U.S. patent number RE36,066 [Application Number 08/506,458] was granted by the patent office on 1999-01-26 for use of selected ester oils in drilling fluids and muds.
This patent grant is currently assigned to Baroid Limited, Henkel KGaA. Invention is credited to Jean-Marc Braun, Douglas J. Grimes, Claus-Peter Herold, Heinz Mueller, Stuart P. T. Smith, Stephan von Tapavicza.
United States Patent |
RE36,066 |
Mueller , et al. |
* January 26, 1999 |
Use of selected ester oils in drilling fluids and muds
Abstract
Invert emulsion muds for drilling of gas and oil, which are
environmentally safe, and which contain: A. a continuous oil phase
composed predominantly of at least one monocarboxylic acid ester of
a C.sub.2 -C.sub.12 monofunctional alkalol wherein the
monocarboxylic acid contains from 16 to 24 carbon atoms and is
olefinically mono- or poly-unsaturated, B. a disperse aqueous
phase, C. at least one emulsifier, D. at least one weighing agent,
E. at least one fluid loss additive, and F. a mild alkaline
reserve.
Inventors: |
Mueller; Heinz (Dusseldorf,
DE), Herold; Claus-Peter (Mettmann, DE),
von Tapavicza; Stephan (Dusseldorf, DE), Grimes;
Douglas J. (Stonehaven, GB6), Braun; Jean-Marc
(Luxembourg, LU), Smith; Stuart P. T.
(Kincardineshire, GB6) |
Assignee: |
Henkel KGaA (Duesseldorf,
DE)
Baroid Limited (London, GB2)
|
[*] Notice: |
The portion of the term of this patent
subsequent to March 16, 2001 has been disclaimed. |
Family
ID: |
46252940 |
Appl.
No.: |
08/506,458 |
Filed: |
August 1, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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452457 |
Dec 18, 1989 |
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Reissue of: |
759097 |
Sep 6, 1991 |
05232910 |
Aug 3, 1993 |
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Foreign Application Priority Data
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Dec 19, 1988 [DE] |
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3842659 |
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Current U.S.
Class: |
507/138;
507/140 |
Current CPC
Class: |
C09K
8/34 (20130101) |
Current International
Class: |
C09K
8/34 (20060101); C09K 8/02 (20060101); C09K
007/02 () |
Field of
Search: |
;507/138,140 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0009746 |
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Apr 1980 |
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EP |
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229912 |
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Nov 1986 |
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EP |
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2560210 |
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Aug 1985 |
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FR |
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3419415 QA1 |
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Nov 1985 |
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DE |
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80940 |
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Nov 1982 |
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RO |
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2158437 |
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May 1985 |
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GB |
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PCT/US86/02598 |
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Jun 1987 |
|
WO |
|
Other References
Oleochemicals, Unichema International Product Specifications, May
1988. .
Article: Ester Base Stocks, JSL, Jul. 1984, pp. 153-169. .
Drilling Fluids Optimization--A Practical Field Approach, Penwell
Books, 1986 By: James L. Lummus, J.J. Azar. .
Parrish et al., "Variability of the Acute Toxicity of Drilling
Fluids to Mysids `Mysidopsis Bahia`", EPA Report No.
EPA/600/D-88/212, 1988. .
P.A. Boyd et al., "New Base Oil Used in Low-Toxicity Muds", Journal
of Petroleum Technology, 1985. .
R. B. Bennett, "New Drilling Fluid Technology--Mineral Oil Mud",
Journal of Petroleum Technology, 1984. .
Translation of FR 2 560 210 (published 30 Aug. 1985); cited as
reference AM in Information Disclosure Statement filed Aug. 1,
1995. .
Translation of DE 34 19 415 (published Nov 28, 1985); cited as
reference AO in Information Disclosure Statement filed Aug. 1,
1995. .
Translation of Article: "Use of Vegetable Oils and Their
Transesterification Products as Diesel Fuels", P. Gateau et al.
Rev. Inst. Fr. Pet. vol. 40, No. 4, Jul./Aug. 1985, pp. 509-528,
cited as reference BL in Information Disclosure Statement filed
Aug. 1, 1995. .
Excerpt from Manual of Drilling Fluids Technology, "Stuck Pipe",
NL/Baroid/NL Industries, Inc., pp. 3, 12 & 13 (1985). .
Analytic Tables, Vegetable Oils, Fatty Acid Components, Ashland
Chemical Company, 2 pages, (1973). .
Composition and Constants of Natural Fats and Oils, 1 page document
(date unknown). .
Sources et monographies des principaux corps gras, p. 315 (date
after 1989--not a reference). (Date Unknown). .
L.G. Zachary et al., Tall Oil and its Uses, F.W. Dodge Co., a
division of McGraw-Hill, pp. 14 and 26, (1965). .
Kirk-Othmer, Encyclopedia of Chemical Technology, vol. 22, third
edition, cover page and pp. 531-541 (1982). .
Ullmans Enzyklopadie der technischen Chemie, 4., neubearbeitele und
erweiterte Auflage, Band 11, Erdol und Erdgas bis
Formazanfarbstoffe, Verlag Chemie, Weinheim/Bergstr., cover page
and p. 542 (date unknown). .
Acides Gras et Cires, p. 405 (date unknown). .
One page document, collection of tables in French (date unknown).
.
Manuel de Rheologie des Fluides de Forage et Laitiers de Ciment
Editions Technip 27, 1979. .
Article: "Use of Vegetable Oils and Their Transesterification
Products as Diesel Fuels", By: Gateau, J.C. Guibet, G. Hilton, R.
Stern; Rev. Pet., 1985 pp. 509-528. .
Article: "Diesel Fuel Derived from Vegetable Oils II: Emission
Tests Using Rape Oil Methyl Ester" Energy in Agriculture 4, (1985)
pp. 207-215. .
Article: "Ester Oils--Structure and Chemical-Physical Properties"
By: M. Wildersohn, Tribologie + Schmierungstechnik, pp. 70-75 No
Date Available. .
Chapter: The Basics of Industrial Oleochemistry: A Comprehensive
Survey of Selected Technologies Based on Natural Oils and Fats, pp.
90-101 No Date Available By G. Dieckelmann & H.J. Heinz. .
Document: Presentation of alternative organic carrier fluids for
drilling sludge, presented at the Forum on Borehole Stability, in
Aberdeen, Sep. 15, 1988. .
Document: Presented at an NIF Course on oil field chemicals held at
Fagernes (Norway) in Mar. 1987. .
Document: Sent by Henkel KGaA to the Operators, dated Jun. 1986.
.
List of oil chemicals, issued by Henkel KGaA in Jul. 1986. .
Letter dated 31 Jul. 1987 from Henkel DGaA Dusseldorf to Anchor
Drilling Fluids. .
Ecological Evaluation of Carrier Fluid/Base Oil OMG 233 (Henkel) No
Date Available. .
Mineral Oil Free Oil-Based Drilling Fluids Developments and Outlook
No Date Available. .
Document: Presented at NIF Course on oil field chemicals held at
Fagerness in Mar. 1987 [{3}] Author: Dr. Claus-Peter Herold. .
Proposal sent by Henkel KGaA to the Operators, dated Jun. 1986
[{4}] Corporate Author: Henkel KGaA Dusseldorf. .
Mineral Oil Free Oil-Based Drilling Fluids Development and Outlook
[{6}] Authors: C.-P. Herold, H. Muller, Dr. von Tapavicza from Labs
of Henkel KGaA Dusseldorf (No Date Available)..
|
Primary Examiner: Tucker; Philip
Attorney, Agent or Firm: Connolly & Hutz
Parent Case Text
This application is a continuation of U.S. application Ser. No.
07/452,457 filed on Dec. 18, 1989 now abandoned.
Claims
We claim:
1. An invert emulsion drilling mud free of mineral oil and
substantially free from highly hydrophilic basic materials selected
from the group consisting of alkali metal hydroxides and amines
selected from diethanolamine and triethanolamine, consisting
essentially of
A. a continuous oil phase composed predominantly of at least one
monocarboxylic acid ester of a C.sub.2 -C.sub.12 monofunctional
alcohol wherein the monocarboxylic acid contains from 16 to 24
carbon atoms and is olefinically mono- or poly-unsaturated,
B. a disperse aqueous phase,
C. at least one emulsifier,
D. at least one weighting agent,
E. a viscosifier,
F. at least one fluid loss additive, and
G. a mildly alkaline alkali reserve component consisting
essentially of lime in a quantity not exceeding about 2 lb/bbl of
said drilling mud.
2. The invert emulsion mud of claim 1 wherein the disperse aqueous
phase B contains at least one of CaCl.sub.2 or KCl as a dissolved
salt.
3. The invert emulsion mud of claim 1 wherein from about 5 to about
45% by weight of component B is present therein.
4. The invert emulsion mud of claim 3 wherein from about 10 to
about 25% by weight of component B is present therein.
5. The invert emulsion mud of claim 1 wherein component A has a
Brookfield (RVT) viscosity at 0.degree. to 5.degree. C. of below 50
mPa.s.
6. The invert emulsion mud of claim 1 wherein the invert emulsion
mud has a plastic viscosity (PV) in the range of from about 10 to
about 60 mPa.s and a yield point (YP) in the range of from about 5
to about 40 lb/100 ft.sup.2, as measured at 50.degree. C.
7. The invert emulsion mud of claim 1 wherein component A also
contains esters of saturated monocarboxylic acids.
8. The invert emulsion mud of claim 1 wherein in component A the
oil phase contains at least about 70% by weight of the at least one
monocarboxylic acid ester.
9. The invert emulsion mud of claim 8 wherein about 80% by weight
of the at least one monocarboxylic acid ester is present.
10. The invert emulsion mud of claim 8 wherein about 90% by weight
of the at least one monocarboxylic acid ester is present.
11. The invert emulsion mud of claim 1 wherein the at least one
monocarboxylic acid ester of component A has a pour point and
setting point below about -10.degree. C., and a flash point above
about 100.degree. C.
12. The invert emulsion mud of claim 11 wherein the pour point and
setting point is below about -15.degree. C., and the flash point is
above about 160.degree. C.
13. The invert emulsion mud of claim 1 wherein in component A the
acid moiety of the at least one monocarboxylic acid ester contains
at least about 60% by weight of monoolefinically unsaturated acids
and no more than about 35% by weight di- and polyolefinically
unsaturated acids.
14. The invert emulsion mud of claim 1 wherein in component A the
acid moiety of the at least one monocarboxylic acid ester contains
more than about 45% by weight of either diolefinically unsaturated
acids, polyolefinically unsaturated acids, or a mixture of di- and
poly-olefinically unsaturated acids.
15. The invert emulsion mud or claim 14 wherein said percentage is
more than about 55%.
16. The invert emulsion mud of claim 1 wherein in component A the
continuous oil phase contains no more than about 20% by weight of
esters of saturated C.sub.16 -C.sub.18 carboxylic acids.
17. The invert emulsion mud of claim 16 wherein said percentage is
no more than about 10% by weight.
18. The invert emulsion mud of claim 1 wherein in the at least one
monocarboxylic acid ester of component A the monocarboxylic acid is
linear.
19. The invert emulsion mud of claim 1 wherein in the at least one
monocarboxylic acid ester of component A the alcohol moiety
contains from 3 to 10 carbon atoms and is saturated, straight chain
or branched.
20. The invert emulsion mud of claim 1 wherein said lime is present
in an amount of from 1 to 1.8 lbs/bbl of said drilling mud.
21. The invert emulsion mud of claim 1 wherein said alkali reserve
component includes a weakly basic metal oxide, zinc oxide, or zinc
compound. .[.22. The invert emulsion mud of claim 1 wherein in
component A the acid moiety of the at least one monocarboxylic acid
ester contains more than about 45% by weight of either
diolefinically unsaturated acids, polyolefinically unsaturated
acids, or a mixture of di- and poly-
olefinically unsaturated acids..].23. .[.A drilling fluid.].
.Iadd.An invert drilling fluid that is .Iaddend.free of mineral oil
.[.for use in an invert drilling mud that.]. .Iadd.and .Iaddend.is
substantially free from highly hydrophilic basic materials selected
from the group consisting of alkali metal hydroxides and amines
selected from diethanolamine and triethanolamine, .Iadd.said fluid
.Iaddend.consisting of
A. a continuous oil phase composed of at least one monocarboxylic
acid ester of a C.sub.2 -C.sub.12 monofunctional alkanol wherein
the monocarboxylic acid contains from 16 to 24 carbon atoms and
comprises at least about 60% by weight of monoolefinically
unsaturated acids and no more than about 35% by weight of di- and
poly- olefinically unsaturated acids, .[.and.].
B. a disperse aqueous phase.[...]. .Iadd., and
C. a mildly alkaline alkali reserve component consisting
essentially of lime in a quantity not exceeding above about 2
lb/bbl of said drilling
fluid. .Iaddend.24. The drilling fluid of claim 23 wherein in
component A has a Brooksfield (RVT) viscosity at 0.degree. to
5.degree. C. of below 50
mPa.s. 25. The drilling fluid of claim 23 wherein in component A
the oil phase contains at least about 70% by weight of the at least
one
monocarboxylic acid ester. 26. The drilling fluid of claim 23
wherein the at least one monocarboxylic acid ester of component A
has a pour point and setting point below about -10.degree. C., and
a flash point above about
100.degree. C. 27. The drilling fluid of claim 23 wherein in the at
least one monocarboxylic acid ester of component A the
monocarboxylic acid is
linear. 28. The drilling fluid of claim 23 wherein in the at least
one monocarboxylic acid ester of component A the alcohol moiety
contains from
1 to 10 carbon atoms and is saturated, straight chain or branched.
29. An invert emulsion drilling mud free of mineral oil and
substantially free from highly hydrophilic basic materials selected
from the group consisting of alkali metal hydroxides and amines
selected from diethanolamine and triethanolamine, consisting
essentially of
A. a continuous oil phase composed predominantly of at least one
monocarboxylic acid ester of a C.sub.2 -C.sub.12 monofunctional
alcohol wherein the monocarboxylic acid contains from 16 to 24
carbon atoms and comprises at least about 60% by weight of
monoolefinically unsaturated acids and no more than about 35% by
weight of di- and poly- olefinically unsaturated acids,
B. a disperse aqueous phase,
C. at least one emulsifier,
D. at least one weighting agent,
E. a viscosifier,
F. at least one fluid loss additive, and
G. a mildly alkaline alkali reserve component consisting
essentially of
lime in a quantity not exceeding about 2 lb/bbl of said drilling
mud. 30. The invert emulsion mud of claim 29 wherein from about 5
to about 45%
by weight of component B is present therein. 31. The invert
emulsion mud of claim 30 wherein from about 10 to about 25% by
weight of component B is
present therein. 32. The invert emulsion mud of claim 29 wherein
component A has a Brookfield (RVT) viscosity at 0.degree. to
5.degree. C. of below
50 mPa.s. 33. The invert emulsion mud of claim 29 wherein the
invert emulsion mud has a plastic viscosity (PV) in the range of
from about 10 to about 60 mPa.s and a yield point (YP) in the range
of from about 5 to
about 40 lb/100 ft.sup.2, as measured at 50.degree. C. 34. The
invert emulsion mud of claim 29 wherein in component A the oil
phase contains at least about 70% by weight of the at least one
monocarboxylic acid ester.
. The invert emulsion mud of claim 29 wherein the at least one
monocarboxylic acid ester of component A has a pour point and
setting point below about -10.degree. C., and a flash point above
about
100.degree. C. 36. In the development of a source of oil or gas by
drilling using a drilling mud, the improvement comprising pumping
the
invert emulsion mud of claim 2 into said source. 37. In the
development of a source of oil or gas by drilling using a drilling
mud, the improvement comprising pumping the invert emulsion mud of
claim 6 into said source.
In the development of a source of oil or gas by drilling using a
drilling mud, the improvement comprising pumping the invert
emulsion mud
of claim 11 into said source. 39. In the development of a source of
oil or gas by drilling using a drilling mud, the improvement
comprising pumping
the invert emulsion mud of claim 13 into said source. 40. In the
development of a source of oil or gas by drilling using a drilling
mud, the improvement comprising pumping the invert emulsion mud of
claim 1 into
said source. 41. In the development of a source of oil or gas by
drilling using a drilling mud, the improvement comprising pumping
the invert
emulsion mud of claim 29 into said source. .Iadd.42. The invert
emulsion mud of claim 19 wherein the alcohol moiety is branched and
the monocarboxylic acid is predominantly oleic acid.
.Iaddend..Iadd.43. The invert emulsion mud of claim 42 wherein the
monocarboxylic acid is derived from rape seed oil. .Iaddend.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to new drilling fluids based on ester oils
and to invert drilling muds based thereon which combine high
ecological compatibility with good stability and performance
properties.
2. State of Related Art
It is known that liquid drilling fluids for sinking bores in rock
and bringing up the rock cuttings are slightly thickened,
water-based or oil-based fluid systems. Oil-based systems are being
increasingly used in practice, particularly in offshore drilling or
in the penetration of water-sensitive layers.
Oil-based drilling fluids are generally used in the form of
so-called invert emulsion muds which consist of a three-phase
system, namely: oil, water and finely divided additives, including
in particular emulsifiers and emulsifier systems, weighting agents,
fluid loss additives, alkali reserves, viscosity regulators and the
like, for stabilizing the system as a whole and for establishing
the desired performance properties. Full particulars can be found,
for example, in the Article by P. A. Boyd et al entitled "New Base
Oil Used in Low-Toxicity Oil Muds" in the Journal of Petroleum
Technology, 1985, 137 to 142 and in the Article by R. B. Bennet
entitled "New Drilling Fluid Technology--Mineral Oil Mud" in
Journal of Petroleum Technology, 1984, 975 to 981 and the
literature cited therein.
Oil-based drilling fluids were originally made from diesel oil
fractions containing aromatic constituents. For the purposes of
detoxification and reducing the ecological problems thus created,
it was then proposed to use hydrocarbon fractions substantially
free from aromatic compounds--now also known as "nonpolluting
oils"--as the continuous oil phase, cf. the literature cited above.
Although certain advances were achieved in this way through
elimination of the aromatic compounds, a further reduction in the
environmental problems caused by drilling fluids of the above type
seems to be urgently required. This applies in particular to the
sinking of offshore wells for the development of oil and gas
sources because the marine ecosystem is particularly sensitive to
the introduction of toxic and non-readily degradable
substances.
The relevant technology has for some time recognized the
significance of ester-based oil pleases for solving these problems.
Thus, U.S. Pat. Nos. 4,374,737 and 4,481,121 describe oil-based
drilling fluids in which nonpolluting oils are said to be used.
Non-aromatic mineral oil fractions and vegetable oils of the peanut
oil, soybean oil, linseed oil, corn oil and rice oil type, and even
oils of animal origin, such as whale oil, are mentioned alongside
one another as nonpolluting oils of equivalent rank. The ester oils
of vegetable and animal origin mentioned here are all triglycerides
of natural fatty acids which are known to be environmentally safe
and which, ecologically, are distinctly superior to hydrocarbon
fractions, even where they have been de-aromaticized.
Interestingly, however, not one of the Examples in the US patents
cited above mentions the use of such natural ester oils in invert
emulsion drilling muds. Mineral oil fractions are used throughout
as the continuous oil phase.
In its general descriptive part, U.S. Pat. No. 4,491,121 mentions
not only triglycerides, but also a commercial product "Arizona 208"
of the Arizona Chemical Company, Wayne, N.J., which is a purified
isooctyl-monoalcohol ester of high-purity tall oil fatty acids. An
ester of a monofunctional alcohol and monofunctional carboxylic
acids, mentioned for the first time here, is described as
equivalent to triglycerides of natural origin and/or
de-aromaticized hydrocarbon fractions.
The cited US patent does not contain any reproducible Examples
relating to the use of such an ester of monofunctional
components.
DESCRIPTION OF THE INVENTION
Other than in the operating examples, or where otherwise indicated,
all numbers expressing quantities of ingredients or reaction
conditions used herein are to be understood as modified in all
instances by the term "about".
The investigations on which the present invention is based have
shown that the use of readily degradable oils of vegetable and/or
animal origin, which was considered in the prior art, is not
feasible for practical reasons. The rheologic properties of such
oil phases cannot be controlled for the wide temperature range
required in practice of 0.degree. to 5.degree. C. on the one hand
up to 250.degree. C. and higher on the other hand.
The teaching of the present invention is based on the observation
that it is in fact possible to produce oil-based invert drilling
fluids based on ester oils of high environmental compatibility
which correspond in their storage and in-use behavior to the best
of the hitherto known oil-based drilling fluids, but have the
additional advantage of increased environmental compatibility. Two
key observations in this regard dominate the teaching according to
the invention:
The triglycerides accumulating in the form of natural oils are not
suitable for the production of mineral-oil-free oil-based invert
drilling fluids, whereas the esters of monofunctional carboxylic
acids with monofunctional alcohols derived from those oils or fats
are suitable for the production of such drilling fluids. The second
key observation is that ester oils of the present type do not in
fact show the same in-use behavior as the mineral oil fractions
used hitherto based purely on hydrocarbons. In practical
application, the ester oils of monofunctional components of the
invention undergo partial hydrolysis, resulting in the formation of
free fatty acids. These free fatty acids react in turn with the
alkaline constituents always present in invert drilling fluids, for
example with the alkali reserve used to prevent corrosion, to form
the corresponding salts. However, salts of highly hydrophilic bases
and the acids in the range of from about C.sub.16 to C.sub.24
commonly encountered in fats and oils of natural origin are known
to be compounds having comparatively high HLB values which lead in
particular to the formation and stabilization of o/w emulsions. Use
is made of this to a very considerable extent in the field of
detergents and cleaning preparations. However, the formation of
undesirably large quantities of such o/w emulsifier systems must
interfere with the w/o emulsions required for solving the problem
addressed by the invention and, hence, leads to problems. The
teaching of the present invention as described in the following
shows how invert drilling fluids based on ester oils can be
effectively used in practice despite these difficulties inherent in
the system.
In a first embodiment, therefore, the present invention relates to
the use of selected esters--flowable and pumpable at temperatures
in the range of from 0.degree. to 5.degree. C.--of monofunctional
C.sub.2-12 alcohols (alkanols) and olefinically mono- and/or
polyunsaturated C16-24 monocarboxylic acids or mixtures thereof
with small quantities of other, more especially saturated
monocarboxylic acids as the oil phase, or at least a substantial
part of the oil phase, of invert drilling muds which contain in a
continuous oil phase a disperse aqueous phase and also emulsifiers,
weighting agents, fluid loss additives and, if desired, other
standard additives together with an alkali (alkaline) reserve, with
the proviso that strong hydrophilic bases, such as alkali metal
hydroxides and/or diethanolamine, are not used in significant
quantities. Lime (calcium hydroxide) is often added as the alkali
reserve, more especially for protection against inrushes of
CO.sub.2 and/or H.sub.2 S into the drilling fluid and hence for
protection against corrosion. An addition of lime such as this may
be used as the alkali reserve in accordance with the invention.
However, it is important to ensure that only comparatively small
quantities of this alkaline component are incorporated. In a
preferred embodiment of the invention, the maximum addition of lime
is of the order of 2 lb/bbl (lime/oil mud) and is thus distinctly
below the quantities typically used in practice in oil-based invert
drilling fluids.
In another embodiment, the invention relates to mineral-oil-free
invert drilling fluids which are suitable for the offshore
development of oil and gas sources and, in a continuous oil phase
based on ester oils, contain a disperse aqueous phase together with
emulsifiers, weighting agents, fluid loss additives and, if
desired, other standard additives. The new drilling fluids are
characterized in that the oil phase consists at least substantially
of esters of monofunctional C.sub.2-12 alcohols and olefinically
mono and/or polyunsaturated C.sub.16-24 monocarboxylic acids and in
that the w/o emulsion is mildly alkalized and, where lime is added,
this alkali reserve preferably does not exceed quantities of about
2 lb/bbl (lime/oil mud). The lime content is preferably slightly
below this limit.
The ester oils selected in accordance with the invention which are
intended to form the entire continuous oil phase of the invert
drilling muds or at least a substantial part thereof (i.e. over 50%
by weight thereof) are discussed first in the following.
As already stated, an important criterion lies in the choice of
esters which may be assigned to the class of reaction products of
monofunctional carboxylic acids with monofunctional alcohols. In
addition, however, it is intended in accordance with the invention
exclusively or at least predominantly to use C.sub.16 -C.sub.24
carboxylic acids within this class. The carboxylic acids may be
derived from unbranched or branched hydrocarbon chains, preferably
linear chains. Monocarboxylic acids of this type and of the
C.sub.16 to C.sub.24 range and esters thereof are unsuitable as
predominantly saturated hydrocarbon compounds due to their
comparatively high solidification points. Even then, however,
esters of this type are flowable and pumpable down to temperatures
of 0.degree. to 5.degree. C. providing an adequate level of
olefinically unsaturated ester constituents is guaranteed. In the
preferred embodiment of the invention, therefore, esters of the
described type of which more than 70% by weight and preferably more
than 80% by weight are derived from olefinically unsaturated
C.sub.16-24 carboxylic acids are used. Important natural starting
materials are carboxylic acid mixtures which contain at least 90%
by weight olefinically unsaturated carboxylic acids in the above C
range. The unsaturated carboxylic acids may be mono- and/or
polyolefinically unsaturated. Where carboxylic acids or carboxylic
acid mixtures of natural origin are used, the double ethylenic
double bond in particular and, to a lesser extent, even a triple
ethylenic double bond per carboxylic acid molecule plays a role in
addition to a single ethylenic double bond in the molecule.
Particulars of this are given in the following.
In conjunction with the choice of esters of monofunctional
reactants in accordance with the invention, the choice of such a
comparatively highly unsaturated carboxylic acid component in the
ester oils ensures that the ester oils and, ultimately, the final
invert emulsions show the rheologic properties required in
practice, particularly at relatively low temperatures. The
comparatively highly unsaturated ester oils containing 16 to 24 C
atoms in the monocarboxylic acid component, which are used in
accordance with the invention, have solidification points (pour
point and setting point) below -10.degree. C. and more especially
below -15.degree. C. in the preferred embodiment. Despite this high
mobility at low temperatures, the molecular size of the ester oil
prescribed in accordance with the invention ensures that the
flashpoints of the ester oils are sufficiently high, being at least
80.degree. C., and generally exceeding a temperature limit of
approximately 100.degree. C. Ester oils having flashpoints above
160.degree. C. are preferred. Ester oils of the described type
showing high mobility, even at low temperatures, and having
flashpoints of 185.degree. C. or higher can be produced without
difficulty.
In conjunction with these high flashpoints determined by the size
of the molecule, it is possible at the same time to ensure that the
viscosity values are within the required limits. Thus, preferred
ester oils of the described type show a Brookfield (RVT) viscosity
at a temperature of 0.degree. to 5.degree. C. of not more than 55
mPa.s and preferably of at most 45 mPa.s or lower. It is possible
to adjust values of 30 or even higher, for example in the range of
from 20 to 25 mPa.s, at temperatures in the range indicated.
Among the unsaturated ester oils suitable for use in accordance
with the invention, there are two sub-classes of particular
importance.
The first of these sub-classes is based on unsaturated C.sub.16-24
monocarboxylic acids of which no more than about 35% by weight are
diolefinically and, optionally, polyolefinically unsaturated. In
their case, therefore, the content of di-and polyunsaturated
carboxylic acid residues in the ester oil is comparatively limited.
Within this sub-class it is preferred that at least about 60% by
weight of the carboxylic acid residues are monoolefinically
unsaturated.
In contrast to the first sub-class described above, the second
sub-class of ester oils of particular significance is derived from
C.sub.16-24 unsaturated monocarboxylic acid mixtures of which more
than 45% by weight and preferably more than 55% by weight are
derived from diolefinically and/or polyolefinically unsaturated
acids within the above C range.
The most important monoethylenically unsaturated carboxylic acids
within the above carbon range are hexadecenoic acids (palmitoleic
acid (C.sub.16)), oleic acid (C.sub.18), the related ricinoleic
acid (C.sub.18) and erucic acid (C.sub.22). The most important
di-unsaturated carboxylic acid within the range in question here is
linoleic acid (C.sub.18) while the most important triethylenically
unsaturated carboxylic acid is linolenic acid (C.sub.18).
Selected individual esters formed from an unsaturated
monocarboxylic acid and a monoalcohol can be used as the ester oil
in accordance with the invention. One example of such esters are
the esters of oleic acid, for example of the oleic acid isobutyl
ester type. So far as the rheology of the system is concerned
and/or for reasons of availability, it is frequently desirable to
use esters from acid mixtures. This is of importance so far as
meeting the above-stated specifications of the two-classes for
preferred ester oils is concerned.
As already mentioned, the first of these two sub-classes is
distinguished by the fact that its content of di-unsaturated and
polyunsaturated acids is limited and does not exceed about 35% by
weight. Vegetable oils of natural origin, of which the hydrolysis
or transesterification gives mixtures of carboxylic acids or
carboxylic acid esters of the type required here, are for example
palm oil, peanut oil, castor oil and, in particular, rapeseed oil.
Suitable rapeseed oils are both traditional types of high erucic
acid content and also the more modern types of reduced erucic acid
content and increased oleic acid content.
Ester oils of the first sub-class which correspond to this
definition are particularly important for the simple reason that
problems possibly arising from the lack of stability to oxidation
are reduced. In practice, the drilling fluid is of course
continuously pump-circulated and, in the process, is brought
constantly into contact with atmospheric oxygen, often over a large
area and at least slightly elevated temperatures, for the purpose
of separating out the rock cuttings brought up, for example by
sieving.
However, carboxylic acid mixtures of the second subclass mentioned
above are also of considerable practical significance for use in
accordance with the invention. This is attributable in part to
their broad accessibility from natural fats of animal and/or
vegetable origin. Classic examples of oils which have a high
content of C.sub.16-18 or C.sub.16-22 carboxylic acids and which,
at the same time, contain at least about 45% of at least
diethylenically unsaturated carboxylic acids are cottonseed oil,
soybean oil, sunflower oil and linseed oil. The tall oil acids
isolated during the recovery of cellulose also fall within this
range. However, starting materials of the last type are generally
distinguished by more or less large additional contents of resin
constituents. A typical animal starting material for the production
of corresponding carboxylic acid mixtures is fish oil, particularly
herring oil.
As already mentioned, the ester oils used in accordance with the
invention can be certain selected individual esters corresponding
to the above definition. However, mixtures of esters of
corresponding monocarboxylic acids and monoalcohols will normally
be present. In this regard, the scope of the invention encompasses
above all those mixtures which, on the one hand, meet the viscosity
requirement according to the invention and of which, on the other
hand, at least 50% comprise the monofunctional esters of the
olefinically mono- and/or polyunsaturated C.sub.16-24 carboxylic
acids. Ester constituents and, in particular, carboxylic acid
esters or monofunctional alcohols and monofunctional carboxylic
acids of different constitution may be present as minor
constituents of the mixture providing the mixture has the required
property profile. This is important where carboxylic acid mixtures
of natural origin are used. Natural starting materials such as
these generally also contain more or less large proportions of
saturated carboxylic acids, often including linear C.sub.16-18
carboxylic acids. Saturated fatty acids of this type and their
esters readily give rise to rheologic difficulties due to their
comparatively high melting points. According to the invention,
therefore, saturated C.sub.16-18 is carboxylic acids preferably
make up no more than 20% by weight and, in particular, no more than
10% by weight of the ester oils.
By contrast, the presence of saturated carboxylic acids containing
less than 16 carbon atoms and, more especially, from 12 to 14
carbon atoms is more acceptable. In small quantities, the contents
of such lower, fully saturated fatty acids often present in natural
starting materials are frequently valuable mixture components in
the context of the problem addressed by the invention. Their esters
are not vulnerable to oxidation under practical inuse conditions
and their rheologic properties promote the objective of the
invention, namely to replace the pure hydrocarbon oils hitherto
solely used in practice by ester oils or ester oil fractions.
The alcohol radicals or the esters or ester mixtures according to
the invention are preferably derived from straight-chain and/or
branched-chain saturated alcohols, particular significance being
attributed to alcohols containing at least 3 C atoms and, more
especially, to alcohols containing up to about 10 C atoms. The
alcohols can also be of natural origin, in which case they have
normally been obtained from the corresponding carboxylic acids or
their esters by hydrogenating reduction. However, the invention is
by no means limited to starting materials of natural origin. Both
on the monoalcohol side and on the monocarboxylic acid side, the
starting materials of natural origin may be partly or completely
replaced by corresponding components of synthetic origin. Typical
examples of alcohols are the corresponding oxo alcohols (branched
alcohols) and the linear alcohols obtained by the Ziegler process.
Similarly, monocarboxylic acid components present in particular in
carboxylic acid mixtures can be derived from petrochemical
synthesis. However, the advantages of starting materials of natural
origin lie in particular in their proven lower toxicologic values,
their ready degradability and their ready accessibility. The
natural destruction of the used oil mud ultimately required
presupposes that ester oils of the type described herein be both
aerobically and anaerobically degradable.
However, one important limitation is associated with the use of
these ester oils in invert oil muds of the type used in the present
invention. This limitation arises out of the difficulty mentioned
at the beginning that, in principle, the carboxylic acid esters are
vulnerable to hydrolysis and, accordingly, have to behave
differently than the pure hydrocarbon oils hitherto used.
Invert drilling muds of the type used herein contain the finely
disperse aqueous phase, normally together with the continuous oil
phase, in quantities of from 5 to 45% by weight and preferably in
quantities of from 5 to 25% by weight. Particularly preferred is
the range of 10 to 25% by weight of disperse aqueous phase. This
pre-condition from the constitution of conventional drilling muds
also applies to the ester-based invert drilling muds of the
invention. It is clear that, in continuous practical operation,
disturbances of the equilibrium can occur in the multiphase system
as a result of partial ester hydrolysis.
The situation is complicated by the fact that, in practice,
drilling muds of the present type always contain an alkali reserve.
This alkali reserve is particularly important in affording
protection against corrosion caused by unexpected inrushes of
acidic gases, particularly CO.sub.2 and/or H.sub.2 S. The danger of
corrosion to the drill pipe requires the safe establishment of pH
values at least in the mildly alkaline range, for example in the
range from pH 8.5 to 9 and higher.
In oil muds based on pure hydrocarbon fractions as the oil phase,
strongly alkaline and, at the same time, highly hydrophilic
inorganic or organic additives are generally used in practice
without any difficulty. Particular significance can be attributed
to the alkali hydroxides and, in particular, to sodium hydroxide on
the one hand or to highly hydrophilic organic bases, diethanolamine
and/or triethanolamine being particularly typical additives for
binding impurities of H.sub.2 S. In addition to and/or instead of
the highly hydrophilic inorganic and organic bases mentioned here,
lime or even more weakly basic metal oxides, especially zinc oxide
or comparable zinc compounds, are particularly important as the
alkali reserve. Lime in particular is widely used an inexpensive
alkalizing agent. It may safely be used in comparatively high
quantities of, for example, from 5 to 10 lb/bbl (lime/oil mud) or
even higher.
The use of the ester-based oil muds of the invention requires a
departure from standard practice so far as these variables are
concerned. It is of course necessary in this case, too, to ensure
that the pH value of the drilling mud is kept at least in the
mildly alkaline range and that a sufficient quantity of alkali
reserve is available for unexpected inrushes of, in particular,
acidic gases. At the same time, however, the ester hydrolysis
should not be undesirably promoted and/or accelerated by such an
alkali content.
Thus, in the preferred embodiment of the invention, no significant
quantities of highly hydrophilic, inorganic and/or organic bases
are used in the oil mud. In particular, the invention does not use
alkali hydroxides or highly hydrophilic amines of the
diethanolamine and/or triethanolamine type. Lime may be effectively
used as the alkali reserve. In that case, however, it is best to
limit the maximum quantity of lime used in the drilling mud to
around 2 lb/bbl or slightly lower, for example to between 1 and 1.8
lb/bbl (lime/drilling mud). In addition to or instead of lime, it
is also possible to use other known alkali reserves, including in
particular the less basic metal oxides of the zinc oxide type and
other comparable zinc compounds. However, even where acid-binding
agents such as these are used, it is important not to use excessive
amounts to prevent unwanted premature ageing of the drilling mud
accompanied by an increase in viscosity and hence a deterioration
in the rheologic properties. The particular aspect of the teaching
according to the invention prevents or at least limits the
formation of unwanted quantities of highly active o/w emulsifiers
to such an extent that the favorable rheologic properties are
maintained for long periods in operation, even in the event of
thermal ageing. In relation to the recommendations of the prior art
which have hitherto remained in the realm of theoretical
considerations, this represents a significant surplus which
actually enables the low toxic properties of ester oils of the
present type to be utilized in practice for the first time.
The esters based on olefinically unsaturated C.sub.16-24
monocarboxylic acids defined in accordance with the invention,
which flow and can be pumped at temperatures in the range from
0.degree. to 5.degree. C., generally make up at least about half
the continuous oil phase of the drilling mud. However, preferred
oil phases are those in which esters or ester mixtures of the type
according to the invention are very much predominantly present. In
one particularly important embodiment of the invention, the oil
phase consists almost entirely of such ester oils. Components
suitable for mixing with the ester oils defined in accordance with
the invention are, in particular, selected other ester oil
fractions which are described in U.S. Ser. No. 07/452,988 now
abandoned "Drilling Fluids and Muds Containing Selected Ester
Oils"), filed of even data herewith. The invention also encompasses
mixtures with such other selected ester oils. These ester oils,
which are described in the above copending application,
incorporated herein by reference, are esters of monofunctional
C.sub.2-12 alcohols and saturated aliphatic C.sub.12-16
monocarboxylic acids.
The following rheologic data apply to the rheology of preferred
invert drilling muds according to the invention: plastic viscosity
(PV) in the range of from 10 to 60 mPa.s and preferably in the
range of from 15 to 40 mPa.s, yield point (YP) in the range of from
5 to 40 lb/100 ft.sup.2 and preferably in the range of from 10 to
25 lb/100 ft.sup.2, as measured at 50.degree. C. Full information
on the determination of these parameters, on the measurement
techniques used and on the otherwise standard composition of the
invert oil muds described herein can be found in the prior art
cited above and, for example, in "Manual of Drilling Fluids
Technology" published by BAROID DRILLING FLUIDS, INC., cf. in
particular the Chapter entitled "Mud Testing--Tools and Techniques"
and "Oil Mud Technology", which is freely available to interested
experts. In the interests of fullness of disclosure, the following
summary observations may be made:
Emulsifiers suitable for use in practice are systems which are
capable of forming the required w/o emulsions. Selected olephilic
fatty acid salts, for example those based on amidoamine compounds,
are particularly suitable, examples being described in the already
cited U.S. Pat. No. 4,374,737 and the literature cited therein. One
particularly suitable type of emulsifier is the product marketed
under the name of "EZ-MUL.TM." by BAROID DRILLING FLUIDS, INC.
Emulsifiers of the above type are marketed in the form of
concentrate and can be used, for example, in quantities of from 2.5
to 5% by weight and more especially in quantities of from 3 to 4%
by weight, based in each case of the ester oil phase.
In practice, organophilic lignite is used as a fluid-loss additive
and forms an impervious coating in the form of a substantially
water-impermeable film over the walls of the well. Suitable
quantities are, for example, in the range of from 15 to 20 lb/bbl
or in the range of from 5 to 7% by weight, based on the ester oil
phase.
In drilling muds of the present type, the thickener normally used
to create viscosity is a cationically modified, finely divided
organophilic bentonite which can be used in quantities of from 8 to
10 lb/bbl or in the range of from 2 to 4% by weight, based on the
ester oil phase. The weighing agent normally used in practice to
establish the necessary pressure equalization is barite which is
added in quantities adapted to the particular conditions to be
expected in the well. For example, it is possible by addition of
barite to increase the specific gravity of the drilling mud to
values of up to about 2.5 and preferably in the range from 1.3 to
1.6.
In invert drilling muds of the present type, the disperse aqueous
phase is charged with soluble salts, generally calcium chloride
and/or potassium chloride, the aqueous phase preferably being
saturated with the soluble salt at room temperature.
The emulsifiers or emulsifier systems mentioned above can also be
used to improve the oil wettability of the inorganic weighting
materials. In addition to the aminoamides already discussed, alkyl
benzensulfonates and imidazoline components are further examples.
Additional information on the relevant prior art can be found in
the following literature references: GB 2,158,437, EP 229 912 and
DE 32 47 123.
One important application for the new drilling fluids is in
offshore drilling for the development of oil and/or gas sources, to
provide technically useful drilling fluids of high ecological
compatibility. The use of the new drilling fluids is of particular
importance in, but is not limited to, the offshore sector. The new
drilling fluids can also be used quite generally for land-supported
drilling, including for example geothermal drilling, water
drilling, geoscientific drilling and mine drilling. In this case,
too, the ester-based drilling fluids selected in accordance with
the invention basically simplify ecotoxic problems to a
considerable extent. In addition, the drilling fluids based in
accordance with the invention on the co-use of ester oils of the
described type are also distinguished by distinctly improved
lubricity. This is particularly important when the path of the
drill pipe and hence the well deviate from the vertical during
drilling, for example at considerable depths. In such cases, the
rotating drill pipe readily comes into contact with the well wall
and embeds itself therein. Ester oils of the type used as oil phase
in accordance with the invention have a distinctly better
lubricating effect than the mineral oils hitherto used, which is an
important advantage of the present invention.
The invention will be illustrated but not limited by the following
examples.
EXAMPLES
EXAMPLE 1
An invert drilling mud was prepared using an undistilled isobutyl
rapeseed oil ester at the continuous oil phase. This rapeseed ester
was based on a mixture of predominantly unsaturated, straight-chain
carboxylic acids which correspond substantially to the following
distribution; 60% oleic acid, 20% linoleic acid, 9 to 10% linolenic
acid, olefinically unsaturated C.sub.20-22 monocarboxylic acids
approximately 4% remainder saturated monocarboxylic acids
predominantly in the C.sub.16-18 range.
The rapeseed oil ester used had the following characteristic data:
density (20.degree. C.) 0.872 g/cm.sup.3 ; pour point below
-15.degree. C.; flash point (DIN 51584) above 180.degree. C.; acid
value (DGF-C-V 2) 1.2; viscosity at 0.degree. C. 32 mPa.s,
viscosity at 5.degree. C. 24 mPa.s; no aromatic compounds.
An invert drilling mud was conventionally prepared using the
following mixture constituents:
______________________________________ 230 ml rapeseed oil fatty
acid ester 26 ml water 6 g organophilic bentonite (GELTONE .TM., a
product of BAROID DRILLING FLUIDS, INC. of Aberdeen, Scotland) 0.2
g line 6 g water in oil emulsifier ("EZ-MUL .TM.", a product of
BAROID DRILLING FLUIDS, INC.) 340 g basis 9.2 g CaCl.sub.2 .times.
2H.sub.2 O 20 g organophilic lignite ("DURATONE .TM.", a product of
BARIOD DRILLING FLUIDS. INC.)
______________________________________
Plastic viscosity (PV), yield point (YP) and gel strength after 10
seconds and 10 minutes were first determined on the material before
ageing by viscosity measurement at 50.degree. C.
The invert drilling mud was then aged for 16 h at 125.degree. C. in
an autoclave in a so-called "roller oven" to determine the effect
of temperature on the stability of the emulsion. The viscosity
values were redetermined at 50.degree. C.
The following results were obtained:
______________________________________ Unaged Aged material
material ______________________________________ Plastic viscosity
(PV) 35 62 Yield point (YP) 21 24 Gel strength (lb/100 ft.sup.2) 10
seconds 12 12 10 minutes 14 15
______________________________________
COMPARISON EXAMPLE 1
Another invert drilling mud was prepared in the same way as in
Example 1, except that on this occasion the quantity of lime was
increased to 4 g, i.e. drastically beyond the limit of
approximately 2 lb/bbl.
Once again, the viscosity values and gel strength of the material
were determined before and after ageing. The following results were
obtained:
______________________________________ Unaged Aged material
material ______________________________________ Plastic viscosity
(PV) 41 cannot be measured Yield point (YP) 22 cannot be measured
Gel strength (lb/100 ft.sup.2) 10 seconds 11 74 10 minutes 17 72
______________________________________
EXAMPLE 2
Another invert drilling mud was prepared with a continuous oil
phase. The oil phase consisted of distilled oleic acid isobutyl
ester which has the following characteristic data: density
(20.degree. C.) 0.86 gg/cm.sup.3 ; viscosity (20.degree. C.) 8 to
10 mPa.s; pour point below -25.degree. C.; flash point (51584)
above 185.degree. C.; acid value (DGF)-CV 2) below 1; no aromatic
compounds.
A drilling mud of the following composition was prepared:
______________________________________ 210 ml isobutyl oleate 6 g
fatty-acid-based emulsifier (INVERMUL .TM., a product of BAROID
DRILLING FLUIDS, INC.) 6 g organophilic bentonite (GELTONE II .TM.,
a product of BAROID DRILLING FLUIDS, INC.) 13 g organophilic
lignite (DURATONE .TM., a product of BAROID DRILLING FLUIDS, INC.)
1 g lime 3 g water in oil emulsifier (EZ-MUL .TM., a product of
BAROID DRILLING FLUIDS, INC.) 270 g barite 58.2 g saturated aqueous
CaCl.sub.2 solution ______________________________________
Plastic viscosity, yield point and gel strength after 10 seconds
and 10 minutes were determined before and after ageing (16 h at
125.degree. C. in a roller oven) in the same way as in Example 1.
The results obtained are shown below. In the formulation used here,
.[.1.2 kg.]. .Iadd.1.9 g .Iaddend.lime substantially corresponds to
the limit of 2 lb/bbl.
______________________________________ Unaged Aged material
material ______________________________________ Plastic viscosity
(PV) 46 41 Yield point (YP) 35 32 Gel strength (lb/100 ft.sup.2) 10
seconds 17 18 10 minutes 21 29
______________________________________
.[.COMPARISON.]. EXAMPLE .[.2.]. .Iadd.3 .Iaddend.
Another invert drilling oil emulsion was prepared using the
formulation of Example 2, except that the addition of lime was
increased to 2 g and hence to .[.clearly beyond.]. .Iadd.within
.Iaddend.the limit of .Iadd.about .Iaddend.2 lb/bbl. The plastic
viscosity, yield point and gel strength of the material before and
after ageing are shown in the following:
______________________________________ Unaged Aged material
material ______________________________________ Plastic viscosity
(PV) 33 46 Yield point (YP) 61 45 Gel strength (lb/100 ft.sup.2) 10
seconds 33 24 10 minutes 40 29
______________________________________
* * * * *