THE DRILLING PROCESS

After choosing a prospect location, based on the geophysical and geological mapping and interpretation, the site is surveyed to determine its boundaries, and environmental impact studies may be done. Lease agreements, titles and right-of way accesses for the land must be obtained and evaluated legally. For offshore sites, legal jurisdiction must be determined.

Figure 45 � Offshore Jack-up Rig

Once the legal issues have been settled, the crew goes about preparing the land:

1. The land is cleared and leveled, and access roads may be built.

2. Because water is used in drilling, there must be a source of water nearby. If there is no natural source, they drill a water well.

3. They dig a reserve pit, which is used to dispose of rock cuttings and drilling mud during the drilling process, and line it with plastic to protect the environment. If the site is an ecologically sensitive area, such as a marsh or wilderness, then the cuttings and mud must be disposed offsite -- trucked away instead of placed in a pit.

Once the land has been prepared, several holes must be dug to make way for the rig and the main hole. A rectangular pit, called a cellar, is dug around the location of the actual drilling hole. The cellar provides a work space around the hole, for the workers and drilling accessories. The crew then begins drilling the main hole, often with a small drill truck rather than the main rig. The first part of the hole is larger and shallower than the main portion, and is lined with a large-diameter conductor pipe. Additional holes are dug off to the side to temporarily store equipment -- when these holes are finished, the rig equipment can be brought in and set up.