NEW WORK GROUP

Revision of Starch Specifications in API 13 A

Saleh Al-Ammari

Saudi Aramco

June 29th, 2010

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 anenergy store. It is contained in potatoes, wheat, maize (corn), rice, and cassava.

What is Starch?

Drilling Fluid MaterialsAPI SPECIFICATION 13A

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 drillingfluids.

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 theproduct produced, and is controlled by the manufacturer.

SECTION 11STARCH

Table 11.1 - STARCH PHYSICAL REQUIREMENTS

Requirement Specification

Suspension Properties:

Viscometer Dial Reading at 600 rpmin 40 g/L Salt Water 18, maximumin Saturated Salt Water 20, maximum

Filtrate Volume

in 40 g/L Salt Water 10 cm3, maximumin Saturated Salt Water 10 cm3, maximum

Residue Greater than2000 micrometers No residue

Drilling Fluid MaterialsAPI SPECIFICATION 13A

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 ml/30min : 10

pH : 9.5

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 ml/30min : NC

pH : 9.5

Example 1 – Clay free 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 2 – Bentonite 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

CaCO3 “fine” lb : 22.0 pH : 9.5

Chloride mg/lmg/l : 357k

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

CaCO3 “fine” lb : 22.0 pH : 9.5

Chloride mg/lmg/l : 357k

Example 3 – CaCl2 mud

1. Increase in concentration2. Thermal degradation at lower temperature3. Use of expensive fluids loss additives4. Encounter more operational problems5. Face interrupted inventories6. Difficulty in controlling the quality7. Ineffective API monogram

Conclusions

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

Suggestions