FLUIDE DE FORAGE ENVIRONNEMENTAL

ENVIRONMENTAL DRILLING FLUID

Abrégé anglais

An environmentally friendly water-based drilling fluid system for hydrocarbon
wellbore use.
Acrylamide and dirnethylaminoethyl acrylate (poly-DMAEA) co-polymers are used
to
stabilize reactive shale and provide viscosity to the drilling fluid. Poly-
DMAEA is used in
conjunction with fluid loss polymers, viscosifying polymers, pH control and a
simple amine
salt.

Revendications

What is claimed is:
1. A drilling fluid having effective rheology and fluid loss control
properties comprising:
water as a continuous phase; and a polyacrylamide copolymer comprising
partially
hydrolyzed polyacrylamide and dimethylaminoethyl acrylate having a cationic
charge density
of from about 25% to about 35%, and a concentration from about 0.1wt% to about
1.2wt% of
the drilling fluid.
2. The drilling fluid of claim 1 further comprising fluid loss control polymer
and
viscosifying polymer.
3. The fluid of claim 2 further comprising a monovalent amine salt (non-
chloride) in an
amount sufficient to increase the shale stabilization aspects of the fluid.
4. The fluid of claim 3 in which the monovalent amine salt is choline
carbonate.
5. The fluid of claim 4 in which the choline carbonate is from about 0.1 wt %
to about 1
wt % of the drilling fluid.
6. The fluid of claim 1 wherein said polyacrylamide copolymer has a molecular
weight
of from about 1 million to about 1.5 million mole weight.
7. The fluid of claim 2 wherein said polyacrylamide copolymer has a molecular
weight
of from about 1 million to about 1.5 million mole weight.
8. A drilling fluid comprising: water as a continuous phase; fluid loss
polymer;
viscosifying polymer; and a polyacrylamide copolymer having a cationic charge
density of
from about 25% to about 35% %, and a concentration from about 0.1wt% to about
1.2wt% of
the drilling fluid and having the following general structure:




8
Image
wherein R¹ are selected from the group consisting of amine groups, amide
groups, cyanide groups, and imide groups.
R² is selected from the group consisting of an alkyl group and a cationic
hetroatom group and n and m is at least 1.
9. The fluid of claim 8 wherein said polyacrylamide copolymer has a molecular
weight
of from about 1 million to about 1.5 million mole weight.

Description

CA 02457698 2003-12-23
ENVIRONMENTAL DRILLING FLUID
BACKGROUND OF THE INVENTION
O1 The described invention relates to drilling fluid systems. A discussion of
the
properties of drilling fluid systems and a general background of the
technological issues
relating to drilling fluid systems is to be found in US patent no. 6,355,600.
SUMMARY OF THE INVENTION
02 There is provided according to an aspect of the invention an
environmentally friendly
water-based drilling fluid system for hydrocarbon wellbore use. Anionic
acrylamide and
cationic dimethylaminoethyl acrylate (poly-DMAEA) co-polymers are used to
stabilize
reactive shale and provide viscosity to the drilling fluid. The co-polymer has
a cationic
charge density of from about 25% to about 35%, and a concentration from about
O.lwt% to
about l.2wt% of the drilling fluid. Poly-DMAEA is used in conjunction with
fluid loss
polymers, viscosifying polymers, pH control and a simple amine salt.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION
03 An exemplary mud system according to the invention incorporates an anionic
chemical base and a cationic chemical base in the same fluid. This system
carries out
functions that reflect both types of ions. Anionic polymers provide viscosity
(Xanthan Gum)
and fluid loss (PAC Super low) and cationic polymers (poly-DMAEA) provide
increased
viscosity and shale inhibition. The invention is in the combination of the two
ionic chemicals
such that the anions and the cations do not react with each other. The mud
system is reactive
towards the wellbore but not to itself.
04 In an exemplary embodiment of the invention, water is a continuous phase
and in the
water there is a quantity of a polyacrylamide copolymer comprising partially
hydrolyzed
polyacrylamide and dimethylaminoethyl acrylate, having a cationic charge
density of from
about 25% to about 35%%, and a concentration from about O.lwt% to about l.2wt%
of the


CA 02457698 2003-12-23
2
drilling fluid. The resulting fluid provides effective pH and fluid loss
protection. An
exemplary poly-DMAEA is CP 944 available from Hychem of Calgary, Alberta,
Canada.
OS The poly-DMAEA copolymer has the following general structure:
--ECH2-C ~--ECH2-CH~-
O n O~ m
R1 O~
R2
wherein R_l are selected from the group consisting of amine groups, amide
groups, cyanide groups, and imide groups,
R₂ is selected from the group consisting of an alkyl group and a cationic
hetroatom group and n and m is at least 1.
06 An amount of a monovalent amine salt (non-chloride), for example choline
carbonate
in an amount from about 0.1 wt % to about 1 wt % of the drilling fluid., may
be added to the
drilling fluid to increase the shale stabilization aspects of the fluid. The
polyacrylamide
copolymer preferably has a molecular weight of from about 1 million to about
1.5 million
mole weight.
07 The poly-DMAEA is used in conjunction with fluid loss polymers,
viscosifying
polymers, pH control and a simple amine salt, typical examples of which are
included in the
examples that follow. The amount of fluid loss polymer, viscosifying polymer,
pH and
amine salt are selected in accordance with known principles of drilling fluid
formulation to
provide a desired amount of fluid loss control, viscosity, pH (basic) and
shale stabilization.
The shale stabilizer provides the known function of controlling clay hydration
and
disintegration during drilling. The shale stabilizer inhibits dispersion and
wetting, and thus
swelling tendencies of clay particles.
08 The amount of amine/viscosifier (poly-DMAEA) should be at least lkg/m3,
preferably
3.5-4.5 kg/m3, and preferably not more than 12 kg/m3 where the volume is the
volume of the
mud excluding the amine/viscosifier. The xanthum gum or an equivalent
thixotrophic
enhancer is present to ensure that the viscosity is adequate.


CA 02457698 2003-12-23
3
09 In the examples that follow, the properties are from API standards. The
indication
600, 300 etc is an rpm test, n indicates power law test, PV is the plastic
viscosity, YP is the
yield point, AV is the apparent viscosity, Gel 0/10 is a gel strength test,
filtrate shows the
fluid loss, microtox is an Alberta Environment test of bacterial sensitivity
and Pierre Shale
Hot Roll is a test of shale rolled in a cylinder with the fluid and the
remaining intact rock at
the end of the test is measured.
Examples
Example #1 Mud properties before and after Hot Roll and 150°F and
100°C. The
chemicals were mixed according to the table and analyzed at Canamara's United
lab, Calgary
Alberta.
Function Product Concentration Charge
Amine CT 300 11/m3 cationic
FL Drispac SL 2.0 kg/m3 anionic
Viscosifier Xanvis 2.5 kg/m3 anionic
PH Caustic 0.2 kg/m3 salt
Amine/Viscosifier 944 4.0 kg/m3 cationic
drilled cuttings 30 kg/m3
Standard test 150oF116 100oC/16
hrs hr


Properties Before Hot After Before After
Roll HR HR HR


600 45 42.5 35 39


300 33 31 25 27


200 27.5 26 20 21.5


100 20 19 14.5 14.5


6 6.5 6 5 2.5


3 5 4.5 4 1.5


N 0.45 0.45 0.44


PV 12 11.5 10 12


YP 10.5 9.8 7.5 7.5


AV 22.5 21.3 17.5 19.5


Gel 0/10 313.5 2.5/3.0 2.5/3.51.0/1.3


Filtrate 14.2 18.9 20.8 14.6


PH 7.3 6.8 10.3 6.8


Pf/Mf 0.00/0.13 0.00/0.150.18/0.70.00/0.58


Ca++ 60 112 188 112


CI- 900 530 400 370


Pierre Shale Hot Roll 91.40%
Microtox pass


CA 02457698 2003-12-23
4
11 Example #2 Mud Properties with 3% salt and saturated gypsum contamination.
The
chemicals were mixed according to the table and analyzed at Canamara's United
lab, Calgary
Alberta.
Function Product Concentration Charge
Amine CT 300 1 Um3 cationic


FL Drispac 2.0 kglm3anionic
SL


ViscosifierXanvis 2.5 kglm3anionic


Ph Caustic 0.2 kglm3salt


AmineNiscosifier944 4.0 kglm3cationic


Drilled 30 kglm3
cuttings


Sat


PropertiesNormal 3% NaCIGypsum


600 41.5 39.5 38


300 30.5 28.5 27.5


200 25.5 23 22.5


100 18.5 17 16.5


6 8 5.5 5.5


3 5 4.5 4


n 0.44 0.47 0.47


PV 11 11 10.5


YP 9.8 8.8 8.5


AV 20.8 19.8 19


Ge10110 3.013.5 314 2.8/12.5


Filtrate14 14.7 12.1


pH 8.9 8 10.8


PfIMf 0.0010.180.0010.170.2310.43


CI- 510 19900 530


Ca++ 108 200 570




CA 02457698 2003-12-23
t 2 Example
#3 Mud
Properties
with 0.3,
0.7 and
1.4% lime
contamination
(cement


contamination).The chemicals
were mixed according
to the table
and analyzed
at


Canamara'sted lab, Calgary
Uni Alberta.


Function Product ConcentrationCharge
~ ~


Amine CT 300 111m3 cationic


FL Drispac SL 2.0 anionic
kglm3


ViscosifierXanvis 2.5 kglm3 anionic


Ph Caustic 0.2 kglm3salt


AmineNiscosifier944 4.0 kglm3 cationic


Drilled 30 kglm3
cuttings


Lime 3.517.0114 kglm3


Total
Lim~ lime Lime


PropertiesNormal 3.5 kg/m37 kglm314
kglm3


600 45 46 31.5 26


300 33 31 21 17.5


200 27.5 26 17.5 13.5


100 20 19 12.5 9


6 6.5 7 5 4


3 5 5.5 4.5 3


n 0.45 0.57 0.58 0.57


PV 12 15 10.5 8.5


YP 10.5 8 5.3 4.5


AV 22.5 23 15.8 13


Gel0110 313.5 2.513.5 2.3/8.51.512.0


Filtrate 14.2 19.2 27.3 38.4


pH 7.3 >13 >13 >13


Pf/Mf 0.0010.131.47/1.871.68/2.222.0112.59




CA 02457698 2003-12-23
6
13 Example #4 Pierre shale experiments. Testing was done to determine the
inhibitive
properties of various chemicals. Tests were done at Canamara.'s United lab,
Calgary Alberta
according to the procedure outlined in US pat# 5403820. The materials listed
under the name
column are various viscosifiers. CP 944 is the product formulated according to
the invention.



Retained Concentration


corrected Name by Wt
Manufacturer


6.5 Water 100%


74 Hychem 247 RD 0.40%


83.5 Hychem CP 944 0.26%


49 Ciba 60RD 0.3090


72.3 Hychem 757 0.80%


58.5 CanamaraK2 0.80%


53.3 CanamaraTMAC 0.80%


108.8 Hychem CP 944 0.40%


89.2 Hychem CP 944~T'MAC
0.26%/0.8%


92.6 Hychem CP 944/K20.26%/0.8%


75.6 CanamaraK2 1.600


71.6 CanamaraTMAC 1.60~


58.7 CanamaraCT 300 0.80%


57.6 CanamaraCT 300 0.80%


96.6 Diesel 100%


14 Immaterial modifications may be made to the embodiment disclosed here
without
departing from the invention.