Earth boring – well treating – and oil field chemistry – Earth boring – Contains organic component
Reexamination Certificate
2000-03-10
2002-06-25
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Earth boring
Contains organic component
C507S203000, C507S904000
Reexamination Certificate
active
06410488
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the field of drilling fluids. In one embodiment, the invention relates to a drilling fluid having oil as a continuous phase. In another embodiment, this invention relates to a rate of penetration enhancer comprising a continuous aqueous phase having a fluid dispersed therein, or a spotting fluid.
BACKGROUND OF THE INVENTION
Drilling fluids used for offshore or on-shore applications need to exhibit acceptable biodegradability, human, eco-toxicity, eco-accumulation and lack of visual sheen credentials for them to be considered as candidate fluids for the manufacturer of drilling fluids. In addition, appropriate fluids used in the drilling arena need to possess acceptable physical attributes. These generally include viscosities of less than 4.0 cSt@ 40° C., flash values of 100° C. (Cleveland Closed Cup) and, for cold weather applications, pour points of −40° C. or lower. These properties have typically been only attainable through the use of expensive synthetic fluids such as hydrogenated poly alpha olefins, as well as unsaturated internal olefins and linear alpha-olefins and esters.
Drilling fluids may be classified as either water-based or oil-based, depending upon whether the continuous phase of the fluid is mainly oil or mainly water. At the same time, water-based fluids may contain oil and oil-based fluids may contain water.
Water-based fluids conventionally include a hydratable clay, suspended in water with the aid of suitable surfactants, emulsifiers and other additives including salts, pH control agents and weighting agents such a barite. Water constitutes the continuous phase of the formulated fluid and is usually present in an amount of at least 50 percent of the entire composition; minor amounts of oil are sometimes added to enhance lubricity.
Oil-based fluids have a hydrocarbon fluid as the continuous phase and include other components such as clays to alter the viscosity, and emulsifiers, gellants, weighting agents and other additives. Water may be present in greater or lesser amounts but will usually not be greater than 50 percent of the entire composition; if more than about 10 percent water is present, the fluid is often referred to as an invert emulsion, i.e a water-in-oil emulsion. In invert emulsion fluids, the amount of water is typically up to about 40 weight percent based on the drilling fluid, with the oil and the additives making up the remainder of the fluid.
Oil-based fluids may be formulated from various hydrocarbon fluids such as synthetically derived poly alpha olefins, internal olefins, esters, low toxicity mineral oils or even diesel oil. Diesel and even low toxicity mineral oils are undesirable since they are toxic to marine life. As a result, the discharge of drilling fluids containing these oils into marine waters is usually strictly controlled because of the serious effects which the oil components may have on marine organisms. For this reason, offshore drilling rigs either use synthetic oil based fluids for drilling, or return the oil-based fluids to shore after they have been used. Synthetic fluids have the disadvantage of being very expensive.
Oil-based fluids may be made environmentally acceptable by the use of oils which posses inherently low toxicity to marine organisms and good biodegradability. Generally, these properties are associated in hydrocarbons with low aromaticity. For these reasons, drilling fluids based on linear paraffins might be considered desirable. On the other hand, however, linear paraffins tend to have high pour points. Further, higher molecular weight fractions of linear paraffins tend to be waxy so that in the low temperature environments frequently encountered in offshore drilling, there is a significant risk that waxy paraffin deposits will be formed in the downhole equipment or in the riser connecting the sea bed to the drilling equipment. In either event, this is unacceptable so that paraffinic oils have not achieved any significant utility as the base fluid in oil based fluids.
Furthermore, several jurisdictions in Europe and North America have either banned the discharge of all drilling cuttings (including drilling fluids) or legislated the reduction of the level of oil-on-cuttings that may be discharged. In light of this, drillers have started to re-inject the oil laced cuttings back into the geological formations. Because of the possibility of accidental spillage in these situations, there is a reluctance to use inexpensive diesel or low toxicity mineral oil based fluids. At the same time, there is a reluctance to use expensive synthetics oil based fluids. Consequently there is a need for an inexpensive environmentally acceptable drilling fluid, which has good environmental credentials and physical properties.
U.S. Pat. No. 5,189,012 to Patel et al. discloses a drilling fluid having synthetic branched chain oligomers synthesized from one or more olefins having a chain length of two to fourteen carbon atoms. The oligomers have an average molecular weight of from 120 to 1000. The synthetic hydrocarbon mixture possesses a viscosity of from 1.0 to 6.0 centistokes, preferably a viscosity of from 1.5 to 3.5 centistokes. The synthetic hydrocarbons may be hydrogenated (saturated), partially hydrogenated or non-hydrogenated.
U.S. Pat. No. 5,589,442 to Gee et al. discloses a drilling fluid composed of “mostly linear” olefins, that is, non-branched olefins with at least one double carbon-carbon bond present in the chain. The chain length of the olefins is at least twelve carbon atoms. The fluid contains substantial amounts of internal olefins, and small amounts of branched olefins.
U.S. Pat. No. 5,432,152 to Dawson et al. discloses an invert drilling fluid which comprises a water-in-oil emulsion which includes at least 50 volume percent of a low toxicity base oil, an emulsifier, and at least one solid additive suspended in the drilling fluid. At least about 25 volume percent of the base oil content of the drilling fluid is one or more linear alpha-olefins which have from about 14 to 30 carbon atoms.
U.S. Pat. No. 5,045,219 to Trahan et al. discloses a polyalphaolefin based downhole lubricant and spotting fluid used as an additive in water-based drilling. The polyalphaolefin contains no more than 0.5% of 1-decene monomer, blended in a concentration range of at least 5% by volume with emulsifiers.
Mercer et al. (U.S. Pat. No. 5,096,883) discloses a synthetic based drilling fluid made from synthetic branched-chain paraffins that may or may not contain ester functionalities. The base-oil has between about 16 and about 40 atoms per molecule. Preferably, the branched-chain paraffin used as the base-oil consists essentially of the dimer of 1-decene, which has a viscosity of about 5 centistokes at 40° C.
Trahan et al. (U.S. Pat. No. 4,876,017) discloses a synthetic hydrocarbon compound, such as a polyalphaolefin, which may be combined with emulsifiers and thinners. The polyalphaolefin may be used as a downhole lubricant in water based fluids. The fluids are non-toxic. The polyalphaolefin may be used at higher ratios to functional additives, to function as a spotting fluid for the removal of lodged tools downhole.
U.S. Pat. No. 5,837,655 to Halliday et al. discloses non-toxic, biodegradable purified paraffins that may be used as lubricants, rate of penetration enhancers, and/or spotting fluids for water-based drilling fluids. The paraffin component may be cycloparaffins having between about 8-28 carbon atoms, preferably between about 8-16 carbon atoms, straight or branched hydrocarbons having between 8 and 28 carbon atoms, or mixtures of the two. Examples include white oils and other technical or food grade paraffins. The white oils and food grade paraffins are manufactured through conventional means such as hyrotreating or through separation technologies. They have conventional pour points of, for example, −18° C.
U.S. Pat. No. 5,605,879 to Halliday et al. discloses the use of olefin isomers, which are added to water-based drilling fluids, for downhole lubrica
Fefer Michael
Pierson Lorne
Bereskin & Parr
Mendes da Costa Philip C.
Petro--Canada
Tucker Philip
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