Themark Corporation

Choline Chloridein Clay and Shale Stabilizerfor the Oil and Natural Gas Industry

Phone: 412-551-9893 • info@themarkcorp.comthemarkcorp.com

The information in this bulletin is believed to be accurate, but all recommendations are made without warranty, since the conditions of use are beyond the manufacturer’s control. The listed properties are illustrative only, and not product specifications. The manufacturer

disclaims any liability in connection with the use of the information, and does not warrant against infringement by reason of the use of any of its products in combination with other materials or in any process.

Choline chloride (HETMAC), CAS number: 67-48-1, (chemical name: 2-hydroxy-N,N,N-trimethylethanaminium chloride) which is widely used as a nutritional additive in animal feeds, now is a very popular commercial clay stabilizer and shale inhibitor in drilling fluid (or called liquid drilling mud).

1. Why choline chloride can be used as clay and shale stabilizer

1.1 Higher efficiencyWith the structure of quaternized amines, a typical “small amines”, choline chloride has the same action as some traditional clay and shale stabilizer (e.g. KCl, TMAC), but with higher efficiency. Figure 1 shows that at the same level of content, choline chloride provides much faster filtration indicating less swelling of the clay. Besides choline chloride can be used directly at the work site, this ready-to-use availability eliminates time for pre-mixing and any saltwater disposal costs.

1.2 Good compatibilityIt is known to all, there are many kinds of chemicals in the hydraulic fracturing process, the number is as high as 78 according to the report. Choline chloride has a good compatibility with brine solutions, calcium chloride (CaCl2), KCl solutions of hydraulic fracturing fluids, cross-linkers and breakers.

1.3 More safetyExcept the higher efficiency, the safety of choline chloride is more attractive. The pollution to groundwater caused by chemicals in drilling fluid is now the most controversial topic of the Hydraulic Fracturing method in shale gas industry in USA. The low toxicity of choline chloride is exciting.

Choline chloride, whose primary non-oilfield use is in animal feeds as an important nutritional additive, normally is considered as a kind of vitamin B4. Figure 2 shows the toxicological information of choline chloride and some other chemicals. In addition, the present of chloride ions will pollute surface water through the soil, and the chloride ions of the choline chloride are almost reduced up to 75% vs KCl, so it can be confirmed that choline chloride itself is more safety than all other commercial clay and shale stabilizers.

Only some chemicals residual which is corrosive in nature should be considered when products are choosed. The most important one is trimethylamine (TMA), which is one of the most important raw materials when choline chloride synthesised. Science research shows that if TMA residual higher than 300ppm, it can cause toxicity. Some manufac-turers can not control TMA residual well with their poor manufacturing process, which cause their choline chloride liquid with a strong fish-like odor and light yellow color. Themark Corporation as the leading manufacturer of choline chloride can promise choline chloride liquid with a TMA residual lower than 200ppm.

Figure 2: Toxilogical information

Name Toxicological information

LD50 - 2600 mg/kg oral (rat) LD50 - 552 mg/kg intraperitoneal (mouse)

NH4Cl LD50 - 1650 mg/kg oral (rat)

LD50 - 125 mg/kg oral (rat) LD50 - 25 mg/kg intraperitoneal (mouse) LD50 - 40 mg/kg subcutaneous (rat) LDLO - 1500 mg/kg (rat) LDLO - 6 mg/kg subcutaneous (rabbit) LD50 - 6 mg/kg subcutaneous (frog)

LD50 - 3400 mg/kg oral (rat) LD50 - 450 mg/kg intraperitoneal (rat) LDLO - 735 mg/kg subcutaneous (mouse) LD50 - 53 mg/kg intravenous (mouse) LDLO - 5 mg/kg intravenous (dog) LDLO - 25 mg/kg intravenous (cat) LDLO - 1100 µg/kg intravenous (rabbit) LDLO - 1000 mg/kg subcutaneous (rabbit) LDLO - 1500 mg/kg (frog)

LD50: Lethal Dose for 50% LDLO: Lethal Dose Low

1.4 Readily biodegradableCholine chloride is also readily biodegradable according to the Organization of Economic Co-operation and Develop-ment (OECD-criteria). MITI-test shows 93% choline chloride occur biodegradation within 14 days. Another method forbiodegradation is by measuring the biochemical oxygen demand (BOD), and a substance is readily biodegradable when 60% biodegradation occurs within 28 days. This result is confirmed by a BOD test performed according to DIN 38409 part 43(German national biodegradation test) where a 75% biodegradation is obtained.

1.5 Better workabilityCholine chloride has a special advantage, it can keep a high efficiency when used in drilling fluid with high NaCl concen-tration. Due to this feature, choline chloride has an unmatched advantage when used in drilling fluid of offshore oilfield. Choline chloride now already is the first choice of clay and shale stabilizer in seawater based drilling fluid. Besides, as highly soluble material, Choline chloride with an activity of 75% does not suffer from crystallization issues when used in a brine solution in cold climates, however, KCl has a limiting 24% activity and can crystallize in cold climates, which limit its application to a certain degree.

2. What is clay stabilizer?

2.1 Shale and/or clay swellingIn oil and gas drilling and hydraulic fracturing, the shale and/or clay may swell in the presence of water, which may cause a series majority of problems including: wellbore instability, cuttings disintegration, bit balling, fines migra-tion, all these issues can result in higher drilling costs, slower well productivity and even destroy the wellbore. Clay stabilizer(also called anti-swelling agents) could reduce and prevent clay swelling during different operations including drilling mud, water injection, acidizing, fracturing, enhanced oil recovery, it is widely used and plays animportant role in the oil and natural gas exploration.

2.2 Characteristic and mechanismIn recent years, clay stabilizer and shale inhibitor have been studied and developed around the world. Generally they have the same structures of quaternized amines besides KCl (potassium chloride), such as NH4Cl (ammonium chloride, AC), [(CH3)4N]Cl (Tetramethylammonium chloride, TMAC), some polymeric amines, etc. “Small cations”(e.g. AC, TMAC) and KCl usually function through ion exchange, they enter into the crystal lattice of clay, where the cations (NH4+, (CH3)4N+, K+) of clay stabilizer replace the Na+ on the surface of clay to prevent swelling. However, the polymeric amines as stabilizer just adsorb on the surface of clay or shale, they have distinct mechanism of stabilizer from the “small cations” and KCl.

2.3 IntroductionSome examples for the commercial clay and shale stabilizer are introduced as follows:

KCl has been the primary choice for the temporary clay stabilizer, but it can be incompatible with other materials, it is only effective in the salt-containing drilling fluid/mud, once fresh water are added, this balance will break and the clay will well once again. In addition, the use of KCL in drilling carries environmental concerns due to its high content of Cl-.

TMAC can replace KCl as the clay and shale stabilizer, especially in the fracturing fluid， the quantity of TMAC is just the 1/10 of KCl, TMAC provides temporary protection because of the NH4+ single cation. TMAC is very cheap and suitable for the short-time operation, the main draw-back is its toxicity and ordor, although it can be used in the oilfields, because of its strong adsorption on the clay, which will reduce the content of that in the drilling fluid.About all, the traditional clay and shale stabilizer have a limited application due to temperature and pH stability, strong odors, bad compatibility or lower level of inhibition,especially they are much more toxic than HETMAC in both onshore and offshore as drilling fluid additives. Figure 3 summarizes the chemistry, functionality and shortcomings of several clay stabilizers.

Figure 1: Filtration time test of KCI and Choline Chloride

0

10

20

30

40

50

60

0 2.5 5 10 15 20 30

Time, mins

Filtr

ate

volu

me,

mls

0.76% KCI0.76% Choline Chloride

Choline chloride (HETMAC), CAS number: 67-48-1, (chemical name: 2-hydroxy-N,N,N-trimethylethanaminium chloride) which is widely used as a nutritional additive in animal feeds, now is a very popular commercial clay stabilizer and shale inhibitor in drilling fluid (or called liquid drilling mud).

1. Why choline chloride can be used as clay and shale stabilizer

1.1 Higher efficiencyWith the structure of quaternized amines, a typical “small amines”, choline chloride has the same action as some traditional clay and shale stabilizer (e.g. KCl, TMAC), but with higher efficiency. Figure 1 shows that at the same level of content, choline chloride provides much faster filtration indicating less swelling of the clay. Besides choline chloride can be used directly at the work site, this ready-to-use availability eliminates time for pre-mixing and any saltwater disposal costs.

1.2 Good compatibilityIt is known to all, there are many kinds of chemicals in the hydraulic fracturing process, the number is as high as 78 according to the report. Choline chloride has a good compatibility with brine solutions, calcium chloride (CaCl2), KCl solutions of hydraulic fracturing fluids, cross-linkers and breakers.

1.3 More safetyExcept the higher efficiency, the safety of choline chloride is more attractive. The pollution to groundwater caused by chemicals in drilling fluid is now the most controversial topic of the Hydraulic Fracturing method in shale gas industry in USA. The low toxicity of choline chloride is exciting.

Choline chloride, whose primary non-oilfield use is in animal feeds as an important nutritional additive, normally is considered as a kind of vitamin B4. Figure 2 shows the toxicological information of choline chloride and some other chemicals. In addition, the present of chloride ions will pollute surface water through the soil, and the chloride ions of the choline chloride are almost reduced up to 75% vs KCl, so it can be confirmed that choline chloride itself is more safety than all other commercial clay and shale stabilizers.

Only some chemicals residual which is corrosive in nature should be considered when products are choosed. The most important one is trimethylamine (TMA), which is one of the most important raw materials when choline chloride synthesised. Science research shows that if TMA residual higher than 300ppm, it can cause toxicity. Some manufac-turers can not control TMA residual well with their poor manufacturing process, which cause their choline chloride liquid with a strong fish-like odor and light yellow color. Themark Corporation as the leading manufacturer of choline chloride can promise choline chloride liquid with a TMA residual lower than 200ppm.

Figure 2: Toxilogical information

Name Toxicological information

LD50 - 2600 mg/kg oral (rat) LD50 - 552 mg/kg intraperitoneal (mouse)

NH4Cl LD50 - 1650 mg/kg oral (rat)

LD50 - 125 mg/kg oral (rat) LD50 - 25 mg/kg intraperitoneal (mouse) LD50 - 40 mg/kg subcutaneous (rat) LDLO - 1500 mg/kg (rat) LDLO - 6 mg/kg subcutaneous (rabbit) LD50 - 6 mg/kg subcutaneous (frog)

LD50 - 3400 mg/kg oral (rat) LD50 - 450 mg/kg intraperitoneal (rat) LDLO - 735 mg/kg subcutaneous (mouse) LD50 - 53 mg/kg intravenous (mouse) LDLO - 5 mg/kg intravenous (dog) LDLO - 25 mg/kg intravenous (cat) LDLO - 1100 µg/kg intravenous (rabbit) LDLO - 1000 mg/kg subcutaneous (rabbit) LDLO - 1500 mg/kg (frog)

LD50: Lethal Dose for 50% LDLO: Lethal Dose Low

1.4 Readily biodegradableCholine chloride is also readily biodegradable according to the Organization of Economic Co-operation and Develop-ment (OECD-criteria). MITI-test shows 93% choline chloride occur biodegradation within 14 days. Another method forbiodegradation is by measuring the biochemical oxygen demand (BOD), and a substance is readily biodegradable when 60% biodegradation occurs within 28 days. This result is confirmed by a BOD test performed according to DIN 38409 part 43(German national biodegradation test) where a 75% biodegradation is obtained.

1.5 Better workabilityCholine chloride has a special advantage, it can keep a high efficiency when used in drilling fluid with high NaCl concen-tration. Due to this feature, choline chloride has an unmatched advantage when used in drilling fluid of offshore oilfield. Choline chloride now already is the first choice of clay and shale stabilizer in seawater based drilling fluid. Besides, as highly soluble material, Choline chloride with an activity of 75% does not suffer from crystallization issues when used in a brine solution in cold climates, however, KCl has a limiting 24% activity and can crystallize in cold climates, which limit its application to a certain degree.

2. What is clay stabilizer?

2.1 Shale and/or clay swellingIn oil and gas drilling and hydraulic fracturing, the shale and/or clay may swell in the presence of water, which may cause a series majority of problems including: wellbore instability, cuttings disintegration, bit balling, fines migra-tion, all these issues can result in higher drilling costs, slower well productivity and even destroy the wellbore. Clay stabilizer(also called anti-swelling agents) could reduce and prevent clay swelling during different operations including drilling mud, water injection, acidizing, fracturing, enhanced oil recovery, it is widely used and plays animportant role in the oil and natural gas exploration.

2.2 Characteristic and mechanismIn recent years, clay stabilizer and shale inhibitor have been studied and developed around the world. Generally they have the same structures of quaternized amines besides KCl (potassium chloride), such as NH4Cl (ammonium chloride, AC), [(CH3)4N]Cl (Tetramethylammonium chloride, TMAC), some polymeric amines, etc. “Small cations”(e.g. AC, TMAC) and KCl usually function through ion exchange, they enter into the crystal lattice of clay, where the cations (NH4+, (CH3)4N+, K+) of clay stabilizer replace the Na+ on the surface of clay to prevent swelling. However, the polymeric amines as stabilizer just adsorb on the surface of clay or shale, they have distinct mechanism of stabilizer from the “small cations” and KCl.

2.3 IntroductionSome examples for the commercial clay and shale stabilizer are introduced as follows:

KCl has been the primary choice for the temporary clay stabilizer, but it can be incompatible with other materials, it is only effective in the salt-containing drilling fluid/mud, once fresh water are added, this balance will break and the clay will well once again. In addition, the use of KCL in drilling carries environmental concerns due to its high content of Cl-.

TMAC can replace KCl as the clay and shale stabilizer, especially in the fracturing fluid， the quantity of TMAC is just the 1/10 of KCl, TMAC provides temporary protection because of the NH4+ single cation. TMAC is very cheap and suitable for the short-time operation, the main draw-back is its toxicity and ordor, although it can be used in the oilfields, because of its strong adsorption on the clay, which will reduce the content of that in the drilling fluid.About all, the traditional clay and shale stabilizer have a limited application due to temperature and pH stability, strong odors, bad compatibility or lower level of inhibition,especially they are much more toxic than HETMAC in both onshore and offshore as drilling fluid additives. Figure 3 summarizes the chemistry, functionality and shortcomings of several clay stabilizers.

KCl

TMAC

Choline Chloride

The information in this bulletin is believed to be accurate, but all recommendations are made without warranty, since the conditions of use are beyond the manufacturer’s control. The listed properties are illustrative only, and not product specifications. The manufacturer

disclaims any liability in connection with the use of the information, and does not warrant against infringement by reason of the use of any of its products in combination with other materials or in any process.

Name

Potassium Chloride (KCl)

Ammonium Chloride (AC)

Tetramethylammo- nium chloride (TMAC)

Choline Chloride (HETMAC)

Structure

K+Cl-

NH4+Cl-

Function/Limitation

Bad compatibility,temperature limita-tions

pH and temperaturelimitations

pH and temperaturelimitations

Good compatibility,ammonia odor, may be eaten by microor-ganisms

Use

On-site preparation

On-site preparation

On-site preparation

Ready to use

Toxicity

High content of Cl-

Obnoxious odor,toxicity

Toxicity, bad odor

Biodegradable,nontoxic

Figure 3: Clay stabilizer summary

CH3

CH3

H3C N+ CH3 C1-

CH3

CH3

H3C N+ CH2 CH2 CH2 OH C1-

The information in this bulletin is believed to be accurate, but all recommendations are made without warranty, since the conditions of use are beyond the manufacturer’s control. The listed properties are illustrative only, and not product specifications. The manufacturer

disclaims any liability in connection with the use of the information, and does not warrant against infringement by reason of the use of any of its products in combination with other materials or in any process.