IE53660B1 - Composition and method for cleaning oil from hard surfaces - Google Patents

Abstract

Hydrocarbon oils may be cleaned from hard, inorganic surfaces by the application of an aqueous solution (e.g. sea water) containing from 0.1 to 10% by weight of a mixture of (A) 5 to 95% by weight of an alkoxylated, alcohol, carboxylic acid, alkyl phenol, alkylamine or nonionic phosphate ester, having in each case at least one alkyl group with from 6 to 22 carbon atoms and from 1 to 20 ethyleneoxy and/or propyleneoxy groups, with (B) from 95% to 5% by weight of at least one alkenyl or alkyl mono- or di-ethanolamide or an ethoxylated or polyethoxylated alkenyl or alkyl mono- or di-ethanolamide wherein the alkyl or alkenyl group has from 5 to 17 carbon atoms and having 1 to 12 total ethoxy groups. The method is of particular value for cleaning drilling oil from rock cuttings in offshore drilling operations.

Description

ALBRIGHT & WILSON LIMITED, A BRITISH COMPANY, OF ALBRIGHT & WILSON HOUSE, HAGLEY ROAD WEST, OLDBURY, WARLEY, WEST MIDLANDS, ENGLAND.

Price 90p The present invention relates to methods of cleaning oil/rock mixtures in oil drilling operations and especially to cleaning of drilling oil from rock cuttings on offshore drilling rigs, removal of oil from the face of newly drilled holes prior to reinforcement with casing, and to the cleaning of oil muds from drilling rigs.

In the process of drilling for oil and gas, it is necessary for a number of reasons, to use a drilling fluid or drilling mud. The types of drilling fluid or mud in common use are:10 a) water based. b) oil based. c) water in oil emulsion based (invert).

Oil based drilling media (b) may also contain water in the form of water in oil emulsion. It is customary in the art to refer to a drilling medium containing up to about 15% aqueous phase by volume as oil based. Those drilling media referred to as invert fluids or muds, (c) generally contain between 15% and 55% water.

This patent application is particularly concerned with types (b and c) both of which are Included in the term “oil as used herein, together with crude and refined mineral oils.

One of the functions of drilling fluid is to carry drill cuttings from the drill bit to the surface, the cuttings are then removed by physical techniques, for example, by using shale shakers, screens, cyclones, and centrifuges. After removal of the cuttings the drilling fluid is re-used and the cuttings are disposed of. If the drilling is offshore then the cuttings are disposed of into the sea, where in the case of aqueous drilling fluids the cuttings disperse and settle without causing significant problems. However, in the case of oil drilling fluids the cuttings are oil wet and settle rapidly to the sea bed below the drilling rig and form an oily, sticky mass, which can interefere with drilling operations, for example, by hindering the movement of divers involved in sub-sea construction and maintenance work. It is thought that the swelling of clays in the cuttings is responsible for the formation of this mass. In addition, the cuttings cause oil pollution through gradual release of the oil.

One technique to remove oil from cuttings is to wash the cuttings with a solvent such as diesel, this has the effect of removing most of the oil but still leaves the surface contaminated with hydrocarbons, which can gradually be released to the environment. Another way is to use a water miscible solvent, such as a glycol ether, but these are expensive. Yet another way is to wash the cuttings in sea water using good agitation to dislodge the oil from the surface of the cuttings. This process can be used either as the sole process for removing the drilling oil from the cuttings, or as a second step to remove an oil solvent from cuttings previously washed with a hydrocarbon. This process can be improved by adding a surfactant to the sea water, to lower the oil/water interfacial tension. The cuttings may then be discharged to the sea where they disperse and settle over a wide area of sea bed rather than accumulate directly in the area of the drilling operations.

The oil in water emulsion which is formed as a result of washing the cuttings may be discharged to the sea where fine dispersion of the oil will facilitate its breakdown by micro-organisms.

A commonly used surfactant for the foregoing purposes Is a alcohol six mole ethoxylate. An object of the present Invention Is to provide more effective methods of cleaning oil from rock cuttings.

A further object of our invention is to provide a method whereby oil 5 can be separated from the emulsion resulting from cleaning of the cuttings.

We have discovered that a particular blend of an ethoxylated nonionic surfactant with an alkanolamide exhibits a synergistic effect permitting the more efficient cleaning of oil from rock cuttings. We have further discovered according to a preferred embodiment of our invention that when the emulsions of oil in water formed by cleaning according to our invention are heated, the emulsion is readily broken and the oil may then he recovered.

Accordingly, our invention provides a method for removal of oil from solid surfaces which comprises contacting the surfaces with an aqueous solution containing at least 0.5% by weight of a mixture of (A) from 5 to 95% by weight of at least one alkoxylated alcohol, carboxylic acid, alkylphenol, or nonionic phosphate ester, having in each case an alkyl group with from 6 to 22 carbon atoms and from 1 to 20 ethyleneoxide groups, with (B) from 95 to 5% by weight of at least one ethylolamide of the formulas0 (CH„CH„0) H II / 2 2 x RCN' X(CH2CH20)yH wherein R is an alkyl group having from 5 to 17 carbon atoms and x and y are each chosen from 0 and integers from 1 to 12, such that the average value of (x + y) is from 1 to 12. 4. 6 6 0 Preferably (A) is primary straight or branched chain alcohol having from 6 to 18 carbon atoms and alkoxylated with from 1 to 10 ethylene-oxy groups.

(A) may alternatively be normal or branched chain alkanoic 5 or alkenoic acid having from 7 to 23 carbon atoms, alkoxylated with from 1 to 10 ethylene-oxy groups; straight or branched chain alkyl phenol with from 6 to 12 aliphatic carbon atoms, alkoxylated with from 1 to 12 ethylene-oxy groups; nonionic phosphoric acid ester having at least one straight or branched chain alkyl group with from 6 to 22 carbon atoms, at least one alkoxy or polyalkoxy group with from 1 to 20 ethylene-oxy units.

(B) typically has from 1 to 4 ethyleneoxy groups. While we have discovered that monoethanol amides are particularly effective synergists, and may be preferred for use in warm climates, concentrated mixture of monoethanol amide with component (A) tend to be insufficiently fluid at low temperatures for convenient handling under the conditions which may be encountered in, for example, North Sea operations. For such low temperatures we prefer to use diethanolamides.

Typically, a mixture of (A) and (B) is supplied as a concentrate which is dissolved in, or diluted with, water to provide the cleansing solution at the site of the rig. Such concentrates optionally contain a solvent such as water or a water miscible alcohol, glycol or glycol ether, e.g. isopropanol, ethylene glycol, propylene glycol, polyethylene glycol, as required to provide a fluid, pourable composition under the conditions likely to be encountered. The concentrate may, additionally, contain minor proportions of hydrotropes, such as alkaline earth, sodium potassium )° mono- di- or tri- alkyl benzene sulphonate salts having less than six aliphatic carbon atoms, e.g. toluene or xylene sulphonates, phosphate esters salts, preservatives, such as formalin, dyes and/or perfumes. Water may be present in any convenient proportion between zero and the final working concentration of the cleaner. Generally, the lower the proportion of the water the greater the convenience for transport and storage of the concentrate. These considerations however must be balanced against the preference for a stable, pourable composition. Organic solvents can add appreciably to the cost of the composition and are preferably, therefore used sparingly e.g. less than 50% and preferably less than 20% of the weight of the concentrate.

The concentrate may typically contain from 5 to 95% by weight of (A) and from 95 to 5% by weight of B. Preferably however (A) is present in concentrations greater than 10% by weight, most preferably greater than 20% and usually greater than 30%. (B) is also preferably present in concentrations of greater than 10% by weight, more preferably greater than 20% and usually greater than 30%. A suitable mixture contains from 40% to 60% of (A), from 60% to 40% of (8) and from 0 to 20% of solvent.

The concentrate 1s dissolved or dispersed in water at the site of application. When used at offshore locations, the concentrate may conveniently be dissolved or dispersed in sea water. Typically, the concentrate is diluted to from 0.5% to 10% active matter by weight preferably from 1 to 6. We do not exclude higher concentrations, but they are unlikely to prove cost effective.

Concentrations below 0.5% are not excluded but are only marginally effective.

When used to clean rock cuttings, the cuttings are preferably agitated with the solution of the concentrate in water or brine, for a sufficient time to emulsify a substantial proportion of the oil. The emulsion may then be separated from the cuttings which, when sufficiently clean, are dumped. The emulsion may be discharged. However, according to a preferred embodiment of our invention the oil is recovered from the emulsion by moderate heating. Typically temperatures in excess of 40°C e.g. 50 to 70°C are sufficient to break the emulsion and permit recovery of the separated oil phase.

The cleaning solution according to our invention may also be injected into bore holes to clean oil from the sides of the rock. This is necessary when a casing is to be bonded with cement to the sides of the bore hole. The solution may also be used according to our invention to clean oil mud from the rigs themselves and generally to remove viscous hydrocarbon oils from hard surfaces.

The solution will be illustrated by the following examples: The products were tested as follows: 33660 Cuttings Wash Test Method a) 43 grams of oil mud cuttings obtained from a North Sea drilling operation were added to 150g of X% active matter surfactant solution in synthetic sea water. b) This was stirred for 5 minutes using a Janke4Kunke1 stirrer at setting 2 at 800 rpm. c) The mixture was allowed to stand for five minutes after which time the liquid was decanted. This liquid contained the emulsified oil which could be separated by warming to above 40°C. d) The mixture was then made up to 150 ml with standard sea water and stirred for a further minute as in b). e) The mixture was then filtered through two layers of muslin. f) 20g of washed cuttings were weighed accurately (Ml) into a 250 ml round bottomed flask and the water content was determined by the Dean and Stark method using 100-120 petroleum ether. The weight of water removed was determined as W2. g) A further lOg of.the washed cuttings were accurately weighed (W3) into an evaporating dish and dried to constant weight (W4) at 110°c).

The weight of oil on the cuttings, W5 = W3 - W4 - / W2 x M3 A \ Hl J The weight of oil left on the cuttings expressed as a percentage of weight of dry cuttings + weight of oil 25 W0 = W5 x 100 W4 + W5 The test was performed 1n duplicate. It should be noted that we have found that the amount of oil removed from the surface of cuttings by any given surfactant or blend of surfactants is dependent on the age of the cuttings, more oil being removed from fresh cuttings than from aged cuttings.

Example 1 Using the test method above, the following results were obtained using oil mud cuttings from the North Sea.

Surfactant 10 None A (5%) B (5%) A (2.5%) + B (2.5%) % Oil Remaining on Cuttings virtually 100% 6.4% 7.1% 3.9% A = C9/CI1 primary alcohol nominal 6 mole ethoxylate. 15 B = coconut monoethanolamide + 2 mole ethylene oxide.

Example 2 Surfactant A (5%) B (5%) A (2.5% + B (2.5%) % Oil Remaining on Cutttings 1.2% 3.5% 0.5% A = C10/C12 primary alcohol nominal 5 mole ethoxylate. B = coconut diethanolamide.

Example 3 Surfactant A (5%) B (5%) A (3.75%) + B (1.25%) % Oil Remaining on Cuttings 4.4% 3.5% 2.8% A = C8/C10 primary alcohol nominal 4 mole ethoxylate. B = coconut diethanol amide.

Example 4 Surfactant % Oil Remaining on Cuttings A (5%) 4.1% B (5%) 3.5% A (1.25%) + B (3.75%) 2.3% A = nonyl phenol nominal 9 mole ethoxylate.

B = coconut diethanolamide.

In addition the emulsion decanted in step c) and obtained using A (1.5%) = B (3.75%) was heated to 40°C and separated into distinct oil and aqueous phases.

Example 5 Surfactant % Oil Remaining on Cuttings (5%) 14.4% (5%) 3.5% (1.25%) + B (3.75%) 3.3% A = oleic acid nominal 8 mole ethoxylate. B = coconut diethanol amide.

Example 6 Surfactant A (5%) B (5%) A (3.75%) + B (1.25%) % Oil Remaining on Cuttings 7.5% 3.5% 2.6% A = mixture of mono and di- C8 CIO alkyl phosphate nominal 5.4 mole ethoxylate.

B = coconut diethanol amide.

The emulsion decanted in step c) and obtained using A (3.75%) + B (1.25%) was heated to 40°C and seperated into distinct oil and aqueous phases.

Example 7 A concentrate was prepared for use according to the invention consisting of 45% by weight of CIO C12 fatty alcohol 5 mole ethoxylate, 45% by weight coconut diethanol amide, 5% by weight propylene glycol, 5% by weight water. The product was fluid and stable at temperatures between -5°c and 35°C and readily dispersed in sea water. When evaluated in the above cuttings cleaning test the results were as follows.

% Oil Remaining on Cuttings A (5% AM) Formulation of Example 7 (5% AM) 4.3% 0.5% A = C9/C11 primary alcohol nominal 6 mole ethoxylate. This is the surfactant most commonly used for cleaning oil mud cuttings.

The emulsion decanted in step c) of the method and obtained using 25 the formulation of Example 7, was heated to 50°C and separated into distinct oil and aqueous phases.

Example 8 The following test was used to show the effectiveness of the blend of nonionic surfactants of types A and B as defined above, for removing oil from metal surfaces. a) A mild steel plate was washed thoroughly in household detergent solution followed by rinsing under the tap and then with acetone. b) One surface of the plate was coated evenly with 0.4g of hydrocarbon oil, e.g. crude oil. c) 0.6g of test solution was then mixed intimately with the surface oil, and the plate was allowed to rest horizontally with the coated face uppermost for 15 minutes. d) The surface was then washed with 200 cm^ of synthetic sea water from a laboratory wash bottle. e) The amount of oil remaining on the plate was assessed visually.

In this test, the test solution used contained 7.5% of a CIO C12 fatty alcohol 5 mole ethoxylate, 7.5% coconut diethanolamide and 85% water. The oil was substantially removed from the surface of the mild steel leaving a clean non-oily surface.

In a further test, the test solution was a commercial hydrocarbon solvent based degreaser believed to contain emulsifiers. The mild steel was less thoroughly cleaned and the surface was oily.

Example 9 The test method described above (examples 1-7) was used, but the concentration of ssrfactant (X%) was changed.

Surfactant (X%) A % Oil Remaining on Cuttings Formulation of Example 7 1 14.0 13.1 3 5.9 2.2 5 4.3 0.5 7 3.7. 0.5 0 3.7 0.5 A = C9/C11 primary alcohol nominal 6 mole ethoxylate.

This is the surfactant most cormionly used for cleaning oil mud cuttings and over the wide concentration range studied was clearly less effective.

ALKYL DISTRIBUTION OF ALCOHOLS USED IN THE EXAMPLES The following are typical distributions.

Example Carbon No. 1 S 7 2,7 S 8 3 6 6 - - 3.5% 3.5% 7 - - - - 8 1.7% - 69.5% 69.5% 9 20.1% - - - 10 39.2% 85.0% 24.5% 24.5% 11 28.3% - - - 12 4.1% 8.5% 2.5% 2.5% 13 - - - - 14 - 6.2% - - 15 - - - - 16 - 0.3% .

In Example 7, surfactant A Is the same as A In Example 1.

Claims (16)

1. A method for the removal of oil from solid surfaces which comprises contacting the surfaces with an aqueous solution containing at least 0.5% by weight of a mixture of (A) from 5 to 95% by weight of at least one alkoxylated alcohol, carboxylic acid, alkyl phenol, or nonionic phosphate ester, having in each case an alkyl or alkenyl group with from 6 to 22 carbon atoms and from 1 to 20 ethylene oxide groups with (B) from 95 to 5% by weight of at least one ethylolamide of the formula 0 (CH,CH,O) H n 2 2 x RCN wherein R is an alkyl group having from 5 to 17 carbon atoms and x and y are each ehoaen from 0 and integers from 1 to 12, such that the average value of (x + y) ia from 1 to 12.

2. A method according to claim 1 wherein (A) is a primary, straight or branched chain alcohol having from 6 to 18 carbon atoms ethoxylated with from 1 to 10 ethylene oxide groups.

3. A method according to claim 1 wherein (A) is a normal or branched chain alkanoic or alkenoic acid having from 8 to 20 carbon atoms alkoxylated with from 1 to 10 ethyleneoxy groups.

4. A method according to claim 1 wherein (A) is a straight or branched chain alkyl phenol having from 6 to 12 aliphatic carbon atoms alkoxylated with from 1 to 12 ethylene oxide groups.

5. A method according to claim 1 wherein (A) is a nonionic phosphoric acid ester having at least one straight or branched chain alkyl group having from 6 to 22 carbon atoms and at least one ethyleneoxy group or polyalkoxy group having up to 20 ethyleneoxy units.

6. A method according to any foregoing claims wherein (B) has from 1 to 4 ethyleneoxy groups.

7. A method according to claim 6 wherein (B) is an alkyl monoethanolamlde.

8. A method according to claim 6 wherein (B) la an alkyl diethanolamide.

9. A method according to any foregoing claims wherein (A) and (B) are 5 each present in a proportion of more than 20% of the total weight of surfactant in the mixture.

10. A method according to any foregoing claim wherein the aqueous solution is sea water.

11. A method according to any foregoing claim wherein the mixture is 10 present in an aqueous solution in a concentration of from 0.52 to 10%.

12. A method according to any foregoing claim for washing oil rig cuttings.

13. A method according to any foregoing claims for washing structures.

14. A method according to claim 13 for cleaning surfaces of oil rigs.

15. 15. A method according to any foregoing claim wherein the aqueous solution is recovered after washing and heated sufficiently to effect separation of any oil emulsified therein.

16. A method for the removal of oil from solid surfaces substantially as described herein with reference to the Thrampl eg -