WO2007011475A1

WO2007011475A1 - Middle phase micro emulsions and process of making and using the same

Info

Publication number: WO2007011475A1
Application number: PCT/US2006/022653
Authority: WO
Inventors: Joel F. Carpenter; Melissa S. Bennett; Joe D. Sauer; Patrick C. Hu
Original assignee: Albemarle Corporation
Priority date: 2005-07-15
Filing date: 2006-06-09
Publication date: 2007-01-25

Abstract

The present invention provides environmentally friendly cleaning formulations that have particular application to oil and gas well drilling. The formulations have been shown to be effective in removing oil-based drilling mud from rock cuttings and metal surfaces.

Description

MIDDLE PHASE MICRO EMULSIONS AND PROCESS OF MAKING AND USING THE SAME

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to United States Provisional Patent Application No. 60/699,687 filed July 15, 2005 and the disclosure herein incorporated by reference in the entirety.

FIELD OF THE INVENTION [0002] The present invention relates to cleaning formulations, particularly cleaning formulations that are applicable in oil field cleaning and that are environmentally friendly. More particularly, the present invention relates to middle phase micro emulsions that are effective in removing oil- based drilling mud from rock cuttings, metal surfaces, wellbore surfaces, drilling equipment surfaces and human beings.

BACKGROUND OF THE INVENTION

[0003] Crude petroleum is routinely recovered from subterranean reservoirs through drilled wells, and drilling fluid (drilling mud) is^*an indispensable component in the drilling process used to drill these wells. Drilling fluids are required in the wellbore to cool and lubricate the drill bit, remove rock fragments, sometimes called drill cuttings, from the wellbore and transport them to the surface. Drilling fluids are also used to counterbalance formation pressure to prevent formation fluids (such as oil, gas and water) from entering the well prematurely and prevent the open (uncased) wellbore from caving in. [0004] The drilling fluids used are selected based on the different drilling conditions encountered such as formation composition, etc. Some common examples of types of drilling fluids used include water based, oil based, or based on synthetic materials, such as oleaginous (oil-like) materials, such as vegetable esters, poly alpha olefins, internal olefins, linear alpha olefins, synthetic paraffins, ethers, and linear alkylbenzenes, and the like. Oil based and synthetic material based drilling muds are commonly used. [0005] During drilling operations, it is not uncommon for the drilling mud to be sprayed or spilled on the drilling platform, equipment and/or workers. . If these spills can be promptly cleaned, any health and safety concerns associated with the sprayed or spilled drilling mud may be alleviated. Further, drill cuttings retrieved from the wellbore are covered with drilling mud, which often makes direct discharge of the cuttings unfeasible due to environmental regulations. For example, EPA regulations {see, CFR Part 435, Subpart A, regarding the National Pollutant Discharge Elimination System General Permit) allow offshore disposal of drill cutting in U.S. waters only if the oil levels on these cuttings is below set criteria, which is based on the chemistry of the drilling mud. Similar regulations (1% retention of oil on cuttings) promulgated by the OSPAR agreement (The Oslo/Paris Convention for the Protection of the Marine Environment of the North-East Atlantic) regulate the ocean disposal of cuttings in the North Sea. The ability to remove drilling mud from the cuttings so they meet the standards regulating ocean disposal would save a substantial cost and time. [0006] It is well known that removing oil-based drilling muds is difficult. The difficulty stems from the formulations of the drilling mud. Inverted drilling muds, in addition to the oil component (which could be mineral oil, diesel oil, olefins, esters or poly alpha olefins) generally contain emulsifiers, wetting agents and clay; these components provide the needed mud rheology and physical characteristics to meet the requirements of a drilling operation. Removal of drilling muds using conventional aqueous detergent formulations are counterindicated, as they can lead to the swelling of shale cuttings, which would result in poorly consolidated drill cuttings and such cuttings create problems for the conventional cuttings cleaning equipments (e.g., shakers, centrifuges). Organic solvents are modestly effective at removing oil-based drilling muds. However, the potential fire hazards of storing large quantities of organic solvents on a drilling platform and the environmental impact of using these quantities of organic solvents make the use of organic solvents as a cleaning agent impractical.

[0007] Thus, since oil based and/or synthetic drilling muds are commonly used in drilling operations, a formulation that is capable of cleaning and removing these types of drilling muds from the surface of drill cuttings, the wellbore, the drilling platform, the drilling equipment, and the workers offers substantial benefits to oil drilling operations.

SUMMARY OF THE INVENTION

[0008] The present invention relates to performance cleaning compositions comprising middle phase microemulsion (MPME) formulations that are effective at removing oil-based drilling mud from rock cuttings, metal surfaces, wellbore surfaces, drilling equipment surfaces and human beings and that are environmentally friendly. The formulations comprise: (a) about 1 to about40 wt % surfactant, (b) about 0.5 to about 40 wt% of at least one co-surfactant, (c) about 0.5 to about 30 wt% electrolyte, (d) about 30 to about 99 wt% of an aqueous phase, and (e) about 0.5 to about 40 wt% oil, wherein the oil is a hydrocarbon, ester, triglyceride, or ether. The formulations may further include other components such as dyes, odorants, viscosity control agents, pH control agents, biocides and the like.

[0009] The electrolyte comprises at least one readily biodegradable salt of an organic acid. In some embodiments, the electrolyte is a salt of formic acid, acetic acid or propionic acid. In other embodiments, the electrolyte is an organic acid salt of an alkali metal, which is selected from potassium, sodium, and lithium.

[0010] The oil of the MPME may be an olefin, an isoparaffin, an ester or any combinations thereof. In some embodiments, the oil includes olefins that are selected from a group that includes 1-alkenes and internal olefins. In some particular embodiments, the oil is a Ci₆-Ci₈ internal olefin. In some embodiments, the oil includes one or more isoparaffins and the isoparaffins may be selected from a group that includes hydrogenated poly-alpha-olefins, highly refined hydro-treated mineral oil basestocks and any combinations thereof. In some other embodiments, the oil includes one or more esters and the esters may be selected from a group that includes triglycerides, condensation products of Ci-C₁O alcohols with fatty acids derived from animal and vegetable oils, and any combinations thereof.

[0011] The surfactants of the MPME may have a hydrophilic head group and a hydrophobic tail group, hi some embodiments, the head group is anionic and in other embodiments, the head group is neutral. In some embodiments, the tail group includes two hydrocarbon chains, each of which is at least five carbon atoms in length. In some embodiments, the hydrocarbon chain is no more than 10 carbon atoms in length. In other embodiments the tail group includes a single hydrocarbon chain of at least 10 carbon atoms in length. In other embodiments, the hydrocarbon chain is no more than 20 carbon atoms in length. In some particular embodiments, the surfactant is an alkyl glyceryl sulfonate. [0012] The MPME used in the performance compositions may include one or more co- surfactants and the co-surfactant may be selected from the group that includes C₂ to Ci₂ primary, secondary and tertiary alcohols. In some particular embodiments, the MPME includes one co- surfactant that is n-butanol. [0013] Another aspect of the present invention relates to a method for cleaning drill fluid contaminated surfaces by contacting these surfaces with the cleaning compositions or formulation of the first and second aspects of the invention. The method is applicable to clean oil-based drilling fluids, synthetic material based drill fluids, and any combinations thereof from surfaces of pipes, casings, drill cuttings, drilling equipment, wellbore, and humans. DESCRIPTION OF THE FIGURES

[0014] FIGURE 1 compares the cleaning efficiency of water (♦), BARASCRUB™ (■), BARAKLEEN™ (A), Sample 1 (*), Sample 2 (•) and Sample 3 in removing ACCOLADE™ drilling mud contaminated metal surfaces. The vertical axis displays the amount of drilling mud (wt. in gm) removed by the cleaning system. The horizontal axis indicates the number of cleaning cycles for a particular volume of cleaner.

[0015] FIGURE 2 compares the efficiency of selected cleaning regiments in removing oil from drilling cuttings. The vertical axis displays the weight of oil that was extractable by pentane (PEM - Pentane Extractable Material) from cuttings that had been pre-cleaned by a selected cleaning regiment. The horizontal axis identified the test drilling fluids, ACCOLADE™ or INVERMUL™ based, and the cleaning regiment used: no cleaning, water, BARASCRUB™, BARAKLEEN™, Sample 115, Sample 1 or Sample 3.

DETAILED DESCRIPTION OF THE INVENTIONS

[0016] For the purpose of promoting an understanding of the principles of the present invention, specific embodiments will be illustrated and specific language will be used to describe the same. It is understood that there is no intention to limit the scope of the invention only to the illustrated embodiments. It is also understood that alterations or modifications to the invention or further application of the principles of the invention are contemplated as would occur to the persons of ordinary skill in the art to which the invention relates.

[0017] The invention relates to middle phase microemulsion (MPME) formulations that are suitable for cleaning surfaces contaminated by oil-based drilling fluids. The MPME are formulated with a high water content but function as if they are an organic solvent in dissolving oil, and additionally the MPME are effective at emulsifying additional oils just like common surfactant systems do. Further, the major components of the formulations are chosen partly because of their biodegradability quality, thus making the formulations environmentally friendly.

I. Definitions

[0018] The terms "dispersion," and "emulsion" have meanings in the art consistent with

Remington, THE SCIENCE AND PRACTICE OF PHARMACY, 20th Edition (2000) and denote multiphasic systems comprised of two or more ingredients that are not completely miscible in one another. Dispersions may be classified into different groups based on the size of the dispersed particles. An "emulsion" is a dispersed system containing at least two immiscible liquid phases, usually water and oil, accompanied by a surfactant/emulsifying agent. [0019] The term "microemulsion" denotes a colloidal emulsion, in which the colloidal particles are micelles made of a blend of surfactants and oleaginous materials. Generally, the micelles are sized in the range of 1-10 nm and have little or no impact on the clarity of the microemulsion solution. A micelle is an aggregate of surfactant molecules in which the hydrophilic portions of the molecules are arranged so that they are in contact with water and the hydrophobic portions are collected together so that they form a separate phase that excludes water molecules. It has been found that the solubility of a variety of hydrocarbon-based and other oleaginous substances, which are not normally very soluble in water, can be enhanced to a remarkable extent in the presence of micelles. These oleaginous substances are then incorporated into the interior of these micelles, or groups of micelles, and carried along with the carrier fluid. See, Schecter, R., OIL WELL STIMULATION, Prentice Hall, 1991. The micellar blends of surfactants and solvents can be formulated to be either oil in water, water in oil, or an equilibrium of water and oil. A "middle phase" microemulsion is one that is formulated in equilibrium with both water and oil, and therefore can be dispersed in either water and oil based carrier fluids. [0020] The term "aqueous phase" means the water or brine phase, which may also be buffered. "Biodegradability" or "readily biodegradable" is an assessment of the breakdown of chemical substances by living organisms, one of the major processes that determine the fate of organic chemicals in the environment. Ready biodegradability is determined under the most stringent of test conditions, using a very small amount of microbial inoculum, where the test chemical is present as the sole carbon source at low concentrations. Consequently, chemicals that are shown to pass a ready biodegradability test also are expected to rapidly degrade in wastewater treatment plants and in the natural environment.

[0021] The term "pipe dope" means lubricating grease for connecting the drill string. Generally pipe dope are oil based; exemplary product includes Bestolife^® 2000 and Eco-Sif. The term "hydro-treated, mineral oil basestock" refers to hydrocarbonaceous materials, i.e. gas oils, vacuum oils, etc., that have been processed in the presence of a catalyst and hydrogen gas to, for example, remove impurities such as sulfur, nitrogen, and/or hydrogenate aromatics; reduce the length of hydrocarbon chains in the hydrocarbonaceous material through cracking; and other similar processes which are well-known in the hydrocarbon refining area. [0022] The terms "optional" and "optionally" denote that the step or component following the terms may but need not be a part of the method or formulation.

[0023] The term "about" means including and exceeding up to 20 % the specific endpoint(s) designated. Thus the range is broadened. [0024] BARAKLEEN™ and BARASCRUB™ are trade names of Halliburton Energy Services's special cleaning solutions.

[0025] WELLFORM™ is Albemarle's trade name for its formate brines. WELLFORM™ 13.2 is a brine of 75 wt% of potassium formate in water.

[0026] ACCOLADE™ is the trade name of Halliburton Energy Services for a special invert mud system comprised of a unique blend of base fluids that are non-aqueous.

[0027] INVERMUL™ is a trade name of Halliburton Energy Services for an invert drilling mud system that is formulated with INVERMUL™ emulsifier.

[0028] INVERMUL™ is a trade name of Halliburton Energy Services for an emulsifier.

II. MPME COMPONENTS AND PREPARATION

1. MPME Components

[0029] The MPME formulation of the present invention comprises from about 1 to about 40 wt %, based on the MPME formulation, of at least one, preferably only one, surfactant. In preferred embodiments the MPME formulation comprises from about 5 to about 35 wt %, on the same basis, of at least one surfactant, more preferably from about 10 to about 30 wt %, on the same basis, and most preferably from about 15 to about 25 wt %, on the same basis. Surfactants suitable for use herein are those capable of creating an oil-and-water microemulsion upon combination with the appropriate aqueous phase and oil. The surfactant may be a single surfactant or a mixture of surfactants. The surfactants useful in the present invention are amphipathic molecules having hydrophilic head groups and hydrophobic tail groups. The surfactants can be neutral, cationic or anionic. Generally, the surfactants are biodegradable and are calcium ion tolerant. [0030] Surfactants that are suitable for the MPME formulation of the present invention typically have head groups that are neutral or anionic, more typically the head groups are anionic. When the head group is neutral, it is generally composed of ethoxylate, amide, amine oxide and the like. When the head group is anionic, it is typically capped by a mono-valent anion, e.g., sulfonate, sulfate, phosphate, and the like. The mono-valent anion may be attached to the head group through a alkoxylate or polyalkoxylate chain [(-OCHRCH₂-)_n], where n = 0 to <20 and the R group is a linear or branched hydrocarbon such as for example an alkyl or alkenyl. Non- limiting examples of exemplary polyalkoxy groups include polyethoxy, polypropoxy and the like. The counter cation is generally a monovalent cation, such as lithium, sodium, potassium, ammonia, and the like.

[0031] Surfactants in the present invention generally have one or two hydrophobic tail chains. Each of the tail chains is at least about 5 carbons in length; typically, the chain is about 10 to about 18 carbons in length, and more typically about 10 to about 16 carbons in length. Exemplary surfactants includes alkyl glyceryl sulfonate, sodium lauryl sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium lauryl phosphate ,and alkyl sulfonates Typically the alkyl glyceryl sulfonate is either a sodium or potassium salt; e.g., AGS 12-14 P, a sodium coconut alkyl glyceryl sulfonate paste from Proctor and Gamble.

[0032] The MPME formulation of the present invention also comprises from about 0.5 to about 40 wt %, based on the MPME formulation, of at least one, preferably only one, oil. In preferred embodiments the MPME formulation comprises from about 0.5 to about 30 wt %, on the same basis, of at least one oil, more preferably from about 1 to about 20 wt %, on the same basis, and most preferably from about 4 to about 12 wt %, on the same basis oils useful in the present invention are base oils that are deemed readily biodegradable. See, 40 CFR Part 435. Non- limiting examples of oils suitable for use herein include vegetable esters, poly alpha olefins, internal olefins, linear alpha olefins, synthetic paraffins, ethers and linear alkylbenzenes, among others. Typically, the oils that are used in the present invention are internal olefins, more typically Ci₆-Ci₈ linear and branched internal olefins, e.g., Amodrilf 1000 olefins sold by BP Petrochemicals, which have a proven history within the oil and gas extraction industry. This oil has passed the stringent "Ready Biodegradability Test" (see below) and is thus deemed readily biodegradable.

[0033] The MPME formulation of the present invention also comprises from about 0.5 to about 40 wt %, based on the MPME formulation, of at least one, preferably only one, co-surfactant. In preferred embodiments the MPME formulation comprises from about 1 to about 30 wt %, on the same basis, of at least one surfactant, more preferably from about 2 to about 20 wt %, on the same basis, and most preferably from about 3 to about 12 wt %, on the same basis [0034] Co-surfactants suitable for use in the present invention are those that modify the primary sufactants' behavior at phase interfaces and are typically non-ionic chemistries capable of hydrogen bonding. Non-limiting examples of suitable co-surfactants include linear and branched alcohols and alkoxylates. Preferred co-surfactants are alcohols that include, but are not limited to, C₂-Ci₂ primary, secondary and tertiary alcohols, such as propanol, isopropanol, n-butanol, s- butanol, t-butanol, n-pentanol, n-hexanol, and the like. [0035] As stated above, the MPME formulation of the present invention also comprises from about 0.51 to about 30 wt %, based on the MPME formulation, of at least one, preferably only one, electrolyte. In preferred embodiments the MPME formulation comprises from about 1 to about 20 wt %, on the same basis, of at least one electrolyte, more preferably from about 1 to about 15 wt %, on the same basis, and most preferably from about 2 to about 10 wt %, on the same basis. The electrolytes are used to adjust the ioinic strength of the aqueous phase, thereby fine-tuning the balance of surfactant and co-surfactant in the aqueous and oleaginous phases. Electrolytes suitable for use herein are organic acid salts. Organic acid salts are advantageous for this application because they are biodegradable and are free of corrosive halide anions. Typically, electrolytes are alkali metals or ammonium salts of formic acid, acetic acid and propionic acid. An exemplary electrolyte is WELLFORM™ 13.2, which is a solution of 75 wt% potassium formate in water.

[0036] The MPME formulation of the present invention also comprises from about 30 to about 99 wt %, based on the MPME formulation, of an aqueous phase. In preferred embodiments the MPME formulation comprises from about 30 to about 80 wt %, on the same basis, of an aqueous phase, more preferably from about 40 to about 70 wt %, on the same basis.

[0037] The aqueous phase of the present invention is generally fresh water or brine. When fresh water is used, the water can optionally be buffered to a pH of about 10, but the pH of the buffered water will depend on the particular application. Non-limiting examples of buffers that are suitable for use herein include Na₂CO₃, K₂CO₃, Li₂CO₃, NaHCO₃, KHCO₃, LiHCO₃, Na₂B₄O₇- 10H₂O (Borax), HCl, NaOH, KOH, LiOH, Na₂HPO₄, Na₃PO₄, K₂HPO₄, K₃PO₄,

Li₂HPO₄, Li₃PO₄, and the like.

[0038] In a particularly preferred embodiment, the MPME formulation according to the present invention comprises about 17 to about 19 wt.%, based on the MPME formulation, of a surfactant, about 4 to about 6 wt.%, on the same basis, of a co-surfactant, about 4 to about 6 wt.%, on the same basis, of a Ci₆-Ci₈ internal olefin, about 60 to about 62 wt.%, on the same basis, buffered water, having a pH ranging from about 9 to about 11, and about 8 to about 10 wt.%, on the same basis, of WELLFORM™ 13.2 electrolyte. [0039] In another particularly preferred embodiment, the MPME formulation according to the present invention comprises about 17 to about 19 wt.%, based on the MPME formulation, of a surfactant, about 8 to about 10 wt.%, on the same basis, of a co-surfactant, about 4 to about 6 wt.%, on the same basis, of a Ci₆-Ci_S internal olefin, about 60 to about 62 wt.%, on the same basis, buffered water having a pH ranging from about 9 to about 11 , and about 4 to about 6 wt.%, on the same basis, of WELLFORM™ 13.2 electrolyte.

[0040] In yet another particularly preferred embodiment, the MPME formulation according to the present invention comprises about 19 to about 21 wt.%, based on the MPME formulation, of a surfactant, about 5 to about 7 wt.%, on the same basis, of a co-surfactant, about 9 to about 11 wt.%, on the same basis, of a C]₆-Ci₈ internal olefin, about 54 to about 56 wt.%, on the same basis, buffered water having a pH ranging from about 9 to about 11, and about 7 to about 9 wt.%, on the same basis, of WELLFORM™ 13.2 electrolyte.

2. Preparation of MPME Formulations

[0041] The MPME formulations of the present invention can be formulated as the middle phase of a three-phased mixture comprised of oils, surfactants, co-surfactants, electrolytes and aqueous phase. The middle phase is isolated and analyzed for the concentration of each of the components. Based on this analysis, a single phased middle-phase microemulsion may be directly prepared from mixing together the known ratio of the components. The MPME of the invention may contain about 1 to about 40 wt% surfactants, about 0 to about40 wt% co- surfactants, about 0 to about 40 wt% oil, about 0 to about 30 wt% electrolytes, and about 0 to about 98 wt% water, all of the weight percents based on the MPME formulation. Typically, the MPME of the invention contains about 15 to about 25 wt% surfactants, about 3 to about 12 wt% co-surfactants, about 3 to about 18 wt% oil, about 2 to about 15 wt% electrolytes, and about 45 to about 75 wt% water, all of the weight percents based on the MPME formulation. More typically, the MPME formulation contains about 16 to about 24 wt% surfactants, about 4 to about 10 wt% co-surfactants, about 5 to about 15 wt% oil, about 3 to about 10 wt% electrolytes, and about 50 to about 65 wt% water, all of the weight percents based on the MPME formulation. Additionally, the MPME formulation can be modified to include other components such as dyes, odorants, viscosity-control agents, pH control agents and biocides without the loss of overall efficacy in the intended application.

[0042] The MPME formulation of the present invention may be prepared by any process or method known such as by simply shearing the components together. If the MPME formulation is prepared by shearing the components together, the shearing can be conducted in a mixer or similar apparatus under conditions that include a rotation rate equivalent to the low setting on a Hamilton Beach mixer and a time of a few minutes, e.g. 3-5 minutes. In one embodiment of the invention, the MPME formulation is prepared by first blending together the surfactants, co- surfactants, and oil, in a Hamilton Beach mixer at low setting for about two minutes to form a blended oil phase. The water, electrolyte and, optionally, a buffer are also mixed to form a premixed aqueous phase. After the blended oil phase and premixed aqueous phase are formed, the blended oil phase is added to the premixed aqueous phase to form a MPME precursor mixture, and the precursor mixture is then sheared at speeds described above for two minutes thus forming a MPME formulation according to the present invention.

III. CHARACTERIZATION OF THE FORMULATIONS

^•) 3. Biodegradability

[0043] The US EPA (Environmental Protection Agency), the ISO (International Organization for

Standardization) and the OECD (Organization for Economic Cooperation and Development) have developed a series of laboratory screening tests that can be used to determine the "ready biodegradability" of organic compounds. The accepted methods for assessing biodegradability in sea water includes the OECD 301 and 306 tests., (1992) (see, OECD Guidelines for Testing of Chemicals, First Addendum, 1993, ISBN: 92-64-12221-4) and the modified ISO 11734 1995 method, see, 40 CFR Part 435, Subpart A, Appendix 4. These tests measure the amount of carbon dioxide released, or oxygen consumed, i.e. biological oxygen demand (BOD), within a 28 day window by a defined microbial inoculum using the test chemicals as the sole carbon source. The term "readily biodegradable" describes a substance that can be degraded to 60 % of the theoretical amount and complete degradation within 10 days of attaining the 10% level. The theoretical CO₂ release (ThCO₂ )and the theoretical oxygen demand (ThOD) can be calculated based on the organic carbon content of the test material. The biodegradabilities of three components of some embodiments of the present invention have been measured, and the compounds have been found to be readily biodegradable. For example, the aerobic biodegradability of the Ci₆-Ci_S internal olefin oil component (e.g., Amodrilf 1000) used in some embodiments of the present invention was measured by the Marine Closed Bottle Method OECD 306 (1992), and the anaerobic biodegradability was measured by the Modified ISO 11734:1995 test protocol as required by EPA's NPDES general permit requirement and AmodrilflOOO met the biodegradation requirement. The anaerobic biodegradability of the surfactant potassium alkyl glycerol sulfonate was measured using the Marine Closed Bottle Method OECD 306 (1992). It has been shown that greater than 83 % of the ThCO₂ was achieved after 10 days; the compound is therefore readily biodegradable. Similarly, the biodegradability of sodium, potassium and cesium formate were evaluated using the Closed Bottle Test OECD 301 D at Huntingdon Research Center. The study was published in the Shell International Exploration and Production (SIEP) publication, 96-5091 , p.21 , Table 4.4. The results show that 102 %, 92 % and 83 % of the ThCO₂ were achieved for sodium formate, potassium formate, and caesium formate, respectively; accordingly, all three salts are readily biodegradable.

B. Cleaning Efficiency and Cleaning Capacity of the Formulations

[0044] The effectiveness of the MPME formulations according to the present invention in cleaning drilling fluid contaminated metal surfaces and cuttings may be evaluated by laboratory tests. Designing such cleaning tests is within the general knowledge of those skilled in the art, and the tests should be designed to resemble cleaning situations that occur during operations. The cleaning efficiency may be assessed, e.g., by determining the amount of contaminant removed from the metal surface and/or cuttings per cleaning cycle, taking into account the volume of the MPME formulation used and the surface area or weight of material cleaned. Additionally, the cleaning capacity of the MPME formulations may be evaluated by determining the contaminant loading of a fixed volume of MPME formulations once that MPME formulations can no longer remove further contaminants. The efficiency of the MPME formulations of the present invention in removing oil on drill cuttings contaminated by oil-based drill mud can be evaluated by recovering any oil that remains on the cleaned cuttings; the smaller the amount recovered, the more efficient the cleaner. Further, the test protocol should include comparisons to other commercial cleaning products and water for comparative purpose. [0045] The effectiveness of the MPME formulations of the present invention in cleaning drilling mud contaminated metal surfaces has been tested by a "Mock Pipe Cleaning" test, described in detail in Example 1 herein. Briefly, the test involves cleaning a metal object, e.g, a stainless steel pipe, which was pre-coated with drilling mud. The weight of the amount of drilling mud removed was recorded. After one cleaning, a specific amount of drilling mud was added to the used MPME formulation and the MPME formulation was then was re-used to clean a second contaminated object. The cleaning efficiency is calculated as the percent amount of contaminant removed in reference to the amount of contaminant originally coated on the metal object. [0046] The above description is directed to several embodiments of the present invention. Those skilled in the art will recognize that other embodiments, which are equally effective, could be devised for carrying out the spirit of this invention. The following examples will illustrate the present invention, but are not meant to be limiting in any manner.

EXAMPLES

[0047] In the following examples, three MPME formulations according to the present invention, Sample 1, Sample 2 and Sample 3, two commercial cleaners, BARAKLEEN™ and B ARASCRUB™, and water were evaluated using the Mock Pipe Cleaning test, described below. The contaminant used in the Examples is ACCOLADE™ invert drilling fluid. The result of the cleaning experiments are reported in Examples 2-6 and plotted in FIG. 1. FIG 1 shows that the MPME formulations according to the present invention remove about 2 to 3.5 time more ACCOLADE™ fluid from stainless steel surfaces than water, BARAKLEEN™ and BARASCRUB™. Compared to BARAKLEEN™ and BARASCRUB™, all three MPME formulations according to the invention have superior cleaning efficiency. The cleaning efficiency of Sample 1 decreases to about 50% after the first two cleaning cycles, but maintains the same level of efficiency for the remaining eight cycles. The cleaning efficiency of Sample 2 and Sample 3 remained high throughout all the test cycles.

[0048] The effectiveness of the MPME formulations according to the present invention in removing oil-based drilling fluids from contaminated drill cuttings was measured by a "Mock Cuttings Cleaning Test." The protocol for the Mock Cuttings Cleaning Test is reported, below. Cuttings coated with ACCOLADE™ drilling fluid or INVERMUL™ drilling fluid were independently cleaned with water, BARAKLEEN™, BARASCRUB™, Sample 1, Sample 2 and Sample 3. A sample of contaminated cuttings was used as a control. Definition of the drilling mud and the cleaning systems are described in Example 7. Residual oil on the cuttings was extracted into pentane and the amount extractable was quantified by weight; the results are graphically displayed in FIG.2. FIG 2 shows that 3-4 times less oil remains on the cuttings after they were cleaned by the three MPME formulations according to the present invention when compared to water, BARAKLEEN™ and BARASCRUB™. Mock Pipe Cleaning Test

[0049] The cleaning efficacy and cleaning capacity of selected cleaning systems of drilling fluids on metal surfaces were evaluated by the following protocol: 1. Pre-heat oven to 15O⁰F.

2. Remove the sleeve and bobbin from a Fann 35 rheometer (a sleeve and bobbin type rheometer marketed by Fann and commonly employed for evaluating drilling fluids in the oil field); weigh the sleeve to two decimal places and record the weight on the table as "empty sleeve". 3. Fill a cup with 100 mL test cleaning system; weigh and record the exact amount. Use the same amount of cleaner in each of the experiments to ensure a direct comparison.

4. Shear test mud for 3 min in a Hamilton Beach mixer at a "low" setting.

5. Immerse sleeve in test mud up to a scribe line for 1 min. Remove. Allow to drip dry for 2 minute. Weigh and record as "weight of sleeve before cleaning." Calculate the "weight of mud before cleaning" (weight of mud coated on the sleeve) by subtracting the weight of the empty sleeve from this total weight. Re-attach the sleeve to the Fann 35.

6. Raise the cup containing the cleaning solution and immerse the sleeve up to the scribe line. Immediately turn on the Fann 35 at 100 rpm for 2 min exactly. Lower the cup and allow the excess cleaning system on the sleeve to drip back into the cup for 3 min. 7. Remove sleeve from the Fann 35, careful not to disturb stuck mud. Place in the preheated oven for 4 min. Remove the sleeve from oven, weigh and record as "weight of sleeve after cleaning." Calculate the "weight of mud after cleaning" (weight of residue mud that was not removed after cleaning) by subtracting the weight of the empty sleeve from this weight of sleeve after cleaning. Calculate the amount of "mud removed" ("leached mud") by subtracting weight of sleeve before cleaning from weight of sleeve after cleaning.

8. Clean sleeve with solvent and detergent to remove all residual drilling mud from the sleeve.

9. Add about 1 g of drill mud directly to the cleaning system. Weigh and record the exact amount of mud added. Agitate the cleaning solution on a Hamilton Beach mixer for 1 min at the lowest setting. Calculate the "total mud loading" by adding together the weight of "mud removed" from the previous experiment, the "total mud loading" from the previous experiment, and the weight of "mud added" at this step. 10. Repeat Steps 5 - 9 up to 10 times or until no significant changes in mud removal is observed by each iteration.

Example 1. : Efficacy of Water in Removing ACCOLADE™ Mud from a Metal Surface

[0050] The experiment was performed according to the protocol stated in Example 1. The tested cleaning system was water and the tested contaminant was ACCOLADE™ drilling mud. The result is tabulated in Table B below. "Leached mud" is the amount of mud that was removed from the sleeve and leached into the cleaning fluid. "Sleeve weight before cleaning" is the weight of the sleeve coated with the drilling mud (Step 5 of the Protocol in Example 1). The "weight of mud before cleaning" is calculated by subtracting the weight of the empty sleeve from total weight of the sleeve before cleaning. The "weight of sleeve after cleaning" is the total weight of the sleeve and residue mud after cleaning (Step 7 of the Protocol in Example 1) The "total mud loading" is calculated by adding the weight of "mud removed" from the previous cycle, the "total mud loading" from the previous cycles, and the weight of "mud added" at this cycle.

Table B: Efficacy of Water in Removing ACCOLADE™ Drilling Fluid

Example 2: Efficacy of BARAKLEEN™ in Removing ACCOLADE™ Drilling Fluid from a Metal Surface [0051] The experiment was performed according to the protocol stated in Example 1. The tested cleaning system was BARAKLEEN™ and the tested contaminant was ACCOLADE™ drilling fluid. The result is tabulated in Table C below. The terms in the table are similarly defined as in Example 2.

Table C: Efficacy of BARAKLEEN^1M in Removing ACCOLADE^IM Drilling Fluid

Example 3: Efficacy of BARASCRUB™ in Removing ACCOLADE™ Mud from a Metal Surface

[0052] The experiment was performed according to the protocol stated in Example 1. The tested cleaning system was BARASCRUB™ was and the tested contaminant was ACCOLADE™ drilling fluid. The result is tabulated in Table D below. The terms in the table are similarly defined as in Example 2.

Table D: Efficacy of BARASCRUB™ in Removing ACCOLADE™ Drilling Fluid

Example 4: Efficacy of Sample 1 in Removing ACCOLADE™ Drilling Fluid from a Metal Surface

[0053] The experiment was performed according to the protocol stated in Example 1. The tested cleaning system was Sample 1 and the tested contaminant was ACCOLADE™. The results are tabulated in Table E below. The terms in the table are defined as in Example 2.

Table B: Efficacy of Sample 1 in Removing ACCOLADE™ Drilling: Fluid

Example 5: Efficacy of Sample 2 in Removing ACCOLADE™ Drilling Fluid from a Metal Surface

[0054] The experiment was performed according to the protocol stated in Example 1. The tested cleaning system was Sample 2 and the tested contaminant was ACCOLADE™. The results are tabulated in Table E below. The terms in the table are defined as in Example 2.

Table F: Efficacy of Sample 2 in Removing ACCOLADE^1M Drilling Fluid

Example 6: Efficacy of Sample 3 in Removing ACCOLADE™ Drilling Fluid from a Metal Surface

[0055] The experiment is performed according to the protocol stated in Example 1. The tested cleaning system was Sample 3 and the tested contaminant was ACCOLADE™. The results are tabulated in Table G below. The terms in the table are defined as in Example 2.

Table G: Efficacy of Sample 3 in Removing ACCOLADE^1M Mud

Protocol for Evaluating the Efficacy of Selected Cleaning Systems in Removing Oil from Drill Cuttings

The efficacy of selected cleaning systems in removing drilling muds from drill cuttings may be evaluated by the following protocol: 1. Take a 16 oz wide mouth glass jar. Add approximately 100 g of drill cuttings contaminated with drilling mud to the jar, then weigh again. Record the weight to the nearest 0.01 g. 2. Add 100 mL of cleaning solution to the jar. Record the volume and the weight of the added cleaning solution. Seal the jar and tape the lid down with electrical tape. 3. Place jar into the roller oven at ambient temperature. Roll for 15 min.

4. Carefully pour off the cleaning solution into a receptacle. Place a filter funnel on top of the jar, invert, and let the remaining cleaning solution drain into the receptacle. Allow this inverted jar to drain for 5 min, then place right side around. 5. Add 100 mL of tap water to the jar with the washed cuttings. Seal and tape as before, then roll for 5 min. Drain off the water as done in step 4.

6. Add 100 mL pentane to thejar. Seal thejar and shake for 1 min. Carefully pour off the pentane wash into the top of a 500 mL seperatory funnel. 7. Repeat step 6 twice more, each time adding the wash to the same separatory funnel. 8. Add 50 mL deionized water to the separatory funnel. Shake for 1 min, allow to stand for 5 min, then carefully drain out the water phase. It may be necessary to tap the separatory funnel to break up the rag layer. Drain the top pentane layer into a 500 mL Erlenmeyer flask. 9. Add approximately 20 g of magnesium sulfate to the Erlenmeyer flask. Allow to stand for 1 h. Filter the pentane extract through a fluted filter paper into a pre-weighed (to the nearest 0.01 g) 500 mL Erlenmeyer flask. 10. Place the flask in a well-ventilated area. Allow the pentane to evaporate over night.

Weigh the flask to the nearest 0.01 g and record. 11. Repeat Step 10 until there appears to be little or no additional weight loss.

Example 7: Evaluating the Efficacy of Selected Cleaning Systems in Removing Oil from Drill Cuttings [0056] A cleaning experiment was performed according to the protocol described immediately above. The drill cuttings were contaminated with either ACCOLADE™ or INVERMUL™ drill muds. The cleaning systems tested were: water, BARAKLEEN™, BARASCRUB™, Sample 1, Sample 2 and Sample 3; a sample of uncleaned drill cuttings was used as control. After a cleaning regiment using one of the above listed cleaning systems on each of the ACCOLADE™ or INVERMUL™ mud contaminated systems, residual oil remaining on the drill cuttings was extracted into pentane. The lower amount of residual oil recovered into pentane is indicative of a more efficient cleaning system. The weight of residual oil was recorded and charted in FIG 2. The results show that water BARAKLEEN™ and BARASCRUB™ cleaning systems left 3.5-4.0 times more residual oil on the drill cutting surfaces than the three MPME formulations according to the present invention.

Claims

1. A performance cleaning composition comprising a middle phase microemulsion (MPME) formulation, said MPME formulation comprising: (a) about 1 to about 40 wt % surfactant, (b) about 0.5 to about 40 wt% of at least one co-surfactant, (c) about 0.5 to about 30 wt% electrolyte, (d) about 30 to about 99 wt% water, and (e) about 0.5 to about 40 wt% oil, wherein the oil is a hydrocarbon, ester, triglyceride, or ether.

2. The performance cleaning composition according to claim 1 wherein wherein said electrolyte is comprised of at least one readily biodegradable salt of an organic acid.

3. The performance cleaning composition according to claim 2 wherein said organic acid is at least one of formic acid, acetic acid and propionic acid.

4. The performance cleaning composition of claim 1 wherein said electrolyte is an organic acid salt of alkali metals selected from potassium, sodium, and lithium.

5. The performance cleaning composition of claim 1 wherein said oil is selected from the group of olefins, isoparaffins, esters and combinations thereof.

6. The performance cleaning composition of claim 4 wherein said oil is an olefin.

7. The performance cleaning composition of claim 6 wherein said olefin is selected from 1-alkenes, olefins, and internal olefins.

8. The performance cleaning composition of claim 4 wherein said oil is a Ci₆ - C₁₈ internal olefin.

9. The performance cleaning composition of claim 4 wherein said oil is comprised of one or more isoparaffins.

10. The performance cleaning composition of claim 9 wherein said isoparaffins are selected from the group of hydrogenated poly-alpha-olefϊns, highly refined hydro-treated mineral oil basestock and combinations thereof.

11. The performance cleaning composition of claim 4 wherein said oil is comprised of one or more esters.

12. The performance cleaning composition of claim 11 wherein said esters are selected from the group of triglycerides and/or condensation products of Ci-Ci o alcohols with fatty acids derived from animal and vegetable oils.

13. The performance cleaning composition of claim wherein said surfactants are selected from those surfactants having a hydrophilic head group and a hydrophobic tail group.

14. The performance cleaning composition of claim 13 wherein said tail group is comprised of two hydrocarbon chains, and each of which is at least five carbon atoms in length.

15. The performance cleaning composition of claim 14 wherein each of said hydrocarbon chains is no more than 10 carbon atoms in length.

16. The performance cleaning composition of claim 13 wherein said tail group is comprised of a single hydrocarbon chain of at least 10 carbon atoms in length.

17. The performance cleaning composition of claim 16 wherein said hydrocarbon chain is no more than 20 carbon atoms in length.

18. The performance cleaning composition of claim 13 wherein said head group is anionic.

19. The performance cleaning composition of claim 13 wherein said head group is neutral.

20. The performance cleaning composition of claim 13 wherein said surfactant is an alkyl glyceryl sulfonate.

21. The performance cleaning composition of claim 1 wherein said co-surfactant is selected from the group of C₂ to C₁₂ primary, secondary and tertiary alcohols.

22. The performance cleaning composition of claim 21 wherein said co-surfactant is n-butanol.

23. The performance cleaning composition of claim 1 wherein said aqueous phase is water buffered to a pH of about 10.

24. The performance cleaning composition according to claim 1 wherein said aqueous phase is brine.

25. A method for cleaning drilling fluid contaminated surfaces comprising contacting said surfaces with a performance cleaning composition comprising an (MPME) formulation, said MPME formulation comprising:

(2) about 1 to about 40 wt % surfactant; (3) about 0.5 to about 40 wt% of at least one co-surfactant;

(4) about 0.5 to about 30 wt% electrolyte;

(5) about 30 to about 99 wt% water, and

(6) (e) about 0.5 to about 40 wt% oil, wherein the oil is a hydrocarbon, ester, triglyceride, or ether.

26. The method of claim 25 wherein said contaminant is selected from oil-based drilling fluids, synthetic material based drill fluids, and any combinations thereof.

27. The method of claim 25 wherein said surface is selected from surfaces of pipes, casings, drill cuttings, drilling equipment, wellbores, and human skin.