| Title | A Review and Comparison of Four Unconventional Drilling Technologies |
|---|---|
| Authors | Rui Gao, Yudan Jia, Wei Zhou |
| Year | 2023 |
| Conference | World Geothermal Congress |
| Keywords | novel drilling; plasma torch; electrical impulse; laser; millimeter wave |
| Abstract | There are three fundamental drilling and rock excavating mechanisms: mechanically induced stress, thermal induced stresses, fusion and vaporization, and chemical reactions and almost all drilling and rock excavation methods can be categorized into the three groups (Maurer 1968, Maurer 1980). The rotary drilling bit, the most common drilling technology today, attacks rock with mechanically induced stress and is usually called the conventional drilling technology. Novel or unconventional drilling technologies refer to methods which attach rock with the other three mechanisms. Scientists and engineers have been trying to improve or replace rotary drilling bits with novel methods ever since 1930s and many concepts were invented and tested in 1960s. However, due to significant improvements of roller cone bits and the invention of PDC bits in 1970s, the drilling technology with rotary bits has been continuously enhanced and meets petroleum or natural gas drilling requirements for most of time. Percussive hammers and abrasive jet drills also developed and applied in petroleum drilling, coal mining, and tunnel excavation as good supplements for rotary drilling bits in this phase. So, the research on other drilling technologies ceased since 1980s. This situation did not change until 2000s when geothermal energy gradually weights more in energy strategy in many countries in the global carbon-reduction trend. High-quality geothermal energy is stored in hot dry rock which is usually granite with more than 150°C and neither roller cone bits or PDC bits could perform efficiently in these hot and hard rocks. In order to improve the geothermal energy drilling efficiency, scientists and engineers regained enthusiasm on unconventional drilling technologies. Based on literature review and on-site survey, this paper chooses three unconventional drilling technologies, the plasma drilling, the electrical discharge drilling, and the laser drilling from dozens of novel drilling concepts and will further review the recent advances of the three technologies. Theories and rock excavating mechanisms will be firstly introduced respectively; recent engineering efforts with test data will be exposed and discussed. The three alternative drilling technologies are chosen because they all require a considerable amount of electricity which leads to challenge of power transmission even though the way they attack rock vary. They all show potentials to replace rotary drilling bits so in the end readiness and challenges of the three technologies will be evaluated and discussed. A method to evaluate drilling technologies was established in (Pierce et al. 1996) considering below 6 functions which are necessary to provide a useful hole: • Transmission of energy to the system-rock interface • Reduction of the rock • Removal of the rock • Maintenance of the borehole (formation stability) while drilling • Control of formation fluids (well control) • Preservation of the borehole (completion) In this review, a similar method will be used to evaluate the technical readiness and foreseeable challenges in future for plasma drilling, electrical discharge drilling, and laser drilling. References Maurer, W.C. 1968. Novel Drilling Techniques. Great Britain: Pergamon Press. Maurer, W.C. 1980. Advanced Drilling Techniques. Tulsa, Oklahoma: The Petroleum Publishing Company. Pierce, K.G. et al. 1996. Advanced Drilling System Study. Sandia National Laboratories, SAND95-0331 |