Rheology modifier for drilling and well treatment fluids

Abstract

Water in oil emulsion drilling and well treatment fluids comprising an ester of trimer fatty acids and polyoxyethyiene glycol, the polyoxyethyiene glycol having average molecular weight from about (150) to about (600) and the trimer acids having at least about 20% of carboxyl acid groups esterified, as rheology modifier.

Claims

1. A method for drilling or completing an oil or natural gas well employing a water in oil drilling fluid comprising introducing the water in oil drilling fluid into a well bore wherein the water in oil drilling fluid comprises: a continuous oil phase, an aqueous internal phase, and an ester of trimer fatty acids and polyoxyethylene glycol, and wherein the polyoxyethylene glycol has an average molecular weight from about 150 to about 600 and the trimer acids comprise at least about 20% of carboxyl acid groups esterified; and drilling or completing the oil or gas well.

2. The method for drilling or completing an oil or natural gas well of claim 1 wherein the ester is present at a concentration of from about 0.1 to about 10% by weight, based on the total weight of the fluid.

3. The method for drilling or completing an oil or natural gas well of claim 2 wherein the ester of trimer fatty acids and polyoxyethylene glycol has an average molecular weight from about 150 to about 250.

4. The method for drilling or completing an oil or natural gas well of claim 2 wherein the trimer acids have from about 25% to about 50% of carboxyl acid groups esterified.

5. The method for drilling or completing an oil or natural gas well of claim 1 wherein the water in oil drilling fluid comprises from about 50 to about 98% by weight of continuous oil phase and from 2 to 50% of internal aqueous phase.

6. A method for treating an oil or natural gas well employing a water in oil treatment fluid comprising introducing the water in oil treatment fluid into a well bore wherein the water in oil treatment fluid comprises: a continuous oil phase, an aqueous internal phase, and an ester of trimer fatty acids and polyoxyethylene glycol, and wherein the polyoxyethylene glycol has an average molecular weight from about 150 to about 600 and the trimer acids comprise at least about 20% of carboxyl acid groups esterified.

7. The method for treating an oil or natural gas well of claim 6 wherein the ester is present at a concentration of from about 0.1 to about 10% by weight, based on the total weight of the fluid.

8. The method for treating an oil or natural gas well of claim 7 wherein the ester of trimer fatty acids and polyoxyethylene glycol has an average molecular weight from about 150 to about 250.

9. The method for treating an oil or natural gas well of claim 7 wherein the trimer acids have from about 25% to about 50% of carboxyl acid groups esterified.

10. The method for treating an oil or natural gas well of claim 6 wherein the water in oil drilling fluid comprises from about 50 to about 98% by weight of continuous oil phase and from 2 to 50% of internal aqueous phase.

11. The method for treating an oil or natural gas well of claim 6 wherein the treatment fluid is employed in operations selected from the group consisting of: work-over, milling, stimulation, fracturing, spotting, cementing, and combinations thereof.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) Trimer fatty acids are mixtures of trimers and dimers of C.sub.18-unsaturated fatty acids containing about 60% of trimers and about 40% by weight of dimers. Trimer fatty acids, also simply named trimers, are obtained by distillation of crude dimer acids (CAS No. 71808-39-4). Dimer and trimer fatty acids are respectively C.sub.36 and C.sub.54 predominantly monocyclic addition compounds of unsaturated fatty acids (primarily of tall oil fatty acids).

(2) For the preparation of the ester of the present invention, trimer fatty acids comprising from about 50% to about 100% by weight of trimers of C.sub.18-unsaturated fatty acids shall be used, the balance to 100% mainly consisting of dimers of C.sub.18-unsaturated fatty acids.

(3) The polyethylene glycols that may be used in the preparation of the esters of the invention have average molecular weight from about 150 to about 600, preferably from 150 to 250, as determined from the hydroxyl number measured according to ASTM test method D4274-05.

(4) In order to perform as thickener in invert emulsion fluids, the ester of trimer fatty acids and polyoxyethylene glycol shall be soluble in the continuous oil phase. As a consequence, the molecular weight of the polyethylene glycol and the percentage of carboxyl acid groups of trimer fatty acids which are esterified shall be regulated accordingly.

(5) The use of polyoxyethylene glycol with average molecular weight from 150 to 250 and esters in which from 25% to 50% of the carboxyl acid groups of trimer fatty acids are esterified is preferred. Best results have been obtained with polyoxyethylene glycol with average molecular weight of about 200 and with esters in which from 30 to 40% of the carboxyl acid groups of the trimer fatty acids are esterified.

(6) The percentage of esterified carboxyl groups may be determined by methods known in the art, such as the standard test method ASTM D5558-95 STANDARD TEST METHOD FOR DETERMINATION OF THE SAPONIFICATION VALUE OF FATS AND OILS and by ASTM D974-12 ACID AND BASE NUMBER BY COLOR-INDICATOR TITRATION (the percentage can be calculated from the saponification value and the acid number of the ester).

(7) The water in oil emulsion drilling and well treatment fluids according to the invention contain from 0.1 to 10% by weight of ester, based on the total weight of the fluid.

(8) In a preferred embodiment, the ester is used in a quantity of 0.5 to 5% by weight, in order to optimally develop its effect as thickener.

(9) Before being added to the water in oil emulsion drilling or well treatment fluid, the ester may be diluted in a suitable solvent, such as a glycol or a glycol ether, for example in butyltriglycol.

(10) The use of an ester of trimer fatty acids and polyoxyethylene glycol, the polyoxyethylene glycol having average molecular weight from about 150 to about 600 and the trimer acids having at least about 20% of the carboxyl acid groups esterified, as rheology modifier of water in oil emulsion drilling and well treatment fluids leads to a remarkably increased viscosity of the fluids when a comparison is made with that of the same fluid without the ester and also with that of the same fluid comprising commercially available thickeners, and in particular trimer fatty acids. Moreover it will be appreciated that invert emulsions fluids thickened with the esters of the invention show a stable rheology, i.e. a rheology profile with little variation before and after heat aging of the fluid.

(11) The water in oil emulsion drilling fluids of the present invention comprise a continuous oil phase, an internal aqueous phase (a water based fluid that is at least partially immiscible with the oil phase), and the above described ester and may be suitable for use in a variety of oil field applications wherein water-in-oil emulsions are used; these include subterranean applications comprising drilling, completion and stimulation operations (such as fracturing), sand control treatments such as installing a gravel pack, cementing, maintenance and reactivation.

(12) The water in oil emulsion drilling fluids or well treatment fluids of the invention comprise from 50 to 98% by weight, preferably from 80 to 98% by weight, of a continuous oil phase and from 2 to 50% by weight, preferably from 2 to 20% by weight of an internal aqueous phase.

(13) The continuous oil phase used in the invert emulsions of the present invention may comprise any oil-based fluid suitable for use in emulsions.

(14) The oil-based fluid may derive from a natural or synthetic source.

(15) Examples of suitable oil-based fluids include, without limitation, diesel oils, paraffin oils, mineral oils, low toxicity mineral oils, olefins, esters, amides, amines, synthetic oils such as polyolefins, ethers, acetals, dialkylcarbonates, hydrocarbons and combinations thereof.

(16) The preferred oil-based fluids are paraffin oils, low toxicity mineral oils, diesel oils, mineral oils, polyolefins, olefins and mixtures thereof.

(17) Factors determining which oil phase will be used in a particular application, include but are not limited to, its cost and performance characteristics, environmental compatibility, toxicological profile and availability.

(18) The invert emulsion fluids of the present invention also comprise an internal aqueous phase that is at least partially immiscible with the oil phase.

(19) Suitable examples of the aqueous phase include fresh water, sea water, salt water, and brines (e.g., saturated salt waters), glycerine, glycols, polyglycol amines, polyols and derivatives thereof, that are partially immiscible with the oleaginous fluid, and combinations thereof.

(20) Suitable brines may include heavy brines.

(21) Heavy brines, for the purposes of this application, include brines with various salts at variable concentrations, that may be used to weight up a fluid; generally the use of weighting agents is required to provide the desired density of the fluid.

(22) Barite, calcium carbonate, dolomite, ilmenite, hematite, ground marble, limestone and mixture thereof are examples of suitable weighting agents. Brines generally comprise water soluble salts.

(23) Suitable water soluble salts are sodium chloride, calcium chloride, calcium bromide, zinc bromide, sodium formate, potassium formate, sodium acetate, potassium acetate, calcium acetate, ammonium acetate, ammonium chloride, ammonium bromide, sodium nitrate, potassium nitrate, ammonium nitrate, calcium nitrate, sodium carbonate, potassium carbonate, and mixtures thereof.

(24) The aqueous phase is chosen taking into account several factors including cost, environmental and health safety profile, density, availability, and which oil phase has been chosen. Another factor that may be considered is the application of the emulsion.

(25) For example, if the application needs an emulsion with a heavy weight, a zinc bromide brine (for example) may be chosen.

(26) The water in oil drilling and well treatment fluids of the invention may further comprise conventional additives including emulsifiers, weighting agents, wetting agents, fluid loss agents, thinning agents, lubricants, anti-oxidants, corrosion inhibitors, scale inhibitors, defoamers, biocides, pH modifiers, and the like.

(27) Such fluids, in particular, also contain at least one filtrate reducer preferably chosen among gilsonite, organophilic lignite, organophilic tannins, synthetic polymers, polycarboxylic fatty acids, or mixture thereof.

(28) When used in certain applications, the fluids may include particulates such as proppants or gravel.

(29) To better illustrate the invention, the following examples are reported to show the effect of the addition of the esters of the invention in exemplary water in oil emulsion drilling fluids.

EXAMPLES

Preparation of a Polyoxyethylene Glycol Partial Ester of Trimer Acids (Ester 1)

(30) In a reaction vessel equipped with heating, stirrer, thermometer, a system of introduction of the reagents, the reaction vessel being connected to a cooler provided with a collector of water, 2469 g of trimer acids and 531 g of polyoxyethylene glycol (MW 200) are added. At about 40 C., 3 g of p-toluenesulphonic acid monohydrate are added under stirring. The temperature is set at 120 C. The reaction mixture is maintained at 120 C. until the acidity number reaches a value between 95 and 105 mg KOH/g.

(31) The product (Ester 1) is then diluted with butyltriglycol (triethylene glycol monobutyl ether) and cooled, to obtain a 80% by weight solution of the partial ester (RM1).

Marine Ecotoxicity Data of Ester 1

(32) The Marine Biodegradation of Ester 1 was measured according to the OECD 306 Test. The Aquatic Ecotoxicity of Ester 1 was evaluated for the following species (according to the method in parenthesis): Algae (test protocol for Skeletonema costatum ISO/DIS 10253). Crustacea (test protocol for Acartia tonsa ISO TC 147/SC5/WG2). Fish (recommended test protocol PARCOM Protocol 1995 part B). Sediment reworker (recommended test protocol PARCOM Protocol 1995 part A).

(33) The following are the results of the tests performed on Ester1: Marine biodegradation >60% (70 days) Aquatic Ecotoxicity (Algae) EC.sub.50>1000 mg/l Aquatic Ecotoxicity (Crustacea) LC.sub.50>1000 mg/l Aquatic Ecotoxicity (Fish) LC.sub.50>1000 mg/l Aquatic Ecotoxicity (Sediment reworker) LC.sub.50>1000 mg/l

Preparation of a Polyoxyethylene Glycol Ester Rheology of Trimer Acids (Ester 2)

(34) In a reaction vessel equipped with heating, stirrer, thermometer, a system of introduction of the reagents, the reaction vessel being connected to a cooler provided with a collector of water, 180.9 g of trimer acids and 117 g of polyoxyethylene glycol (MW 200) are added. At about 40 C., 0.91 g of p-toluenesulphonic acid monohydrate are added under stirring. The temperature is set at 120 C. The reaction mixture is maintained at 120 C. for 2 hours. After this step, the temperature is increased to 140 C. and the reaction mixture is maintained at this temperature until the acidity number reaches a value below 5 mg KOH/g. The product (Ester 2) is then diluted with butyltriglycol (triethylene glycol monobutyl ether) and cooled, to obtain a 80% by weight solution of the ester (RM2).

Application Tests

Example 1

(35) Three water in oil emulsion fluids were prepared by mixing the here below ingredients with an Hamilton Beach mixer, as described in A.P.I. Specification 13B-2, in the reported order and with the following stirring times:

(36) TABLE-US-00001 g in the Stirring Ingredients fluid time EDC 99-DW (*) 165.6 Emulsifier 9.8 10 min Bentone 38 (**) 5.95 10 min Rheology modifier 0.7 5 min Ca(OH).sub.2 7 10 min Brine CaCl.sub.2 18.6% 62.68 10 min Barite 303 20 min (*) mineral paraffinic oil available from TOTAL UK. (**) organophilic clay available from Elementis

(37) The rheology modifiers RM1 and RM2 and trimer fatty acids available from Oleon diluted with butyltriglycol (triethylene glycol monobutyl ether) to obtain a 80% by weight solution (RM3) were used as the rheology modifiers respectively in Fluid 1, Fluid 2 and Fluid 3.

(38) A blank water in oil fluid was prepared with the same operating mode and recipe, but without the addition of any rheology modifier (Blank Fluid).

(39) The characteristics of the fluids are shown in the following table:

(40) TABLE-US-00002 Units Oil/water v/v 80/20 Density g/ml 1.56 Specific weight ppg.sup.(*.sup.) 13.0 .sup.(*.sup.)pounds per gallon (1 ppg = 119 kg/m.sup.3)

(41) The rheological properties of the invert emulsion drilling fluids were measured at 50 C. with a viscometer, as reported in ISO standard 10414-2.

(42) Electrical stability has been measured at a temperature of 50 C. by means of an electrical stability meter as reported in ISO standard 10414-2.

(43) The results are reported in Table 1

(44) It can be observed that the use of a polyoxyethylene glycol ester of trimer fatty acids leads to a remarkably increased viscosity.

(45) TABLE-US-00003 TABLE 1 Rheological properties at 50 C. Blank Units fluid* Fluid 1 Fluid 2 Fluid 3* Rheology 600 rpm 64 116 76 78 300 rpm 35 80 51 47 200 rpm 24 65 42 35 100 rpm 14 48 32 22 6 rpm 4 24 17 8 3 rpm 3 22 16 7 gels 10 lbs/100 ft.sup.2** 3 22 20 11 gels 10 lbs/100 ft.sup.2** 4 28 30 37 AV mPa * s 32 58 38 39 PV mPa * s 29 36 25 31 YP lbs/100 ft.sup.2** 6 44 26 16 Electrical stability @ 50 C. volts 760 1020 1010 970 *comparative **1 lbs/100 ft = 47.88 Pa

Example 2

(46) To study the behaviour of the rheology modifier in a different system, another test was analogously conducted in another mineral oil based fluid prepared by mixing the here below ingredients with an Hamilton Beach mixer as described in A.P.I. Specification 13B-2, in the reported order and with the following stirring times.

(47) TABLE-US-00004 g in the Stirring Ingredients fluid time Clairsol NS (*) 189.7 Emulsifier 9 10 min Geltone II (**) 6 10 min Duratone HT (***) 9 5 min RM1 1 5 min Ca(OH).sub.2 7 10 min Brine CaCl.sub.2 20% 79.25 10 min Barite 292.6 20 min (*) mineral paraffinic oil available from Carless Petrochem. (**) organophilic clay available from Baroid (***) Obm fluid loss reducer available from Baroid

(48) The characteristics of the Blank Fluid and of the fluid containing RM1 (Fluid 1a) are shown in the table here below.

(49) TABLE-US-00005 Units Oil/water v/v 80/20 Density g/ml 1.6 Specific weight ppg.sup.(*.sup.) 13.3 .sup.(*.sup.)pounds per gallon (1 ppg = 119 kg/m.sup.3)

(50) The rheological properties of the invert emulsion drilling fluids were measured at 50 C. before and after hot rolling (BHR and AHR) with a viscometer, as reported in ISO standard 10414-2.

(51) Electrical stability has been measured at a temperature of 50 C. by means of an electrical stability meter as reported in ISO standard 10414-2.

(52) The following operating conditions were used:

(53) TABLE-US-00006 Operating conditions Units Aging period hours 16 Aging temperature C. 120 Dynamic/Static aging D/S D

(54) The results are reported in Table 2 and 3

(55) TABLE-US-00007 TABLE 2 Rheological properties BHR Blank Units Fluid* Fluid 1a Rheology 600 rpm 56 58 300 rpm 33 37 200 rpm 25 29 100 rpm 17 21 6 rpm 8 10 3 rpm 7 9 gels 10 lbs/100 ft.sup.2** 9 9 gels 10 lbs/100 ft.sup.2** 11 14 AV mPa * s 28 29 PV mPa * s 23 21 YP lbs/100 ft.sup.2** 10 16 Electrical stability @ 50 C. volts 500 700 *comparative **1 lbs/100 ft = 47.88 Pa

(56) TABLE-US-00008 TABLE 3 Rheological properties AHR for 16 hours at 120 C. Blank Units fluid* Fluid 4 Rheology 600 rpm 54 56 300 rpm 32 36 200 rpm 24 26 100 rpm 17 18 6 rpm 5 6 3 rpm 4 5 gels 10 lbs/100 ft.sup.2** 5 6 gels 10 lbs/100 ft.sup.2** 5 11 AV mPa * s 27 28 PV mPa * s 22 20 YP lbs/100 ft.sup.2** 10 16 Electrical stability @ 50 C. volts 480 700 *comparative **1 lbs/100 ft = 47.88 Pa

(57) It can be observed that the use of a polyoxyethylene glycol ester of trimer fatty acids leads to a remarkably increased viscosity and to a stable rheology, i.e. a rheology profile with little variation before and after heat aging of the fluid.