NEW WORK GROUP
Revision of Starch Specifications in API 13 A
Saleh Al-Ammari
Saudi Aramco
June 29th, 2010
What is Starch?
Starch or amylum is a carbohydrate consisting of a large
number of glucose units joined together by glycosidic bonds.
This polysaccharide is produced by all green plants as an
energy store. It is contained in potatoes, wheat, maize (corn),
rice, and cassava.
Drilling Fluid Materials
API SPECIFICATION 13A
SECTION 11
STARCH
11.1 Description
a. Drilling grade starch can be manufactured from several kinds of
native starches. The starch should be made cold water hydratable
(pregelatinized) and may be treated further in such a way that it is
suitable for use as a filtrate reducing agent in water-base drilling
fluids.
b. Drilling grade starch should be free-flowing and free from lumps.
Drilling grade starch shall be deemed to meet this specification if a
composite sample representing no more than one day's production
conforms to the physical requirements of Table 11.1, represents the
product produced, and is controlled by the manufacturer.
Drilling Fluid Materials
API SPECIFICATION 13A
Table 11.1 - STARCH PHYSICAL REQUIREMENTS
Requirement
Specification
Suspension Properties:
Viscometer Dial Reading at 600 rpm
in 40 g/L Salt Water
in Saturated Salt Water
18, maximum
20, maximum
Filtrate Volume
in 40 g/L Salt Water
in Saturated Salt Water
10 cm3, maximum
10 cm3, maximum
Residue Greater than
2000 micrometers
No residue
Example 1 – Clay free mud
Formulation and order of addition:
(one barrel)
Average Fluid Properties:
Water
bbl
:
0.97
Density
lb/ft3
:
66
XC-Polymer
lb
:
1.0
PV
cp
:
10
Starch
lb
:
4.0
YP
lb/100ft2
:
14
Lime
lb
:
0.5
10 sec gel lb/100ft2
:
3
CaCO3 “fine” lb
:
32.0
10 min gel lb/100ft2
:
6
Filtrate
:
10
:
9.5
pH
ml/30min
Example 1 – Clay free mud
Formulation and order of addition:
(one barrel)
Average Fluid Properties:
Water
bbl
:
0.97
Density
lb/ft3
:
66
XC-Polymer
lb
:
1.0
PV
cp
:
10
Starch
lb
:
4.0
YP
lb/100ft2
:
14
Lime
lb
:
0.5
10 sec gel lb/100ft2
:
3
CaCO3 “fine” lb
:
32.0
10 min gel lb/100ft2
:
6
Filtrate
:
NC
:
9.5
pH
ml/30min
Example 2 – Bentonite mud
Formulation and order of addition:
(one barrel)
Average Fluid Properties:
Water
bbl
: 0.92
Density
pcf
:
80
Bentonite
lb
: 10.0
PV
cp
:
18
Lime
lb
: 0.5
YP
lb/100ft2
:
16
Starch
lb
: 4.0
Gels
lb/100ft2
:
3/6
Barite
lb
: 122
Filtrate
ml/30 min
:
8
pH
: 9 - 10
Example 2 – Bentonite mud
Formulation and order of addition:
(one barrel)
Average Fluid Properties:
Water
bbl
: 0.92
Density
pcf
:
80
Bentonite
lb
: 10.0
PV
cp
:
18
Lime
lb
: 0.5
YP
lb/100ft2
:
16
Starch
lb
: 10.0
Gels
lb/100ft2
:
3/6
Barite
lb
: 122
Filtrate
ml/30 min
:
8
pH
: 9 - 10
Example 3 – CaCl2 mud
Formulation and order of addition:
(one barrel)
Average Fluid Properties:
Water
bbl
:
0.67
Density
lb/ft3
:
89
Defaomer
gal
:
0.01
PV
cp
:
16
XC-Polymer
lb
:
1.0
YP
lb/100ft2
:
20
Starch
lb
:
6.0
10 sec gel
lb/100ft2
:
4
Lime
lb
:
0.5
10 min gel
lb/100ft2
:
8
CaCl2
lb
245
Filtrate
ml/30min
:
6
22.0
pH
:
9.5
:
357k
CaCO3 “fine” lb
:
Chloride
mg/l
Example 3 – CaCl2 mud
Formulation and order of addition:
(one barrel)
Average Fluid Properties:
Water
bbl
:
0.67
Density
lb/ft3
:
89
Defaomer
gal
:
0.01
PV
cp
:
16
XC-Polymer
lb
:
1.0
YP
lb/100ft2
:
20
Starch
lb
:
12.0
10 sec gel
lb/100ft2
:
4
Lime
lb
:
0.5
10 min gel
lb/100ft2
:
8
CaCl2
lb
245
Filtrate
ml/30min
:
6
22.0
pH
:
9.5
:
357k
CaCO3 “fine” lb
:
Chloride
mg/l
Conclusions
1. Increase in concentration
2. Thermal degradation at lower temperature
3. Use of expensive fluids loss additives
4. Encounter more operational problems
5. Face interrupted inventories
6. Difficulty in controlling the quality
7. Ineffective API monogram
Suggestions
1. Improve the suspension properties
2. Specify more particles size distributions
3. Include temperature limitation
4. Introduce classifications
5. Develop analytical methods
6. Standardize nomenclature