Systematic HDD Drilling Fluid Recycling
economical, sustainable, eco-minded
The drilling fluid consisting of Bentonite and water for HDD techniques has a number of key functions. It loosens the soil, discharges the bore spoil continuously, stabilises the bore hole, supports the free cut, cools the drilling tools and bears the product pipe. Its major function is bore hole stabilisation, however, as gravity exerts a permanent pressure on the horizontal bore and the fluid must protect the bore hole from collapsing and make sure that the loosened bore spoil is properly discharged. By adding Bentonite, consisting of natural clay material with excellent swelling properties, the drilling fluid receives these physical characteristics. The layered molecular texture of the clay minerals can absorb water really well and causes the drilling fluid to adopt a jelly-like, supporting structure when coming to rest and at the same time flowing and transporting matter when on the move without losing its supporting power. This specific consistency of the clay mineral makes Bentonite an indispensable medium for HDD drilling fluids.
Other drilling fluids like for example mixtures of water and carboxy-methyl cellulose (CMC) used for deep bore holes, are unsuitable for horizontal drilling. CMC is a kind of cellulose with a chain-like structure; it has no supporting effect at all but poses a hazard for the groundwater. Using compressed air as a drilling fluid can only work for HDD operations through particularly soft rock formations in lengths up to 80 m. The discharge with air is limited and there is no support of the bore hole - the same goes for plain water when used as a drilling fluid. Using water/Bentonite drilling fluid is the only way to stabilise the horizontal bore hole completely, irrespective of length and diameter. Additives like polymers can boost the supporting effect with a network structure; they are no substitute for the Bentonite, however.
Economical re-use and disposal
Top-quality Betonites contain a share of 80 - 90 % montmorillonite, the clay mineral with the strongest swelling properties of all. The price of this mineral is high accordingly, as are the costs for polymers. Depending on the drilling fluid volume, the HDD fluid is therefore a valuable operating resource; fortunately, a suitable recycling technology allows reprocessing so it can be used again. By separating the solid matter which is taken up by the HDD fluid in the process of drilling, the cleaned drilling fluid can be used time and again in a closed drilling fluid cycle. This speeds up the drilling progress, reduces wear of the drilling tools and pumps considerably and decreases the water and Bentonite consumption, which on the whole increases the profitability of a HDD operation in a sustainable manner.
Even though the used drilling fluid can be reused by means of recycling, finally it will have to be disposed of. In some countries like for example Germany the used drilling fluid is by law rated as waste which may not be spread over agricultural surfaces without official permission and a complete chain of evidence to prove its harmlessness. Additional legal specifications and issues often demand a declaration of the used drilling fluid as waste matter which has to be disposed of verifiably and professionally..The costs for regular disposal, which depend on the volume of drilling fluid, have been rising since and can have a very negative influence on the profitability of a HDD operation. The contractor, who is responsible for the professional disposal of the used drilling fluid according to the costs-by-cause principle, can separate the compounds of the fluid, turbid water and semi-solid thickened sludge by means of recycling, thus reducing the amount of waste matter demanding disposal and clearly decreasing the costs for dumping. The water is discharged via sewerage or in a wastewater treatment plant, as the case may be, while the thickened sludge is taken care of in a soil aggregate deposit at a low rate.
Advantages of HDD drilling fluid recycling:
- the drilling fluid can be re-used
- the consumption of drilling fluid and water is diminished
- the amount of waste matter subject to mandatory disposal is reduced
- costs for disposal are minimised
- the required deposit working face is lessened
- environmental protection is improved
AMC – Customised recycling technology
Every drilling fluid is specifically and individually composed, therefore a universal solution for recycling techniques does not exist. A basic rule is: the more efficient the separation ability of a recycling system to segregate solid matter from the HDD fluid, the lower the costs for operating resources and disposal. Solid matter separation is effected according to the grain size with the following modules:
- Shakers: removal of the coarse solid matter
- Hydrocyclones: removal of the sandy / silty grain share
- Centrifuges: removal of the fine grain share
Only if these modules match the drilling fluid perfectly, 100 % of all loosened solid matter particles except for the Bentonite can be removed from the fluid, thus allowing reuse and ecologically sound disposal without worry. For this reason TRACTO-TECHNIK counts on the proven high-performance recycling systems by AMC, connecting well-tried expertise in HDD machine technology with the leading competence in recycling technology.
The Australian Mud Company - abridged AMC - is a leading, internationally active producer of drilling fluid additives and recycling technology, represented in Germany by AMC Europe with headquarters in Rastede. All products and services are based on comprehensive know-how and long-standing practical experience; this also goes for the recycling systems by AMC. The spectrum ranges from small recycling units up to systems for large projects with a cleaning capacity from 150 l/min. to 3,000 l/min.
The single modules shakers, hydrocyclones and centrifuges can also be assembled individually to suit the soil conditions on hand and comply with the required drilling fluid volume. This is crucial for recycling with HDD systems up to 300 kN pulling force - only the application of centrifuges can prevent wear of the Bentonite high-pressure pumps. The AMC recycling technology meets every single relevant safety demand according to CE certification; it is technically mature and maintenance-friendly.
Competent Training and Consulting Service
To support the users in decision-making as soundly and individually as possible, we offer comprehensive training courses covering all aspects of recycling. The cooperation with the professionals of AMC and brain trusts like the "DCA work group drilling fluid disposal” guarantees state-of-the-art training course contents covering all geological, technical and legal aspects.
The range of up-to-date training courses related to practice comprises all areas of horizontal drilling from basics to detection and drilling fluid techniques as well as rock drilling to site management. The geo-services also offer the complete range of geological services for HDD technology. Individual consultation on HDD and recycling systems, drilling fluid technology, live demonstrations and hiring conditions is provided by our flexible customer service team.