GB2182345A - Method for improving production of viscous crude oil - Google Patents

Abstract

A method for improving the mobility and pipeline transport of a viscous crude oil by forming an oil-in-water emulsion with said oil and from 20 to 80% by weight of water in the presence of 170 to 4000 parts by weight per million parts by weight of oil of a surfactant blend, said blend comprising from 30 to 70 parts by weight of an anionic or amphoteric surfactant (A) selected from those of the formulae Ar(OCH2CH2)nOSO3H,Ar(OCH2CH2)nOCH2COOH, R<1)<OCH2CH2)nOCH2COOH, <IMAGE> a sodium and ammonium salt thereof, and from 30 to 70 parts by weight of a nonionic surfactant selected from (B) of the formula Ar(OCH2CH2)pOH or (C) of the formula <IMAGE> the latter having an HLB value of from 10 to 20; where Ar is octylphenyl or nonylphenyl, n is 2 to 10, p is 10 to 100, m is 20 to 40, r is 20 to 50, R<1> is C8 to C18 alkyl and R<2> is C12 to C18 alkyl.

Description

SPECIFICATION Method for improving production of viscous crude oil The invention relates to methods for i m provi ng the production rate of a viscous crude oil by forming an oil-in-water emulsion with blends of certain surfactants.

The pumping of viscous crude oils from production wells and subsequent pipeline transport is difficult because of the low mobility of the oil. Prior methodsforovercoming this problem included addition of lighter hydrocarbons, such as kerosine or light condensate, and heating the crude oil. These prior art methods are expensive and wasteful of energy.

Still another method of reducing the viscosity of heavy crude oils is by means of an oil-in-wateremulsion.

The following patents disclose such methods using a variety of agents to form emulsions for this purpose: U.S.3,380,531; U.S. 3,467,195; U.S.4,108,193; U.S.4,152,290; U.S.4,153,573; U.S. 4,153,575; U.S.4,162,989; U.S. 4,192,767 and U.S. 4,214,999.

However, each of these methods has serious drawbacks in that, for example, the resulting emulsion is still relatively viscous, they require heating to give an emulsion of sufficiently low viscosity, or subsequent separation of oil is difficult.

U.S. 4,239,052 discloses the use of a combination of an ethoxylated alkylphenol and a low molecuiarweight alkaryl sulfonate to reduce the viscosity of viscous hydrocarbons. U.S. 4,246,919 discloses a method employing a combination of an ethoxylated alkylphenol and an ethoxylated polypropylene glycol. U.S. 4,249,554 discloses an emulsion from using a combination of an ethoxylated alkylphenoi and a salt of an ethoxylated alcohol sulfate. U.S. 4,265,264 relates to a method employing a combination of a salt of an ethoxylated alcohol sulfate and certain polyoxyethylene polyoxypropylene copolymers or an ethoxylated alcohol. U.S.

4,285,356 discloses a method for reducing the viscosity of viscous hydrocarbons by forming an emulsion with a combination of certain alkylpolyether ethoxylated sulfates and an alcohol ethersulfate.

The present invention relatesto a method having distinct advantages overthose of the prior art inthat oil-in-water emulsions of very low viscosity at ambienttemperature are obtained which afford marked impro- vement in the productivity of wells producing various crude oils.Thus, the invention discloses a method for improving the mobility of a viscous crude oil and a method fortransporting a viscous crude oil through a pipeline, where each of said methods comprises forming an oil-in-water emulsion with the viscous crude oil and 20 to 80 percent by weight of water in the presence of from 170 to 4000 parts by weight of a surfactant blend per million parts by weight of oil, where said blend comprises from 30 to 70 parts by weight of an anionic or amphoteric surfactant (A) which is selected from those of the formulae Ar(OCH2CH2)nOSO3H, Ar(OCH2CH2)nOCH2COOH, (A1) (A2) R1 (OCH2CH2)nOCH2COOH, (A3)

a sodium and am moniu m salt thereof; and from 30 to 70 parts by weight of a nonionic su rfactant selected from those oftheformula: (B) Ar(OCH2CH2)DOH, or

said surfactant (C) having an HLBvalueoffrom 10 to 20; where Ar is octylphenyl or nonylphenyl nisanumberfrom2to10, pisa numberfrom 10to 100, m isa numberfrom20to40, ris a numberfrom 20to 50, R' is Csto C18 alkyl and R2isC12toC18alkyl.

The invention also relates to the emulsion formed by the above methods.

In the above emulsion and methods for its use, a particularly preferred amount of water present in the emulsion is from 25to 50 percent by weight of viscous crude oil. A particularly preferred blend of surfactants consists of 50 parts by weight of said surfactant (A) and 50 parts by weight of said surfactant (B) or said surfactant (C).

A particularly preferred amount of said surfactant blend employed in the emulsion is from 200 to 1500 parts by weight of said blend per million parts by weight of said viscous crude oil.

A class of particularly preferred surfactant blends are those wherein (A) is an anionic surfactant selected from (A), (A) or (A ), as defined above, or a sodium or ammonium salt thereof and said nonionic surfactantis (B), as defined above; also included in said class are blends wherein (A) isthe anionic surfactant (A1 ), as defined above, and said nonionicsurfactant is (C), as defined above, but having an HLB value offrom 12to 16.

Specific surfactant blends that are especially preferred for preparation ofthe emulsions of the invention and for carrying out the invention methods are those having equal weight of the following active ingredients: 1. (A) The sodium or ammonium salt of 4-C9H19C6H4(OCH2CH2)4OSO3H and (B) 4-C8H17C6H4(OCH2CH2)70OH; 2. (A1) Thesodiumorammoniumsaltof 4-CgH19C6H4(OCH2CH2)4OSO3H and (B) 4-C8H17C5H4(OCH2CH2)30OH; 3. (A) The sodium or ammonium salt of 4-C9H19C6H4(OCH2CH2)4OSO3H and

having an HLB of 16; 4. (A1) Thesodiumorammoniumsaltof 4-CsH19C5H4(OCH2CH2)4OSO3H and (B) 4-CgH19C6H4(OCH2CH2)100OH; 5. (A) The sodium or ammonium salt of 4-C9H19C6H4(OCH2CH2)4OSO3H and (B) 4-C8H17C5H4(OCH2CH2)10OH; 6. (A5) The sodium or ammonium salt ofthe amphotericsurfactant

where R2 is C12to C15alkyl and (B) 4-C8H17C5H4(OCH2CH2)30OH; 7. (A4) Thedisodiumsaltof

where R' is C5to C18 alkyl and (B) 4-CgH19CsH4(OCH2CH2)1000H; 8. (A2) The sodium or ammonium salt of (B) 4-C8H17C5H4(OCH2CH2)30OH;; 9. (A3) The sodium or ammonium salt of C10H21(OCH2CH2)4OCH2COOH and (B) 4-C8H17C5H4(OCH2CH2)30OH.

As noted above the invention relates to a method for increasing the productivity of a viscous crude oil by improving the mobility ofthe oil atthewellhead and its transport through pipelines by forming an oil-in-water emulsion with certain novel blends of surfactants.

The surfactants and mixtures thereof were screened initially in the laboratory forthose having the abilityto form oil-in-water emulsions of substantially reduced viscosity at ambienttemperature and also having adequate stability to allow for transporting the emulsion to the site of oil recovery. Preferred emulsions, of course, would not be so stable that subsequent oil separation would be difficult. Thus, the ideal emulsion is one that is highly mobile at ambienttemperature at the wellhead and during transport, and readily gives substantially complete oil separation at the recovery site.

The laboratory testing was carried out by forming oil-in-water emulsions with samples of various viscous crude oils and measuring their viscosity and emulsion stability by methods well known in the art. Thesetests were carried out employing either water or a brine as the aqueous phase. The brines employed were either natural brines obtained from a well site or synthetic brines which simulated those which occur naturally.

As a result of these tests it was found that blends of certain known anionic or amphotericsurfactants designated herein as surfactant (A) with certain known nonionic surfactants, designated herein as either surfactant(B) or surfactant (C), gave water-in-oil emulsions that demonstrated superior mobility atambient temperature and had the desired stability, indicated above.

The anionic or amphoteric surfactant designated as (A) in the above-mentioned surfactant blends isselected from those oftheformulae (A1): Ar(OCH2CH2)OSO3H, where Ar is octylphenyl or nonylphenyl and n is a number from 2 to 1 Owhich represents the average number of ethylene oxide units, a sodium and ammonium saltthereof; (A2): Ar(OCH2CH2)nOCH2COOH, a sodium or ammonium salt thereof, where Ar and n are as defined for (A1), above; (A3):R1(OCH2CH2)nOCH2COOH, a sodium or ammonium salt thereof, where R1 is a straight chain or branched C8toC15alkyl; (A4):

a sodium and ammonium saltthereof,where R1 is straight chain or branched C8to C18alkyl; and (A5):

a sodium and ammonium salt thereof, where R2 is a straight chain or branched C12to C18alkyl.

The nonionic surfactant designated as (B) in the above-mentioned surfactant blends is selected from those ofthe formula Ar(OCH2CH2)pOH where Ar is as previously defined and p is a number from 10 to 100which represents the average number of ethylene oxide units.

The alternatively used nonionic surfactant designated as (C) in the above-mentioned surfactant blends is selected from those of the formula

where r represents the average number of ethylene oxide units and m represents the average number of propylene oxide units.

Examples of suitable surfactants (A1), above, which are commercially available inciudeAlipal8C0-433 and Alipa18CO-436 availablefrom GAF Corporation, NewYork, NY 10020. Othersuppliers of surfactants (Al) wherein the average value of n is from 2 to 10 include Witco Chemical Corporation, New York, NY 10022; Onyx Chemical Company, Jersey City, NJ 07302; Conoco Chemicals, Houston, Texas and Rohm and Haas Co., Philadelphia, PA 19105.

Examples of suitable surfactants (A2), above, which are commercially available are Huls0BW 1142 and its homologs, available from ChemischeWerke HülsAG, Postfach 1230, D-4370, Marl, Federal RepublicofGermany.

Examples of suitable surfactants (A3), above, which are commercially available are HijlsBW 1109 and its homologs, also available from Chemische Werke Huls AG.

Examples of suitable surfactants (A4), above, which are commercially available include Eleminol#MON-7 from Sanyo Chemical Industries, Ltd., Kyoto, Japan; and the Dowfax Surfactants 2AO, 2A1 and 3B2 from Dow Chemical U.S.A., Specialty Chemicals Department, Midland, Michigan 48640.

Examples of suitable surfactants (A5), above, which are commercially available include Miranol(0)C2MSF, Miranol()H2M, MiranolL2MSF, MiranolO2M and MiranolC2M available from Miranol Chemical Company, Dayton, NJ, 08810; and Cycloteric()DC-SFfrom Cyclo Chemical Corp., Miami, Florida.

Suitable nonionic surfactants (B) which are commercially available include TritonX-l 00, Triton8X-305, TritonORX405, Triton8X-705 and Triton()N-998, containing respectively an average of 10,30,40,70 and 100 oxyethylene units, available from Rohm and Haas Co., Philadelphia, PA 19105; T-DET8N-407 andTDETOR507 from Thompson Hayward, Kansas City, KS66110 and Tergitol#NP-40 from Union Carbide Corp., Danbury, CT 06817.

Suitable nonionic surfactants (C), above, which are commercially available include several ofthe Pluronic(B) Surfactants from BASF Wyandotte Corp., Wyandotte, Michigan 48192, including PluronicBL35 (HLB 18.5), L43 (HLB 12), L44 (HLB 16), P65 (HLB 17), L64 (HLB 17), L63 (HLB 11), P75 (HLB 16.5), P85 (HLB 16), P84 (HLB 14), P94 (HLB 13.5), P104 (HLB 13) and P105 (HLB 15). As is well known in the artof surface active agents, HLB is the hydrophile-lipohile balance, which is a measure of the relative simultaneous attraction of an emulsifying agentforthetwo phases (oil and water) in an emulsion system. The higher HLB values are indicative of higher hydrophilicity.

Assuming facile separation of phases in each case, it will be recognized by one of skill in the artthatthe higherthe level of oil in the emulsions of the invention, the more efficient the recovery process will be. Thus, effective emulsions of the invention are those containing from 20 parts by weight of oil and 80 parts byweight of water to those having 80 parts by weight of oil and 20 parts by weight of water. Especially preferred emulsions are those having from 50 to 75 parts by weight of toil and from 25 to 50 parts by weight of water.Of course, as indicated above, the "water" employed in the emulsion can be eitherfresh water, containing little or no dissolved solids, or a brine, containing relatively high levels (up to 15% by weight) oftotal dissolved solids (TDS), including ordinary salt.ln most cases, the "water" employed in the emulsion is that water prod- uced from the well along with the heavy crude oil.

In some instances the fluid produced by a well is a very viscous water-in-oil emulsion. It has been foundthat upon introduction of a surfactant blend ofthe invention down the well annulus with moderate downhole mixing, the viscous water-in-oil emulsion will invertto form a very low viscosity oil-in-water emulsion.

While levels of the surfactant blend, which is based on the oil weight, may vary over a wide range, preferred levels are those within the range of l70to 4000 parts by weight of surfactant blend per million parts byweight of oil, and especially preferred blends are those having from 200 to 1500 parts by weight ofsurfactant per million parts by weight of oil.

In all cases herein the parts of surfactant refers to the parts of active ingredient, excluding inert diluents ordinarily employed in theirformulations, e.g. water.

Preferred surfactant blends are those comprising from 30 to 70 parts by weight of surfactant (A) and 30 to 70 parts by weight of eithersurfactant(B) or surfactant (C) and especially preferred arethose having 50 parts by weight of each ofthe above active ingredients, (A) and (B), or (A) and (C).

Thefollowing Examples are illustrative ofthe invention.

Example 1 Viscosity reduction and emulsion stability of a 13.5- gravity California crude oil with various emulsify- ing agents Method The crude oil sample, 280 g, brine,120g, and emulsifying agent, 0.224 g (800 ppm based on weight of oil), were placed in a blender and mixed at a high shear speed for 30 seconds. The viscosity ofthe resulting emulsion was measured with a Brookfield LVTD Viscometer at spindle speeds of 6, 12,30 and 60 rpm. All viscosity readings were approximately the same. A 100 ml portion ofthe emulsion was poured into a gradu ated cylinder and allowed two stand at 250 C. Aftersix hours, each graduated cylinderwas inverted threetimes in orderto redispersethe mixture. The viscosity was remeasured and recorded as the viscosity at6 hours. The extent of viscosity reduction and the ease of redispersibility after standing are measures of the amount of coalescence of the oil phase and are thus a measure of the stability of the emulsion. The results are sum marized in the table below.

*The brine contained 10% by weight total dissolved solids (TDS) and 1% hardness.

Thinning Effectiveness, Emulsion Stability, Emulsifying Initial Viscosity at 25 C. Viscosity after 6 hours at Agent (centipoise) 25"C. (centipoise)2 None 20,000 N.A.

Surfactantl 9,450 N.A.

Surfactantll 200 4,200 Surfactantlll 250 5,200 Surfactant IV 200 5,000 SurfactantV 180 6,800 SurfactantVi 400 5,500 (Blend of U.S. 4,239,052) SurfactantVll 320 5,840 (Blend of U.S. 4,249,554) BIendl(l+lll) 200 4,400 Blend2(1+11) 300 1,100 Blend3(1+V) 300 1,700 1800 ppm of active surfactant below based on weight of oil.

Surfactant Chemical Name and Formula Nonylphenoxytri(ethyleneoxy)ethanol sulfate CgH19CGH4(OCH2CH2)30CH2CH20S03H.

II Octylphenoxypoly(ethyleneoxy)ethanol (30 moles ethylene oxide) C8H17C8H4(OCH2CH2)30OH.

Ill Octylphenoxypoly(ethyleneoxy)ethanol (70 moles ethylene oxide) C8H17C8H4(OCH2CH2)70OH.

IV Nonylphenoxypoly(ethyleneoxy)ethanol (100 moles ethyleneoxide) C5H19C8H4(OCH2CH2)100OH.

V Block copolymer of ethylene oxide and propylene oxide (40% ethylene oxide), HLB = 16*.

VI Dodecylbenzenesulfonate and nonylphenoxypoly(ethyleneoxy)ethanol C12H25C5H4SO3H and CgH19C6H4(OCH2CH2)40OH 50/50 blend.

VII Alfonic 1412-A#**[C12-14H25-29(OCH2CH2)3OSO3NH4] plus T-DET-N407#** [C9H19C6H4(OCH2CH2)40OH] 50/50 blend (w/w).

Blend 1 50/50 (w/w) blend of surfactants land III, above.

Blend 2 50/50 (w/w) blend of surfactants land II, above.

Blend 3 50/50 (w/w) blend ofsurfactants I and V, a bove.

2N.A. = Not applicable 'Plumnic L-44, BASF Wyandotte.

**Alfonic is a registered trademark of Conoco Chemicals. T-DET is a registered trademark of Thompson Hayward Chemical Co.

Example 2 The effect ofvarying surfactant ratio of Blend 2 of Example 1 was determined employing the same Ca Iifornia heavy crude oil designated as Oil Type A below and a second California heavy crude, Type B, bythe method of Example 1, except that the ratio of surfactants in the blend is as shown below.

Ratio of Surfactantlill Oil Thinning Emulsion {Total=800ppm) Type Effectiveness Stability2 0/100 A 200 4200 25/75 A 240 3100 50/50 A 300 1100 75/25 A 7280 N.A.3 100/0 A 9450 N.A.3 50/50 B4 300 700 Footnotes: 1 Initial viscosity at 25 C., centipoise.

2Viscosity after standing at 25 C. for six hours, centipoise.

3N.A. = Not applicable.

4California heavy crude oil, 11-12 API gravity, viscosity at 33 C. is 15,000 centipoise.

Example 3 The effect of varying the total weight of surfactants employing Blend 2 of Example 1 was carried out with a 120 API Central California heavy crude oil having Brookfield viscosity (centipoise) as follows: at 25 C. > 20,000 cps.

at 33 C. 18,500 cps.

at 40 C. 6,320 cps.

and a paraffin/asphaltene ratio of 10.9. The method employed was that of Example 1, except that emulsion stability was determined after standing for two hours, rather than six hours. The percent of phase separation afterthe emulsion stood fortwo hours was also recorded. The results are summarized below.

Effect concentration of blend2 on on emulsion viscosity andstability AmountofBlend2, ppm Initial Viscosity, ViscosityAfter Two Hours % Phase Separation Based on WeightofOil {Centipoise) at25" C. {Centipoise) After Two Hours None > 20,000 > ,20,000 100 400 130 600 32 800 180 400 20 1600 160 400 10 Example 4 The effect of various surfactant blends, each at 800 ppm (based on weight of oil) on the viscosity and stability of 70:30 (oil :water) emulsions of a northern Montana heavy crude oil was determined by the above method. The heavy crude oil used had the viscosity shown below: at 70" F. (22 C.) 12,000 cps.

at 1000 F. (38 C.) 2,700 cps.

at 1200 F. (49 C.) 1,100cps.

In each case, duplicate emulsions were prepared in the Waring Blender at 1400 F. (60' C.) employing tapwater and brine containing 5% by weight total dissolved solids (TDS). Emulsion viscosity was determined after cooling to 25 C. and phase separation per hour was determined over a two-hour period. The results are summarized below: Initial viscosity andstability of Northern Montana heavy crude oil emulsions (70:30 waterloil) with various surfactant blends at800ppm (based on weight oil) Initial Viscosity, cps.Phase Separation (%/Hr.) SuffactantBlendt Tap H20 5% TDSBrine Tap H20 5% TDSBrine Blend 1 62 74 18 23 Blend2 214 70 28 31 Blend4 108 84 21 33 Blend 5 70 35 37 69 Example 4 (Cont.) 'Blend 1 - a 50:50 by weight mixture of surfactants I (Alipal CO-436, GAF Corporation, New York, NY 10020) and Ill (Triton X-705, Rohm and Haas Co., Philadelphia, PA 19105) of Example 1; Blend 2 - a 50:50 (weight) mixture of surfactant 1, above, and surfactant II of Example 1 (Triton X-305, Rohm and Haas Co, Philadelphia, PA 19105); Blend 4-a 50:50 (weight) mixture of surfactant I, above, and surfactant IV of Example 1,nonylphen- oxypoly(ethyleneoxy)ethanol (Triton N-998, Rohm and Haas, Philadelphia, PA 19105).

Blend 5 - a 50:50 (weight) mixture of surfactant I, above, and octylphenoxypoly(ethyleneoxy)ethanol, C8H17C6H4O(CH2CH2O)10H (Triton X-100, Rohm and Haas, Philadelphia, PA 19105).

Example 5 A highly asphaltic Peruvian heavy crude oil, 280 g, 10% TDS brine, 120 g and 800 ppm of a 50/50surfactant blend (by weight) was emulsified and the initial Brookfield viscosity measured as in Example 1 to determine the thinning effectiveness of the surfactant blend at 25 C. The emulsion was then shaken for 24 hours at 27"C.

at a rate of 150 cycles/minuteto determine emulsion stability based on oil coalescence by determination of oil globule size. Aglobulesize of lessthan 2 millimeters underthese conditions (size 1) passesthetest.

Thinning Effectiveness, Emulsion Stability Viscosityat25 C. after24Hours, Surfactant Blend (Centipoise) Shaker Test None > 20,000 Not Applicable 112 mg each of nonylphenoxytri(ethyl eneoxy(ethanol sulfate and ethylene oxide, propylene oxide block copolymer (40% ethylene oxide) (I + IV of Example 1) 230 1-2 112 mg each of ethylene oxide, propylene oxide block copolymer (40% ethylene oxide), (V of Example 1) and disodium [(C4Hg-C18H37)-4-(su If onyl phenoxy)]- benzenesulfonate* 230 1 *Eleminol MON-7, a registered trademark of Sanyo Chemical KK.

Example 6 The effect of total concentration ofsurfactantblend2 on emulsion stability with California heavy crude oil Mixtures of 380 g of crude oil, 163 g 10% (w/w) brine and 100,200,400 or800 ppm by weight, based on weightofoil, oil,ofSurfactantBlend 2 [a 50/50 (w/w) blend of surfactants land li of Example 1]were emulsified by pumping the mixture through a 0.25 inch (0.635 cm) diametertubing loop at 1000 sec-l wall shearforfive minutes.The initial I a ppeara nce and viscocitywere obtained as in Example 1 and the emulsion was then pumped through the tube at 500 sec-1 wall shear and the appearance and water breakout noted after passing through 25 feet of the tubing. The results are summarized below: Surfactant Initial Viscosity Emulsion Appearance Blend2, ofEmulsion After25ft.

ppm* (centipoise) Initial oftubing WaterBreakout 100 130 Smooth Considerable 170 ml coalescence clear after 10 minutes 200 100 Smooth Slight 170ml coalescence clear after 30 minutes 400 80 Smooth Smooth 160 ml muddy after 20 hours 800 90 Smooth Smooth 150 ml muddy after 20 hours *Based on weight of oil.

Example 7 Emulsion stability with a California heavy crude Employing a Cat Canyon, California heavy crude, viscosity 7860 cps. at70" F. (21" C.) 70:30 oil/brine emulsions (brine contained 6260 ppm TDS, 42 ppm hardness) containing from 200 to 1000 ppm surfactant blend were prepared by pumping the mixture at 80 F. (27 C.) for 30 seconds through a 0.25 inch (0.635 cm) diameter tubing loop at 1000 sec-1 shear. Pumping at 500 sec-1 shear rate was then continued until the emulsion broke. The breakdown timeforemulsionstested in this manner are summarized below.

Surfactant Blend Breakdown Time, Hours Concentration, ppm Blend 1 ofExample 1 Blend2 of Example 1 200 0.25 400 0.50 0.6 600 0.75 800 1.4 1.5 1,000 1.5 1.7 *Based on weight of oil.

Example 8 Performance with South American heavy crude oil A South American crude oil having a Brookfield Viscosity of 11,000 cps. at 20 C. and 2,800 cps. at 27 C. and a paraffin/asphaltene ratio of 4.1 was emulsified in brine containing 6.7% or9.1 %total dissolved solids with three differentsurfactant blends as shown below. In each case the emulsions contained 70% oil and 30% brine byweight and 800 ppm of surfactant blend. Emulsions were prepared in aWaring Blender at 60"C., cooled to 25 C. and the initial Brookfield Viscosity determined using spindle #3 at 6 rpm.The emulsion stability was determined by the oil droplet size after shaking for 24 hours at 27" C. as described in Example5.

The results are summarized below.

Emulsion Stability Initial Em ulsion at24hours, SurfactantBlend(800ppml Brine, % TDS Viscosity, cps. droplet size Blend 6-a 50:50 (weight) blend of Miranol C2MSF* and Surfactant li of Example 1 6.7 40 completely coalesced Blend 4 of Example4 6.7 420 2-5 mm Blend 4 of Example 4 9.1 230 2mm Blend 7-a 50::50 (weight) blend of Eleminol MON-7** and Surfactant IV of Example 1 9.1 230 1 mm *MiranolB C2M-SF, Miranol Chemical Co., Inc., Dayton, N.J. 08810; a dicarboxylic coconut derivative of imidazoline oftheformula

**Eleminol MON-7, Sanyo Chemical Co. is a disodium alkyl-4-(sulfophenoxy)benzenesulfonate of thefor- mula

where R is C4H9 to C18H37 which may be straight chain or branched.

Example 9 Performance with Western Canada Bitumen The procedure of Example 8 was repeated with a Western Canada Bitumen having Brookfield viscosity 34,800 cps. at 25 C. In addition to the initial viscosity and emulsion stability,the percent of preparation after standing for 24 hours was determined. The results are summarized in the table below.

Surfactant Initial Emulsion Stabilityat24hours Blend* Emulsion Drop Size %Phase (ppm, byweight Weight Ratio Viscosity, AfterShaking, Separation of oi/) oillwater cps. mm on Standing Blend 1(400) 70/30 180 5-10 100 Blend 1(800) 70/30 100 < 1 6 Blend 2 (400) 70/30 160 5-10 100 Blend 2 (600) 70/30 160 < 1 100 Blend 2(800) 70/30 60 < 1 10 Blend 4(400) 70/30 140 5-10 100 Blend 4 (800) 70/30 80 < 1 6 Blend 7 (800) 70/30 50 1-2 100 Blend 2 (800) 80/20 1250 < 1 < 3 *AIl surfactant blends are 50:50 by weight. Blends 1,2 and 4are as defined in Example 4. Blend 7 is as defined in Example 8.

Example 10 Performance of surfactant blends 2,8 and 9 with Geisinger, California heavy crude Samples of Geisinger, California heavy crude oil having a Brookfield viscosity of > 10,000 centipoise (13.5 API) at 259 C were emulsified in brine having 10% total dissolved solids art a ratio of 70 parts by weight oil and 30 parts by weight brine, with the surfactant blends indicated below at 400 ppm of each component(total surfactant blend, 800 ppm based on oil). The initial viscosity (cps) and phase separation upon standing at25" C. was determined. The results are summarized below.

Initial Emulsion Phase Separation, SurfactantBlend** (800ppm) Viscosity, at25" C., cps.* milhour None > 10,000 Blend 2 600 0.9 Blend 8 300 1.0 Blend 9 600 1.0 "Using a Brookfield Viscometer, LVT, spindle *3 at6 rpm, and 25" C.

**Blend 2 is an equal weight mixture of AlysalCO436 and TritonX305 brands of surfactants I and II, respectively, as defined in Example 1.

Blend 8 is an equal weight mixture of Hulls BW1 142 andTritonX305; theformerisC,0H2, (OCH2CH2)OCH2COONa (90% active). Blend 9 is an equal weight mixture of Hulls BW0R1 109 and TrkonX305; HulsBBW1 109 is C10H21 (OCH2CH2)4OCH2COONa (90% active). Both HulsBW1 109 and BW1 124 are available from Chemische Werke Hüls AG, Postfach 1230, D-4370 Marl, Federal Republic of Germany.

Example 11 Do whole emulsification trail at Reward Field, McKittrick, California A marginally productive well was employed which during a pretrial period of 26 days had an average daily oil production of 0.7 barrels with an average gravity of 12"API [0.986 c/cm3j and average Brookfield viscosity > 20,000 cps. The viscosity of various samples of thins crude oil was reduced to 130 to 180 cps. with 400-800 ppm of Surfactant Blend 2 by the method of Example 1. During the 10 day trial period an aqueous solution of Blend 2, containing 250 ppm of each of thetwo active surfactants, *was continuously injected downthe annulus.Thefluid produced during this period contained, on the average, 36% of aqueous phase and 64% oil, by weight. The average fluid production of the well increased 240% and the oil production increased by450%.

The average wellhead temperature was 30"C. In addition, the surface flowline pressure was reduced from a pretrial 300 psig to 26 psig during the trial period.

During a 15 day post trial period oil production dropped to 1.2 bbl/day which is still 70% above the pretrial rate. The data are summarized in the table, below.

Summary of averaged data from trialatReward Field Well, McKittrick, California, with surfactantblend2(500 ppm) Fluidperday, Oilperday, Flowline Viscosity Ambient Temp., "C., Barrels Barrels pressure, psig cps** HighlLow Pretrial (26 Days) 1.8 0.7 300 20,000 9.5/-0.6 Trial (10 Days) 6.1 3.9 26 10-20 13/2 Post-trial (28 Days) 5.0 1.2 177 41,200 19/6 *The surfactant blend employed a 5% aqueous solution of equal parts by weight of the active ingredients: (A1) sulfated nonylphenoxytri(ethylenexy)ethanol(Alipal#CO436 from GAF Corporation, New York, NY 10020) and (B) octylphenoxypoly(ethyleneoxy)ethanol with 30 moles of ethylene oxide (Triton(g)X-305, from Rohm and Haas, Philadelphia, PA 19105.) Itwas pumped into the annulus at a rate calculated to give the desired level of surfactant blend, oil and water.

**Using a Brookfield Viscometer, LV & um;3 spindle at 60 rpm, HA#4 spindle at 10 rpm.

Example 12 Downhole emulsification trial at Midway-Sunset Field, Fellows, California This trial was carried outwith a well which was already moderately productive, yielding an average of 6 barrels of oil per day during the eight day pretrial period, having consistent Brookfield viscosity at40" C. of 29,000 cps. On the 9th day continuous injection of 440 ppm (based on weight of oil) of surfactant Blend 2 was started. Sincetheviscosity remained high (28,400 cps.),the level of Blend 2was increased to 650 ppm on day 10 and 740 ppm on day 11, during which period the viscosity dropped to 12,800 cps. (day 10) and 12 cps. (day 11). Dosing was maintained atabout740 ppm until day 13 on which it was further increased to 1040 ppm and maintained at 1000 to 1300 ppm until the end of the trial period on day 18.During days 1 1 -18 theviscosity remained low (12-90 cps.) except four readings of 5200 and 2000 on day 12.

During the 10 day trial period,fluid production increased by 30% and oil production by 63% to an average of 9.8 barrels per day. During the trial period the wellhead temperature was 390 C. The results are summarized below.

Summary of averaged data from trial at Midwell-Sunset Field, Fellows, California with surfactantblend2 at 440 to 1300ppm Fluidperday, Oilperday, Flowline Viscosity, Ambient Temp., 'C, Barrels Barrels pressure, psi cps. HighlLow Pretrial (8 Days) 13 6 130 29,000 26/7 Trial (10Days) 17 9.8 100 540* 19/7 PostTrial 12 6 290 21,800** 19/7 (5 Days) *Using a Brookfield Viscometer, HA*4 spindle at 10 rpm.

*During days 13-18 the viscosity remained in the range of 12-90 cps.

# *The post-trial viscosity ranged from 13,200 cps. on day 19 to 31,360 cps. on day 22, the final reading taken.

Claims (24)

1. A method for improving the mobility of a viscous crude oil which comprises forming an oil-in-water emulsion with said oil and 20 to 80 percent by weight of water in the presence of from 170 to 4000 parts by weightofa surfactant blend per million parts byweight of oil, said blend comprising from 30to 70 parts by weight of an anionic or amphoteric surfactant (A) selected from those of the formulae Ar(OCH2CH2)nOSO3H, Ar(OCH2CH)nOCH2COOH, R1(OCH2CH2),OCH2COOH,

a sodium orammonium saltthereof; and from 30to 70 parts by weight ofa nonionicsurfactantselectedfrom (B) ofthe formula Ar(OCH2CH2)DOH, or (C) oftheformula

said surfactant (C) having an HLB value of from 10 to 20; where Ar is octylphenyl or nonylphenyl, n isa numberfrom 2to 10, pisa numberfrom 10to 100, mis a numberfrom 20 to 40, risanumberfrom20to50, R1 is C8to C18 alkyl and R2 is cato C18 alkyl.

2. The method of claim 1 wherein said water is present in an amount offrom 25 to 50 percent by weight of said oil.

3. The method of claim 1 wherein said blend consists of 50 parts by weight of surfactant (A) and 50 parts by weight of surfactant (B) or surfactant (C).

4. The method of claim 1 wherein said surfactant blend is present in from 200 to 1500 parts by weight per million parts by weight ofsaid oil.

5. The method of claim 1 wherein (A) is Ar(OCH2CH2)nOSO3H our a sodium or ammonium saltthereof.

6. The method of claim 1 wherein said nonionicsurfactant is (B).

7. The method of claim 1 wherein said nonionicsurfactant is (C) having an HLB value of 12to 16.

8. The method of claim 6 wherein (A) is Ar(OCH2CH2)0OCH2COOH, R1 (OCH2CH2)nOCH2COOH or a sodium orammonium salt thereof.

9. A method for transporting a viscous crude oil through a pipe which comprises forming an oil-in-water emulsion with said oil and 20 to 80 percent by weight of water in the presence of from 170 to 4000 parts by weight of a surfactant blend per million parts by weight of oil, said blend comprising from 30 to 70 parts by weight of an anionic or amphoteric surfactant (A) selected from those of the formula Ar(OCH2CH2)OSO3H, AR(OCH2CH2)nOCH2COOH, R1(OCH2CH2)nOCH2COOH,

our a sodium or ammonium salt thereof; and from 30 to 70 parts by weight of a nonionicsurfactantselected from (B) of the formula Ar(OCH2CH2)pOH, or (C) oftheformula

said surfactant (C) having an HLB value of from 1 Oto 20; where Ar is octylphenyl or nonylphenyl, n is a numberfrom 2 to 10, p is a numberfrom 10 to 100, mis a numberfrom 20to40, risa numberfrom 20to50, R' isC8toC,8alkyland R2iaC12toC15alkyl.

10. The method of claim 9wherein said water is present in an amountoffrom 25to 50 percent by weight of said oil.

11. The method of claim 9wherein said blend consists of50 parts by weight of surfactant (A) and 50 parts by weight of surfactant (B) orsurfactant (C).

12. The method of claim 9 wherein said surfactant blend is present in from 200 to 1500 parts by weight per million parts by weight of said oil.

13. The method of claim 9 wherein (A) isAr(OCH2CH2)nOSO3H or a sodium or ammonium saltthereof.

14. The method ofclaim 9wherein said nonionic surfactant is (B).

15. The method of claim 9 wherein said nonionic surfactant is (C) having an HLB value of 12to 16.

16. The method of claim 14wherein (A) isAr(OCH2CH2)nOCH2COOH, R1(OCH2CH2)nOCH2COOH ora sodium or ammonium salt thereof.

17. An oil-in-water emulsion comprising 20 to 80 percent by volume of a viscous crude oil, 20 to 80 percent by weight of water and from 170 to 4000 parts by weight of a surfactant blend per million parts by weight of oil, said blend comprising from 30 to 70 parts by weight of an anionic or amphoteric surfactant (A) selected from those of the formula Ar(OCH2CH2)nOSO3H,Ar(OCH2CH2)nOCH2COOH, R1 (OCH2CH2)nOCH2COOH,

ora sodium orammonium salt thereof; and from 30to 70 parts by weight of a nonionicsurfactantselected from (B) oftheformulaAr(OCH2CH2)pOH,or (C) oftheformula

said surfactant (C) having an HLB value of from 10 to 20; where Ar is octylphenyl or nonylphenyl, n is a numberfrom 2 to 10, pisanumberfrom10to100, m isa numberfrom 20to40, ris a numberfrom 20 to 50, R1 is C8to C18 alkyl and R2 is C12to C18 alkyl.

18. The emulsion of claim 17 wherein said water is present in an amountoffrom 25to 50 percent by weightofsaid oil.

19. The emulsion of claim 17 wherein said blend consists of 50 parts by weight of surfactant (A) and 50 parts by weight of surfactant (B) orsurfactant (C).

20. The emulsion of claim 17 wherein said surfactant blend is present in from 200 to 1 500 parts by weight per million parts by weight of said oil.

21. The emulsion of claim 17 wherein (A) is Ar(OCH2CH2)nOSO3H or a sodium or ammonium salt thereof.

22. The emulsion of claim 17 wherein said nonionic surfactant is (B).

23. The emulsion of claim 17 wherein said nonionicsurfactantis (C) having an HLB value of 12to 16.

24. The emulsion of claim 22 wherein (A) is Ar(OCH2CH3)OCH2COOH, R8(OCH2CH2)nOCH2COOH or a sodium or ammonium saltthereof.