Uses of Borates in Oil Field Chemicals and Fracking Fluids

History

More than 4000 years ago, asphalt was used in the construction of the walls and towers of Babylon. By approximately 350 AD, oil was being produced from bamboo-drilled wells in China.

The story of petroleum can also be traced back to Biblical times when it was noted that Noah used pitch (a crude form of petroleum oil) to build his ark. Still other regions found value in Egyptian times where mummies were bathed in olive oil and their bodies encased in pitch. Boats that sailed the Euphrates River were composed of woven reeds that were encased in pitch. Those from Mesopotamia, Persia and Assyria used pitch to hold their city walls together.

As time progressed so did the many uses of petroleum. The natural resource was used in medicine and eventually fuel in rather crude forms. Up until Drake’s discovery this slippery and smelly substance was scarce and generally found seeping from the ground on to the surface or finding its way to already established water wells and other mining operations.

The US natural gas industry started in 1821 at Fredonia, New York. William Hart dug a well piped to a nearby building for illumination. It was not long until other wells were drilled in the area, and soon the gas-lit streets of Fredonia became an attraction for tourists.

Use of the first horizontal wells was in 1930. The first hydraulic fracturing job took place in Velma, Oklahoma in 1949 and later commercialized in 1950. However, it is not clear when borates began to see influence in the market.

Moving forward, the demand for oil and later gas continues to be at the forefront of primary energy sources. Historically, these sources have been readily available and easy to secure, however, as sources become increasingly difficult to remove due to deeper and less accessible regions within the earth, more sophisticated techniques have been developed to take advantage of these challenging geological deposits.

Borate Benefits

Alkaline buffer to reduced water hardness
Anodic inhibitor, passive anticorrosion
Anti-microbial
Cross-linking polymer systems
Improvement of dissolution rates and aqueous solubility
Lubricant
Oxidizer of Hydrogen sulfide gas (perborates*)

Borates used in the oil fields today are well known and found at the various phases including drilling and oil recovery.

Drilling phase

The first process is to locate these energy deposits using seismic technology and determine whether a more invasive technology is required. The following are various techniques of drilling the well hole to make any initial repairs or plug the hole for future extraction.

Cement as a set retardant

After drilling, a steel casing is used to reinforce the well hole. Steel casing surrounds the cement for additional support. The drilling mud is pumped and recirculated down to the bottom of the well and up along its walls. Typically Portland cement must be slowed during the curing phase to prevent it from hardening before it reaches its proper depth. These setting rates are dictated by the temperature of the well hole several thousand feet down. Borates are used as a set retardant for these cements.

Borates react with the calcium portion of the Portland cement by creating a calcium borate coating which slows the setting of cement. Borates typically are not used exclusively as a set retardant but are included with other polymer-based systems.

The amount of borates is critical toward having an efficacious set retardant that does not adversely affect the strength of the cement used or its setting time. Different alkaline borates available create different rates of dissolution and solubility.

Completion Fluids

Brines are used to prepare oil and gas production wells for completion and initiation of production. They are referred to as completion fluids. The proper type and concentration of brine is needed to prevent blowouts and ensure well safety by attempting to balance the well’s pressure. Insoluble borates such as Colemanite and Ulexite act to prevent the flow of fluids into the brine reservoir during this phase of operation. These borates suspend themselves in these aforementioned brines that contain polymers plus other additives. This provides the proper viscosity and density.

However, when these borate-based fluids do come in contact with the main brine solution, they will dissolve away cleanly and thus not damage the well at the end of this operational phase.

It should be noted that “work over” fluids are considered similar to completion fluids but “work over” fluids are used for maintenance purposes when the well needs to increase productivity.

Loss of Circulation

Sometimes there are large fractures in the well hole that need to be filled. In such cases the use of fiber-based liquids may not be as efficacious as borate-based polymers that could prevent drilling fluids from escaping from the well hole via these fractures. Borates increase the viscosity of these polymer gel compounds. Typically guar, xanthum gum and starches will cross-link with these compounds to enhance this gelation process.

Production & Oil recovery phase

Once the well hole has been reopened, fluids are pumped into an oil or gas well under high pressure to split rocks and create more cracks thousands of feet below the earth’s surface. Fracturing fluid carries particles of sand or ceramic material. The fluid helps to keep these cracks open by packing them with these spherical shapes once the pumping is complete and the pressure diminishes in the well hole.

Hydraulic fracturing fluids

Hydraulic fracturing is often called fracking. It is the process of creating a fracture in the rock layer where a reservoir of energy is located.

The hydraulic fluid is pumped down the wellbore hole which forces additional cracks in the rock thus allowing the removal of fossil fuels that would normally not be removed based on past technologies.

Once these rock fractures are formed, proppants are added into this injection fluid. Proppants are spherical shaped silica sand, resin coated sand or ceramic materials that will help to prevent the fractures from closing when the injection process is suspended. Gelation of the fracturing fluid prevents the suspended particles from settling before they enter the fractures. Borate’s use in fracking fluids is well known as they react with soluble polymers both natural and manmade for gelation. Borates act as cross-linkers to increase or decrease the viscosity of these gels due to bond formation and breaking during variations of extreme pressure and temperature.

Borate-based cross-linkers are applied to link with polymer chains and create the viscosity required with pump pressure to fracture the rock where the oil and gas are located.

Borate based cross-linkers are used in low to mid-range polymer systems, while metallic based cross-linkers (i.e.; zirconium, titanium) are used for high temperature polymer systems. It should also be noted that borates are self-buffering, not requiring other additives to adjust the pH of the fracking solution. In addition, the alkaline borates offer an anticorrosive value when systems can become acidic.

Fluid breaking solutions

Once the fracturing process has been completed the fracking fluid needs to be removed from the well bore hole. These high molecular weight fluids are reduced in viscosity by using either enzymes or oxidizing agents.

Among these oxidizing agents are perborates as they release hydrogen peroxide and sodium borate. Perborates are a reaction of Etibor 48 (Borax 5 Mol) and hydrogen peroxide and are offered as a dry granular material. Once solubilized, perborates release the borax as a buffering compound and the hydrogen peroxide as the oxidizing agent offering another way of fluid breaking.

Hydrogen Sulfide (Sour Gas) Scavenger

Hydrogen sulfide (H2S) occurs naturally in the oil and gas industry. It can also be produced by the breakdown of organic materials due to bacteria. Specifically, sulfate reducing bacteria excrete H2S. H2S is a colorless, flammable, and extremely hazardous gas with a characteristic odor similar to "rotten egg.”

It is an irritant and can asphyxiate. It is also corrosive to steel pipes and other oil drilling equipment. Sodium perborate is typically used as an oxidant to not only oxidize the sulfide portion of the gas to sulfur or sulfate but also to offer antimicrobial value in destroying the sulfide producing bacteria that produces this dangerous gas.

American Borate Company Products:

Refined Borates

Mineral

Note: Perborates are currently not commercially offered by American Borate Company however please contact us as we have a source for this alternative borate-based compound coming from Turkey.

Investigate this potentially helpful link:

Society of Petroleum Engineers