WorldWide Drilling Resource

21 JANUARY 2022 WorldWide Drilling Resource® New Fluidic Switch for DTH Hammer Deep Geothermal Drilling Adapted from Information by Geo-Drill The Geo-Drill consortium is made up of 12 partners across Europe, a compilation of skills and expertise, including product developer to end user/geothermal drilling operator, engineering firm, universities and research institutes, as well as dissemination organizations. This complementary expertise works well to develop, disseminate, and exploit the Geo-Drill project. Addressing the challenge of developing novel and cost-effective drilling technology for geothermal resources, the consortium aims to remediate the high investment costs and long development cycle for this underutilized renewable resource. More specifically, their objective is to develop holistic drilling technologies having the potential to drastically reduce the cost of drilling to large depths (16,000 feet or more) and at high temperatures (482ºF/ 250ºC or more). When they first began, the drilling technology proposed plan included: a bistable, fluidic, amplifier-driven mud hammer; low cost 3D printed sensors and cables; drill monitoring system; as well as graphene-based materials and coatings. Their goal was increased rate of penetration (ROP) and reduced tripping with improved tool life. The down-the-hole hammer commonly referred to as DTH, is a tool with a piston powered by either compressed air or high-pressure fluids. Widely used for deep drilling in hard rocks, the DTH hammer concentrates percussive energy at the base of the wellbore, imposing high stress points to break the rock into small chips which can be carried out of the wellbore, either by the exhaust air or by the exhaust fluid. Fluids range from water to complex mixtures of polymers and sometimes suspended colloids of hydratable clays, although these are very rarely used with hammers. Air-powered DTH hammers use compressed air to power the pneumatic tool; however, they are less effective at larger depths due to the difficulty of removing cuttings and overcoming the ingress of fluids. On the other hand, water-powered DTH hammers are energy efficient with deeper drilling capabilities. Despite this advantage, when drilling deeper, most fluid hammers suffer poor performance as the volume of water required to ensure proper cleaning of the hole is too great for the piston to cycle effectively. The challenges associated with cuttings transport/removal can lead to increased tripping times due to reduced lifetime of drilling components. A Geo-Drill enabled DTH hammer uses a fluidic oscillator without any moving parts to wear out, rather than the conventional valve; allowing much less strict tolerances in the percussion mechanism; thereby, enabling usage of drilling fluids with high solids content. These hammers offer the following advantages: very high reliability due to few moving mechanical parts; and independence from environmental influences due to the bistable fluidic switch, which can be used autonomously of shocks, vibrations, accelerations, and temperature. It is also functional under high pressures and flows. The fluidic switch consists of one inlet port and two outlet ports connected to the respective upper and GEO 3D printed fluidic switch prototype. Photo courtesy of Geo-Drill. New Fluidic Switch continued on page 24