Earth boring – well treating – and oil field chemistry – Earth boring – Contains organic component
Reexamination Certificate
2000-01-25
2001-11-27
Tucker, Philip (Department: 1712)
Earth boring, well treating, and oil field chemistry
Earth boring
Contains organic component
C507S905000
Reexamination Certificate
active
06323157
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to compositions which are mixtures of olefins and olefin isomers having utility as base oils for well fluids. More specifically, the base oils of this invention are environmentally friendly and have very low pour point temperatures. These properties make the base oils of this invention ideal candidates for use as components of well fluids for cold climates and offshore applications.
BACKGROUND OF THE INVENTION
Historically, first crude oils, then diesel oils and, more recently, mineral oils have been used in formulating well fluids. Due to problems of toxicity and persistence which are associated with these oils, and which are of special concern of offshore use, the industry is developing well fluids which are based on “pseudo-oils”. Examples of such oils are fatty acid esters and synthetic hydrocarbons such as poly(alpha)olefins. Fatty acid ester based oils have excellent environmental properties, but well fluids made with these esters tend to have lower densities and are prone to hydrolytic instability. Poly(alpha)olefin based well fluids can be formulated to high densities, have good hydrolytic stability and low toxicity. They are, however, somewhat less biodegradable than esters, they are expensive and the fully weighted, high density fluids tend to be overly viscous, especially when used in cold climates. A most recent trend in the industry is the use of base oils comprising mixtures of predominantly linear internal olefins. Well fluid base oils comprised of mainly linear internal olefins are acceptably environmentally friendly and have pour point temperatures in the range of about −10° C. which is borderline for cold climates. What is needed is an environmentally acceptable well fluid base oil having a pour point lower than −25° C. The present invention addresses this need.
INVENTION SUMMARY AND PRIOR ART REVIEW
In a broad sense, therefore, this invention relates to novel compositions suitable for use as well fluid base oils which have especially advantageous and unexpectedly low pour point temperatures as low as −39° C. This quantum leap in the lowering of pour point temperatures has been achieved without the degradation of other required salient properties of well fluid base oils, including retention of environmental acceptability.
U.S. Pat. No. 5,589,442 (Gee et al.) discloses well fluid base oil which is predominantly unbranched (linear) internal olefins. The Gee et al. patent discloses the use of C12 to C24 olefins in their mixture, preferably C14-C18 olefins. The disclosure of the Gee et al. patent permits the presence of some branched olefins in their mixtures (0-50 wt %) with the remainder being linear olefins. The disclosure of the Gee et al. patent also permits the presence of some alpha olefins in their mixture (0-20 wt %) with the remainder being internal olefins. The pour point of the preferred embodiment of the Gee et al. disclosure is −5° C. with some formulations having pour points as low as −9° C.
This invention is directed to well fluid base oils having pour points lower than −25° C. The base oils of this invention are comprised of mixtures of predominantly linear (unbranched) internally isomerized olefins of tetradecene (C14) and hexedecene (C16). In one embodiment of this invention, a well fluid base oil having a pour point of −39° C. is disclosed. In an especially preferred embodiment of this invention, a well fluid base oil having a pour point of −33° C. is disclosed.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
For the purposes of this invention, a well fluid is intended to be any fluid or near fluid used in the rotary method of drilling wells, chiefly for gas and oil, and is not intended to be restricted only to so-called drilling muds. A non-limiting list of well fluids includes drilling muds, spotting fluids, lubricating additives, and other products for the treatment of subterranean wells. Also, for the purposes of this invention, internally isomerized olefins are defined to comprise olefins having only a single double bond (mono-olefin) located adjacent to a carbon atom other than the terminal (or alpha) carbon atom of the carbon chain. Mixtures of internal olefin isomers implied that several different skeletal isomers are present, e.g., some of the olefins may have a double bond connecting carbon atom #2 to carbon atom #3, some double bonds may connect carbon atom #3 to carbon atom #4, etc. For each skeletal isomer, there will be at lest two stereo isomers commonly referred to as the cis and trans forms.
The present invention relates to a group of synthetic hydrocarbons and to well fluids based on them, especially to well fluids which are useful in the rotary drilling process used for making wells into subterranean formations containing oil, gas or other minerals.
The rotary drilling process is used for making wells for the production of oil, gas and other subterranean minerals such as sulfur. In rotary drilling operations, a drill bit at the end of a drill string is used to penetrate the subterranean formations. This drill bit may be driven by a rotating drill string or a drill motor powered, for example, by hydraulic power. During the rotary drilling operation, a fluid, conventionally referred to as a drilling mud, is circulated from the drilling equipment on the surface down to the drill bit where it escapes around the drill bit and returns to the surface along the annular space between the drill bit and the surrounding subsurface formations. The drilling mud lubricates the downhole equipment and serves as a carrier to bring the formation cuttings to the surface where they can be separated from the mud before it is recirculated. In addition, the drilling mud serves to counterbalance formation pressures and may also form a cake around the walls of the borehole to seal the formations.
The lubricating action of the drilling mud is particularly important with the conventional rotating drill string since it provides a lubricant or cushion between the rotating drill pipe and the walls of the borehole, helping to prevent sticking of the drill string in the hole. The characteristics and performance of drilling muds are described, for example, in Kirk-Othmer, Encyclopedia of Chemical Technology, Third Edition, John Wiley and Sons, 1982, under Petroleum (Drilling Muds). This reference discloses a description of drilling muds and the materials used in formulating them.
Drilling muds are usually classified as either water based muds or oil-based muds, depending upon the character of the continuous phase of the mud, although water-based muds may contain oil and oil-based muds may contain water. Water-based muds conventionally comprise a hydratable clay, usually of the montmorillonite family, suspended in water with aid of suitable surfactants, emulsifiers and other additives including salts, pH control agents and weighting agents such as barite. The water makes up the continuous phase of the mud and is usually present in any amount of at least 50 volume percent of the entire composition. Oil is also usually present in minor amounts but will typically not exceed the amount of the water so that the mud will retain its character as a water-continuous phase material. Oil-based muds generally use a hydrocarbon oil as the main liquid component with other materials such as clays or colloidal asphalts added to provide the desired viscosity together with emulsifiers, gellants and other additives including weighting agents. Water may be present in greater or lesser amounts but will usually not be greater than 50 volume percent of the entire composition. If more than about 10 weight percent water is present, the mud 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 with the oil and the additives making up the remainder of the fluid. Under appropriate conditions, the well fluid base oils of the present invention may comprise any
Carpenter Joel F.
Toye Jose
BP Corporation North America Inc.
DiSalvo Joseph
Tucker Philip
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