U.S. patent application number 13/602928 was filed with the patent office on 2012-12-27 for drilling composition, process for its preparation, and applications thereof.
This patent application is currently assigned to COGNIS OLEOCHEMICALS GMBH. Invention is credited to Michael Fefer, Nadja Herzog, Jun Liu, Diana Maeker, Heinz Mueller.
Application Number | 20120325492 13/602928 |
Document ID | / |
Family ID | 38752522 |
Filed Date | 2012-12-27 |
United States Patent
Application |
20120325492 |
Kind Code |
A1 |
Fefer; Michael ; et
al. |
December 27, 2012 |
Drilling Composition, Process for its Preparation, and Applications
Thereof
Abstract
A drilling composition is provided. The composition includes: I)
an organic phase comprising components: i. from about 20 wt. % to
about 99.999 wt. %, based on the total weight of components i. and
ii., of at least one linear or branched, cyclic or non-cyclic,
saturated hydrocarbon; ii. from about 0.001 wt. % to about 25 wt.
%, based on the total weight of components i. and ii., of at least
one ester; II) from 0 to about 50 wt. %, based on the total weight
of the composition, of water or aqueous phase; III) from 0 to about
60 wt. %, based on the total weight of the composition, of at least
one additive, wherein the sum of the weight components I) to III)
is 100 wt. %.
Inventors: |
Fefer; Michael; (Whitby,
CA) ; Liu; Jun; (Oakville, CA) ; Mueller;
Heinz; (Monheim, DE) ; Herzog; Nadja;
(Korschenbroich, DE) ; Maeker; Diana; (Monheim,
DE) |
Assignee: |
COGNIS OLEOCHEMICALS GMBH
Duesseldorf
DE
|
Family ID: |
38752522 |
Appl. No.: |
13/602928 |
Filed: |
September 4, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12724385 |
Mar 15, 2010 |
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13602928 |
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PCT/EP2008/064423 |
Oct 24, 2008 |
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12724385 |
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Current U.S.
Class: |
166/369 ;
175/324; 175/65; 507/103 |
Current CPC
Class: |
E21B 43/00 20130101;
C09K 8/34 20130101; C09K 8/18 20130101; C09K 8/36 20130101; E21B
21/00 20130101; E21B 21/01 20130101; E21B 10/00 20130101; E21B 7/00
20130101 |
Class at
Publication: |
166/369 ;
507/103; 175/324; 175/65 |
International
Class: |
C09K 8/06 20060101
C09K008/06; E21B 43/00 20060101 E21B043/00; E21B 7/00 20060101
E21B007/00; E21B 41/00 20060101 E21B041/00; C09K 8/18 20060101
C09K008/18; E21B 17/00 20060101 E21B017/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2007 |
EP |
07020796.4 |
Claims
1. A drilling composition comprising I) an organic phase comprising
components i. from about 20 wt. % to about 99.999 wt. %, based on
the total weight of components i. and ii., of at least one linear
or branched, cyclic or non-cyclic, saturated hydrocarbon, ii. from
about 0.001 wt. % to about 25 wt. %, based on the total weight of
components i. and ii., of at least one ester, II) from 0 to about
50 wt. %, based on the total weight of the composition, of water or
aqueous phase, III) from 0 to about 60 wt. %, based on the total
weight of the composition, of at least one additive, wherein the
sum of the weight components I) to III) is 100 wt. %.
2. The composition according to claim 1, wherein the at least one
hydrocarbon is at least one alkane.
3. The composition according to claim 1, wherein the at least one
ester is at least one ester selected from the group consisting of
esters formed from at least one C.sub.1 to C.sub.24 monocarboxylic
acid with at least one mono-functional alcohol.
4. The composition according to claim 1, wherein the composition is
in the form of an emulsion, preferably in the form of a
nanoemulsion or a microemulsion, preferably in the form of a
water-in-oil emulsion with droplet sizes in the range from about 5
nm to about 1000 .mu.m.
5. The composition according to claim 1, wherein the at least one
additive is at least one additive selected from the group
consisting of weighting agents, clays, fluid loss additives, pH
modifiers, viscosity modifiers, filtration control agents,
emulsifiers, salts, wetting agents, dispersants.
6. The composition according to claim 1, wherein the at least one
ester has a carbon chain distribution of the acid-derived component
determined according to ISO 5508 with carbon numbers in the ranges
of from 0 to 2.00% C.sub.6, from 3.00% to 10.00% C.sub.8, from
3.00% to 10.00% C.sub.10, from 50.00% to 94.00% C.sub.12, from 0 to
25.00% C.sub.14, from 0 to 5.00% C.sub.16 and from 0 to 1.00%
C.sub.18.
7. The composition according to claim 1, wherein the at least one
ester has a carbon chain distribution of the acid-derived component
determined according to ISO 5508 with carbon numbers in the ranges
of from 0 to 2.00% C.sub.6, from 0 to 10.00% C.sub.8, from 0 to
10.00% C.sub.10, from 50.00% to 95.00% C.sub.12, from 5.00% to
35.00% C.sub.14, from 0 to 5.00% C.sub.16 and from 0 to 1.00%
C.sub.18.
8. A process for preparation of a drilling composition, comprising
the steps: a) providing as component i. from about 20 wt. % to
about 99.999 wt. %, based on the total amount of i. and ii., of at
least one linear or branched, cyclic or non-cyclic, saturated
hydrocarbon, b) providing as component ii. from about 0.001 wt. %
to about 25 wt. %, based on the total amount of i. and ii., of at
least one ester, wherein the sum of the weight amounts provided in
a) and b) is 100 wt. %, c) combining the at least one hydrocarbon
and the at least one ester.
9. A process for preparation of a drilling composition, comprising
the steps: A) preparation of an organic phase comprising components
i. from about 20 wt. % to about 99.999 wt. %, based on the total
weight of components i. and ii., of at least one linear or
branched, cyclic or non-cyclic, saturated hydrocarbon, ii. from
about 0.001 wt. % to about 25 wt. %, based on the total weight of
components i. and ii., of at least one ester, B) preparation of an
aqueous phase comprising from about 50 wt. % to 100 wt. % water,
based on the total amount of aqueous phase, C) combination of the
organic phase prepared in step A) with from 0 to 50 wt. %, based on
the total weight of the composition, of the aqueous phase prepared
in step B), and D) combination of at least one of the organic
phase, the aqueous phase and the combination of the organic phase
and the aqueous phase with from 0 to about 60 wt. %, based on the
total weight of the composition, of at least one additive.
10. The process according to claim 9, further comprising the step
E) homogenisation.
11. A process according to claim 9, wherein the composition at the
end of at least one of steps C), D) and E) is in the form of an
emulsion.
12. The process according to claim 11, wherein the emulsion is a
nanoemulsion or a microemulsion with droplet sizes in the range
from 5 nm to 1000 .mu.m.
13. The process according to claim 8, wherein the at least one
ester is at least one ester selected from the group consisting of
esters formed from at least one C to C.sub.24 monocarboxylic acid
with at least one monofunctional alcohol.
14. The process according to claim 8, wherein the at least one
ester has a carbon chain distribution of the acid-derived component
determined according to ISO 5508 with carbon numbers in the ranges
of from 0 to 2.00% C.sub.6, from 3.00% to 10.00% C.sub.8, from
3.00% to 10.00% C.sub.10, from 50.00% to 94.00% C.sub.12, from 0 to
25.00% C.sub.14, from 0 to 5.00% C.sub.16 and from 0 to 1.00%
C.sub.18.
15. The process according to claim 8, wherein the at least one
ester has a carbon chain distribution of the acid-derived component
determined according to ISO 5508 with carbon numbers in the ranges
of from 0 to 2.00% C.sub.6, from 0 to 10.00% C.sub.8, from 0 to
10.00% C.sub.10, from 50.00% to 95.00% C.sub.12, from 5.00% to
35.00% C.sub.14, from 0 to 5.00% C.sub.16.
16. A drilling composition obtainable by a process according to
claim 8 and having at least one of the properties: .gamma.1) a
plastic viscosity measured at 50.degree. C. according to the herein
described test method in the range from 15 to 75 mPas; .gamma.2) a
yield point measured at 50.degree. C. according to the herein
described test method in the range from 5 to 45 lb/100 ft.sup.2
(2.4 to 21.6 Pa); .gamma.3) a gel strength measured at 50.degree.
C. according to the herein described test method in the range from
4 to 25 lb/100 ft.sup.2 (1.9 to 12 Pa).
17. The use of a composition according to claim 1, or of a
composition prepared according to claim 8, in or as a drilling
fluid.
18. A drilling system comprising a drill head, a drill string, a
reservoir for drilling composition and a drilling composition
according to claim 1 or a drilling composition prepared according
to claim 8.
19. A process for making a borehole comprising the steps: a1)
providing a composition according to claim 1 or a composition
prepared according to claim 8; a2) drilling a hole in a
subterranean formation; a3) circulating the composition provided in
a1) at least partially in the hole at least partially while
drilling.
20. A process for conveying cuttings from a hole drilled in a
subterranean formation, comprising the steps: b1) providing a
composition according to claim 1 or a composition prepared
according to claim 8, b2) circulating the composition provided in
b1) at least partially in the hole.
21. The process according to claim 20, wherein the composition is
circulated at least partially while drilling the hole.
22. A process for treatment of a drill head comprising the steps:
c1) providing a composition according to claim 1 or a composition
prepared according to claim 8, c2) circulating the composition
provided in c1) at least partially through the drill head at least
partially while the drill head is operated in a subterranean
formation.
23. The process according to claim 22, wherein the treatment is at
least one of cleaning, cooling and lubrication.
24. A process for production of at least one of oil and gas,
comprising process steps: d1) providing a composition according to
claim 1 or a composition prepared according to claim 8, d2)
drilling at least one hole in a subterranean formation while at
least partially circulating the composition provided in d1) at
least partially in the hole; d3) obtaining at least one of oil and
gas from the subterranean formation at least partially by means of
the at least one hole drilled in d2); d4) optionally, subjecting
the at least one of oil and gas to at least one processing step
selected from purifying, refining and treating.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Continuation of U.S. patent
application Ser. No. 12/724,385, filed on Mar. 15, 2010, which is a
Continuation of International Patent Application No.
PCT/EP2008/064423, filed on Oct. 24, 2008, which claims priority to
foreign Patent Application EP 07020796.4, filed on Oct. 24, 2007,
the disclosures of which are incorporate herein by reference in
their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to a drilling composition, to
a process for preparation of a drilling composition, to uses of a
drilling composition, to a drilling system, to a process for making
a borehole, to a process for conveying cuttings, to a process for
treating a drill head, to a process for production of at least one
of oil and gas.
BACKGROUND
[0003] In rotary drilling of subterranean wells a drilling fluid,
also referred to as drilling mud, is used for various functions,
such as suspending and removing cuttings from the well, controlling
formation pressures, sealing permeable formations, maintaining
wellbore stability, minimising formation damage, cooling,
lubricating and supporting the bit and drilling assembly,
transmitting hydraulic energy to tools and bit, ensuring adequate
formation evaluation, controlling corrosion of the drilling
assembly as far as possible, and facilitating cementing and
completion of the well. A further, more recent aspect is minimising
the effect on the environment.
[0004] Drilling fluids are well known from the prior art. They are
typically classified according to their base material. In oil base
fluids, solid particles are suspended in oil, and water or brine
may be emulsified with the oil, usually assisted by a surfactant,
whereby the oil is typically the continuous phase. In water base
fluids, solid particles are suspended in water and oil may be
emulsified therewith, usually in the presence of a surfactant.
Oil-based drilling fluids are generally used in the form of invert
emulsion muds, where the oil phase typically forms the continuous
phase. Earlier drilling fluids relied on heavier oils derived from
petrochemicals, such as diesel oil. Such oils are now less favoured
because of their negative environmental impact and there have been
a number of publications in the last few years proposing
biodegradable drilling fluids or drilling fluid components.
[0005] Drilling fluids comprising reduced toxicity hydrocarbon as
main component of the oil phase are known, for example from EP 449
257 A2, U.S. Pat. No. 5,569,642 and U.S. Pat. No. 4,787,990. One
disadvantage of such systems is, however, that increased amounts of
structure-building agents such as viscosifiers are often required
in order to obtain suitable rheological properties for a drilling
fluid.
[0006] DE 39 07 391 A1, DE 39 07 392 A1, DE 38 42 703 A1 and DE 38
42 659 A1 describe inverse drilling fluids comprising ester as main
component of the oil phase. These drilling fluids are distinguished
by improved lubricity and biodegradability compared to mineral
oil-based drilling fluids.
DETAILED DESCRIPTION
[0007] An object of the present invention was to reduce or even
overcome the problems associated with the prior art.
[0008] A further object of the present invention was to provide a
composition suitable for use as a drilling fluid, preferably for a
wide range of onshore and offshore oilfield applications. The
composition should preferably allow faster, more efficient and/or
more effective drilling operations, under a range of operating
conditions, as well as helping to contribute to reduced wear on
drilling equipment.
[0009] Another object of the present invention was to provide a
more ecologically-friendly composition suitable for use as an
improved drilling fluid.
[0010] Another object of the present invention was to provide a
process for preparation of such a composition.
[0011] A contribution to solving at least one the above objects or
further objects arising from the state of the art is made by the
subject matter of the category-forming claims. Further developments
and preferred embodiments are described in the dependent
claims.
[0012] In particular, a contribution to solving at least one of the
above objects is made by a drilling composition comprising [0013]
I) an organic phase comprising components [0014] i. from about 20
wt. % to about 99.999 wt. %, preferably from about 40 wt. % to
about 99.990 wt. %, preferably from about 60 wt. % to about 99.900
wt. %, preferably from about 70 wt. % to about 99 wt. %, more
preferably from about 80 wt. % to about 98.5 wt. %, yet more
preferably from about 85 wt. % to about 98 wt. %, even more
preferably from about 90 wt. % to about 98 wt. %, more preferably
from about 92 wt. % to about 97 wt. %, most preferably from about
93 wt. % to about 96 wt. %, based on the total weight of components
i. and ii., of at least one linear or branched, cyclic or
non-cyclic, saturated hydrocarbon, [0015] ii. from about 0.001 wt.
% to about 25 wt. %, preferably from about 0.5 wt. % to about 20
wt. %, more preferably from about 1 wt. % to about 15 wt. %, yet
more preferably from about 2 wt. % to about 10 wt. %, even more
preferably from about 2 wt. % to about 8 wt. %, more preferably
more preferably from about 3 wt. % to about 7 wt. %, most
preferably from about 4 wt. % to about 7 wt. %, based on the total
weight of components i. and ii., of at least one ester, wherein the
sum of the weight components i. and ii. in the organic phase is 100
wt. %, [0016] II) from 0 to about 50 wt. %, preferably from about 5
wt. % to about 50 wt. %, preferably from about 5 wt. % to about 45
wt. %, more preferably from about 5 wt. % to about 35 wt. %, more
preferably from about 10 wt. % to about 25 wt. %, based on the
total weight of the composition, of water or aqueous phase, [0017]
III) from 0 to about 60 wt. %, based on the total weight of the
composition, of at least one additive, wherein the sum of the
weight components I) to III) is 100 wt. %.
[0018] The drilling composition according to this aspect of the
invention is preferably an oil phase for an emulsion to be used as
a drilling fluid, or an emulsion to be used as a drilling fluid,
the emulsion being preferably a water in oil (W/O) emulsion.
[0019] In a preferred form of the organic phase I) according to the
invention, component i. comprises at least one synthetic or
natural, linear or branched, cyclic or non-cyclic hydrocarbon,
preferably at least one synthetic or natural, linear or branched,
cyclic or non-cyclic alkane, preferably at least one alkane
selected from the group consisting of n-alkanes, i-alkanes,
sec-alkanes, tert-alkanes, preferably at least one C.sub.5 to
C.sub.40, more preferably at least one C.sub.5 to C.sub.40, yet
more preferably at least one C.sub.10 to C.sub.30, more preferably
at least one C.sub.10 to C.sub.25 alkane selected from the group
consisting of n-alkanes, i-alkanes, sec-alkanes, tert-alkanes, or a
mixture of two or more thereof, whereby at least one branched
and/or cyclic alkane is preferred and at least one iso-alkane is
particularly preferred. In a particularly preferred embodiment of
the invention, component i. is a mixture of at least one isoalkane,
preferably at least one synthetic isoalkane, and at least one
mineral oil, preferably at least one low toxicity or non-toxic
mineral oil. Component i., or at least a part thereof, is
preferably obtainable by a process described in detail in CA
2,265,197 or U.S. Pat. No. 6,410,488 B1, whose disclosure in this
respect is introduced by reference and forms part of the present
disclosure. Component i. according to the invention can be
characterised by its properties. Component i. preferably has a
content of aromatic organic compounds of less than about 10 wt. %,
preferably of less than about 8 wt. %, most preferably of less than
about 6.5 wt. %, with a preferred polynuclear aromatic content
measured by high resolution mass spectrometry (HRMS) according to
the United States Environmental Protection Agency (EPA) method of
less than 50 ppm, preferably of less than 40 ppm, more preferably
less than 30 ppm, yet more preferably less than 20 ppm, most
preferably of less than 10 ppm, whereby wt. % and ppm amounts are
based on the total amount of component i. Component i. preferred
according to the invention also has low sulphur content, for
example less than about 10 ppm, more preferably less than about 7
ppm, yet more preferably less than about 5 ppm, most preferably
less than about 3 ppm. Preferred components i. also have a
viscosity determined according to ASTM D445 at 40.degree. C. of
between 1 and 10 centistokes, preferably of less than 7
centistokes, more preferably of less than 5 centistokes, most
preferably of between 2 centistokes and 4 centistokes, as well as a
pour point determined according to ASTM D97 in the range from about
-60.degree. C. to about -10.degree. C., more preferably in the
range from about -58.degree. C. to about -15.degree. C. The
preferred component i. according to the invention also has low
toxicity to animals, to marine life, and to humans, as measured by
standard tests such as the mysid shrimp test, and defined by LC50
and/or LD50 values. Preferred components i. are commercially
available products with trade names PureDrill.RTM. HT-40,
PureDrill.RTM. HT30 and PureDrill.RTM. IA35 (all from Petro-Canada,
Canada), EDC 95-11 (from Total Fluides, France), and Saraline.RTM.
185V (from Shell in Malaysia), whereby PureDrill.RTM. HT-40 is
particularly preferred according to the invention.
[0020] In a preferred aspect of the organic phase I) according to
the invention, the at least one ester is at least one ester
selected from the group consisting of esters formed from at least
one C.sub.1 to C.sub.24 monocarboxylic acid with at least one
monofunctional alcohol.
[0021] The at least one ester of the organic phase I) according to
the invention can be selected from natural and synthetic esters, or
mixtures of at least two thereof. By natural esters are understood
esters which themselves occur naturally, for example esters of
plant or animal origin, as well as esters formed from at least one
naturally occurring carboxylic acid and/or at least one naturally
occurring alcohol. The at least one ester according to the
invention preferably has solidification values (pour point and
setting point) below -10.degree. C. and more preferably below
-15.degree. C. The at least one ester according to the invention is
preferably fluid and pumpable at temperatures at least in the range
from about -10.degree. C. to about 5.degree. C., preferably at
temperatures in the range from about 0.degree. C. to about
5.degree. C., as well as above 5.degree. C. At the same time,
particularly for safety reasons, the flash points of these esters
are preferably as high as possible, whereby the at least one ester
preferably has a flash point measured according to ASTM D93 above
about 80.degree. C., preferably above about 100.degree. C., more
preferably above about 120.degree. C., yet more preferably above
about 150.degree. C., even more preferably above about 160.degree.
C. The esters preferred according to the invention also
advantageously have viscosity values (measured according to ASTM
D2983, using a Brookfield RVT viscometer) at temperatures of
0.degree. C. to 5.degree. C. of not more than 50 mPas and
preferably of at most 45 mPas or lower. Esters which are preferred
according to the invention are described in DE 39 07 391 A1, DE 39
07 392 A1, DE 38 42 703 A1 and DE 38 42 659 A1, whose disclosure
concerning esters is hereby incorporated into the present
disclosure.
[0022] When selecting the appropriate alcohol components for the
esters it is recommended to take account of the following
additional considerations: When the ester is used in practice, it
is not always possible to exclude partial saponification of the
ester. Free alcohols form, in addition to the free carboxylic acids
thus formed or carboxylic acid salts forming together with the
alkali reserves. They should be selected such that even after
partial hydrolysis operational conditions are ensured which are
ecologically and toxicologically harmless, with
inhalation-toxicological considerations in particular being taken
into account. The alcohols used for the ester formation preferably
in particular possess such a low volatility that in the free state
under conditions to be expected in practice, they do not result in
any nuisance on the working platform.
[0023] The at least one ester of component ii. of the composition
according to the invention can be described by means of the
following sub-classes.
[0024] In a first sub-class of the at least one ester of component
ii. of the present invention, the at least one ester is preferably
selected from C.sub.1-C.sub.5 mono carboxylic acid esters. The
esters of C.sub.1-C.sub.5 monocarboxylic acids are reaction
products of monofunctional alcohols, i.e. alcohols with one hydroxy
group. In this case the carbon number of the alcohol is at least 6,
but is preferably higher, for example at least 8 to 10 carbon
atoms.
[0025] In this sub-class of the at least one ester of component ii.
of the composition according to the invention the most preferred
esters are derived from monocarboxylic acids with 2 to 4 carbon
atoms, with acetic acid being particularly preferred as the
ester-forming component.
[0026] For this sub-class of esters based on very short-chain
(C.sub.1-C.sub.5) monocarboxylic acids, it is preferred to use
comparatively long-chain monofunctional alcohols, preferably with
up to 24 carbon atoms, preferably with from 6 to 24, more
preferably from 8 to 24 carbon atoms, so as to reduce sufficiently
the volatility of the ester. It is regarded as particularly
preferred that even after partial hydrolysis in use, the drilling
fluids are ecologically and toxicologically harmless, particularly
inhalation-toxicologically harmless under working conditions. In
practical use it is assumed that the at least slightly heated
drilling fluid is re-circulated and freed, particularly by
screening, from the drill cuttings it takes up. With progressive
ageing and the partial hydrolysis thus caused, problems can arise
not only from the formation of free fatty acids and their salts,
but the freed alcohol components can also cause difficulties in
practical operation. This alcohol content must always be taken into
consideration if alcohol vapour nuisance is to be expected as a
result of its volatility and the required operation
temperatures.
[0027] Suitable alcohols, particularly suitable monofunctional
alcohols can be of natural and/or synthetic origin. Straight-chain
and/or branched alcohols can be used here. If monofunctional
alcohols of natural and/or synthetic origin which are predominantly
aliphatic saturated are present in the esters used according to the
invention, then such alcohols with 8 to 15 carbon atoms are thus
preferably used for ester formation. Their vapour pressure is so
low in the operational conditions occurring in practice that the
problem area addressed above does not apply here. Olefin mono-
and/or poly-unsaturated alcohols are also suitable, such as can be
obtained, for example, by the selective reduction of naturally
occurring unsaturated carboxylic acids, for example fatty acids, or
their esters. The alcohols can, however, also be of synthetic
origin.
[0028] Esters of monofunctional alcohols are not, however, limited
to this carbon number range. Higher monofunctional alcohols can
also be considered, of which the esters with the carboxylic acids
of medium chain length defined according to this embodiment of the
invention yield oils or oil components with usable rheological
properties. Particularly to be considered here are olefin mono-
and/or polyunsaturated alcohols which can, for example, have up to
24 carbon atoms or even higher numbers of carbon atoms. Alcohols of
this type can be obtained in particular by the selective reduction
of corresponding natural fatty acids.
[0029] In a second sub-class of the at least one ester of component
ii. of the composition according to the invention, the esters,
fluid at room temperature and having flash points above 80.degree.
C., are derived from monocarboxylic acids of synthetic and/or
natural origin with 6 to 11 carbon atoms and monofunctional
alcohols.
[0030] In this embodiment it is also preferred that alcohol
components are used in the esters which even after a partial ester
cleavage are ecologically and toxicologically harmless in practical
use, in particular the invention takes into account in this regard
the inhalation-toxicological problems which can become significant
when dealing with the oil-base composition in practical use.
[0031] In this sub-class of the at least one ester of component ii.
of the composition according to the invention, the esters are
based, on the carboxylic acid side, on synthetic and/or natural
monocarboxylic acids with 6 to 11 carbon atoms, which can be
straight-chain and/or branched. Straight-chain and as a rule
even-numbered carboxylic acids in this range can be derived
particularly from oils or fats of natural origin and are known to
form the so-called pre-fatty-acids with from 6 to 10 carbon atoms.
Synthetic carboxylic acids of this type are also easily obtainable,
for example, by the oxidation of Ziegler alcohols. Branched, or
mixtures of branched and straight-chain carboxylic acids in this
range can be obtained from numerous processes in the petrochemical
industry. Esters of this type preferably contain at least 6 and
better still at least 7 carbon atoms in the alcohol component. With
this comparatively high lower limit value for the alcohol
component, it is possible to ensure that in practical use, even
after a partial ester cleavage, toxicological and particularly
inhalation-toxicological problems can be overcome by simple means.
Particularly preferred alcohols are those having up to 24 or more
carbon atoms and the C.sub.8 to C.sub.15 alcohols mentioned above
in connection with the first sub-class of the at least one ester of
component ii. of the composition according to the invention.
[0032] In a third sub-class of the at least one ester of component
ii. of the composition, these are esters of saturated aliphatic
C.sub.12-C.sub.16 monocarboxylic acids and monofunctional
C.sub.2-C.sub.12, preferably C.sub.4-C.sub.12 alcohols or mixtures
thereof.
[0033] The presence of saturated carboxylic acids containing less
than 16 carbon atoms and, more especially, from 12 to 14 carbon
atoms is preferred in this context. In small quantities, the
contents of such lower, fully saturated fatty acids often present
in natural starting materials are frequently valuable mixture
components. Their esters are not vulnerable to oxidation under
practical in-use conditions and their rheological properties allow
them to replace to a certain extent pure hydrocarbon oils in
practice.
[0034] In one particularly preferred aspect of this sub-class of
the at least one ester of component ii. of the composition of the
invention as described above, at least the predominant part, i.e.
at least 50%, preferably at least 60%, of the ester used is based
on saturated aliphatic C.sub.12-C.sub.14 monocarboxylic acids.
[0035] The esters used in accordance with this sub-class of the at
least one ester of component ii. of the composition of the
invention of monofunctional alcohols and selected monocarboxylic
acids can be derived from either straight chain or branched
hydrocarbon chains. Preferred are the esters of straight chain
acids, in particular the esters of saturated C.sub.12-16 and more
especially C.sub.12-14 monocarboxylic acids and monofunctional
alcohols having the C chain lengths defined in accordance with this
sub-class of the at least one ester of component ii. of the
composition of the invention. These can form esters which show
adequate rheological properties, even down to temperatures in the
range of from 0 to 5.degree. C., and in particular are flowable and
pumpable in that temperature range. In the context of this
sub-class of the at least one ester of component ii. of the
composition of the invention, preferred esters are saturated
compounds which have a Brookfield (RVT) viscosity, measured as
described above, at a temperature of 0 to 5.degree. C., of no more
than 50 mPas and preferably of no more than 40 mPas. By selecting
suitable components for the ester-forming reaction, it is possible
to adjust the viscosity at temperatures in the above-mentioned
range to values of at most 30 mPas, for example in the range of
from 10 to 20 mPas. It is clear that this affords important
advantages for offshore drilling where the surrounding water can
have very low temperatures.
[0036] The alcohol components of the esters or ester mixtures
according to this embodiment of the invention are preferably
derived from straight-chain and/or branched-chain saturated
alcohols, preferably alcohols containing at least 3 carbon atoms
and, more especially, to alcohols containing up to about 10 carbon
atoms, whereby alcohols with 4, 5, 6, 7, 8, or 9 carbon atoms can
also be used. 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.
[0037] In a preferred embodiment, the esters used in accordance
with this aspect of the composition according to the invention
based on selected individual components or on ester mixtures have
solidification values (pour point and setting point) below
-10.degree. C. and more especially below -15.degree. C. Despite
this high mobility at low temperatures, the molecular size of the
ester in accordance with the invention ensures that the flash
points of the esters are sufficiently high, being at least
80.degree. C., but generally exceeding a temperature limit of about
100.degree. C. Esters having flash points above 150.degree. C. to
160.degree. C. are preferred. It is possible to produce esters of
the described types which have flash points of 185.degree. C. or
higher.
[0038] In another preferred aspect of this third sub-class of the
at least one ester of composition ii. according to the invention,
the esters of the range required in accordance with the invention
for the saturated C.sub.12-C.sub.16 monocarboxylic acids are
derived from materials of predominantly vegetable origin.
Carboxylic acids or carboxylic acid mixtures predominantly
containing saturated monocarboxylic acids within the stated range
can be obtained, for example, from renewable triglycerides, such as
coconut oil, palm kernel oil and/or babassu oil. Fatty acid
mixtures of this origin normally contain a limited quantity of
lower fatty acids (C.sub.6-C.sub.10) of generally at most about
15%. Their content of C.sub.12-C.sub.14 acids is by far
predominant, generally making up at least 50% and normally 60% or
more of the carboxylic acid mixture. The small remainder consists
of higher fatty acids, with unsaturated components playing a
considerable role. Accordingly, carboxylic acid mixtures of this
type, by virtue of their natural structure, readily lead to
materials having satisfactory rheological properties.
[0039] In a fourth sub-class of the at least one ester of component
ii. of the composition according to the invention these can be
esters of monofunctional C.sub.2-C.sub.12 alcohols (alkanols) and
olefinically mono- and/or polyunsaturated C.sub.16-C.sub.24
monocarboxylic acids or mixtures thereof with small quantities of
other, more especially saturated monocarboxylic acids.
[0040] The esters according to this embodiment may be assigned to
the class of reaction products of monofunctional carboxylic acids,
preferably C.sub.16-C.sub.24 carboxylic acids, with monofunctional
alcohols. The carboxylic acids may be derived from un-branched or
branched hydrocarbon chains, preferably linear chains.
Monocarboxylic acids of this type and of the C.sub.16-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. C. to
5.degree. C. providing an adequate level of olefinically
unsaturated ester constituents is provided. In this sub-class of
the at least one ester of component ii. of the composition 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-C.sub.24 carboxylic
acids are preferably used. Preferred 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.
[0041] In conjunction with the choice of esters of monofunctional
reactants in accordance with the fourth sub-class of the at least
one ester of component ii. of the composition of the invention, the
choice of such a comparatively highly unsaturated carboxylic acid
component in the esters ensures that the esters, and invert
emulsions comprising them, show the rheological properties required
in practice, particularly at relatively low temperatures. The
comparatively highly unsaturated esters containing 16 to 24 carbon
atoms in the monocarboxylic acid component, which are used in
accordance with this embodiment of the invention, have
solidification points (pour point according to ASTM D97 and setting
point) below -10.degree. C. and more especially below -15.degree.
C. Despite this high mobility at low temperatures, the molecular
size of the ester prescribed in accordance with this aspect of the
invention ensures that the flashpoints of the esters are
sufficiently high, being at least 80.degree. C., and generally
exceeding a temperature limit of approximately 100.degree. C.
Esters having flashpoints above 160.degree. C. are preferred.
Esters 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 by processes known to the
skilled person.
[0042] 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 esters of the type described for this embodiment
according to the invention show a viscosity (measured with a
Brookfield RVT viscometer as above) at a temperature of 0.degree.
C. to 5.degree. C. of not more than 55 mPas and preferably of at
most 45 mPas or lower. It is possible to adjust values of 30 or
even higher, for example in the range of from 20 to 25 mPas, at
temperatures in the range indicated.
[0043] Among the unsaturated esters suitable for use in accordance
with this fourth sub-class of the at least one ester of component
ii. of the composition of the invention, there are two preferred
types of ester.
[0044] The first of these preferred types of ester is based on
unsaturated C.sub.16-C.sub.24 mono-carboxylic 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 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.
[0045] The second preferred type of ester is derived from
C.sub.16-C.sub.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.
[0046] Preferred 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). A preferred
di-unsaturated carboxylic acid within the range in question here is
linoleic acid (C.sub.18) while a preferred triethylenically
unsaturated carboxylic acid is linolenic acid (C.sub.18).
[0047] Selected individual esters formed from an unsaturated
monocarboxylic acid and a monoalcohol can be used as the ester in
accordance with this fourth sub-class of the at least one ester of
component ii. of the composition of the invention. One example of
such esters is given by 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
preferred so far as meeting the preferred specifications of the
esters according to this aspect of the invention is concerned. This
can also be preferred for all embodiments of the ester in the
composition according to the invention, not only for this
sub-class.
[0048] As already mentioned, the first of these two types 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.
[0049] Esters of the first type according to this sub-class of the
at least one ester of component ii. of the composition according to
the invention which correspond to this definition have the
advantage that problems possibly arising from the lack of stability
to oxidation are reduced. In practice, the drilling composition is
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.
[0050] However, carboxylic acid mixtures of the second type
mentioned in connection with this fourth sub-class of the at least
one ester of component ii. of the composition of the invention are
also of 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.
Examples of oils which have a high content of C.sub.16-C.sub.18 or
C.sub.16-C.sub.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.
[0051] The alcohol components of the esters or ester mixtures
according to this fourth aspect of the composition ii. of the
invention are preferably derived from straight chain and/or
branched-chain saturated alcohols, preferably alcohols containing
at least four carbon atoms and, more preferably alcohols containing
up to about ten carbon atoms, as described above. 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, or they can be of synthetic origin.
[0052] Esters which are particularly preferred according to the
invention are based on C.sub.8-C.sub.14 fatty acids or difatty
acids thereof, or on C.sub.8-C.sub.10 or C.sub.12-C.sub.14 fatty
acids or di-fatty acids thereof, of which C.sub.8-C.sub.14 fatty
acids or C.sub.12-C.sub.14 fatty acids are preferred. Particularly
preferred esters are based on Cs to C.sub.14, C.sub.8 to C.sub.10
and/or C.sub.12 to C.sub.14 fatty acids, esterified with a branched
alcohol, preferably with a branched C.sub.4 to C.sub.12 alcohol,
yet more preferably with a branched C.sub.6-C.sub.10 alcohol, yet
more preferably with a branched C.sub.7-C.sub.9 alcohol, more
preferably with an ethylpentyl alcohol, a propylpentyl alcohol, an
ethylhexyl alcohol, a propylhexyl alcohol, an ethylheptyl alcohol,
a propylheptyl alcohol, more preferably with an ethylhexyl alcohol,
preferably with 2-ethylhexyl alcohol or with 3-ethylhexyl alcohol,
most particularly preferably with 2-ethylhexyl alcohol. 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.
[0053] In a preferred embodiment, the at least one ester has a
carbon chain distribution of the acid-derived component determined
by gas chromatography (GC) according to ISO 5508 with carbon
numbers in the ranges of from 0 to 2.00%, preferably in the range
of from 0 to 1.00%, more preferably in the range of from 0 to 0.5%
C.sub.6, in the range of from 3.00% to 10.00%, preferably in the
range of from 3.00 to 8.00%, more preferably in the range of from
4.00 to 7.00% C.sub.8, in the range of from 3.00% to 10.00%,
preferably in the range of from 3.00 to 9.00%, more preferably in
the range of from 5.00 to 8.00% C.sub.10, in the range of from
50.00% to 94.00%, preferably in the range of from 55.00 to 90.00%,
more preferably in the range of from 60.00 to 85.00% C.sub.12, in
the range of from 0 to 25.00%, preferably in the range of from 5.00
to 20.00%, more preferably in the range of from 10.00 to 20.00%
C.sub.14, in the range of from 0 to 5.00%, preferably in the range
of from 1.00 to 4.00%, more preferably in the range of from 2.00 to
4.00% C.sub.16 and in the range of from 0 to 1.00%, preferably in
the range of from 0.01 to 0.90%, more preferably in the range of
from 0.1 to 0.6% C.sub.18. The acid-derived component determined by
gas chromatography of an ester refers to the chromatographic
equivalent of an acid, which would have been formed upon hydrolytic
cleavage of that ester into an alcohol and an acid.
[0054] In another preferred embodiment, the at least one ester has
a carbon chain distribution of the acid-derived component
determined by gas chromatography (GC) according to ISO 5508 with
carbon numbers in the range of from 0 to 2.00%, preferably in the
range of from 0 to 1.00%, more preferably in the range of from 0 to
0.5% C.sub.6, in the range of from 0 to 10.00%, preferably in the
range of from 1.00 to 7.00%, more preferably in the range of from
2.00 to 5.00% C.sub.8, in the range of from 0 to 10.00%, preferably
in the range of from 1.00 to 7.00%, more preferably in the range of
from 2.00 to 5.00% C.sub.10, in the range of from 50.00% to 95.00%,
preferably in the range of from 60.00 to 90.00%, more preferably in
the range of from 65.00 to 85.00% C.sub.12, in the range of from
5.00% to 35.00%, preferably in the range of from 8.00 to 30.00%,
more preferably in the range of from 10.00 to 25.00% C.sub.14, in
the range of from 0 to 5.00%, preferably in the range of from 1.00
to 4.00%, more preferably in the range of from 2.00 to 4.00%
C.sub.16 and in the range of from 0 to 1.00%, preferably in the
range of from 0.01 to 0.90%, more preferably in the range of from
0.1 to 0.6% C.sub.18. The acid-derived component determined by gas
chromatography of an ester refers to the chromatographic equivalent
of an acid, which would have been formed upon hydrolytic cleavage
of that ester into an alcohol and an acid.
[0055] The at least one ester used as component ii. of the
composition according to the invention preferably has at least one,
preferably at least two, more preferably at least three, yet more
preferably at least four, more preferably at least five, more
preferably all of the following properties, in any combination with
each other: [0056] .alpha.1) a viscosity determined according to
ASTM D2983 using a Brookfield RVT viscometer (Brookfield, RVT
viscosity) at temperatures of 0.degree. C. to 5.degree. C. of not
more than 50 mPas, preferably of not more than 10 mPas and
preferably in the range of from about 2.0 to 5.0 mPas, more
preferably in the range of from about 2.5 to 4.5 mPas, yet more
preferably in the range of from about 2.7 to 4.0 mPas; [0057]
.alpha.2) an acid value determined according to ISO 660 in a range
of from 0 to 2.0 mg KOH/g, preferably in a range of from 0001 to
1.8 mg KOH/g, preferably in a range of from 0.01 to 1.5 mg KOH/g,
preferably in a range of from 0.05 to 1.0 mg KOH/g; [0058]
.alpha.3) a hydroxyl value determined according to DIN 53240 in a
range from 0 to 1.5 mg KOH/g, preferably in a range from 0 to 1.0
mg KOH/g, more preferably in a range from 0 to 0.8 mg KOH/g; [0059]
.alpha.4) biodegradability in seawater measured according to OECD
Guideline for Testing of Chemicals, No. 306, adopted 17 Jul. 1992,
in the range of from 90% to 100%, preferably in the range of from
92% to 100%, more preferably in the range of from 95% to 100%;
[0060] .alpha.5) non-toxicity measured by the 96 hour LC50 Mysid
shrimp acute toxicity bioassay test result of greater than 800,000,
preferably of greater than 900,000, more preferably of greater than
1,000,000 and most preferably of greater than 1,100,000. [0061]
.alpha.6) a flashpoint measured according to ASTM D93 of above
150.degree. C., more preferably of above 160.degree. C., even more
preferably of above 170.degree. C., yet more preferably above
175.degree. C., more preferably in a range from 175.degree. C. to
200.degree. C., even more preferably in a range from 177.degree. C.
to 182.degree. C.
[0062] It is also possible according to a further embodiment of the
composition according to the invention that the at least one ester
is a mixture of at least two esters selected from any of the esters
described above.
[0063] The composition as preferred according to the invention can
comprise only or predominantly starting materials of natural
origin, but is by no means limited to starting materials of natural
origin. Both on the alcohol side and on the carboxylic acid side,
the starting materials may be of natural origin or may be partly or
completely of synthetic origin. Starting materials of natural
origin are advantageous in their proven lower toxicological values,
their ready degradability and their ready accessibility. The
ultimately desired destruction, preferably natural destruction, of
the used composition is favoured if esters of the type described
herein are both aerobically and anaerobically degradable.
[0064] The water or aqueous phase according to component II) of the
composition according to the invention is preferably a salt
solution, preferably a saturated salt solution, preferably a
saturated solution of CaCl.sub.2 and/or KCl.
[0065] Multi-substance mixtures further comprising one or more
additives also fall within the framework of the invention. In
principle, any mixtures can be used provided that they fulfil the
basic rheological requirements for drilling fluids, in particular
for invert-drilling fluids.
[0066] Additives according to the invention can be any additives
which are commonly used in drilling compositions and which are
known to the skilled person. In a preferred aspect of the
composition according to the invention, the at least one additive
is at least one additive selected from the group consisting of
weighting agents, fluid loss additives, pH modifiers such as, for
example, alkali reserves, viscosity modifiers, filtration control
agents, emulsifiers, salts, wetting agents, dispersants.
[0067] Weighting agents suitable for use in drilling compositions
are well known to the skilled person. Weighting agents suitable
according to the invention are preferably water-insoluble weighting
agents such as barite, calcite, mullite, galena, hematite,
manganese oxides, iron oxides, or combinations of these, or
water-soluble weighting agents such as water soluble salts of zinc,
iron, barium, calcium or combinations of these and similar
compounds. Further examples of suitable weighting agents are
Fe.sub.2O.sub.3, MnO.sub.4 and CaCO.sub.3. The weighting agent
preferred according to the invention to establish the necessary
pressure equalization is barite, which comprises predominantly
barium sulphate, 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 2.5 and preferably in the
range of from 1.3 to 1.6.
[0068] Fluid loss additives can be used in embodiments of the
composition according to the invention. In a preferred embodiment
according to the invention, organophilic lignite is used as a fluid
loss additive and, hence, for forming an impervious coating in the
form of a substantially liquid-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 20 to 60% by weight,
preferably in a range of from 30 to 50% by weight, based on the
ester phase.
[0069] Use may also be made according to the invention of agents
which modify the pH of the composition: Examples are given in EP
382 070 A1. The teaching of this earlier application is based on
the concept of using a further additive in ester-based invert
drilling fluids, which is suited to keeping the desired rheological
data of the drilling fluid in the required range even when, in use,
increasingly large amounts of free carboxylic acids are formed by
partial ester hydrolysis. These liberated carboxylic acids should
not only be trapped in a harmless form, it should moreover be
possible to reform these free carboxylic acids, preferably into
valuable components with stabilizing or emulsifying properties for
the whole system. According to this teaching, alkaline amine
compounds of marked oleophilic nature and at best limited water
solubility, which are capable of forming salts with carboxylic
acids, can be used as additives in the oil phase. The oleophilic
amine compounds can at the same time be used at least in part as
alkali reserves in the invert drilling fluid, they can however also
be used in combination with conventional alkali reserves,
particularly together with lime. The use of oleophilic amine
compounds which are at least largely free from aromatic
constituents is preferred. In particular, optionally olefin
unsaturated aliphatic, cycloaliphatic and/or heterocyclic
oleophilic basic amine compounds, can be considered, which contain
one or more N-groups capable of forming salts with carboxylic
acids. In a preferred embodiment the water-solubility of these
amine compounds at room temperature is at most about 5% by weight
and is most preferably below 1% by weight.
[0070] Typical examples of such amine compounds are primary,
secondary and/or tertiary amines, which are at least predominantly
water-insoluble, and which can also to a limited extent be
alkoxylated and/or substituted particularly with hydroxyl groups.
Further examples are corresponding aminoamides and/or heterocycles
containing nitrogen as ring constituent. For example, basic amine
compounds are suitable which have at least one long-chain
hydrocarbon radical with preferably 8 to 36 carbon atoms,
particularly with 10 to 24 carbon atoms, which can also be olefin
mono- or poly-unsaturated. The oleophilic basic amine compounds can
be added to the drilling fluid in amounts of up to about 10 lb/bbl,
preferably in amounts up to about 5 lb/bbl and particularly in the
range of about 0.1 to 2 lb/bbl. It has emerged that the use of such
oleophilic basic amine compounds can effectively prevent thickening
of the mud system, which has previously been attributed to a
disturbance in the W/O invert system and also to the formation of
free carboxylic acids by ester hydrolysis.
[0071] One preferred limitation is associated with the use of the
esters according to the third and fourth embodiments in invert oil
drilling fluids of the type used in the present invention. This
limitation arises out of the difficulty that, in principle, the
carboxylic acid esters are vulnerable to hydrolysis.
[0072] It is preferred in all embodiments, but particularly in the
third and fourth embodiments that strong hydrophilic bases of
inorganic and/or organic nature, such as alkali metal hydroxides or
strongly hydrophilic amines such as diethanolamine and/or
triethanolamine, are not used in significant quantities as alkali
reserve. Lime (calcium hydroxide) is often added as the alkali
reserve, more especially for protection against inrushes of acidic
gases such as CO.sub.2 and/or H.sub.2S 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 preferred 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/drilling
composition), and it may be preferred to work with lime contents in
the drilling mud slightly below this, e.g., therefore from about
0.5 to about 1.8 lb/bbl (lime/drilling fluid). Other known alkali
reserves can be used in addition to or in place of the lime. The
less basic metal oxides, such as zinc oxide, should particularly be
mentioned here. Even when these acid traps are used, care is still
taken that the amounts used are not too large, so as to prevent
undesired premature ageing of the drilling fluid, associated with
an increase in viscosity and therefore a deterioration in the
rheological properties. The special features discussed here of the
process according to the invention prevent, or at least restrict,
the formation of undesirable amounts of highly active OAV
emulsifiers, so that the good rheological properties are maintained
for a sufficiently long time in use even when there is thermal
ageing.
[0073] Viscosity modifiers suitable for use in drilling
compositions are well known to the skilled person. Viscosity
modifiers can be viscosifiers (also known as structure building
agents or thickeners) which increase viscosity, or deflocculants
which decrease viscosity, whereby in the present invention
viscosifiers are preferred. Viscosifiers can be selected from
organic or inorganic thickeners, for example, xanthan gum, guar
gum, glycol, carboxymethylcellulose, polyanionic cellulose or
starch. Deflocculants can be selected from anionic polyelectrolytes
such as acrylates, polyphosphates, lignosulfonates or tannic acid
derivatives such as Quebra-cho. A viscosifier preferred according
to the invention is a cation-modified finely particulate bentonite,
which can be used particularly in amounts of about 8 to 10 lb/bbl
(pounds per barrel) or from about 1 to about 60 wt. %, preferably
from about 2 to about 55% by weight, based on the total weight of
the composition.
[0074] The emulsifiers which can be used in practice according to
the invention are systems which are capable of forming water in oil
(W/O) emulsions. In particular, selected oleophilic fatty acids or
salts thereof, for example, those based on amidoamine compounds, in
particular polyaminated fatty acids, can be considered. Examples of
these are described in U.S. Pat. No. 4,374,737 and the literature
cited therein. Particularly preferred emulsifiers are reaction
products of a polyamine with a fatty acid or fatty acid anhydride
to give a fatty amide, which is subsequently reacted with an
anhydride, preferably maleic acid anhydride, acrylic acid anhydride
or fumaric acid anhydride, most preferably maleic acid anhydride,
in the presence of at least one crosslinker. Examples of these are
described in U.S. Pat. No. 4,658,036 and the literature cited
therein, whose disclosures are hereby incorporated by reference. A
particularly suitable type of emulsifier is the product sold by
Halliburton (Baroid Fluid Services) under the brand name
"EZ-MUL.RTM.".
[0075] Emulsifiers of the type in question are sold commercially as
highly concentrated active-substance preparations and in one
embodiment can, for example, be used in amounts of about 20 to 80%
by weight, particularly in amounts of about 30 to 70% by weight,
based on the organic phase. It is, however, preferred that
emulsifiers are used in amounts in the range from about 0.5 wt. %
to about 15 wt. %, preferably in amounts in the range from about
0.5 wt. % to about 10 wt. %, more preferably in amounts in the
range from about 1 wt. % to about 8 wt. %, more preferably in
amounts in the range from about 1 wt. % to about 6 wt. %, based on
the organic phase.
[0076] The aforementioned emulsifiers or emulsifier systems can
optionally also be used to improve the oil wettability of the
inorganic weighting materials. In addition to the aminoamides
already discussed, alkyl benzenesulfonates and imidazoline
compounds are further examples. Additional information regarding
these and also regarding the relevant prior art can be found in the
following publications: GB 2 158 437, EP 229 912 and DE 32 47 123,
whose disclosures are hereby incorporated by reference.
[0077] The at least one salt is preferably selected from the group
consisting of metal halides, particularly preferably alkali metal
or alkaline earth metal halides. The dispersed aqueous phase in the
composition according to the invention, which is preferably in the
form of an invert drilling fluid, is preferably loaded with soluble
salts. Calcium chloride and/or potassium chloride are preferably
used here, and saturation of the aqueous phase with the soluble
salt at room temperature is preferred.
[0078] In the aspect of the composition according to the invention
comprising water or aqueous phase, the composition is preferably in
the form of an emulsion, preferably in the form of a nanoemulsion
or a microemulsion, preferably in the form of a water-in-oil
emulsion with number average droplet sizes smaller than 1000 .mu.m,
preferably in the range from about 5 nm to about 1000 .mu.m,
preferably in the range from 10 nm to 850 .mu.m, more preferably in
the range from 20 nm to 700 .mu.m, more preferably in the range
from 50 nm to 500 .mu.m. The terms "microemulsion" and
"nanoemulsion" according to the invention are used to refer to
emulsions with droplet sizes in the micrometer and nanometer ranges
respectively, whereby there is a certain amount of overlap between
the two ranges and thus the two terms. According to some
definitions in the prior art, microemulsions are generally
considered to form spontaneously on combination of the emulsion
components, whereas the formation of nano emulsions is generally
considered to require input of energy, for example in the form of
homogenisation, in particular high pressure homogenisation.
[0079] The drilling composition according to the invention
preferably has at least one, preferably at least two, more
preferably at least three of the following properties: [0080]
.beta.1) a plastic viscosity (PV) measured at 50.degree. C.
according to the herein described test method in the range from 15
to 75 mPas, preferably in a range of from about 15 to about 60
mPas, more preferably in a range of from about 15 to about 40 mPas,
more preferably in a range of from about 15 to about 30 mPas, yet
more preferably in a range of from about 15 to about 25 mPas;
[0081] .beta.2) a yield point (YP) measured at 50.degree. C.
according to the herein described test method in the range from 5
to 45 lb/100 ft.sup.2 (about 2.4 to about 21.6 Pa), preferably in a
range of from about 5 to about 40 lb/100 ft.sup.2 (about 2.4 to
about 20 Pa), preferably in a range of from about 6 to about 25
lb/100 ft.sup.2, (about 2.9 to about 12 Pa), more preferably in a
range of from about 8 to about 20 lb/100 ft.sup.2, (about 3.8 to
about 10 Pa); [0082] .beta.3) a gel strength (GS) measured at
50.degree. C. according to the herein described test method in the
range from 4 to 25 lb/100 ft.sup.2 (1.9 to 12 Pa), preferably in a
range of from about 4 to about 15 lb/100 ft.sup.2 (about 1.9 to
about 7.2 Pa), preferably in a range of from about 4 to about 10
lb/100 ft.sup.2, (about 1.9 to about 4.8 Pa), more preferably in a
range of from about 4 to about 8 lb/100 ft.sup.2, (about 1.9 to
about 3.8 Pa); [0083] .beta.4) viscosity values (measured according
to ASTM D2983, using a Brookfield RVT viscometer) at temperatures
of 0.degree. C. to 5.degree. C. of not more than 50 mPas,
preferably of not more than 15 mPas and preferably in the range of
from about 2.0 to 5.0 mPas, more preferably in the range of from
about 2.5 to 4.5 mPas, yet more preferably in the range of from
about 2.7 to 4.0 mPas; [0084] .beta.5) storage stability at
20.degree. C. of at least two weeks, preferably of at least one
month, more preferably of at least three months, more preferably of
at least six months, more preferably of at least one year, whereby
the combinations of properties .beta.1).beta.2), .beta.1).beta.3),
.beta.2).beta.3), .beta.1).beta.2).beta.3),
.beta.1).beta.2).beta.3).beta.4), .beta.1).beta.2).beta.3).beta.5),
.beta.1).beta.2).beta.3).beta.4).beta.5) are preferred, whereby the
property combinations .beta.1).beta.2).beta.3),
.beta.1).beta.2).beta.3).beta.4), .beta.1).beta.2).beta.3).beta.5),
and .beta.1).beta.2).beta.3).beta.4).beta.5) are particularly
preferred.
[0085] One application for the drilling compositions according to
the invention is in offshore drilling for the development of oil
and/or gas sources, to provide technically useful drilling fluids
of good ecological compatibility. The use of the new drilling
fluids is, however, 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-comprising drilling compositions in accordance with
the invention simplify ecotoxic problems. The drilling compositions
according to the invention exhibit a good solubility of organic and
inorganic components. In addition, the drilling compositions based
in accordance with the invention on the co-use of esters of the
described type are further distinguished by improved storage
stability, improved lubricity and good rheological properties.
[0086] A contribution to solving the above problems is also made by
a process for preparation of a drilling composition, comprising the
steps: [0087] a) providing as component i. from about 20 wt. % to
about 99.999 wt. %, preferably from about 40 wt. % to about 99.990
wt. %, preferably from about 60 wt. % to about 99.900 wt. %,
preferably from about 70 wt. % to about 99 wt. %, more preferably
from about 80 wt. % to about 98.5 wt. %, yet more preferably from
about 85 wt. % to about 98 wt. %, even more preferably from about
90 wt. % to about 98 wt. %, more preferably from about 92 wt. % to
about 97 wt. %, most preferably from about 93 wt. % to about 96 wt.
%, based on the total weight of components i. and ii., of at least
one linear or branched, cyclic or non-cyclic, saturated
hydrocarbon, [0088] b) providing as component ii. from about 0.001
wt. % to about 25 wt. %, preferably from about 0.5 wt. % to about
20 wt. %, more preferably from about 1 wt. % to about 15 wt. %, yet
more preferably from about 2 wt. % to about 10 wt. %, even more
preferably from about 2 wt. % to about 8 wt. %, more preferably
from about 3 wt. % to about 7 wt. %, most preferably from about 4
wt. % to about 7 wt. %, based on the total weight of components i.
and ii., of at least one linear or branched, cyclic or non-cyclic,
saturated hydrocarbon, wherein the sum of the weight amounts
provided in a) and b) is 100 wt. %, [0089] c) combining the at
least one hydrocarbon and the at least one ester.
[0090] A contribution to solving the above problems is also made by
a process for preparation of a drilling composition, comprising the
steps: [0091] A) preparation of an organic phase comprising
components [0092] i. from about 20 wt. % to about 99.999 wt. %,
preferably from about 40 wt. % to about 99.990 wt. %, preferably
from about 60 wt. % to about 99.900 wt. %, preferably from about 70
wt. % to about 99 wt. %, more preferably from about 80 wt. % to
about 98.5 wt. %, yet more preferably from about 85 wt. % to about
98 wt. %, even more preferably from about 90 wt. % to about 98 wt.
%, more preferably from about 92 wt. % to about 97 wt. %, most
preferably from about 93 wt. % to about 96 wt. %, based on the
total weight of components i. and ii., of at least one linear or
branched, cyclic or non-cyclic, saturated hydrocarbon, [0093] ii.
from about 0.001 wt. % to about 25 wt. %, preferably from about 0.5
wt. % to about 20 wt. %, more preferably from about 1 wt. % to
about 15 wt. %, yet more preferably from about 2 wt. % to about 10
wt. %, even more preferably from about 2 wt. % to about 8 wt. %,
more preferably from about 3 wt. % to about 7 wt. %, most
preferably from about 4 wt. % to about 7 wt. %, based on the total
weight of components i. and ii., of at least one ester, [0094] B)
preparation of an aqueous phase comprising from about 50 wt. % to
100 wt. %, preferably from about 55 wt. % to about 99 wt. %, more
preferably from about 70 wt. % to about 95 wt. % water, based on
the total amount of aqueous phase, [0095] C) combination of the
organic phase prepared in step A) with from 0 to about 50 wt. %,
preferably from about 5 wt. % to about 50 wt. %, preferably from
about 5 wt. % to about 45 wt. %, more preferably from about 5 wt. %
to about 35 wt. %, more preferably from about 10 wt. % to about 25
wt. %, based on the total weight of the composition, of the aqueous
phase prepared in step B), and [0096] D) combination of at least
one of the organic phase, the aqueous phase and the combination of
the oil phase and the aqueous phase with from 0 to about 60 wt. %,
based on the total weight of composition, of at least one
additive.
[0097] The at least one linear or branched, cyclic or non-cyclic,
saturated hydrocarbon is preferably selected from the hydrocarbons
mentioned above in connection with the composition according to the
invention.
[0098] The at least one ester is preferably at least one ester
selected from the esters described above in connection with the
composition according to the invention, preferably from the group
consisting of esters formed from at least one C.sub.1 to C.sub.24
monocarboxylic acid with at least one monofunctional alcohol.
[0099] The aqueous phase is preferably a salt-saturated aqueous
phase as described above in connection with the composition
according to the invention.
[0100] The at least one additive is preferably at least one
additive selected from the additives mentioned above in connection
with the composition according to the invention.
[0101] The amounts of each of the above components are preferably
selected as described above for the composition according to the
invention.
[0102] The combination in step C) can occur by adding the organic
phase to the aqueous phase, by adding the aqueous phase to the
organic phase, or by introducing the organic phase and the aqueous
phase at substantially the same time into a vessel in which they
are to be combined. The combination preferably occurs with input of
energy, preferably in the form of mixing or stirring, preferably
rapid stirring, preferably stirring at a rate above 50 rpm,
preferably in the range from about 100 rpm to about 500 rpm, more
preferably in the range from about 200 rpm to about 450 rpm. The
combination can occur at decreased, ambient or elevated
temperature, depending on factors such as the components to be
combined, the location at which they are combined (for example,
indoors or outdoors), and the desired emulsion droplet size. A
combination at ambient temperature is preferred.
[0103] The at least one additive can be introduced before, during
or after any or all of steps A), B) and C). If one or more
additives are introduced in step C), this additive may be
introduced at substantially the same time as combining the organic
phase with the aqueous phase as described above, or it may be added
to either the organic phase or the aqueous phase or to both, for
example with at least one additive being added to the organic phase
and at least one further additive being added to the aqueous phase,
before combination in step C), or the at least one additive may be
added to the composition obtained after combination of the organic
phase with the aqueous phase in step C).
[0104] In a variant of the process according to the invention, the
at least one ester according to the invention can be added to an
already existing drilling composition comprising at least one
hydrocarbon, aqueous phase and at least one additive, in a
so-called post-treatment step. In this case it is conceivable that
the already existing drilling composition has already been used at
least once in a drilling operation, prior to the post-treatment
with the at least one ester. It is also possible that the already
existing drilling composition has not yet been used in a drilling
operation before the post-treatment.
[0105] The process according to the invention preferably further
comprises the step E) homogenisation.
[0106] The homogenisation is preferably a homogenisation of the
composition obtained in step C) or step D) of the process according
to the invention. It is also possible that steps C) and E), or
steps C), D) and E) are combined with each other, so that the
combination of the oil phase and the aqueous phase with each other
and/or with any additive used takes the form of a homogenisation.
It is preferred in the process according to the invention that the
homogenisation occurs during or after at least one of steps C) and
D). The homogenisation is preferably carried out at temperatures in
the range from 0 to 100.degree. C., preferably in the range from 5
to 80.degree. C., more preferably in the range from 10 to
60.degree. C., yet more preferably in the range from 20 to
50.degree. C., most preferably at ambient temperatures. The
homogenisation may also be a high pressure homogenisation carried
out at pressures in the range from 1.times.10.sup.7 Pa to
18.times.10.sup.7 Pa, preferably in the range from 3.times.10.sup.7
Pa to 18.times.10.sup.7 Pa, more preferably in the range from
5.times.10.sup.7 Pa to 15.times.10.sup.7 Pa.
[0107] It is preferred in the process according to the invention
that the composition at the end of at least one of steps C), D) and
E) is in the form of an emulsion. Thus, an emulsion may be formed
by combining the oil phase with the aqueous phase as described for
step C) above, optionally in the presence of at least one additive,
which may be, for example, at least one emulsifier. Alternatively,
an emulsion may be formed by subjecting the oil phase and the
aqueous phase together, optionally in the presence of at least one
additive, which may be, for example, at least one emulsifier, to a
homogenisation step, as described for step E) above.
Homogenisation, in particular high pressure homogenisation,
generally results in emulsions with smaller droplet sizes compared
to simple combination of the oil phase and the aqueous phase. In a
preferred embodiment of the process according to the invention, the
emulsion is a nanoemulsion or a microemulsion as described above in
connection with the composition according to the invention, with
number average droplet sizes smaller than 1000 .mu.m, preferably in
the range from 5 nm to 1000 .mu.m, preferably in the range from 10
nm to 850 .mu.m, more preferably in the range from 20 nm to 700
.mu.m, more preferably in the range from 50 nm to 500 .mu.m.
[0108] In a preferred aspect of the process according to the
invention, the at least one ester has a carbon chain distribution
of the acid-derived component determined by gas chromatography (GC)
according to ISO 5508 with carbon numbers in the ranges of from 0
to 2.00%, preferably in the range of from 0 to 1.00%, more
preferably in the range of from 0 to 0.5% C.sub.6, in the range of
from 3.00% to 10.00%, preferably in the range of from 3.00 to
8.00%, more preferably in the range of from 4.00 to 7.00% C.sub.8,
in the range of from 3.00% to 10.00%, preferably in the range of
from 3.00 to 9.00%, more preferably in the range of from 5.00 to
8.00% C.sub.10, in the range of from 50.00% to 94.00%, preferably
in the range of from 55.00 to 90.00%, more preferably in the range
of from 60.00 to 85.00% C.sub.12, in the range of from 0 to 25.00%,
preferably in the range of from 5.00 to 20.00%, more preferably in
the range of from 10.00 to 20.00% C.sub.14, in the range of from 0
to 5.00%, preferably in the range of from 1.00 to 4.00%, more
preferably in the range of from 2.00 to 4.00% C.sub.16 and in the
range of from 0 to 1.00%, preferably in the range of from 0.01 to
0.90%, more preferably in the range of from 0.1 to 0.6% C.sub.18.
The acid-derived component determined by gas chromatography of an
ester refers to the chromatographic equivalent of an acid, which
would have been formed upon hydrolytic cleavage of that ester into
an alcohol and an acid.
[0109] In another preferred embodiment of the process according to
the invention, the at least one ester has a carbon chain
distribution of the acid-derived component determined by gas
chromatography (GC) according to ISO 5508 with carbon numbers in
the range of from 0 to 2.00%, preferably in the range of from 0 to
1.00%, more preferably in the range of from 0 to 0.5% C.sub.6, in
the range of from 0 to 10.00%, preferably in the range of from 1.00
to 7.00%, more preferably in the range of from 2.00 to 5.00%
C.sub.8, in the range of from 0 to 10.00%, preferably in the range
of from 1.00 to 7.00%, more preferably in the range of from 2.00 to
5.00% C.sub.10, in the range of from 50.00% to 95.00%, preferably
in the range of from 60.00 to 90.00%, more preferably in the range
of from 65.00 to 85.00% C.sub.12, in the range of from 5.00% to
35.00%, preferably in the range of from 8.00 to 30.00%, more
preferably in the range of from 10.00 to 25.00% C.sub.14, in the
range of from 0 to 5.00%, preferably in the range of from 1.00 to
4.00%, more preferably in the range of from 2.00 to 4.00% C.sub.16
and in the range of from 0 to 1.00%, preferably in the range of
from 0.01 to 0.90%, more preferably in the range of from 0.1 to
0.6% C.sub.18. The acid-derived component determined by gas
chromatography of an ester refers to the chromatographic equivalent
of an acid, which would have been formed upon hydrolytic cleavage
of that ester into an alcohol and an acid.
[0110] The invention also relates to a drilling composition
obtainable by a process according to the invention and having at
least one, preferably at least two, more preferably at least three
of the following properties: [0111] .gamma.1) a plastic viscosity
(PV) measured at 50.degree. C. according to the herein described
test method in the range from 15 to 75 mPas, preferably in a range
of from about 15 to about 60 mPas, more preferably in a range of
from about 15 to about 40 mPas, more preferably in a range of from
about 15 to about 30 mPas, yet more preferably in a range of from
about 15 to about 25 mPas; [0112] .gamma.2) a yield point (YP)
measured at 50.degree. C. according to the herein described test
method in the range from 5 to 45 lb/100 ft.sup.2 (about 2.4 to
about 21.6 Pa), preferably in a range of from about 5 to about 40
lb/100 ft.sup.2 (about 2.4 to about 20 Pa), preferably in a range
of from about 6 to about 25 lb/100 ft.sup.2, (about 2.9 to about 12
Pa), more preferably in a range of from about 8 to about 20 lb/100
ft.sup.2, (about 3.8 to about 10 Pa); [0113] .gamma.3) a gel
strength (GS) measured at 50.degree. C. according to the herein
described test method in the range from 4 to 25 lb/100 ft.sup.2
(1.9 to 12 Pa), preferably in a range of from about 4 to about 15
lb/100 ft.sup.2 (about 1.9 to about 7.2 Pa), preferably in a range
of from about 4 to about 10 lb/100 ft.sup.2, (about 1.9 to about
4.8 Pa), more preferably in a range of from about 4 to about 8
lb/100 ft.sup.2, (about 1.9 to about 3.8 Pa). [0114] .gamma.4)
viscosity values (Brookfield, RVT, determined according to ASTM
2983) at temperatures of 0.degree. C. to 5.degree. C. of not more
than 10 mPas, preferably of not more than 8 mPas and preferably in
the range of from about 2.0 to 5.0 mPas, more preferably in the
range of from about 2.5 to 4.5 mPas, yet more preferably in the
range of from about 2.7 to 4.0 mPas; [0115] .gamma.5) storage
stability at 20.degree. C. of at least two weeks, preferably of at
least one month, more preferably of at least three months, more
preferably of at least six months, more preferably of at least one
year, whereby the combinations of properties .gamma.1).gamma.2),
.gamma.1).gamma.3), .gamma.2).gamma.3),
.gamma.1).gamma.2).gamma.3), .gamma.1).gamma.2).gamma.3).gamma.4),
.gamma.1).gamma.2).gamma.3).gamma.5),
.gamma.1).gamma.2).gamma.3).gamma.4).gamma.5) are preferred,
whereby the property combinations .gamma.1).gamma.2).gamma.3),
.gamma.1).gamma.2).gamma.3).gamma.4),
.gamma.1).gamma.2).gamma.3).gamma.5), and
.gamma.1).gamma.2).gamma.3).gamma.4).gamma.5) are particularly
preferred.
[0116] The compositions according to the invention further
preferably have improved lubricity compared to previous drilling
compositions.
[0117] The invention also relates to the use of a composition
according to the invention or of a composition prepared according
to a process according to the invention as a drilling fluid.
[0118] The invention also relates to a drilling system comprising a
drill head, a drill string, a reservoir for drilling composition
and a drilling composition according to the invention or prepared
according to a process according to the invention.
[0119] The invention also relates to a process for making a
borehole comprising the steps: [0120] a1) providing a composition
according to the invention or a composition prepared according to a
process according to the invention, [0121] a2) drilling a hole in a
subterranean formation; [0122] a3) circulating the composition
provided in a1) at least partially in the hole at least partially
while drilling.
[0123] Suitable methods and equipment for drilling in step a2) are
well known to the person skilled in the art, as are methods and
means, for example using pumps, for circulating a drilling fluid
according to step a3). The drilling composition according to the
invention has been found to be particularly advantageous, owing to
the combination of properties such as environmental compatibility
and biodegradability, low toxicity, viscosity, rheological
properties, while providing good lubricity and allowing a good
penetration rate of the drill into the subterranean formation.
[0124] The invention also relates to a process for conveying
cuttings from a hole drilled in a subterranean formation,
preferably a process for conveying cuttings from a hole drilled in
a subterranean formation to the surface, comprising the steps:
[0125] b1) providing a composition according to the invention or a
composition prepared according to a process according to the
invention, [0126] b2) circulating the composition provided in b1)
at least partially in the hole.
[0127] It is preferred in the process for conveying cuttings from a
hole drilled in a subterranean formation that the composition is
circulated at least partially while drilling the hole. The
composition will generally be circulated by passing through the
drill assembly and out via the drill head, then passing back along
the drill hole towards the surface, conveying the cuttings in the
flow.
[0128] The invention also relates to a process for treatment of a
drill head comprising the steps: [0129] c1) providing a composition
according to the invention or a composition prepared according to a
process according to the invention, [0130] c2) circulating the
composition provided in c1) at least partially through the drill
head at least partially while the drill head is operated in a
subterranean formation.
[0131] In a preferred embodiment of the process for treatment of a
drill head, the treatment is at least one of cleaning, cooling and
lubrication. The drilling composition according to the invention
has been found to be particularly suitable for such treatment owing
to the combination of hydrophilic and hydrophobic components
comprised therein.
[0132] The invention also relates to a process for production of at
least one of oil and gas, comprising process steps: [0133] d1)
providing a composition according to the invention or a composition
prepared by a process according to the invention, [0134] d2)
drilling at least one hole in a subterranean formation while at
least partially circulating the composition provided in d1) at
least partially in the hole; [0135] d3) obtaining at least one of
oil and gas from the subterranean formation at least partially by
means of the at least one hole drilled in d1); [0136] d4)
optionally, subjecting the at least one of oil and gas to at least
one processing step selected from purifying, refining and
treating.
[0137] Steps d1) and d2) may be carried out by methods known to the
skilled person, as described above. Step d3) may also be carried
out by methods known to the skilled person, and may comprise stages
such as pumping, collecting, storing, and the like. Step d4) may be
carried out at the same location as the operation described by
steps d1) to d3), or it may be carried out at a different location.
If step d4) is carried out at a different location to steps d1) to
d3), in particular a different location to step d3), the process
will also comprise a step of transporting or conducting at least
one of oil and gas from the location of at least step d3) to the
location of step d4). The invention is now more closely illustrated
by means of examples, which are not intended to limit the scope of
the invention.
EXAMPLES
Test Methods
Plastic Viscosity (PV). Yield Point (YP). Gel Strength
[0138] Plastic viscosity, yield point and gel strength were
measured using a Fann.RTM. direct reading viscometer (Model 35 from
Fann Instrument Company, Houston, Tex., USA) according to the
method described in "Recommended Practice for Field Testing of
Oil-based Drilling Fluids", Upstream Segment, API (American
Petroleum Institute) recommended practice 13B-2, Fourth Edition,
March 2005, section 6.3, p. 8-10.
Electrical Stability
[0139] Electrical stability was measured using a Fann.RTM.
electrical-stability tester (Model 23D from Fann Instrument
Company, Houston, Tex., USA) according to the method described in
"Recommended Practice for Field Testing of Oil-based Drilling
Fluids", Upstream Segment, API (American Petroleum Institute)
recommended practice 13B-2, Fourth Edition, March 2005, section 10,
p. 22-24.
Example 1
[0140] An oil phase was prepared by combining 249.4 ml of
PureDrill.RTM. HT-40 (Petro-Canada, Canada) with 13.1 ml of a
2-ethylhexyl ester of C.sub.8-C.sub.14 fatty acids obtainable from
Cognis Oleochemicals GmbH, Dusseldorf, Germany, under the trade
name OMC 586. This oil phase was then combined with 4.2 g of EZ
MUL.RTM. NT (from the company Halliburton (Baroid), Texas, USA),
87.5 ml of a 25% (by weight) aqueous calcium chloride solution, 3.5
g of DURATONE.RTM. HT (from the company Halliburton (Baroid),
Texas, USA), 3.5 g of GELTONE.RTM. II (from the company Halliburton
(Baroid), Texas, USA), Texas, USA), and 280 g of barite.
Rheological parameters were determined at 50.degree. C. as shown in
Table 1 under the heading "before ageing".
[0141] The mixture was aged by treatment in an autoclave in a
Baroid roller oven model 70040 at 121.degree. C. (250.degree. F.)
for 16 hours according to the method described in "Recommended
Practice for Laboratory Testing of Drilling Fluids", API (American
Petroleum Institute) Recommended practice 131, Seventh Edition,
February 2004/ISO 10416:2002 (modified), section 21, p. 66-73. The
electrical stability and rheological parameters were then
determined at 50.degree. C. as shown in Table 1 under the heading
"after ageing".
TABLE-US-00001 TABLE 1 Before ageing After ageing Electrical
stability (V) n.d. 490 Measured values 600 rpm 49 50 300 rpm 30 31
200 rpm 22 23 100 rpm 14 15 6 rpm 5 6 3 rpm 4 5 Plastic viscosity
(cP) 19 19 Yield point (lbf/100 ft.sup.2) 11 12 Gel strength 10
s/10 min 5/6 5/6 (lbf/100 ft.sup.2)
[0142] The same procedure was followed as that for Example 1, with
the difference that 26.2 ml of OMC 586 was used.
Example 3
[0143] To a composition consisting of 249.4 ml of PureDrill.RTM.
HT-40 (Petro-Canada, Calgary, Canada), 4.2 g of EZ MUL.RTM. NT
(from the company Halliburton (Baroid Fluid Services), Texas, USA),
87.5 ml of a 25% (by weight) aqueous calcium chloride solution, 3.5
g of DURAT ONE.RTM. HT (from the company Halliburton (Baroid Fluid
Services), Texas, USA), 3.5 g of GELTONE.RTM. II (from the company
Halliburton (Baroid Fluid Services), Texas, USA), Texas, USA), and
280 g of barite, was added 13.1 ml of OMC 586 (Cognis Oleochemicals
GmbH, Dusseldorf, Germany).
Example 4
[0144] The same procedure was followed as that for Example 3, with
the difference that 26.2 ml of OMC 586 was added.
Example 5
[0145] The procedure of Example 1 was followed, with the difference
that 1.5 g of the structure building agent GELTONE II was used. The
yield point of the product before ageing by heat rolling as
described for Example 1 was 8 lb/100 ft.sup.2. The yield point of
the product after ageing by hot rolling as described for Example 1
was 10 lb/100 ft.sup.2.
Example 6
Rate of Penetration (ROP)
[0146] Boreholes were drilled using the compositions of Examples 1
to 4 as drilling fluid, and the respective rate of penetration
measured as distance per hour. The rock formation which was drilled
into, the drilling equipment, weight on bit, and rotation speed
(rpm), were maintained effectively constant for each test, so that
the only variable was the drilling fluid. In this way, comparative
data were obtained for the different compositions. The results are
shown in Table 2.
TABLE-US-00002 TABLE 2 Example Penetration rate test result 1 very
good 2 good 3 satisfactory 4 satisfactory
[0147] Drilling into subterranean formations, whether onshore or
offshore, is accompanied by substantial costs. It is thus
advantageous to reduce overall drilling time. Penetration rate,
while not being the sole factor determining overall drilling time,
provides a considerable contribution thereto. Faster penetration
rates are therefore desirable. The above results show that the
composition according to the invention, and in particular the use
of the above-described esters in combination with a saturated
hydrocarbon (paraffin) as described above, results in improved
penetration rates when drilling, thereby contributing to reducing
overall drilling time.
* * * * *