Note: Descriptions are shown in the official language in which they were submitted.
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 Rl 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.
