Earth boring – well treating – and oil field chemistry – Earth boring – Contains organic component
Reexamination Certificate
2000-04-07
2002-09-24
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Earth boring
Contains organic component
C507S905000, C585S001000, C585S734000, C585S739000
Reexamination Certificate
active
06455474
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to base oils and drilling fluids or muds made from such base oils, which are substantially non-toxic, essentially non-polluting, biodegradable and highly useful in low temperature operations.
BACKGROUND
In pending U.S. application Ser. No. 08/620,983, filed Mar. 22, 1996, supra, there is disclosed base oils which are non-toxic, non-polluting, biodegradable and suitable for use in forming drilling fluid compositions by dispersing therein at least one additive selected from the group consisting of weighting agents, emulsifiers, wetting agents, viscosifiers, fluid loss control agents, proppants and other particulate agents. In forming the drilling fluids a continuous oil phase, or water-in-oil invert emulsion phase (where water or brine is present and emulsified in the solvent), provide a medium for the dispersed additive, or additives. The base oil is constituted of a mixture of normal paraffins (n-paraffins) and isoparaffins having from about 10 to about 24 carbon atoms, i.e., C
10
-C
24
n-paraffins and isoparaffins, preferably C
12
-C
18
paraffins, having an isoparaffin:n-paraffins molar ratio ranging generally from about 0.5:1 to about 9:1, and the isoparaffins of the mixture contain greater than 50 percent, generally 70 percent, by weight of the isoparaffins in the mixture, of mono-methyl species, e.g., 2-methyl, 3-methyl, 4-methyl, ≧5-methyl or the like, with minimal formation of isoparaffins having branches with substituent groups of carbon number greater than 1, e.g., ethyl, propyl, butyl or the like.
These base oils form high performance drilling fluids of low toxicity, and they are environmentally friendly. Like conventional diesel fuels they form drilling fluids, or muds, which have excellent rheological properties for rotary drilling, but unlike conventional diesel fuels do not pose a serious and costly disposal problem for offshore operators. Thus, with conventional diesel operators must barge spent mud and cuttings to shore for land disposal, because diesel fuel cannot meet U.S. Environmental Protection Agency Standards regarding discharge limitations and/or permit requirements. In contrast, this new base oil admirably meets this need, and provides excellent rheological properties. However, the oil and drilling fluids made from the new base oil is lacking in that it is of low pour point, and its low temperature performance leaves much to be desired. It does not perform well under cold temperature conditions which are frequently encountered in drilling operations, e.g., in Alaskan or North Sea operations. Accordingly, there remains a need for a further improved base oil; and drilling fluid made from such base oil, of low toxicity, biodegradable, and environmentally friendly, but yet will be useful at low temperature conditions.
SUMMARY OF THE INVENTION
This invention, which supplies this need and others, accordingly relates to a substantially non-toxic, essentially non-polluting, biodegradable, low temperature base oil, and drilling fluid, or mud composition made by dispersing in said base oil one or more of the weighting agents, emulsifiers, wetting agents, viscosifiers, fluid loss control agents, proppants, and particulate agents are mixed with the paraffinic solvent composition to form an emulsion in which the latter forms a continuous oil phase, or water-in-oil invert emulsion phase.
The base oil is constituted of a mixture of n-paraffins and isoparaffins ranging from about C
10
to about C
24
, preferably from about C
12
to about C
18
, wherein the isoparaffins component of the mixture contains at least about 30 percent, preferably from about 30 percent to about 50 percent, based on the weight of the isoparaffins component in the mixture, of the mono-methyl species (e.g., 2-methyl, 3-methyl, 4-methyl, ≧5-methyl or the like), and at least 30 percent, preferably from about 30 percent to about 50 percent, based on the weight of the isoparaffins component in the mixture, of isoparaffins which are of a multi-methyl branched species (e.g., dimethyl, trimethyl, etc.), or contains one or more branches of carbon number higher than methyl (e.g., ethyl, propyl, etc.), or both. The base oil composition has a molar isoparaffin:n-paraffin ratio ranging from about 0.5:1 to about 9:1, preferably from about 1:1 to about 3:1, and boils within a range of from about 320° F. to about 700° F., preferably from about 500° to about 700° F. The presence of these concentrations of multi-methyl branched isoparaffins, or isoparaffins with branches of higher carbon number than methyl in the mixture effectively increases the low temperature performance of a drilling fluid made from such base oil thereby enabling use of the drilling fluid under cold temperature conditions; and yet, the drilling fluid retains its desirable high performance and outstanding environmental characteristics.
The C
10
-C
24
, or C
12
-C
18
solvent composition of the drilling fluid, or drilling mud, in all embodiments constitutes, a continuous liquid phase, or continuous invert emulsion phase where water or brine is present and emulsified within the solvent composition. Where water is present, the solvent:water volume ratio generally ranges from about 90:10 to about 60:40; preferably from about 80:20 to about 70:30.
The continuous, or invert emulsion phase of the drilling fluid, or drilling mud, of this invention is emulsified by dispersing therein at least one additive selected from the group consisting of weighting agents, emulsifiers, wetting agents, viscosifiers, fluid loss control agents, proppants for use in fracturing subterranean formations, and particulate agents as used in gravel packs.
In forming the drilling fluid, or mud, generally one or more of the weighting agents, emulsifiers, wetting agents, viscosifiers, fluid loss control agents, proppants, and particulate agents are mixed with the paraffinic solvent composition to form an emulsion in which the latter forms a continuous oil phase, or water-in-oil invert emulsion phase. In such systems, the high purity solvent composition constitutes generally from about 50 percent to about 95 percent, and more often-and preferably, from about 60 percent to about 80 percent of the total drilling fluid, or mud, based on the total volume of the composition; with the balance of the drilling fluid, or mud, being water, brine or other additive, or additives. A drilling fluid, or mud, of this character provides excellent rheological properties under a wide variety of drilling conditions. Exemplary of additives useful in the practice of this invention are: weighting materials such as barite, iron oxide, calcium oxide, etc.; emulsifiers such as fatty acids, soaps of fatty acids, and fatty acid derivatives such as a amido-amines, polyamides, polyamines, esters, e.g., sorbitan monoleate polyethoxylate, etc.; wetting agents such as crude tall oil, organic phosphate esters, modified imidazolines and amido-amines, alkyl aromatic sulfates and sulfonates, etc.; viscosifiers such as organophilic clays, oil soluble polymers, polyamide resins, polycarboxylic acids and soaps, etc.; fluid loss control materials such as modified lignites, polymers, asphaltic compounds and the like, etc.; proppant materials such as sand grains, walnut shells, etc.; gravel and the like. Water, or brine, as suggested, can also be present in or added to the drilling fluid, or mud. Typically, the weighting agent is added in concentrations ranging up to about 18 pounds per barrel of paraffinic solvent; the emulsifiers and wetting agents, respectively, in concentrations ranging from about 2 to about 6 pounds, per barrel of paraffinic solvent; the viscosifiers in concentrations ranging from about 1 to about 10 pounds per barrel of paraffinic solvent; and the fluid loss control agents in concentrations ranging from about 1 to about 20 pounds per barrel of paraffinic solvent.
DETAILED DESCRIPTION
The paraffinic oil base, or solvent, component for the drilling fluid, or mud, can be obtained from a Fischer-Tropsch reaction product or wax, or from slack waxes w
Cook Bruce Randall
Mart Charles John
Ryan Daniel Francis
Wittenbrink Robert Jay
Brumlik Charles J.
ExxonMobil Research and Engineering Company
Tucker Philip
LandOfFree
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