Drilling fluids or mud is a chemical substance, used at the drilling sites for various purposes. These generally are water, polymer or clay-based. These were first introduced to keep up the subsurface pressure of the bore well. With time, their demand increased tremendously. Drilling fluids are water-based, mud-based or gaseous substances. The most common among the water-based is polymer drilling fluid. These are biodegradable and used in a case where the use of clay is restricted. Use of these fluids is a continuous process. Drilling fluids have various features, these are as follows:
- Drilling fluids help in controlling formation pressure: It is very important to keep the pressure of the bore-well stable. The fluid’s ability changes as per the change in the pressure. Like in a case where the bore well pressure increases, mud density also increased.
- They help to remove excess cuttings: The drilling fluids ensure that chances of stuck pipes reduce. The continuous rotation of the fluid in the bit helps to bring the rock pieces to the surface.
- They keep up the bore-well’s stability: The well’s stability is maintained by appropriately mixing the chemical and mud. The stability is determined with help of regulated density, minimised hydraulic erosion and controlled clays. This further ensures that the size and shape of the hole are maintained.
- They cool and lubricate the bit: The continuous rotation of the fluid in the bit helps to lubricate the bit, keeping it cool. The thermal energy transfers to the fluid which further carries the heat to the surface. This increases operating efficiency and prolongs the life of the drill bit.
- They transmit the hydraulic energy to bit and the tools: Nozzles used, discharge the fluid into the bit at its face. This leads to a reduction in the hydraulic energy against the formation and takes the cuttings away from the formation. The hydraulic energy also helps to power the downhole motors and gather the data in real-time. The data such collected is transferred through mud pulse telemetry.
Generally, water-based fluids are more environmentally friendly as compared to the mud-based. Mud- based is more toxic, difficult and expensive to dispose of. Various drilling mud chemicals are manufactured by different chemical manufacturers. They provide customisations for the same. The product category includes:
- shale inhibitors
- Shale stabiliser
- ROP enhancer
- Lubricating products
- Foaming agents
- Pipe freeing products
- Wetting agents, and many others.
Thus, for repeated use, drilling fluids are adequately designed. This is an ongoing cycle. These control the pressure of the well by offsetting the pressure of the hydrocarbons and the rock formations. These are usually affected by the conditions that exist on and off the surface i.e. downhole conditions and surface temperatures. Special additives ensure that drilling fluid is not absorbed by rock formations. As the hole deepens, the temperature and pressure keep on changing. The onsite engineers and specialists determine the type and nature of the chemical mixture used in drilling fluid. Thus, it is important to use these drilling fluids to ensure effective operations and maintain well-bore’s stability.