Drilling Additive s are critical to success in horizontal directional drilling (HDD) applications. Since drilling fluid is required to perform a variety of functions, it is important to know why and how it can be such an effective tool. Furthermore, at fundamental level, it really is all about chemistry.
The selection of constituents, concentrations used and resultant properties are driven by the chemical interactions that occur. The following is a basic overview of the chemistry of four drilling fluid components.
Make-up water comprises the greatest percentage of a drilling fluid — as much as 97% — the chemistry is often overlooked. The major issue to address in water is the identity and concentration of anions and cations. The ions, or charged atoms, present in water source can impact hydration and property development of additives. For example, hardness at >100 ppm and/or anionic species (chlorides and sulfates are two examples) at >500 ppm can reduce viscosity development in polymers and bentonite, occupy reactive sites on surfactants and polymers and increase filtration volume. The bottom line is, know your water source. In harmful states for fluid performance, a treatment such as soda ash is usefule. It reduce hardness or design a fluid which can tolerate the water chemistry.
Bentonite is a naturally occurring mineral that is primarily comprised of montmorillonite, a water swellable phyllosilicate. Due to its morphology (platelets) and ability to absorb water, it provides viscosity, suspension and carrying capacity while. Also reducing penetration of water into porous formations or filtration control. Although bentonite can be highly effective at providing the properties listed above, not all results with bentonite are equall. It`s mixture with water, stacks of platelets exfoliate and interact in solution. Additionally, there are also various ions associated with the bentonite.
Calcium chloride uses for all types of drilling and completion applications. These fluids are used in oilfield completion and workover operations to reduce water activity and create osmotic forces to prevent absorption of water . The divalent calcium ion inhibits clay swelling, dispersion and migration. Water containing high concentrations of calcium chloride can be used as a kill fluid in production wells, especially those containing heavy concentrations of carbon dioxide.