Water Gelling Agents
Water gelling agents viscosify fresh water and light salt brines enhancing the frac fluids proppant transport properties. These gels are easily cross-linked to greatly increase the amount of proppant they may carry. Selection of the proper gelling agent is dependent on downhole conditions and formation characteristics.
WGA-1 - Low residue hydroxypropyl guar (HPG) gelling agent that contains internal buffers to make it self-dispersing and easy to mix. Contains 1 to 3% insoluble residue and is readily cross-linked with antimony, borate, and titanium based activators. Usually used at concentrations from 20 to 50 lb/1,000 gal (2.4 to 6.0 kg/m3).
WGA-2 - Guar gum gelling agent that self-hydrates for continuous addition or “on-the-fly” mixing. pH buffers and dispersants allow easy lump-free mixing to quickly develop maximum viscosity. Can be cross-linked with borate or antimony cross-linkers. Usually used at concentrations from 20 to 50 lb/1,000 gal (2.4 to 6.0 kg/m3).
WGA-5 - Carboxymethylhydroxypropyl guar (CMHPG) that is slightly anionic and double derivatized. Contains less than 1% residue and is easily cross-linked with zirconate based activators. Usually used at concentrations from 20 to 50 lb/1,000 gal (2.4 to 6.0 kg/m3).
WGA-15 - Fast hydrating guar gelling agent that self-hydrates through internal dispersants and buffers to enable lump-free, continuous mixing. Achieves 85 to 90% viscosity within the first three minutes. Usually used at concentrations from 15 to 50 lb/1,000 gal (1.8 to 6.0 kg/m3).
WGA-21 - Low residue, water soluble, hydroxyethyl cellulose (HEC) polymer that provides high viscosity and excellent friction reduction. Compatible with both nitrogen (N2) and carbon dioxide (CO2). Unaffected by water hardness or salt concentration. Usually used at concentrations from 20 to 50 lb/1,000 gal (2.4 to 6.0 kg/m3).
WGA-50 - Self-hydrating, hydroxypropyl guar (HPG) slurry that provides rapid viscosity development and eliminates the need for pre-mixing. The slurry concentration contains 4 lb (1.81 kg) active HPG per gal. Usual loading rate is 5.0 to 12.5 gal per 1,000 gal (5.0 to 12.5 L/m3). This equals a dry HPG loading of 20 to 50 lb/1,000 gal (2.4 to 6.0 kg/m3).
WGA-209 - Surfactant used to create a zero residue fracturing fluid with no polymeric gelling agents. Used at a loading of 9 to 10% and combines with sodium chloride at a loading of 5% by weight of water (BWOW) to reach maximum viscosity. The upper temperature limit is around 175°F (79°C).
Zeta Gel - Easily mixed, two-component (one anionic and one cationic), surfactant based gel system. Effective temperature range up to 300°F (149°C). Active solids of 1.1 to 2.0%. Salt tolerant up to 2% total chlorides. Rapid gel development, environmentally friendly, and compatible with nitrogen (N2) and carbon dioxide (CO2). Components include:
• WGA-300: liquid anionic surfactant, or
• WGA-300P: dry blended anionic surfactant plus nonionic friction reducer
• WGA-305: cationic surfactant plus boosters
Water Gel Breakers
The proper breaker selection for a given gel system is very important to the success of the fracturing treatment. The high viscosity frac fluid must sufficiently degrade with time to allow for high fracture fluid recovery rates on the flowback and minimal damage to the formation.
AP-1 - High temperature oxidizing breaker that returns guar gelled fluid to water-like consistency. Temperature range of 120 to 185°F (49 to 85°C) but can be effective at lower temperatures when used together with BXL-A, breaker activator. Use 0.5 to 1.0 pound/1,000 gal (0.06 kg/m3) of AP-1 as a starting point in break tests.
BXL-A - Liquid organic mixture that activates the breaking mechanism in AP-1 when the downhole temperature is at or below 120°F (49°C). Usual concentration is 1 gal/1,000 gal (1 L/m3) with 0.5 to 1.0 pound/1,000 gal (0.06 kg/m3) of AP-1.
DRB-BR - Encapsulated bromate for use as a delayed release oxidizing breaker for high pH fluids at temperatures from 220 to 300°F (104 to 149°C). Typical loading is 0.4 to 3.0 lb/1,000 gal (0.048 to 0.36 kg/m3).
DRB-EZ - Encapsulated enzyme for use as a delayed release breaker in fluids with a pH below 8.5 and a temperature up to 180°F (82°C). Can be used in conjunction with DRB-SB in fluids above pH 8.5. Typical loading is 1 to 5 lb/1,000 gal (0.12 to 0.6 kg/m3).
DRB-HT - Encapsulated oxidizer for use as a delayed release breaker at temperatures from 140 to 225°F (60 to 107°C). Allows high breaker concentrations to be used without compromising the fluid viscosity. Typical loading is 0.5 to 10 lb/1,000 gal (0.06 to 1.2 kg/m3).
DRB-KPHT - Encapsulated oxidizer for used as a delayed release breaker at temperatures from 180 to 220°F (82 to 104°C). Typical loading is 0.05 to 2.0 lb/1,000 gal (0.006 to 0.24 kg/m3).
DRB-LT - Encapsulated oxidizer for use as a delayed release breaker from 80 to 140°F (27 to 60°C). At temperatures below 120°F (49°C), a breaker activator, BXL-A, must be used. The typical loading is 0.5 to 10 lb/1,000 gal (0.06 to 1.2 kg/m3).
DRB-SB - Encapsulated sodium bisulfate for use as a delayed release breaker for borate cross-linked fracturing fluids at temperatures from 60 to 175°F (15 to 79°C). Can be used in conjunction with DRB-EZ in low temperature, high pH fluids. Typical loading rate is 1-5 lb/1,000 gal (0.12 to 0.6 kg/m3).
HTB-1 - High temperature oxidizing breaker used at temperatures from 185 to 260°F (85 to 127°C). Not compatible with gel stabilizers containing sodium thiosulfate. Usual concentration range is 0.1 to 0.5 gal/1,000 gal (0.1 to 0.5 L/m3).
LEB-10X - Mixture of ethylene glycol, water, sugar, hemicelluase enzyme and a safe biocide for use as a water gel breaker for temperatures up to 150°F (66°C) and pH range of 2.0 to 8.0. Highly concentrated; one gal (3.8 L) equals 20 lb (9 kg) of powdered breaker having 1500 HCU activity. Generally, one (1) quart (0.95 L) is used per 10,000 gal (38 m3) of 40 pound/1,000 gal (4.8 kg/m3) gel.
WGB-1 - Powdered enzyme breaker for HPG and guar gelled fluids for temperature range of 50 to 140°F (10 to 60°C) and pH range of 3.5 to 6.0. Compatible with KCl, brine and oxidizing breakers. Typical concentration is 1 to 2 lb/1,000 gal (0.12 to 0.24 kg/m3).
Zeta-Break - Dry additive breaker for the Zeta Gel system. Provides clean and efficient breaks over a wide temperature range. Also provides fluid loss control properties. Concentration range from 0.3 to 0.6%.
Metallic cross-linkers connect the polymer chains and greatly increase the apparent viscosity of a gelled fluid, which increases the proppant carrying efficiency, allowing for higher proppant concentrations to increase the fracture width. Fluid loss is also reduced, which assists in increasing the fracture length.
BXL-10.0C - Aqueous borate cross-linker that contains internal buffers to automatically raise the pH of the gelled fluid to the range of 9.0-11.0 (optimally 10.0). Provides an immediate cross-link and is stable to 250°F (121°C). Has a low pour point of -67°F (-55°C). Usual concentration is 2 gal/1,000 gal (2 L/m3).
BXL-8.5C - Aqueous borate cross-linker that contains internal buffers to automatically raise the pH of the gelled fluid to the range of 8.5 to 8.7 and enable the use of enzyme breakers. Provides an immediate cross-link for low temperature applications below 140°F (60°C). Usual concentration range is 1 to 3 gal/1,000 gal (1 to 3 L/m3).
BXL-STD / BXL-MTD / BXL-LTD - Delayed borate systems help to minimize friction pressures by delaying the cross-link time of the base gel. Usual concentration is 2 gal/1,000 gal (2 L/m3). BXL-STD provides a 2 to 3 minute delay for HPG gels. BXL-MTD provides a 3.5 to 5 minute delay in HPG gels and a 1.5 minute delay in guar gels. BXL-LTD provides a 5.5 to 6.5 minute delay in HPG gels and a 3.5 minute delay in guar gels.
ZXL-1 - Aqueous zirconium based cross-linker for CMHPG gels at applications above 225°F (107°C). Provides an immediate cross-link at low pH (3.5 to 4.8) and a temperature delayed cross-link at high pH (8.5 to 9.75). Compatible with carbon dioxide (CO2). Usual concentration is 1 to 2 gal/1,000 gal (1 to 2 L/m3).
ZXL-1A - Accelerated zirconium-based cross-linker for use with CMHPG gels to provide much faster closure and crowning at low pH (3.5 to 4.8) and temperatures above 225°F (107°C). Compatible with carbon dioxide (CO2). Usual concentration is 1 to 2 gal/1,000 gal (1 to 2 L/m3).
ZXL-2 - Aqueous zirconium based cross-linker for CMHPG gels at applications above 225°F (107°C). Provides an immediate cross-link at both low pH (3.5 to 4.8) and high pH (8.5 to 9.75). Compatible with carbon dioxide (CO2). Usual concentration is 1 to 2 gal/1,000 gal (1 to 2 L/m3).
pH Buffer-Z1 - Buffer for high temperature zirconate fluids to raise and hold the pH to the desired level of 8.5 to 10.0, depending on base fluid. The starting concentration is 10 lb/Mgal (1.2 kg/m3).
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