________________ Rising oil prices as well as reductions in oil production in important oil producing countries have repeatedly given rise to concerns about problems of scarcity. In scientific circles and the public at large, discussions are taking place about what effects the approaching maximum extraction volume will have. The economic focus is no longer on the exploration of large conventional deposits, but also increasingly on the many smaller deposits and oil and gas reserves that can be explored using unconventional methods.
The strengths of horizontal and vertical drilling technology for oil and gas exploration
The development of Slant Directional Drilling has provided an alternative drilling method for exploring near-surface, conventional or unconventional oil and gas deposits. The result is a symbiosis of the two familiar drilling methods, Horizontal (HDD) and Vertical (VDD) Directional Drilling. While the entry angle in HDD lies between 8 and 18 degrees, in VDD it is 90 degrees to the Earth's surface. Both drilling methods have been used successfully in mechanical engineering by Herrenknecht for years. While the machine technology and modularity were taken from the area of horizontal drilling, the focus in machine and borehole safety lies in vertical drilling.
With an entry angle between 8 and 90 degrees to the horizontal, the necessary depth can be drilled down pretty fast. Deposits at shallow depths can be quickly reached at an angle of 30 degrees, for example, and the angle allows for a fast horizontal deflection in order to drill further in the interesting layer.
With SDD and without diversions to the energy source
One important area of application is coal seam gas (no fracking). The USA and Australia are already highly active in this area and cover a large part of their gas requirements in this way. Instead of many vertical drills into the horizontal seams of coal, you can drill down to the corresponding depth using SDD and then deflect into the horizontal. In this way, you can follow and drill into the respective soil layer. Since, as with HDD rigs, a rack & pinion drive is used, in addition to the weight of the drill string an additional push force can be applied. This means that considerably longer horizontal deflections can be achieved than with conventional vertical rigs with a cable winch. The longer you can drill in the corresponding formation, the higher the efficiency factor of the drilling.
In CSG drills, two drills are usual (Surface to In-Seam Drilling). One of these follows the respective coal seam as described, while the other is a vertical drill that crosses the horizontal. Developing a rig for use between 8 and 90 degrees has made it possible to carry out both drills with one system.