| Popis: |
Current drilling methods may only achieve relatively low penetration rates in hard formations found in deep wellbores. The relatively high wear rates of drill bits used in such applications can cause the overall economy of deep drilling to be non-feasible. Therefore, a step change is necessary for such formations. This paper presents update in development of the pulsed plasma drilling technology which allows controlled thermo-mechanical rock breakage efficient mainly for hard rock formations. Pulsed plasma drilling technology does not melt rock but uses very short high energy pulses with high frequency which suddenly increase rock surface temperature and, thus, disintegrate its surface. Since the process is very swift, there is not enough time for creation of melt, which is viscous, difficult to remove and may act as a prevention for further penetration. Based on extensive experimental work done on 23 rock types we identified working windows for all of them. Based on this work, there is an "overlap window" where keeping the same parameters should enable drilling through any rock type. The development team performed 1500+ various tests of pulsed plasma technology. During these tests we focused on qualitative parameters like efficiency of the process, sustainability of the process, etc. Quantitative parameters were not decisive when trying to make the process work in various operational cases. In total, we've run hundreds of testing hours of the technology. Now the team focus on quantitative parameters with the milestone of deepening the existing geothermal wellbores of other entities in 2023 to demonstrate the PLASMABIT technology at great depths. The system of this technology is composed of three main parts: PLASMABIT tool (Bottom Hole Assembly - BHA)Transfer line delivering fluid and power into PLASMABIT BHASurface equipment including rig, fluid and waste management, etc. PLASMABIT BHA which is the major innovation is composed of the following modules which are under development within dedicated development programme: Pulse plasma drilling head disintegrating rockFluid and power distribution moduleControl and electronics moduleLogging moduleTwo tractoring modules securing movement and anchoringActive and passive cooling modules maintaining temperature of BHATransfer line connector For the commercial application we intend to combine conventional drilling technology with plasma in the following way: Conventional technology would be used for initial hundreds/thousands of feet to overcome sedimentary/soft rock formations where it achieves competitive Rate of Penetration (ROP). Then, in deeper/hotter/harder formations we intend to apply plasma technology where it is much more efficient than conventional technology. Based on this, we intend to use hybrid rig combining rotary drilling and coiled tubing operations. |
