COMPOSITION WITH FOAMING PROPERTIES

Abstract

The present invention discloses a composition for enhanced oil recovery comprising olefin sulfonate, sulfo-betaine, betaine and about 0.5 wt % to about 1.5 wt % magnesium chloride.

Claims

1. A composition for enhanced oil recovery comprising: olefin sulfonate; sulfo-betaine; betaine; and about 0.5 wt % to about 1.5 wt % magnesium chloride.

2. The composition according to claim 1, wherein the olefin sulfonate is a sodium alpha-olefin sulfonate; or wherein the olefin sulfonate corresponds in structure to Formula (I): ##STR00020## wherein R.sup.1 is an optionally substituted C.sub.10 to C.sub.12 alkyl, alkenyl or alkynyl; and M is a counter ion; or wherein the olefin sulfonate is selected from the group consisting of the following compounds: ##STR00021##

3. (canceled)

4. (canceled)

5. The composition according to claim 1, wherein the sulfo-betaine corresponds in structure to Formula (II): ##STR00022## wherein R.sup.2 is optionally substituted alkylene, alkenylene or alkynylene; R.sup.3 is optionally substituted alkyl, alkenyl or alkynyl; and R.sup.5 and R.sup.6 each are independently optionally substituted alkyl, alkenyl, alkynyl, aryl, heteroaryl, carbocyclyl, or heterocyclyl; or wherein the sulfo-betaine corresponds in structure to Formula (IIA) ##STR00023## wherein R.sup.4 is optionally substituted alkyl, alkenyl, alkynyl, or optionally substituted C.sub.11 to C.sub.13 alkyl; or wherein the sulfo-betaine is selected from the group consisting of the following compounds: ##STR00024##

6. (canceled)

7. (canceled)

8. (canceled)

9. The composition according to claim 1, wherein the betaine corresponds in structure to Formula (III): ##STR00025## wherein R.sup.7 is optionally substituted alkylene, alkenylene or alkynylene; R.sup.10 is optionally substituted alkyl, alkenyl or alkynyl; and R.sup.8 and R.sup.9 each are independently optionally substituted alkyl, alkenyl, alkynyl, aryl, heteroaryl, carbocyclyl, heterocyclyl; or wherein the betaine corresponds in structure to Formula (IIIA) ##STR00026## wherein R.sup.11 is optionally substituted alkyl, alkenyl, alkynyl, or optionally substituted C.sub.11 to C.sub.13 alkyl; or wherein the betaine is selected from the group consisting of the following compounds: ##STR00027##

10. (canceled)

11. (canceled)

12. (canceled)

13. The composition according to claim 1, comprising: an olefin sulfonate corresponding in structure to Formula (I): ##STR00028## wherein R.sup.1 is an optionally substituted C.sub.10 to C.sub.12 alkyl, alkenyl or alkynyl; and M is a counter ion; a sulfo-betaine corresponding in structure to Formula (IIA): ##STR00029## wherein R.sup.4 is optionally substituted alkyl, alkenyl, or alkynyl; a betaine of Formula (IIIA): ##STR00030## wherein R.sup.11 is optionally substituted alkyl, alkenyl, or alkynyl; and about 0.5 wt % to about 1.5 wt % magnesium chloride.

14. The composition according to claim 1, comprising: C.sub.14 to C.sub.16 alpha-olefin sulfonate; cocaamido propyl hydroxy sulfo-betaine; cocaamido propyl betaine; and about 0.5 wt % to about 1.5 wt % magnesium chloride.

15. The composition according to claim 1, comprising: an olefin sulfonate selected from the group consisting of the following compounds: ##STR00031## a sulfo-betaine selected from the group consisting of the following compounds: ##STR00032## about 0.5 wt % to about 1.5 wt % magnesium chloride.

16. The composition according to claim 1, comprising about 0.5 wt % to about 0.7 wt % magnesium chloride.

17. The composition according to claim 1, further comprising an aqueous medium, preferably wherein the aqueous medium is selected from the group consisting of distilled water, water, ground water, brackish water, surface water, brine and seawater.

18. The composition according to claim 1, wherein said composition comprises: a solution comprising an aqueous medium and a mixture comprising about 18.0 wt % to about 20.50 wt % olefin sulfonate, about 10.5 wt % to about 12.5 wt % sulfo-betaine, and about 11.5 wt % to about 12.5 wt % betaine, wherein said mixture is diluted in the aqueous medium to about 0.3 w/w % to about 0.5 w/w %; and about 0.5 wt % to about 1.5 wt % magnesium chloride.

19. (canceled)

20. The composition according to claim 1, wherein said composition does not comprise a polymer.

21. The composition according to claim 1, when used to generate stable foams at high temperature and salinity; of when used to generate stable foams at a temperature of about 95° C. to about 110° C.; or when used to generate stable foams at a salinity of more than 35,000 ppm; or when used to generate stable foam lamellae.

22. (canceled)

23. (canceled)

24. (canceled)

25. The composition with foaming properties according to claim 21, wherein the viscosity of the stable foam generated is between 30 to 100 cP (mPa.Math.s) at 25° C.

26. The composition according to claim 1, further comprising a foaming gas, preferably wherein the foaming gas is selected from the group consisting of nitrogen, oxygen, carbon dioxide, natural gas, methane, propane, butane, and a mixture thereof.

27. (canceled)

28. The composition according to claim 26, wherein the foaming gas generates a stable foam upon contact with said composition.

29. The composition according to claim 28, wherein the stability of the generated foam is sustained after multiple contacts with a foaming gas.

30. The composition according to claim 1, wherein the composition has a foam half-life between 180 to 525 seconds; or wherein gas mobility reduction factor (MRF) of the composition is in the range of 1 to 16, or wherein the composition is biodegradable, and wherein the biodegradability of the composition is more than 60% in theoretical oxygen demand (THOD), or wherein the composition has a low bioaccumulation tendency of partition coefficient (Log P.sub.ow) less than 3 and BCF (bioconcentration factor) less than 100.

31. (canceled)

32. (canceled)

33. (canceled)

34. The composition according to claim 1, when used in offshore direct discharge after use; or when used in an oil recovery process.

35. (canceled)

36. A process for preparing a composition according to claim 1, comprising: (a) preparing a solution comprising about 18.0 wt % to about 20.50 wt % olefin sulfonate, 10.5 wt % to about 12.5 wt % sulfo-betaine, and about 11.5 wt % to about 12.5 wt % betaine; (b) preparing a mixture by diluting the solution of step (a) with aqueous medium to a concentration of about 0.3 w/w % to about 0.5 w/w %; and (c) adding magnesium chloride to the mixture of step (b) to obtain a composition comprising a final concentration of about 0.5 wt % to about 1.5 wt % magnesium chloride.

37. A method for recovering oil from a subterranean oil-containing formation comprising: (a) introducing a composition with foaming properties according to claim 1 into the subterranean oil-containing formation; (b) introducing a gas into the subterranean oil-containing formation, wherein the presence of the composition with foaming properties lowers the gas mobility within said formation; and (c) recovering oil from the formation.

38. (canceled)

Description

BRIEF DESCRIPTION OF DRAWINGS

[0141] The accompanying drawings illustrate a disclosed embodiment and serves to explain the principles of the disclosed embodiment. It is to be understood, however, that the drawings are designed for purposes of illustration only, and not as a definition of the limits of the invention.

[0142] FIG. 1 shows a schematic representation of the mechanism of magnesium chloride in improving foam stability in foam composition of present invention (Example 2).

[0143] FIG. 2 shows a foam half-life comparison study of foam composition of present invention (Example 2) with two other comparative foam compositions in Oil Field A (96° C.), Oil Field B (98° C.) and Oil Field C (106° C.) field, respectively. The dominant gas of Oil Fields A, B and C are CO.sub.2, CH.sub.4 and CH.sub.4, respectively.

DETAILED DESCRIPTION OF DRAWINGS

[0144] FIG. 1 shows that magnesium chloride salt exhibits synergistic activity and compatibility with ionic surfactant (1) and amphoteric surfactants (2). As magnesium chloride lattice complex bridges thick foam lamellae (3) at the gas interface (4), the foam composition of the present invention advantageously provides a viscosity similar to polymer. This bridging effect reduces the drainage rate of liquid from foam lamellae and allows high foam stability to be achieved.

EXAMPLES

[0145] Non-limiting examples of the invention and a comparative example will be further described in greater detail by reference to specific Examples, which should not be construed as in any way limiting the scope of the invention.

Materials

[0146] Witconate AOS obtained from AkzoNobel N.V.
Betadet SHR obtained from Kao Chemicals Europe S.L.
Betadet HR-50K obtained from Kao Chemicals Europe S.L.

Example 1: Preparation of Composition

[0147] A surfactant composition was prepared as follow. 75 g of Witconate AOS was weighed into a 500 mL beaker. Within the same beaker, 37.50 g of Betadet SHR and 37.50 g of Betadet HR-50K were weighed. By using a laboratory stand mixer, the three chemicals were mixed together at 400 rpm until the mixture was observed to be homogenous. The mixture was then left to stand overnight or until the bubbles have disappeared. The concentration of active components in the surfactant mixture is shown in Table 1.

TABLE-US-00001 TABLE 1 (Specific) Active concen- tration in the mixture % of each component Components (wt %) in the mixture Witconate AOS 20.00 50.0 (Alpha olefin sulfonate C14-C16) Betadet SHR 11.00 25.0 (sulfo-betaine) Betadet HR-50K 11.75 25.0 (betaine) TOTAL 42.75% 100%

[0148] Subsequently, the mixture was diluted by weighing 1.39 g of the solution and topping up with 200 g of brine from an oil field (Oil Field C). The surfactant mixture was stirred until fully dissolved, making 0.3 w/w % of surfactant mixture.

[0149] The brine from Oil Field C contains salts of such metals as sodium, potassium, calcium, magnesium, and barium which is typical of sources of water found in or near oil fields. The amount of magnesium chloride added to the mixture may be adjusted such that the total final concentration of magnesium chloride in the composition is about 0.5 wt % to about 1.5 wt %. The properties of the brine from Oil Field C are shown in Table 2.

TABLE-US-00002 TABLE 2 Brine Properties of Oil Field C Ions Concentration (mg/L) Na.sup.+ 9,776 K.sup.+ 352 Ca.sup.2+ 295 Mg.sup.2+ 1,265 Ba.sup.2+ 0.049 Cl.sup.− 17,371 HCO.sub.3.sup.− 133 SO.sub.4.sup.2− 1,900

[0150] The MgCl.sub.2 concentration calculated from the brine of Oil Field C was 4.956 g/L (i.e. about 0.9912 g in 200 g Oil Field C brine). 0.1904 g of magnesium chloride (MgCl.sub.2) salt (powder) was dispensed into the 0.3 w/w % solution using a spatula, to make a total MgCl.sub.2 concentration of 0.59 wt %. The powder mixture was mixed until fully dissolved.

Example 2: Foam Stability Test of Composition

[0151] Foam stability test was conducted using FoamScan Teclis Instrument (Teclis, France). Foam stability was investigated using foam half-life of its initial volume created in the foam column. 80 mL of the prepared foam composition of Example 2 was injected into the foam column. The foam stability test parameters are summarized in Table 3. The temperature of the test was set to 96-106° C. and the pressure was fixed at 1 bar. The test was carried out in two conditions—with crude oil and without crude oil. In the with crude oil condition, 10 v/v % of 80 mL of crude oil was injected together with the foam composition.

[0152] The foam stability test parameters are shown in Table 3. The foam stability half life test results are shown in Table 6.

TABLE-US-00003 TABLE 3 Foam stability test parameters Foam stability test parameters Values Temperature: Oil Field A 96° C. Oil Field B 98° C. Oil Field C 106° C. Gas flow rate 100 mL/min Pressure 1 bar Oil saturation 10 v/v %
The properties of the brine from Oil Fields A and B are shown in Tables 4 and 5.

TABLE-US-00004 TABLE 4 Brine Properties of Oil Field A Ions Concentration (mg/L) Na.sup.+ 10,070 K.sup.+ 393 Ca.sup.2+ 382 Mg.sup.2+ 1,172 Ba.sup.2+ 0 Cl.sup.− 19,455 HCO.sub.3.sup.− 133 SO.sub.4.sup.2− 2,040
The MgCl.sub.2 concentration calculated from the brine of Oil Field A was 4.59 g/L (i.e. about 0.918 g in 200 g Oil Field A brine). A foam composition using Oil Field A brine was prepared in a similar manner according to Example 1. 0.1904 g of magnesium chloride (MgCl.sub.2) salt (powder) was dispensed into the 0.3 w/w % solution using a spatula, to make a total MgCl.sub.2 concentration of 0.55 wt %. The powder mixture was mixed until fully dissolved.

TABLE-US-00005 TABLE 5 Brine Properties of Oil Field B Ions Concentration (mg/L) Na.sup.+ 9,376 K.sup.+ 325 Ca.sup.2+ 289 Mg.sup.2+ 1,189 Ba.sup.2+ 0 Cl.sup.− 16,328 HCO.sub.3.sup.− 183 SO.sub.4.sup.2− 2,500
The MgCl.sub.2 concentration calculated from the brine of Oil Field B was 4.65 g/L (i.e. about 0.93 g in 200 g Oil Field B brine). A foam composition using Oil Field A brine was prepared in a similar manner according to Example 1. 0.1904 g of magnesium chloride (MgCl.sub.2) salt (powder) was dispensed into the 0.3 w/w % solution using a spatula, to make a total MgCl.sub.2 concentration of 0.56 wt %. The powder mixture was mixed until fully dissolved.

TABLE-US-00006 TABLE 6 Foam Half life without Half-life with Formulation crude oil Crude oil Foam composition using Oil 324 343 Field A brine (methane) Foam composition using Oil 267 203 Field B brine (CO.sub.2) Foam composition using Oil 500 411 Field C brine (nitrogen)

Example 3: Gas Mobility Reduction Factor (MRF) Test

[0153] Gas Mobility Reduction Factor (MRF) is defined as a ratio of the measured sectional pressure drop for foam flow to the corresponding pressure drop for the flow of methane gas at the same superficial velocity. A high differential pressure and MRF will indicate the presence of strong foam inside the core. A sustained MRF and differential pressure trend can be attributed to the stability of the foam. MRF is defined in the equation below:

[00001]$MRF=\frac{\Delta P\mathrm{Foam}}{\Delta P\mathrm{No}\mathrm{Foam}}$

Where:

[0154] ΔP foam=pressure drop of foam injection at same velocity as gas (psi)
ΔP no-foam=pressure drop of gas injection at same velocity as foam (psi) MRF was measured from coreflood experiments, the ΔP foam and ΔP no-foam are measured as the differential pressure across the core, with and without foam, respectively. In a surfactant-alternating-gas (SAG) approach, firstly, the differential pressures are recorded for gas (only) at flow rate of 0.1, 0.2, 0.4 and 0.6 mL/min. When foam composition is injected through the core, the differential pressures are then recorded at gas injection flow rate is of 0.1, 0.2, 0.4 and 0.6 mL/min. The MRF is then calculated as per equation above for the same flow rates.
The MRF test parameters are shown in Table 7 and the results are shown in Table 8.

TABLE-US-00007 TABLE 7 Coreflood conditions (Oil Field C) Value Temperature 106° C. Pressure 2000 psi Type of gas Methane (pure) Core dimension (length × diameter) 7.0 cm × 3.7 cm Permeability of core (Kw) 50-300 mD

TABLE-US-00008 TABLE 8 Average MRF Rate Present invention Injection Stage (cc/min) (Example 2) Surfactant SAG1 0.1 1 Gas 0.1 1 Surfactant SAG2 0.1 8 Gas 0.1 2 Surfactant SAG3 0.2 12 Gas 0.2 4 Surfactant SAG4 0.4 16 Gas 0.4 4 Surfactant SAG5 0.6 16 Gas 0.6 7

Example 4: Chemical Hazard Assessment and Risk Management (CHARM) Dilution Modelling of Composition

[0155] CHARM dilution modelling under the OSPAR Convention was conducted to determine the risk and extent of chemical movement in the ocean. This is a vital decision-making tool to determine if the chemicals are safe to be discharged overboard. To be determined safe to discharge overboard, the chemicals should at least rank GOLD or SILVER band, indicating a low hazard quotient (HQ).

[0156] Extensive ecotoxicology evaluations on the degree of toxicity, biodegradability and persistency of a foam composition of the present invention were performed using recognised standard methods for eco-toxicity evaluation from the Organisation for Economic Co-operation and Development (OECD). A composition of the present invention has the following eco-toxicological values:

Persistency (Bioaccumulation) for each component:
All components of a composition of the present invention are non-persistent. All components meet the persistency criteria of either: Log Pow >3 or BCF<100, MW >300)

Biodegradability of Formulation:

[0157] A composition of the present invention is readily biodegradable=89.05% degradation after 28 days.
Toxicity of organisms from three trophic levels: [0158] Acute toxicity on fish, LC.sub.50=2.55 mg/L [0159] Acute toxicity on invertebrate (Daphnia magna), EC.sub.50=9.4 mg/L [0160] Acute toxicity on algae, EC.sub.50=7.79 mg/L

[0161] Based on the above, the composition of the present invention has met the Applicability check (Persistency and Biodegradation criteria) set by OSPAR. The next step was to evaluate/calculate the extent of toxicity over time through a risk assessment known as the hazard quotient (HQ) using the CHARM dilution model.

[0162] The PNEC (predicted no effect concentration) is derived on the basis of the results obtained in the ecotoxicology studies with algae, invertebrate and fish, by dividing the lowest observed effect concentration by an appropriate assessment factor which is found in the ECHA Guidance Document R.10. Here, the lowest toxicity value is LC.sub.50=2.55 mg/L from acute toxicity to fish. According to the ECHA Guidance R.10, an assessment of 10,000 for the derivation of PNEC should be applied, i.e.:

[00002]$\mathrm{PNEC}\left(\mathrm{ug}/L\right)=\frac{\mathrm{Lowest}\mathrm{Toxicity}\mathrm{Value}\left(\mathrm{ug}/L\right)}{\mathrm{Assessment}\mathrm{Factor}}$$\begin{array}{c}=2.55\mathrm{mg}/L/10,000\\ =0.000255\mathrm{mg}/L\\ =0.255\mathrm{\mu g}/L\end{array}$

[0163] Then, the PEC (predicted environmental concentration) for the on-going discharge is calculated using the following equation:

[00003]$PE{C}_{wat\mathrm{er},\mathrm{on}-\mathrm{going}}=\frac{\frac{f_r.Math.F_{\mathrm{squeezing}\mathrm{treatment}}.Math.C_{\mathrm{squeezing}\mathrm{treatment}}}{\Delta t}}{F_{pw}}.Math.D_{\mathrm{distance},x}$

In which: [0164] fr=fraction released (=0.33) [0165] C.sub.squeezing treatment=initial concentration of chemical in the chemical solution [0166] F.sub.squeezing treatment=the total amount in mg/L of chemical solution pumped into the well in the squeezing treatment [0167] Δt is the duration in days of the on-going release. This was set to 90 days [0168] F.sub.Pw is the volume of produced water discharged per day (m.sup.3/d). A value of 14,964 m.sup.3/d is the CHARM default value. [0169] D.sub.distance,x is the dilution factor at distance x from the platform. The dilution factor is set to 0.001 at distance of 500 according to CHARM, i.e. D.sub.distance,_=0.001. [0170] Calculations of the on-going PECs were carried out by assuming different ratios between F.sub.squeezing treatment and F.sub.pw.

[0171] The Hazard Quotient (HQ) is then calculated by dividing the PEC with the PNEC, or HQ=PEC/PNEC. The HQ results are shown in Table 9 and how HQ values are colour banded is shown in Table 10.

TABLE-US-00009 TABLE 9 Hazard Quotient (HQ) and Colour Banding of the composition of Example 2. HQ C.sub.sq D.sub.distance, x PEC PNEC (=PEC/ Colour (mg/L) F.sub.r (500 m) F.sub.sq/F.sub.pw (mg/L) (mg/L) PNEC) band 3000 0.33 0.001 1/20 5.5 × 10.sup.−4 0.000255 2.16 Silver (0 < HQ < 1)

TABLE-US-00010 TABLE 10 Colour banding indicating hazard rating from CHARM dilution model. Minimum HQ Maximum HQ Value Value Colour banding >0 <1 Gold Lowest Hazard ≥1 <30 Silver ≥30 <100 White ≥100 <300 Blue ≥300 <1000 Orange Highest Hazard ≥1000 Purple

[0172] The foam composition of Example 2 is considered a Silver ranked chemical if this chemical was to be listed against other chemicals used at North Sea under OSPAR system. A Gold ranked chemical is considered to pose a low hazard to the environment.

[0173] As CHARM Model does not model inorganic compounds such as metal salts, magnesium chloride was pre-screened prior to CHARM modelling. During the pre-screening process. Magnesium chloride was evaluated as a single component. Based on the safety data sheet (SDS) of magnesium chloride, LC50 or bioaccumulation values are not applicable and the compound has good biodegradability. Hence, magnesium chloride is considered non-toxic as an individual substance. As a result, having magnesium chloride as part of the foaming composition does not affect the CHARM dilution results presented above.

COMPARATIVE EXAMPLES

Comparative Example 1: Foam Stability Comparison

Preparation of Comparative Foam Composition 1:

[0174] 75 g of Witconate AOS was weighed into a 500 mL beaker. Within the same beaker, 37.50 g of Betadet SHR, and 37.50 g of Betadet HR-50K were weighed. By using laboratory stand mixer, the three chemicals were mixed together at 400 rpm until the mixture was observed to be homogenous. An acrylic copolymer amphiphilic surfactant solution was prepared by preparing 1.0% of acrylic copolymer amphiphilic surfactant, i.e., 1 mL in 100 mL double distilled water. The solution was stirred and subsequently allowed to stand for 24 hours to form a surfactant blend.

[0175] 100 mL of acrylic copolymer amphiphilic surfactant solution (that was left to stand for 24 hrs) and 100 mL of the surfactant blend were blended in a ratio of 1:1 using an overhead stirrer at <400 rpm. 200 mL of double distilled water was added during blending until a homogenous solution is obtained. The formulation was left to stand overnight.

Preparation of Comparative Foam Composition 2:

[0176] 75 g of Witconate AOS was weighed into a 500 mL beaker. Within the same beaker, 37.50 g of Betadet SHR, and 37.50 g of Betadet HR-50K were weighed. Using a laboratory stand mixer, the three chemicals were mixed together at 400 rpm until the mixture was observed to be homogenous. 66.67 g of Schleroglucan liquid (obtained from Cargill, Incorporated) from its original bottle (supplied as 0.15%) was then weighed into a separate beaker. Under stirring condition, 33.33 g of distilled water was added slowly to dilute Schleroglucan to 0.10%. Thereafter, the diluted Schleroglucan was mixed with the previous surfactant mixture of Witconate AOS, Betadet SHR and Betadet HR-50K to form a homogenous solution.

[0177] Subsequently, 150 g of distilled water was added into the above solution and stirred at 200 rpm until homogenous. The solution was then left to stand overnight or until the bubbles have disappeared.

[0178] The active concentrations of the two comparative foam compositions are shown in Table 11.

TABLE-US-00011 TABLE 11 Active concentration in the composition (wt %) Comparative foam Comparative foam Components composition 1 composition 2 Witconate AOS 10.00 7.50 (Alpha olefin sulfonate C14-C16) Betadet SHR 5.5 4.13 (sulfo-betaine) Betadet HR-50K 5.88 4.41 (betaine) Atlox 4913 0.44 0.00 (Polymeric Amphiphilic Surfactant) Schleroglucan 0.00 0.04 (Exopolysaccharide) TOTAL active 21.81% 16.07% concentration

[0179] A comparison between the foam composition of the present invention (Example 2) and two other comparative compositions are shown in FIG. 2 and the comparison results are shown in Tables 12 and 13. During the foam stability test, comparative foam compositions 1 and 2 are tested at an active concentration of 0.3 w/w % and the foam composition of present invention (example 2) is tested at an active concentration of 0.3 w/w % with 0.59 wt % M total magnesium chloride concentration.

TABLE-US-00012 TABLE 12 Summary of foam half-life (seconds) results tested in the presence of crude oil. Foam half-life (seconds) With Crude Oil Oil Field A Oil Field B Oil Field C Present invention (Example 2) 343 203 196 Comparative composition 1 265 155 130 Comparative composition 2 212 197 121

TABLE-US-00013 TABLE 13 Summary of foam half-life (seconds) results tested in the absence of crude oil. Foam half-life (seconds) Without Crude Oil Oil Field A Oil Field B Oil Field C Present invention (Example 2) 324 267 500 Comparative composition 1 258 108 163 Comparative composition 2 267 173 326
The results shown in Tables 12 and 13 show that foams produced using the foam composition of the present invention are more stable when compared against comparative compositions 1 and 2 which use similar surfactant mixtures, but do not contain MgCl.sub.2.

Comparative Example 2: Gas Mobility Reduction Factor (MRF) Comparison

[0180] The Gas Mobility Reduction Factor (MRF) comparison between the composition of the present invention (Example 2) and comparative compositions 1 and 2 of Comparative Example 1 are shown in Table 14.

TABLE-US-00014 TABLE 14 Gas Mobility Reduction Factor (MRF) comparison between the foam compositions, tested using a Surfactant- Alternating-Gas (SAG) injection method. Average MRF Comparison (SAG) Average MRF Present Comparative Comparative Rate invention composition composition Injection Stage (cc/min) (Example 2) 1 2 Surfactant SAG1 0.1 1 1 1 Gas 0.1 1 1 1 Surfactant SAG2 0.1 8 2 6 Gas 0.1 2 2 1 Surfactant SAG3 0.2 12 11 11 Gas 0.2 4 1 1 Surfactant SAG4 0.4 16 20 13 Gas 0.4 4 3 1 Surfactant SAG5 0.6 16 21 15 Gas 0.6 7 7 2

[0181] As shown in Table 14, the average Gas Mobility Reduction Factor (MRF) of a composition of the present invention (Example 2) is comparatively higher than the other two comparative compositions for SAG2 and SAG3. In addition, the average Gas Mobility Reduction Factor (MRF) of a composition of the present invention (Example 2) is comparatively higher than the comparative composition 2 but slightly lowered than comparative composition 1 for SAG4 and SAG5.

[0182] Although the MRF of comparative composition 1 is slightly higher than a composition of the present invention for SAG4 and SAG5, it has lower foam stability than the present invention (Example 2) as shown in Comparative Example 1. Additionally, the comparative composition 1 is less environmentally friendly compared to the composition of the present invention (Example 2) as shown in Comparative Example 3 below. Further, the composition of comparative composition 1 is also less cost-effective than the composition of the present invention (Example 2) as shown in Comparative Example 4 below.

Comparative Example 3: Comparison of Biodegradation, Bioaccumulation and Toxicity Between the Foam Compositions

[0183]

TABLE-US-00015 TABLE 15 Comparison of biodegradation, bioaccumulation and toxicity between foam compositions. Toxicity (CHARM Biodegradation Bioaccumulation dilution modelling) Present ✓ ✓ ✓(SILVER band) invention (Example 2) Comparative X ✓ ✓(Gold band) composition 1 Comparative ✓ ✓ ✓(Silver band) composition 2

[0184] As shown in Table 15, the composition of the present invention (Example 2) achieves silver band which is comparable to comparative composition 2 but poorer than comparative composition 1.

[0185] Although the composition of comparative composition 1 achieves gold band, the polymeric amphiphilic surfactant component in it has poor biodegradability and is therefore not safe to be discharged overboard as stated in the OSPAR Regulations. Additionally, the composition of comparative composition 1 is also hard to be treated in water treatment and may cause hazards to the environment.

[0186] The extent of environmental friendliness depends on all three factors—toxicity, biodegradability, and bioaccumulation. The composition of the present invention in Example 2 only achieves silver band but meets all 3 factors (toxicity, biodegradability and bioaccumulation). Although the composition of comparative composition 1 achieves the gold band, comparative composition 1 has only met 2 factors (bioaccumulation and toxicity). Hence, the composition of the present invention (Example 2) is considered to be more environmentally friendly than the composition of comparative composition 1. Table 16 shows the HQ results of the three compositions.

TABLE-US-00016 TABLE 16 Hazard Quotient (HQ) and Colour Banding of the foam composition of comparative composition 1 and comparative composition 2 HQ C.sub.sq D.sub.distance, x PNEC PEC (=PEC/ Colour (mg/L) F.sub.r (500 m) F.sub.sq/F.sub.pw (mg/L) (mg/L) PNEC) band Present 3000 0.33 0.001 1/20 0.000255 5.5 × 2.16 Silver Invention 10.sup.−4 (0 < HQ < 1) (Example 2) Comparative 5000 0.33 0.001 1/20 0.0218 9.17 × 0.04 Gold composition 1 10.sup.−4 (HQ < 1) Comparative 3000 0.33 0.001 1/20 0.000255 5.5 × 2.16 Silver composition 2 10.sup.−4 (1 < HQ < 30)

Comparative Example 4: Cost Comparison

[0187]

TABLE-US-00017 TABLE 17 Cost comparison study with a commercial composition. Unit cost of Application chemical foam Company/ concentration surfactant Supplier (%) (USD/kg) Present invention Petroliam 0.3 foam 3.03 (Example 2) Nasional composition + Berhad 0.59 total MgCl2 concentration Comparative Petroliam 0.5 3.33 composition 1 Nasional (Comparative Berhad example 1) Comparative Petroliam 0.3 3.12 composition 2 Nasional (Comparative Berhad example 1) Commercial DuPont, USA 0.5 4.54 composition (Capstone ® FS-50)

[0188] As shown in Table 17, the composition of the present invention (Example 2) requires a lower application concentration and this translates to an appreciable cost advantage over the comparative composition 1, and a significant cost advantage over Capstone® FS-50.

[0189] Although the composition of the present invention (Example 2) requires a higher application concentration as compared to comparative composition 2, the composition of present invention (Example 2) comprises magnesium chloride which is cheaper than components such as exopolysaccharide used in comparative composition 2 Therefore, the foam composition of the present invention (Example 2) still offers a cost advantage over comparative composition 2 despite requiring a slightly higher application concentration.

[0190] As the composition of the present invention displays biodegradability and non-toxicity, and is thus safe to be discharged overboard after use, it eliminates the use of end-of-pipe solution and facilities and translates to substantial cost savings. Furthermore, as the composition of the present invention requires a lower application concentration, cheaper components in its composition and lower concentration of each component, it translates to cost-effectiveness and further cost savings.

Comparative Example 5: Comparison with Different Magnesium Salts

[0191]

TABLE-US-00018 TABLE 18 Foam Half-life (s) at 106° C. using nitrogen gas (Oil Field C) Without With crude oil Remarks/Observation Example no. Magnesium salt crude oil (from Oil Field C) (if any) Present 0.59 wt % total 500 411 Fully soluble in foam invention concentration of composition (0.3 (Example 2) MgCl.sub.2 w/w %) Comparative 0.45 wt % total 336 333 Precipitation Composition concentration of observed 3 MgO Comparative 0.54 wt % total 290 383 Precipitation Composition concentration of observed 4 Mg(OH).sub.2

[0192] Comparative Compositions 3 and 4 were prepared in a similar manner to Example 1, except that instead of MgCl.sub.2 being added to the surfactant mixture, MgO was added for Comparative Composition 3 and Mg(OH).sub.2 was added for Comparative Example 4. The total concentration of MgO in Comparative Composition 3 was 0.45 wt %, and the total concentration of Mg(OH).sub.2 in Comparative Composition 4 was 0.54 wt %.

[0193] As shown in Table 18, the selection of magnesium chloride as a foam stabilizer shows better foam stability when compared to the other magnesium salts. This is hypothesized to be because in water, MgCl.sub.2 can form the anion complex MgCl.sub.4.sup.2− to form a network of—[MgCl.sub.4].sup.2−—[MgCl.sub.4].sup.2−—H2O-(bridging between 2 ions and hydrogen bonds with H2O), which is not observed for MgO and Mg(OH)2, primarily because of their insolubility in water. MgCl.sub.2 is fully soluble in brine, while MgO and Mg(OH).sub.2 are insoluble in brine, resulting in undesirable precipitation).

Comparative Example 6: Comparison with Different Concentrations of MgCl.SUB.2

[0194]

TABLE-US-00019 TABLE 19 Total Foam Half-life (s) at 106° C. using concentration nitrogen gas (Oil Field C) Remarks/ of MgCl.sub.2 Without With crude oil Observation wt % crude oil (from Oil Field C) (if any) 0.11 116 321 Fully soluble in foam composition (0.3 w/w %) 0.59 500 411 Fully soluble in foam composition (0.3 w/w %) 0.97 207 245 Slightly turbid 1.44 201 251 Turbid

[0195] As shown in Table 19, the optimal concentration for MgCl.sub.2 is 0.5 wt % to 1.5 wt % because foaming compositions containing below 0.5 wt % of magnesium chloride result in a short foam half life, and above 1.5 wt %, turbidity is observed in the foaming composition.

[0196] It is hypothesized that the short foam half life observed for foaming compositions containing less than 0.5 wt % of magnesium chloride results as the bridging effect between the crystal lattice complex and surfactants does not occur. In other words, when magnesium chloride is present at a concentration of less than 0.5 wt %, it is unable to bridge between adjacent foam lamellae generated by the surfactant (foam formulation) and does not strengthen the foams any further.

[0197] It is also hypothesized that at a concentration higher than 1.5 wt %, too much ions are present at the lamellae, leading to the ‘congestion’ (=turbidity) at the plateau border, competing with surfactants in building lamella, leading to the collapse of the foam.

INDUSTRIAL APPLICABILITY

[0198] The disclosed composition with foaming properties advantageously comprises a divalent metal salt that may be an efficient foam stabilizer, and is readily biodegradable and non-toxic.

[0199] Advantageously, the composition with foaming properties may be used to generate a foam that exhibits good foam generation and stability under severe reservoir conditions of high temperatures, high salinity and in the presence of crude oil.

[0200] Therefore advantageously, the disclosed composition with foaming properties may be used in improved oil recovery methods and may be directly discharged offshore after use.

[0201] There is therefore also provided a method for recovering oil from a subterranean oil-containing formation.

[0202] The composition with foaming properties advantageously may be used to generate foam which exhibits a low adsorption rate on reservoir rock and high Mobility Reduction Factor. The lowered gas mobility advantageously results in improved sweep efficiency.

[0203] Further advantageously, the composition with foaming properties may be used to generate a stable foam even after repeated contacts with a foaming gas.

[0204] It will be apparent that various other modifications and adaptations of the invention will be apparent to the person skilled in the art after reading the foregoing disclosure without departing from the spirit and scope of the invention and it is intended that all such modifications and adaptations come within the scope of the appended claims.