I. Preparation of the Rheological Agent

(2) The rheological agents according to the invention have been prepared by emulsion polymerization of monomers (a) and (b) (if present) and copolymerisable and/or non polymerisable surfactants, optionally in the presence of a crosslinking agent such as divinyl benzene. The monomer(s) and surfactant(s) used are as follows:

(3) TABLE-US-00003 Copolymerisable Non polymerisable N° Monomers (a) and optionally (b) surfactant surfactant  1* PTBS/IBOMA in wt ratio 75/25 — Dowfax ® 2A1**  2 PTBS/IBOMA in wt ratio 75/25 — Emulsogen ® EPA 073  3 PTBS/IBOMA in wt ratio 75/25 Emulsogen ® APS 100 Emulsogen ® EPA 073  4 PTBS/IBOMA in wt ratio 75/25 Reasoap ® ER-10 Emulsogen ® EPA 073  5 PTBS/IBOMA in wt ratio 75/25 Reasoap ® SR-10 Emulsogen ® EPA 073  6 PTBS/IBOMA in wt ratio 75/25 Reasoap ® SR-20 Emulsogen ® EPA 073  7 PTBS/IBOMA in wt ratio 75/25 Reasoap ® PP-70 Emulsogen ® EPA 073  8 PTBS/IBOMA in wt ratio 75/25 Emulsogen ® APS 100 Empicol ® LX 28/D***  9 PTBS/IBOMA in wt ratio 75/25 Emulsogen ® APS 100 Emulsogen ® LA 083 10 PTBS/IBOMA in wt ratio 75/25 Emulsogen ® APS 100 Rhodafac ® RS-610 A25 11 PTBS/IBOMA in wt ratio 75/25 Emulsogen ® APS 100 Disponil ® FES 993 12 PTBS/IBOMA in wt ratio 75/25 Reasoap ® SR-10 — Reasoap ® PP-70 13 PTBS/IBOMA in wt ratio 50/50 Emulsogen ® APS 100 Emulsogen ® EPA 073 14 PTBS/PMS in wt ratio 50/50 Emulsogen ® APS 100 Emulsogen ® EPA 073 15 PTBS Emulsogen ® APS 100 Emulsogen ® EPA 073 16 PTBS/IBOA in wt ratio 75/25 Emulsogen ® APS 100 Emulsogen ® EPA 073 *Comparative example **Alkyldiphenyloxide disulfonate (it is not a non polymerisable surfactant according to the invention) ***Sodium dodecyl sulfate (it is not a non polymerisable surfactant according to the invention) All these examples contain about 4 wt % of surfactant on a dry basis. The rheological agents were obtained in a latex form and were used in this form in the preparation of oil-based drilling fluids but could be used in a powder form. 10
II. Preparation of the Oil-Based Drilling Fluid The rheological agents prepared in previous example I have then been added to the following composition A, which was then hot rolled 16 h at 300° F. (149° C.), to give the oil-based drilling fluids according to the invention.

(4) TABLE-US-00004 Ingredient Activity Composition A Synthetic isomerized olefin Oil phase 137 ppb Polyaminated fatty acid Emulsifier  10 ppb Pliolite ® DF Filtration control agent  2 ppb Lime (Ca(OH).sub.2) Alkalinity modulator  1 ppb 25% CaCl.sub.2 brine Aqueous phase  62 ppb Finely ground altered calcium Artificial drill solids  20 ppb montmorillonite clay Barite Weighting agent 440 ppb
III. Thixotropic Effect The rheological profiles of the various oil-based drilling fluids tested in this part have been determined according to the API (American petroleum Institute) 13A norm. The rheological agents according to the invention have been compared with an organoclay and the comparative rheological agent 1, when added to the above-mentioned oil-based drilling fluid composition A. The following abbreviations have been used in this part: ES@RTC: Electrical Stability at Room temperature H.R.: Hot Rolling HTHP: High temperature High Pressure (mL) PV: Plastic Viscosity (cP) YP: Yield Point (lb/100 ft.sup.2) The results obtained are presented in the tables below:

(5) TABLE-US-00005 TABLE 1 Comparison of rheological agent 2 according to the invention with organoclay and comparative rheological agent 1 optionally with Emulsogen ® EPA 073 A + 1.0 A + 0.44 ppb* ppb A + 0.44 of 1 + A + 0.35 Drilling fluid organoclay ppb* of 1 EPA073** ppb* of 2 Before ageing Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 76 76 75 88 300 rpm 44 44 43 52 200 rpm 33 33 32 40 100 rpm 22 21 21 26  6 rpm 7 6 6 10  3 rpm 6 5 5 9 Plastic viscosity (cP) 32 32 32 36 Yield point (lb/100 ft.sup.2) 12 12 11 16 After ageing 16 hrs at 300° F. (149° C.) Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 110 90 90 108 300 rpm 66 50 49 61 200 rpm 49 35 35 45 100 rpm 32 21 21 28  6 rpm 11 5 5 7  3 rpm 10 4.5 4 6 Plastic viscosity (cP) 44 40 41 47 Yield point (lb/100 ft.sup.2) 22 10 8 14 HTHP at 300° F. 24.0 26.0 26.0 19.2 (149° C.)/500 psi/2 × vol 30′ (ml) *on a dry basis of the rheological agent which is introduced in a latex form **in the same amount as in rheological agent 2 These results demonstrate the importance to introduce the non polymerisable surfactant with monomers (a) and optionally (b) during the emulsion polymerization step and not after this step to obtain an improved rheological agent.

(6) TABLE-US-00006 TABLE 2 Thixotropic effects obtained with rheological agents 3, 8 and 12 according to the invention A + A + A + Drilling fluid 1 ppb* of 3 1 ppb* of 8 1 ppb* of 12 Before ageing Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 124 127 138 300 rpm 78 84 92 200 rpm 60 66 72 100 rpm 42 48 50  6 rpm 21 28 21  3 rpm 19 26 19 Plastic viscosity (cP) 46 43 46 Yield point (lb/100 ft.sup.2) 32 41 36 After ageing 16 hrs at 300° F. (149° C.) Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 159 176 152 300 rpm 105 122 101 200 rpm 84 101 80 100 rpm 59 75 56  6 rpm 24 30 23  3 rpm 21 26 21 Plastic viscosity (cP) 54 54 51 Yield point (lb/100 ft.sup.2) 51 68 50 *on a dry basis of the rheological agent which is introduced in a latex form

(7) TABLE-US-00007 TABLE 3 Thixotropic effects obtained with rheological agents 3, 4 and 6 according to the invention A + A + A + Drilling fluid 0.39 ppb* of 3 0.39 ppb* of 4 0.39 ppb* of 6 Before ageing Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 95 100 103 300 rpm 58 62 64 200 rpm 44 49 50 100 rpm 30 34 34  6 rpm 13 13 13  3 rpm 12 12 12 Plastic viscosity (cP) 37 38 39 Yield point (lb/100 ft.sup.2) 21 24 25 After ageing 16 hrs at 300° F. (149° C.) Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 114 109 123 300 rpm 68 66 74 200 rpm 50 50 54 100 rpm 30 32 34  6 rpm 10 10 11  3 rpm 8 9 9 Plastic viscosity (cP) 46 43 49 Yield point (lb/100 ft.sup.2) 22 23 25 *on a dry basis of the rheological agent which is introduced in a latex form The results shown on tables 2 and 3 demonstrate that a large variety of copolymerisable and non polymerisable surfactants can be used in the rheological agents according to the invention and that other surfactants can also be present.

(8) TABLE-US-00008 TABLE 4 Thixotropic effects obtained with rheological agents 13, 3 and 15 according to the invention A + A + A + Drilling fluid 0.39 ppb* of 13 0.39 ppb* of 3 0.39 ppb* of 15 Before ageing Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 97 95 82 300 rpm 59 58 48 200 rpm 45 44 36 100 rpm 31 30 25  6 rpm 13 13 10  3 rpm 12 12 8.5 Plastic viscosity (cP) 38 37 34 Yield point (lb/100 ft.sup.2) 21 21 14 After ageing 16 hrs at 300° F. (149° C.) Fann ® 35 dial readings at 122° F. (50° C.) (cP) 600 rpm 115 114 101 300 rpm 68 68 56 200 rpm 50 50 40 100 rpm 32 30 24  6 rpm 10 10 6  3 rpm 8 8 5 Plastic viscosity (cP) 47 46 45 Yield point (lb/100 ft.sup.2) 21 22 11 *on a dry basis of the rheological agent which is introduced in a latex form