NO830032L - COMPOSITION AND PROCEDURE FOR CLEANING HYDROCARBON OIL FROM HARD SURFACES - Google Patents

Description

The present invention relates to methods for cleaning oil/rock mixtures in oil drilling operations and in particular cleaning drilling oil from drill cuttings on offshore drilling platforms, removing oil from the surface in newly drilled holes before reinforcement with casing, and cleaning oil sludge from drilling plate casings.

When 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 that are usually used are:

a) water-based,

b) ' oil-based,

c). water-in-oil emulsion-based (invert).

Oil-based drilling media (b) can also contain water in form

of water-in-oil emulsion. It is common in the art to refer to a drilling medium containing up to approx. 15% aqueous phase, calculated by volume, as oil-based. The drilling media referred to as interwoven fluids or mud, (c) generally contain between 15% and 55% water. The present invention relates in particular to types (b and c), both of which are covered by the term "oil" as used herein, together with crude oils and refined mineral oils.

One of the functions of drilling fluid is to . bring drill cuttings from the drill bit to the surface, after which the cuttings are removed using physical techniques, e.g. using sieves, sieves, cyclones or centrifuges. After removal of the cuttings, the drilling fluid is reused and the cuttings are discarded. If the drilling is carried out offshore, the cuttings will be discharged into the sea, where in the case of aqueous drilling fluids the cuttings are dispersed and sedimented without causing significant problems. In the case of oil drilling fluids, however, the cuttings are oil-moistened and quickly settle to the seabed below the drilling rig, forming an oily, sticky mass that can interfere with drilling operations, e.g. by preventing the movement of divers involved in work with underwater structures and maintenance. It is believed that the swelling of clay materials in drill cuts is responsible for the formation of this mass. In addition, the drill cuttings cause oil pollution by gradually releasing the oil.

One technique for removing oil from drill cuttings is to wash the drill 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 into 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 drill cutting material in seawater using good agitation to loosen the oil from the drill cutting surface.

This process can be used either as the only method for removing drilling oil from the cuttings, or as another step to remove an oil solvent from cuttings that have been previously washed with a hydrocarbon. This process can be improved by adding a surfactant to the seawater to reduce the oil/water interface. the tension. The drill cuttings can then be emptied into the sea where it disperses and sediments over a large seabed area instead of accumulating directly in the area of the drilling operations. The water-in-water emulsions formed as a result of washing the cuttings can be discharged into the sea where fine dispersion of the oil will facilitate its breakdown by microorganisms.

A commonly used surface-active agent for the above purposes are C8--alcohols with six moles of ethoxy groups. One purpose of the present invention is to provide more efficient methods for cleaning oil from drill cuttings of rocks.

A further object of the invention is to provide■

a process by which oil can be separated from the emulsion resulting from the cleaning of drill cuttings. It has been discovered that a particular mixture of an ethoxylated nonionic surfactant with an alkanolamide exhibits

a synergistic effect that allows a more efficient cleaning of oil from drill cuttings. According to a preferred embodiment of the invention, it has further been discovered that when the emulsions of oil-in-water formed by purification according to the invention are heated, the emulsion is easily broken and the oil can then be extracted.

The present invention accordingly provides a method for cleaning which comprises bringing an oil-coated rock into contact with an aqueous solution containing an effective amount of a mixture of (A) 5-95% by weight of at least one alkylated alcohol, carboxylic acid, alkylphenol or nonionic phosphate ester, which in each case has at least one alkyl- . group with 6-22 carbon atoms and 1-20 ethyleneoxy group, med

(B) 95-5% by weight of. at least one alkanolamide of the formula:

where R is a saturated or unsaturated alkyl group of 5-17 carbon atoms, and x and y are each selected from 0 and whole numbers from,

1 to 12, so x + y is from 1 to 12.

(A) is preferably a primary straight-chain or branched alcohol with 6-18 carbon atoms and alkylated with 1-10

ethyleneoxy groups.

(A) can alternatively be normal or branched alkano- or '• alkenoic acid with 7-23. carbon atoms, alkoxylated with 1-10 ethyleneoxy groups; straight-chain or branched alkylphenol with 6-12 aliphatic carbon atoms, alkoxylated with i-12 ethyleneoxy-

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groups; non-ionic phosphoric acid ester with at least one straight-chain or branched alkyl group with 6-22 carbon atoms, at least one alkyloxy or polyalkyloxy group with 1-20 ethyleneoxy units (B) typically has 1-4 ethyleneoxy groups. While one has discovered

that monoethanolamides are particularly effective synergistic agents and. can be preferably used in places with a warm climate, h.ar Concentrated mixture of monoethanolamide with component (A) tends to be insufficiently fluid at low temperatures for appropriate handling under the conditions that can be encountered in e.g. operations in the North Sea. For such low temperatures, it is preferred to use diethanolamides.

A mixture of (A) and (B) is typically supplied as a concentrate which is dissolved or diluted with water to provide the cleaning solution at the site of the drilling platform. 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 needed to provide a liquid, pourable composition under the conditions likely to be encountered. The concentrate may also contain smaller amounts of hydrotropic agents, such as alkaline earth metal, sodium, potassium, mono-, di- or tri-alkylbenzene sulphonate salts with less than 6 aliphatic carbon atoms, e.g. toluene or xylene sulfonates, phosphate ester salts, preservatives such as formalin, dyes and/or perfumes.- Water may be present in any suitable amount between zero and the final working concentration of the cleaning agent. In general, the lower the proportion of water, the greater the suitability for transport and storage of the concentrate. However, these considerations must be balanced against the preference for a stable, pourable composition. Organic solvents can noticeably increase the price of the composition and are therefore preferably used sparingly, e.g. less than 50% by weight and preferably less than 20% by weight of the concentrate.

The concentrate can typically contain 5-95% by weight of (A) and

95-5% by weight of (B). (A) is, however, preferably present - in concentrations above 10% by weight, preferably above 20% and

usually over 30%. (B) is preferably also present in concentrations above 10% by weight, preferably above 20% and usually above 30%. A suitable mixture contains 40-60% of (A),

60-40% of-(B) and 0-20% solvent.

The concentrate is dissolved or dispersed in water at the point of use. For offshore applications, the concentrate can be suitably dissolved - or dispersed - in seawater. The concentrate is typically diluted to from 0.5 to 10% active substance, calculated by weight, preferably from 1-6. Higher concentrations are not ruled out>but are unlikely to prove cost effective. Concentrations below 0.5% are not excluded, but are only marginally effective.

Used for cleaning drill cuttings from rocks, these drill cuttings are preferably stirred with the solution of the concentrate in water or salt solution for a sufficient period of time to emulsify a significant proportion of the oil. The emulsion can then be separated from the drill cutting material which, when it is sufficiently clean, is dumped. The emulsion can be discarded. According to a preferred embodiment of the present invention, however, the oil is extracted from the emulsion by moderate heating. Typical temperatures in excess of 40°C, e.g. 50-70°C is sufficient to break the emulsion and allow recovery of the separated oil phase.

The cleaning solution according to the present invention can also be injected into boreholes to clean oil from the sides of the rock material. This is necessary when a casing is to be cemented to the sides of the borehole. The solution can also be used according to the invention to clean oil sludge from the drilling platforms themselves and generally to remove viscous hydrocarbon oils from hard surfaces.

The resolution shall be illustrated by the following examples:

The products were tested as following:

Test method for washing drill cuttings

a) 43 g of oil mud drill cuttings obtained from a drilling operation in the North Sea were added to 150 g of surfactant solution with X% active substance in synthetic seawater. b) This was stirred for 5 minutes using a Janke4Kunkel stirrer at setting 2 at 800 rpm. c) The mixture was left for 5 minutes after which the liquid was decaritated. This liquid contained the emulsified oil

which could be separated by heating above 40°C.

d) The mixture was then made up to 150 ml with standard seawater and stirred for a further 1 minute as ib). e) The mixture was then filtered through two layers of muslin. f) 20 g of washed drill cuttings were weighed accurately (Wl) into a 250 ml round bottom flask and the water content was determined according to the Dean and Stark method using 100-120 petroleum ether. The weight of water removed was determined as W2. g) A further 10 g of the washed drill cutting material was accurately weighed (W3) into an evaporating dish and dried to

constant weight (W4) at 110°C.

The weight of oil on the cutting material, ,\

The weight of oil that remained on cuttings materials expressed as a weight % share of dry cuttings + weight of oil

The test was carried out twice. It should be pointed out that it has been found that the amount of oil removed from the surface of the drill cutting material by any given surfactant or mixture of surfactants is dependent on the age of the drill cutting material. taking more oil.

is removed from fresh drill cuts than from old drill cuts.

Example 1

Using the test method stated above, the following results were obtained by using oil mud drill cuttings from the North Sea.

Example 4

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 separate oil and aqueous phases.

Example 5

Example 6

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

Example 7

A concentrate was prepared for use according to the invention consisting of 45% by weight CIO C12 fatty alcohol 5 mol ethoxylate,

45% by weight coconut diethanolamide, 5% by weight propylene glycol, 5% by weight water. The product was liquid and stable at temperatures between -5°C and 35°C and dispersed easily in seawater. When judged in the cleaning test for drill cuts stated above, the following results were obtained:

A = C9/C1<1>''primary alcohol with nominally 6 mol ethoxy groups. This is the surfactant that is most commonly used for cleaning oil mud drill cuttings.

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

Example 8

The following test was used to demonstrate the effectiveness of the mixture of non-ionic surfactants of types A and B as defined above, for the removal of oil from metal surfaces. a) A mild steel plate was washed thoroughly with a household detergent solution followed by rinsing with tap water and then with acetone. b) One surface of the plate was coated evenly with 0.4 g of hydrocarbon oil, e.g. crude oil. c) 0.6 g of test solution was then mixed intimately with the surface oil and the plate was placed horizontally with the coated surface at the top for 15 minutes.. d) The surface was then washed with 200 ml of synthetic seawater from a laboratory wash bottle . e) The amount of oil remaining on the plate was determined visually.

In this test, the test solution used contained 7.5% of a CIO C12 fatty alcohol 5 mol 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

.fleet.

In another test, the test solution was a commercial hydrocarbon solvent-based degreaser that was assumed to contain emulsifiers. The soft steel was smaller, thoroughly cleaned and the surface was oily.

Example 9

The test method described above (Examples 1-7) was used, but the concentration of the surfactant (X%) was changed.

This is the surfactant most commonly used for cleaning oil mud drill cuttings and was clearly less effective over the wide concentration range studied. Alkyl distribution for alcohols. used in the examples The following are typical distributions.

Claims (9)

Procedure for removing oil from fixed over- .. surfaces, characterized by bringing the surfaces into contact with an aqueous solution containing an effective amount of a mixture of (A) 5-95% by weight of at least one alkylated alcohol, carboxylic acid, alkylphenol, or nonionic phosphate ester, which in each case has an alkyl or alkenyl group of 6-22 carbon atoms and 1-20 ethylene oxide groups, with (B) 95-5% by weight of at least one ethylol anide of the formula: where R is a saturated alkyl group with 5-17 carbon atoms, <p> g x and y .each is chosen from 0 and whole numbers from 1 to 12,' so that the average value for (x and y) is from 1 to 12. 2. Method according to claim 1, characterized in that the aqueous solution is seawater. 3. Method according to claim 1, characterized in that drilling cuttings are washed on an oil platform. 4. Procedure ..according to requirements. 1, characterized in that surfaces on oil plate forms are cleaned. 5. Concentrate for use in the preparation of aqueous "solutions" for use according to the method in claims 1-4, characterized in that it essentially consists of 20-60% by weight of (A), 20-60% by weight of (B) , up to 10% by weight of water and up to 10% by weight of a water-miscible, hydroxyl-containing organic solvent. 6. Concentrate according to claim 5, characterized in that (A) is an ethoxylated alcohol with 8-14 carbon atoms and 2-7 ethyleneoxy groups. 7. Concentrate according to claim 5 or 6, characterized in that (B) is an alkyldiethanolamide. 8. Concentrate according to claims 5-7, characterized in that the solvent is a water-miscible, mono-, di- or trihydroxy alcohol or alcohol ether with ■ 2-8 carbon atoms. 9. Aqueous solutions, characterized in that they are obtained by diluting a concentrate according to any one of claims 5-8 with water and containing at least 0.5% surfactant.