Petroleum exploration companies vie for properties bearing minerals. 

 Since the seismic survey is the major source of information regarding potential 

 for mineral resources, the survey results are kept in strict confidence. 

 Thus, a single property ray be surveyed by different interested explorers. In 

 addition, changes in seismic survey techniques sometimes prompt exploration 

 companies to resurvey sites. 



Land acquisition. When a potential wellsite has been located, it is 

 necessary to secure permission and legal authorization to explore for minerals. 

 A lease or sale is sought to allow mineral extraction. In many areas where 

 there are wetlands, permits must now be sought from the Corps of Engineers for 

 any dredge and fill activities. Other permits must be sought regarding water 

 quality and publicly owned lands. On national and state wildlife refuges, 

 special permits may be required for oil and gas exploration. 



Exploration. . The actual exploration phase begins with the movement of 

 equipment and personnel to the vicinity. First there must be access to the 

 wellsite via road or canal, or a combination of the two. The wellsite location 

 must be cleared and prepared for the entrance and placement of large pieces of 

 equipment and supplies. Often special levees are necessary, either for the 

 retention or exclusion of fluids. Auxiliary services such as water, electric 

 "nwer, and natural gas are sometimes required before the largest pieces of 

 _quipment enter the site and are erected. 



A drill bit bores a hole to the petroleum-bearing strata. The bit is 

 suspended from a long string of drill pipe connected end to end in order to 

 lower the bit to the hole bottom. The entire string of drill pipe rotates, 

 ran by engines at the rig. The rotation and weight of the drill string allows 

 the bit to bore through the substrata. Drilling mud is used to lubricate and 

 cool the drill bit and to clear it of cuttings and transport them to the 

 surface. In addition, the fluid is used to control pressure deep within the 

 well and to form an impermeable seal on the bore hole sides to control seepage 

 and contamination of other strata. 



The drilling fluid is managed in pits or tanks so that cuttings may be 

 separated and the physical and chemical characteristics of the mud may be 

 carefully controlled. The handling of drilling mud is a technology unto 

 itself, and there are many subtleties to the preparation, chemical composition, 

 and rranagement of the fluid. 



Because of tremendous force and wear on the bit, it must be replaced 

 periodically. In many cases, different types of substrata require different 

 kinds of drill bits. Thus, all of the drill pipe must be withdrawn from the 

 well for bit replacement, and then restrung for drilling. 



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