Cable Tool Drilling

• Cable tool drilling is a form of onshore drilling. It is the oldest method, dating back to the 1800s. A heavy metal bit is repeatedly dropped into the ground, breaking up rocks and earth until it reaches the proper depth. The bit is shaped like a chisel and varies based on the type of terrain being drilled. Today these drills are powered by steam and can dig thousands of feet into the earth, with the record being 11,145 feet.
  
  

Horizontal Drilling

• Horizontal drilling is useful because it can reach natural gas deposits that are not reachable by the cable tool method. Rather than drilling directly into the deposit, the well curves underground and runs parallel to the deposit. Long pipes or "legs" branch out from the main well. These pipes allow a single well to tap several deposits at a time. A big advantage of this method is that it minimizes environmental impact by disturbing less ground. In other words, a single horizontal well can have the same efficiency as several regular wells.
  
  

Mobile Offshore Drilling

• Offshore drills are always positioned above a natural gas deposit, connecting directly down into the source. One method of offshore drilling employs ships equipped with built-in drills. The vehicles are referred to as drill ships, and they can be moved from place to place, drilling deep into the sea floor. Another type of drilling ship is called a floating production system. The wellhead is actually attached directly to the sea floor and natural gas is brought to the surface. The production platforms also allow extracted petroleum to be processed, rather than just collected. Regardless, mobile rigs are not meant for large-scale drilling. If a significant deposit is found, a large drilling rig is built.
  
  

Drilling Rigs

• While drill rigs seem to look the same, there are many variations. Submersible rigs are limited to shallow areas and are lowered to the lake or sea floor to drill. Semisubmersible rigs follow the same general principle as their submersible counterparts, but they do not go down to the sea floor. Instead, they are partially submerged to provide stability for the rig. Unlike submersible rigs, they can drill in deep water. The fixed platform is a rig that sits on large legs above the sea floor. These rigs are very secure, since they are essentially tied down. However, they are not meant for very deep water, since building longer legs is expensive.