Additives for Drilling Fluids

Just as drilling fluids are integral to the borewell drilling process, additives that are very much a part of their composition, have a unique role to play. Most of these additives have distinct properties that specifically help in countering specific challenges encountered during the drilling process. They help in accomplishing the drilling work with efficiency and precision. They also help in minimizing human hazards.

Basic Classification of Additives

Typically, a particular compound of drilling fluid or drilling mud would have myriads of additives in them. This is quite unlike foam or air based drilling fluids that may not be containing too many drilling fluids because most of these additives are either available in solid or in liquid form. Therefore, they would not mix well with foam based or an air based substance. Some of the significant compounds that work well as additives have been detailed out below:

  1. Weighting Compounds —Primarily, weighting materials or compounds are used for increasing the mud density. Common examples would be barium sulfate or barite. The density of the mud needs to be increased because it is important to equilibrate the wellbore pressure and the formation pressure, especially when the challenge is to drill through zones that are heavily pressurized. In case of oil based drilling fluids or mud, Hematite which is an iron compound is also considered to be an excellent weighting additive.

  2. Corrosion Inhibitors —Since drilling would involve the installation and usage of several metallic components, it would be essential to introduce corrosion inhibitors through the drilling fluids that are being used for the process. Considering that the metallic parts would encounter a slew of acidic compounds during the course of the drilling process, corrosion maybe rampant. Popular anti corrosives that are used as additives would include aluminum bisulfate, iron oxides, protect- pipes of zinc chromate, zinc carbonate and so on.

  3. Dispersants —During the drilling process, it is essential to introduce agents that can help in breaking up solid clusters in smaller particles that can be easily carried by the drilling fluid from one place to the another, without causing any unnecessary obstructions. This is specifically what dispersants do. Examples include iron lignosulfonates.

  4. Flocculants —Flocculants are nothing but acrylic polymer compounds that help in the cluster formation of suspended particles, so that they can be grouped together and removed from the resultant fluid when they reach the surface.

  5. Surfactants —Surfactants are nothing but compounds like soaps and fatty acids that would emulsify and defoam the drilling mud or fluid.

  6. Biocides —The drilling mud or fluid compound would be a fertile ground of breeding bacteria that could lead to complete souring of the compound. In order to reduce the sourness and thwart the growth of bacteria, biocides would have to be introduced in the form of cholorophenols, formaldehydes or organic amines.

  7. Reducers of Fluid Loss — Drilling may often involve working with highly permeable formations that might also be under pressurized. Typically, one has to introduce fluid loss reducing compounds like organic polymers and starches.

  8. Fluid Viscosifiers/Rheology modifiers — Viscosifiers help in controlling the rhelogy of the fluid. Some of the natural polymeric rheology controllers are :-

  • Guar Gum PowderGuar Gum is a unique substance derived from the Guar plant, with numerous usages. Primarily, there are two types of Guar Gum being used these days. First is the food grade Guar Gum that is used as a national food thickener in ice creams, cakes and other confectionary items. Second is the industrial grade Guar Gum used across various industries like oil well drilling, paper, textiles, batteries, explosives, mining and many more. When it comes to well drilling, Guar Gum works as an excellent additive for drilling fluids and mud on account of some unique characteristics it possesses. Some of these include:

  1. The industrial grade powdered Guar Gum can be effectively used in the fracturing of oil wells, stimulation of oil wells, for mud drilling, and also as a stabilizing, thickening and suspending agent for drilling fluids.

  2. It is fast hydrating and highly dispersing in nature and is also diesel slurriable.

  3. Specifically in the oil field domain, Guar Gum is being increasingly used as a deformer, a synthetic polymer and also a surfactant for all types of rheological needs with respect to brine based as well as water based drilling fluids.

  4. Guar Gum is also used as a viscosity enhancer for maintaining the viscosity levels of the drilling mud, thus enabling the drilling fluids to move the drill waste from the deepest of holes.

  5. Guar Gum based compounds also help in reducing friction in the holes, minimizing the requirement of power. They also help in minimizing water loss.

  • Xanthan Gum—Xanthan Gum has also emerged as a highly preferable drilling mud additive that helps in minimizing associated work problems. Basically, it is a polysaccharide and an immensely essential biological polymer that is made from carbohydrates. Some of the most distinct properties of Xanthan Gum that makes it an idea additive for drilling fluids have been discussed below:

  1. It can be used as a stabilizer, a thickener, an emulsifier and a suspending agent for drilling fluids.

  2. It can effectively enhance the viscosity of drilling mud or fluids as well as enhance shear force. Therefore, it is widely used in drilling fluids for the non solid phases, for workover fluids as well as completion fluids in order to restrict formation damage.

  3. It is highly pH stable and heat stable too.

  4. It possesses unique rheological properties. The viscosity of the drilling fluid decreases fast though shear action once the shearing ceases. Subsequently, the viscosity levels are restored within no time.

  5. It also possesses fairly strong anti oxidant as well as anti enzyme properties.

  • CMC—CMC is another popular additive being increasingly considered for easing the challenges associated with borehole drilling mechanisms. CMC is basically a technical grade, low viscosity, and dispersible additive. Chemically, it is a Carboxymethyl Cellulose compound. It reduces the API filtration rate through minimum enhancement in viscosity with respect to aqueous drilling fluids. Some of the advantages associated with the usage of CMC as additives would include:

  1. It is a widely acceptable as well as a cost effective solutions for controlling fluid loss during the course of the drilling process.

  2. It can provide for filtration control in an effective manner in most aqueous drilling fluids.

  3. It considered highly effective even when used in low concentrations.

  4. It is completely non toxic, reducing human hazards substantially.

  5. It is not subjected to calcium contamination or bacterial fermentation.

 

It can be easily deduced therefore that the choice of additives for drilling fluids has an immensely crucial role to play in the success of a drilling exercise. Therefore, they need to be chosen well with respect to the needs and challenges offered during the drilling process.

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