Horizontal directional drilling has been around for several decades, and practices have changed since the earliest adoption of this technique. Trenchless pipe drilling and installation typically involve using some form of drilling fluid to facilitate the smooth movement of the drill head underground. In the past, water mixed with polymer got the job done. But drilling companies today are adopting advanced drilling fluid techniques for a good reason.
Why is drilling fluid essential to the success of a project?
Specially formulated drilling fluids play a vital role in the drilling process, which is not achievable using water. These functions are:
- Ensure that the borehole is stable
- Suspend drill cuttings, dirt, and spoils
- Facilitate the movement of cutting heads outside the borehole
What these functions mean for directional drilling companies, is that the fluid also protects the drilling equipment. If for example, you are drilling clay-based soil, using water will cause the clay to swell, which will eventually stick to the tools and halt the drilling process.
Drilling fluid is mostly composed of water and additives like polymers and Bentonite. These additives will affect the hardness and pH level of the fluid. Other properties that drilling experts take note of in choosing the right drilling fluid are density, viscosity, fluid cake, filtration loss, and gel strength.
Understanding what type of fluid to use before drilling
Since the properties of drilling fluid have a direct impact on the result of the drilling process, it is critical to pay attention to selecting and managing the right type of fluid. There are significant ramifications if the contractor chooses the wrong kind of fluid. Contractors are aware the drilling fluid is costly, and there are instances when companies have had to back out because fluid disposal proved to be too challenging.
Why is fluid disposal an issue? Drilling fluid is considered a hazardous product of an industrial process. There are strict regulations in place to ensure that drilling companies follow the right protocols in fluid disposal. Therefore, project managers need to figure out factors such as water source, fluid disposal, and whether or not the project can do without using a specially formulated drill fluid.
Knowing the properties of the soil
In choosing the right drill fluid composition for a project, contractors agree that the primary consideration is the soil condition. For directional drilling purposes, the soil is categorised as either non-cohesive or cohesive.
Non-cohesive soil pertains to ground with loose particles such as gravel or sand. On the other hand, cohesive soil has better structure and retains its shape. Examples of cohesive soil are shale and clay. When working with sandy soil, drilling fluid requires Bentonite additive because it forms the filter cake, which in turn stabilises the drill path.
These general principles guide contractors in choosing the right type of drilling fluid to use, but there are also special conditions. Sometimes, the ground condition can change in the middle of a project. In such instances, contractors typically consult an expert to assess the ground condition and come up with the most suitable drill fluid formulation.