COMPOUNDS AND COMPOSITIONS FOR OIL RECOVERY

Abstract: An aqueous surfactant composition, suitable for injec­ tion into an oil being formation to assist in the recovery of oil, comprises an aqueous medium having dispersed therein an alkylpolyalkyleneoxy monosaccharide or reduced monosac­ charide.

Description: COMPOUNDS AND COMPOSITIONS FOR OIL RECOV The invention relates tX surfactant compositions suitable for injection into oil bearing formations, to novel organic compounds suitable for use as surfactants and to a method for using the surfactant compositions in the recovery of crude oil. The displacement of oil in a formation by the use of surfactant compositions is known and numerous surfactant compositions have been described for this purpose. We have now discovered that certain alkylpolyalkyleneoxy monosaccharides or reduced monosaccharides are particularly effective for the displacement of crude oil. Thus according to one aspect of the present invention there is provided an aqueous surfactant composition suitable for injection into an oil bearing formation to assist in the recovery of oil, the composition comprising an aqueous medium having dispersed therein an alkylpolyalkyleneoxy monosaccharide or reduced monosaccharide of general formula I R - (O CH2CE2)n - 0 - [monosaccharide] or EMI1.1 [reduced monosaccharide] wherein R is an alkyl group containing 8 to 24 carbon atoms and n is O or an integer from 1 to 20 inclusive. Suitable monosaccharides include galactose, glucose and mannose. Suitable reduced monosaccharides include sorbitol, mannitol and dulcitol. The compositions are preferably used in concentrations in the range 200 to 10,000 ppm. The surfactant composition can be used in an enhanced oil recovery operation in which the surfactant composition is injected and then followed by a drive fluid such as water. It may also be used to increase the injectivity of water injection wells. Thus according to another aspect of the present invention there is provided a method for recovering oil from a formation which method comprises the steps of injecting a composition as hereinbefore described into the formation via an injection well and recovering the oil from a production well spaced apart from the injection well. The preparation of galactose and glucose derivatives corresponding to Formula I in which the symbol n is zero has been described by Havlinova et al in Tenside Detergents, 1978, 15, 72. German patent specification 1206877 discloses the preparation of certain sorbitol derivatives corresponding to Formula II in which. the symbol n is zero. These are said to be useful as wetting agents and detergents. Neither reference describes compounds of Formulae I or II in which the symbol n is other than zero. Thus according to a further aspect of the present invention there is provided a novel alkylpolyalkyleneoxy monosaccharide or reduced monosaccharide of general formula I R - (O C112CR2)n - 0 - [monosaccharide] or EMI2.1 [reduced monosaccharide] wherein R is as hereinbefore defined and n is an integer from 1 to 20 inclusive. The compounds may be prepared by reacting the monosaccharide or reduced monosaccharide with the corresponding alkylpolyalkyleneoxy compound or by alkylating the corresponding polyalkyleneoxy monosaccharide or reduced monosaccharide. The invention is illustrated by the following Examples. Example 1 Preparation of 6-0-[3:6:9 - trioxaheneicosyl]-D-galactose EMI3.1 Sodium hydride (80X dispersion in oil, 2.4g disperslon,O.08M) was added portionwise to a solution of 1,2:3,4-di-0-isopropylidene- alpha-D-galactopyranose (l3g,0.05H) in anhydrous xylene (250 ml) maintained under an atmosphere of nitrogen at 50 C. After 0.5 hours l-chloro-3:6:9-trioxaheneicosane (16.85g, 0.05M) in anhydrous xylene (50 ml) was added slowly and the mixture was heated at 130 C for 6 hours. The mixture was allowed to cool to room temperature and methanol (5ml) was added followed by water (lOOml). Solvent was evaporated and water (lOOml) was added to the residue. The aqueous solution was extracted. with chloroform (3 x IsOmi) and the combined organic layers were washed with water (2 x 300 ml). The organic solution was evaporated and the residue was dissolved in acetic acid (150ml). Water (30ml) was added and the mixture was heated at 1000C for 7 h. Evaporation of solvents gave the compound as a brown oil. Pure compound could be obtained, if required, by purification of the brown oil by silica gel column chromatography using dichloromethane: methanol 8:1 as eluent. Pure compound was analysed by TLC, 13C NMR, MS and C,R analysis. Example 2 Preparation of 2-hydroxy - 4:7:10:13:16 - pentaoxatriacont -l-yl sorbitol EMI3.2 Sodium hydride (80% dispersion in oil, 3g dispersion, 0.1M) was added portionwise to a solution of 3:6:9:12 - tetraoxahexacosan-l-ol (39g, 0.1M) in anhydrous toluene (150ml). After 1 hour at 70"C epichlorohydrin Cli. ig, 0.12M) was added slowly and the mixture was heated at 110 0C for 3 hours. The mixture was then allowed to cool and was filtered through glass paper. Evaporation of solvent gave a brown semi-solid which was slurried with anhydrous DMF (50ml). This.slurry was added dropwise to sorbitol (18.2g, 0.1M) dissolved in anhydrous DMF (50ml) at 60"C. The mixture was heated at 1300C for 4 hours. The brown solution was allowed to cool and was filtered through celite. The solution was extracted with hexane (3xlOOml) and then the DMF was removed by vacuum distillation. The brown gummy residue was digested with boiling isopropanol and unchanged solid sorbitol could be filtered off through celite. Evaporation of solvents from the filtrate gave an amber gum which was found by TLC-Iatroscan to contain 66Z sorbitol ether. The pure compound could be obtained, if required, by purification of the amber gum by silica gel column chromatography using chloroform:methanol 6:1 as eluent. The pure compound was analysed by TLC and MS. PROPERTIES OF COMPOUNDS The compounds prepared in Examples 1 and 2 and other related compounds prepared in a similar manner were evaluated by determining two properties:- (1) the capillary oil displacement time against Forties crude and (2) the dynamic interfacial tension, also against Forties crude. In (1) a small sample of crude-oil is placed in a capillary tube which is placed in a narrow tube so that the capillary remains upright at least to some extent. Both tubes are then placed in a bath of sea water containig 0.2Z surfactant at a desired temperature. Oil is released from the capillary and floats to the surface. The time taken to release all the oil from the capillary is noted. The oil release time varies from seconds with a good surfactant to hours or not at all. The dynamic interfacial tension is measured by a spinning drop interfacial tensiometer by the method disclosed by J Lucassen in the Journal of Colloidal and Interface Science, Vol 20, No 2, June 15 1979, 355. It is expressed in milliNewtons/metre after a specified time at a specified temperature. The lower the value, the more effective is the surfactant. COMPOUND Capillary Oil Displacement Dynamic Time against Forties crude Interfacial 2000 ppm solution in sea water Tension, against Forties Crude mN/m Example 1 8 sec/250C 0.2/5 min/43 C 3 sec/85 C 0.232/equilib./43 C Example 2 5 min/25 C 0.094/equilib/96 C 6 minJ43 C Example 3 EMI5.1 10 sec/25 C 0.242/2.3 min/420C after 7 min delay 0.288/equilib/43 C Example 4 EMI5.2 3 min/42 0.065/equilib/70 C 35 sec/78 C By way of comparison, similar measurements were carried out on an alkyl galactose having no alkylene oxide groups, ie with n = O in Formula 1. EMI6.1 35 min/25 C 0.288/3 min/40 C 5 sec/800C 0.5/equilib./650C Oil Displacement A test of oil displacement was made in a packed column containing sand obtained from the Forties Field. The sand bed was flooded at 70 C with Forties crude oil and then with the water again at 700C so as to simulate an oil bearing formation at the residual level after a waterflood operation. The surfactant dispersed in sea water was then passed through the sand column at 70"C to displace residual oil. Tests were carried out with the compounds of Examples 1 and 4 with the following results: Example -1 compound: 11X oil displaced over 1.4 to 2.0 pore volumes Example 4 compound: 37Z oil displaced over 1.3 to 3.9 pore volumes The concentration of surfactant in the sea water was 2000 ppm in each case.

Claims: Claims: 1. An aqueous surfactant composition suitable for injection into an oil bearing formation to assist in the recovery of oil, the composition comprising an aqueous medium having dispersed therein an alkylpolyalkyleneoxy monosaccharide or reduced monosaccharide of general formula: I R - (O CR2 CR2)n - 0 - [monosaccharide] or EMI7.1 seduced monosaccharide] wherein R is an alky group containing 8 to 24 carbon atoms and n is O or an integer from to 20 inclusive. 2. A composition according to claim 1 wherein the monosaccharide is galactose, glucose or mannose. 3. A composition according to claim 1 wherein the reduced monosaccharide is sorbitol, mannitol or dulcitol. 4. A method of recovering oil from a formation which method comprises the steps of injecting a composition according to any of the preceding claims into the formation via an injection well and recovering the oil from a production well spaced apart from the injection well. 5. Compounds of general formula: I R ( OCH2CR2)n - 0 - [monosaccharide] or EMI7.2 [reduced monosaccharide] wherein R is an alkyl group containing 8 to 24 carbon atoms and n is an integer from 1 to 20 inclusive.

Inventors: HODGSON, PHILIP KENNETH GORDON
Applicants: THE BRITISH PETROLEUM COMPANY P.L.C.
Application year: 1982
Main classification: E21B43
IPC codes: C09K8