Use of selected fatty alcohols and their mixtures with...

Earth boring – well treating – and oil field chemistry – Earth boring – Contains organic component

Reexamination Certificate

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C507S139000, C507S141000, C507S145000

Reexamination Certificate

active

06716799

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to water-based drilling fluids of the type used in particular as so-called drilling muds in geological exploration by drilling. In the following, the invention is described with reference to pure water-based drilling fluids and drilling muds based thereon. However, the modification according to the invention of auxiliary fluids of the type in question is by no means confined to this particular application and may also be applied in particular to auxiliary fluids for tackling problems arising from differential sticking, more particularly to spotting fluids and to fluids used for workover stimulation and comparable geological drilling applications.
2. Discussion of Related Art
In the relevant technology of the geological exploration of, for example, oil and/or gas occurrences, there are three basic types of auxiliary fluids, more particularly corresponding drilling muds, used in practice, namely: oil-based systems which generally comprise a continuous oil phase mixed with a disperse water phase in the form of so-called w/o invert muds, water-based oil/water systems in which the aqueous phase with its dissolved and dispersed auxiliaries forms the continuous phase and the oil phase is dispersed therein in the form of a fine emulsion and, finally, pure water-based drilling fluids.
The pure water-based systems are the oldest in the historical development of drilling fluids. However, their use is attended by such serious disadvantages that, hitherto, only limited application has been possible. Above all, the interaction of the water-based drilling fluids with the water-sensitive layers of rock—more particularly corresponding layers of clay—to be drilled leads to unacceptable interference with the drilling process.
Very recently, however, a fairly old proposal has been taken up again and, even in highly sensitive shale formations, can lead to adequate stability where purely water-based drilling fluids are used. It involves the use of corresponding systems based on soluble alkali metal silicates which are also known as waterglasses or waterglass-based systems, cf. for example the seminar on “The Prevention of Oil Discharge from Drilling Operations” held in public in Aberdeen on 18th/19th June 1996 (organized by IBC Technical Services, London) and, in particular, the publications appearing in this connection by M. Eigner entitled “Field Trials with a Silicate drilling Fluid in Shell-Expro” and by I. Ward and B. Williamson entitled “Silicate Water Based Muds—a Significant Advance in Water Based Drilling Fluid Technology”.
However, the use of purely water-based drilling fluids, particularly of the last-mentioned type, makes the presence of components with a lubricating effect desirable. Relevant specialist knowledge is relevant in this regard. It is known that carboxylic acid esters have a particularly pronounced lubricating effect which is utilized in many respects in geological exploration. However, their use in water-based systems and, in particular, in comparatively highly alkaline waterglass systems can lead to serious difficulties. Ester cleavage can result in the formation as secondary products of components with a marked tendency to foam which then introduce unwanted problems into the drilling fluid. The above-cited publication by I. Ward et al. refers specifically to this problem.
The problem addressed by the present invention was to provide lubricants for water-based drilling fluids and, more particularly, for high-pH silicate-containing waterglass-based drilling fluids which would be at least partly stable to hydrolysis, but which at the same time would also enable carboxylic acid esters to be used if required and would thus preclude the adverse effects of potential hydrolysis through their pronounced foam-suppressing effect.
SUMMARY OF THE INVENTION
A The present invention relates to the use of selected linear and/or branched fatty alcohols containing at least 12 carbon atoms in the molecule and to the use of mixtures of these fatty alcohols with carboxylic acid esters as a lubricating additive in water-based drilling fluids for their use in geological exploration by drilling.
More particularly, the invention relates to the use of these fatty-alcohol-based lubricants as an additive in water-based alkali metal silicate drilling fluids.
Particulars of the Teaching According to the Invention
In the course of the development work for new water-based drilling fluids, it was found that special alcohols have favourable lubricating properties in such drilling fluids. Fatty alcohols of the type according to the present invention have the additional advantage that they are stable even in highly alkaline water-based fluids. Because of this, they were also tested in particular in modern silicate drilling fluids (waterglass systems).
It was surprisingly found that certain fatty alcohols of the type according to the invention—described in detail hereinafter—exhibit extremely good lubricating properties even though their lubricating effect in other clay-containing water-based drilling fluids is not particularly remarkable.
The positive effects of the selected fatty-alcohol-based auxiliaries on which the invention is based can be further enhanced by using the fatty alcohols together with carboxylic acid esters characterized by good lubricity. Further observations in this regard will again be made hereinafter. It is remarkable that, despite the expected partial ester cleavage and the resulting theoretical danger of an increase in the tendency to foam, there are no unwanted effects in this direction. The foam-suppressing effect of the fatty alcohols compulsorily used in accordance with the invention—in the form of their intimate mixture with the esters—is evidently so great that the desired advantage of the enhanced lubricating effect can be utilized here without having to accept disadvantages in the form of increasing foaming in practice. Even as hydrolysis products, certain selected esters (see the following disclosure) provide special effects in helping to solve the problem addressed by the invention.
The fatty alcohols used in accordance with the invention are first described in broader and in preferred definitions in the following, after which suitable and particularly preferred ester mixing components are similarly discussed.
Fatty alcohols are known to be monohydric alcohols with comparatively long hydrocarbon chains which in turn may be linear and/or branched. Corresponding fatty alcohols in the C
12-30
range are particularly suitable, fatty alcohols in the C
12-24
range being particularly preferred for use in accordance with the invention.
The fatty alcohols may be of natural and/or synthetic origin. It is known that fatty alcohols of natural origin are obtained from the corresponding fatty acids by reduction of the terminal carboxyl group to the alcohol group. The fatty acids of natural origin in the C chain length range in question are generally present in the form of mixtures of aliphatically saturated and/or olefinically unsaturated acids. The olefinically unsaturated acids with at least 14 to 16 carbon atoms in the molecule contain varying amounts of mono- and/or polyolefinically unsaturated compounds, depending on the natural material source. By suitably selecting the reduction conditions, it is possible to achieve at least substantially specific reduction of the carboxyl group without any effect on the olefinic double bonds in the carbon chain so that correspondingly mono- and/or polyunsaturated fatty alcohols, for example in the C
16-24
range and more particularly in the C
16/18
range, are available. The relevant specialist literature on this subject is represented, for example, by the book published by applicants entitled “Fettalkohole, Rohstoffe, Verfahren und Verwendung (Fatty Alcohols, Raw Materials, Processes and Uses)” which contains detailed information on industrial processes for the production of fatty alcohols, on the analysis and characteristic data of fatty alcohols and on th

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