Periodic Reporting for period 1 - ORCHYD (Novel Drilling Technology Combining Hydro-Jet and Percussion for ROP Improvement in deep geothermal drilling)
Reporting period: 2021-01-01 to 2022-06-30
Geothermal energy harnesses the heat of underground rocks to convert water to steam and supply an uninterrupted power as opposed to wind and solar energy sources. This makes geothermal energy a leading candidate for carbon neutral, efficient, non-intermittent and reliable source of renewable energy supply across the globe. However, the current drilling methods to reach the rocks at a depth of more than 4 km are slow and inefficient – making geothermal sources supply less than 2% to the global energy share.
The ORCHYD project aims to increase the unit drilling rate (measured in rate of penetration, ROP) by four times the average rate currently possible – drastically reducing the drilling costs by up to 65%. This first-of-its-kind drilling approach, combining two established rock cutting technologies - High Pressure Water Jet (HPWJ) for rock cutting (up to 250 MPa) and percussive drilling using down-the-hole (DTH) hammer - will make the utilization of geothermal energy cheaper and more widely available, facilitating the energy transition to tackle the global climate crisis.
The overall objective of the ORCHYD project is to develop a non-conventional and fully fluid driven drilling process combining the following systems to achieve the envisioned 4X increase in ROP:
- HPWJ system to be able to slot circumferential grooves of desired depth in the bottom-hole conditions.
- In-hole production of the HPWJ using pressure intensifier(s).
- High power advanced mud driven DTH hammer.
- Diamond-enhanced-insert hammer bit.
The ORCHYD project aims to increase the unit drilling rate (measured in rate of penetration, ROP) by four times the average rate currently possible – drastically reducing the drilling costs by up to 65%. This first-of-its-kind drilling approach, combining two established rock cutting technologies - High Pressure Water Jet (HPWJ) for rock cutting (up to 250 MPa) and percussive drilling using down-the-hole (DTH) hammer - will make the utilization of geothermal energy cheaper and more widely available, facilitating the energy transition to tackle the global climate crisis.
The overall objective of the ORCHYD project is to develop a non-conventional and fully fluid driven drilling process combining the following systems to achieve the envisioned 4X increase in ROP:
- HPWJ system to be able to slot circumferential grooves of desired depth in the bottom-hole conditions.
- In-hole production of the HPWJ using pressure intensifier(s).
- High power advanced mud driven DTH hammer.
- Diamond-enhanced-insert hammer bit.
One of the main reasons for the drop in ROP while drilling deep geothermal wells is the increase in geostatic and overburden stresses with the increase in depth. One way to release the stress concentration while drilling is to slot a peripheral groove of a required depth ahead of the drilling face. The numerical studies show that this grooving process reduces the mean stress at the zone of the drill bit action, encouraging the rock to fail. A new full scale hybrid drilling system combining HPWJ and DTH hammer bit was constructed and tested in the laboratory. In hard granites, it was shown that the new system has the potential to provide ROP about 2.5 times higher than those of the hammer drill bit without the HPWJ.
We studied how to maximize the effect of stress release process through numerical simulations which have shown that it is possible to find an optimal depth of the groove for a given drill bit shape. We then studied how to efficiently slot the groove of desired depth using HPWJ of up to 250 MPa. The study also showed that the distribution of the impinging pressure of a HPWJ striking the rock can be predicted by the operational parameters set for a given jet nozzle shape and for a range of orifice diameters. It was then possible to learn the maximum stand-off distance to fully assist DTH hammer drilling. A feasibility study was conducted on how to produce in-hole the required high pressure for the HPWJ using a down hole pressure intensifier.
The preliminary studies on the hydraulic means of rock breakage, i.e. HPWJ, were conducted parallel to the mechanical methods, i.e. percussion drilling. We carried out numerical simulations highlighting that the drill bit profile can also be selected to modify the mode of rock fracturing (tensile vs shear) occurring at the groove's bottom during an impact. Rock microstructures models are now being developed to investigate further the relationship between the rock breaking efficiency and the bottom hole drilling conditions. Additionally, a characterization study performed showed that the use of environmentally friendly additives in the drilling fluid can significantly reduce friction (up to 70%) while increasing the fluid viscosity.
We have also evaluated the project’s environmental impacts. Using certain techniques like Life Cycle Analysis (LCA), noise risk assessment, ecological footprint assessment and a basic version of Risk Analysis (RA) it was concluded that the improvement in ROP is favourable on the environmental impact. Thus, the studies thus far highlight the importance of ORCHYD in the path toward sustainable geothermal drilling.
We studied how to maximize the effect of stress release process through numerical simulations which have shown that it is possible to find an optimal depth of the groove for a given drill bit shape. We then studied how to efficiently slot the groove of desired depth using HPWJ of up to 250 MPa. The study also showed that the distribution of the impinging pressure of a HPWJ striking the rock can be predicted by the operational parameters set for a given jet nozzle shape and for a range of orifice diameters. It was then possible to learn the maximum stand-off distance to fully assist DTH hammer drilling. A feasibility study was conducted on how to produce in-hole the required high pressure for the HPWJ using a down hole pressure intensifier.
The preliminary studies on the hydraulic means of rock breakage, i.e. HPWJ, were conducted parallel to the mechanical methods, i.e. percussion drilling. We carried out numerical simulations highlighting that the drill bit profile can also be selected to modify the mode of rock fracturing (tensile vs shear) occurring at the groove's bottom during an impact. Rock microstructures models are now being developed to investigate further the relationship between the rock breaking efficiency and the bottom hole drilling conditions. Additionally, a characterization study performed showed that the use of environmentally friendly additives in the drilling fluid can significantly reduce friction (up to 70%) while increasing the fluid viscosity.
We have also evaluated the project’s environmental impacts. Using certain techniques like Life Cycle Analysis (LCA), noise risk assessment, ecological footprint assessment and a basic version of Risk Analysis (RA) it was concluded that the improvement in ROP is favourable on the environmental impact. Thus, the studies thus far highlight the importance of ORCHYD in the path toward sustainable geothermal drilling.
The state of stress regimes in highly stressed deep rocks as well as the stress release process and their application to improve ROP of deep geothermal drilling. have not, to our knowledge, been studied.
In this context, progress has been made on several aspects concerning the improvement of ROP in deep geothermal drilling. On the front of using HPWJ for rock destruction, numerical modelling techniques beyond the state of the art have been introduced that extends adaptive mesh Computational Fluid Dynamics (CFD) to tackle the concentrated zone of impinging pressure time history at extremely high Reynolds number and for a rotating jet scenario applicable for comparing with high confining pressure and back pressure laboratory jetting tests. The details of the surface pressures are then directly used as realistic inputs to solid deformation models. Once further validated, the model results will show under what depths and rock types such stress relieving grooves of the required depth can be achieved.
Contributing towards the improvement on ROP using percussion for rock destruction, a multiscale modelling framework was proposed in ORCHYD to optimize the percussive drilling action to the new bottomhole configurations (bit & bottom hole profile, shape & position of inserts, groove depth, weight on bit (WOB), impact energy, etc). Discrete and continuum approaches are used in a complementary fashion to capture and the bit-rock interface and is seen as the linking scale between a dynamic model of the HPWJ system and models of the rock fracturing (and microstructural fracturing). A valuable database on the mechanical behaviour of hard rock has been extended to support the calibration/validation of the models. In addition, a characterization study of enhanced drilling fluids has shown the good potential for using environmentally friendly additives to improve the tool life and rock particles transportation. During the next period of the project, the environmental impacts of the ORCHYD technology will be studied in great detail providing new insights on the impact of this technology on global energy security.
It has been shown in the first period that the ORCHYD technology can improve ROP by at least 100% while testing only moderate rock confining regimes. We are confident that the improvements to the process in the second period by optimizing the operational parameters and at higher stress regimes should lead to saving up to 65% of the current drilling operation costs of hard rock sections, as expected by the project. The gains in drilling costs would have significant direct impacts on investments as well as on the development ambitions of deep geothermal projects. The new drilling process combining a HPWJ and DTH hammer can be envisaged in various applications of shallow to medium depth drilling in hard rocks: mining exploration, deep underground energy storage, geological CO2 storage, environmental monitoring, and remediation, etc. The numerical tools as well as the experimental devices developed will naturally be very useful for optimising specific drilling systems for each of these applications.
In this context, progress has been made on several aspects concerning the improvement of ROP in deep geothermal drilling. On the front of using HPWJ for rock destruction, numerical modelling techniques beyond the state of the art have been introduced that extends adaptive mesh Computational Fluid Dynamics (CFD) to tackle the concentrated zone of impinging pressure time history at extremely high Reynolds number and for a rotating jet scenario applicable for comparing with high confining pressure and back pressure laboratory jetting tests. The details of the surface pressures are then directly used as realistic inputs to solid deformation models. Once further validated, the model results will show under what depths and rock types such stress relieving grooves of the required depth can be achieved.
Contributing towards the improvement on ROP using percussion for rock destruction, a multiscale modelling framework was proposed in ORCHYD to optimize the percussive drilling action to the new bottomhole configurations (bit & bottom hole profile, shape & position of inserts, groove depth, weight on bit (WOB), impact energy, etc). Discrete and continuum approaches are used in a complementary fashion to capture and the bit-rock interface and is seen as the linking scale between a dynamic model of the HPWJ system and models of the rock fracturing (and microstructural fracturing). A valuable database on the mechanical behaviour of hard rock has been extended to support the calibration/validation of the models. In addition, a characterization study of enhanced drilling fluids has shown the good potential for using environmentally friendly additives to improve the tool life and rock particles transportation. During the next period of the project, the environmental impacts of the ORCHYD technology will be studied in great detail providing new insights on the impact of this technology on global energy security.
It has been shown in the first period that the ORCHYD technology can improve ROP by at least 100% while testing only moderate rock confining regimes. We are confident that the improvements to the process in the second period by optimizing the operational parameters and at higher stress regimes should lead to saving up to 65% of the current drilling operation costs of hard rock sections, as expected by the project. The gains in drilling costs would have significant direct impacts on investments as well as on the development ambitions of deep geothermal projects. The new drilling process combining a HPWJ and DTH hammer can be envisaged in various applications of shallow to medium depth drilling in hard rocks: mining exploration, deep underground energy storage, geological CO2 storage, environmental monitoring, and remediation, etc. The numerical tools as well as the experimental devices developed will naturally be very useful for optimising specific drilling systems for each of these applications.