that is, in water depths over 600 ft. (Offshore, 1975: 46) 

 Drillships already have the capability to drill in depths of 

 4000 to 6000 ft. of water (Carmichael, 1975: 52), and, in fact, 

 the Seagap Group (consisting of Getty Oil, Hispanoil, Phillips, 

 and AGIP) is planning a well in 4,500 ft. of water off the 

 west coast of Africa (Leblanc, 1976: 58). However, there are 

 several new developments which are coming into use that are necessary 

 in the exploration phase of deepwater operations before these wells 

 are able to be completed and brought to production. These include 

 dynamic positioning of drillships (no anchors ), sonar wellhole 

 re-entry (without guidelines) of drill string, electric blowout 

 preventor (BOP) valves for fast response, and marine riser 

 systems capable of supporting the weight of the greater lengths 

 of the drill string, mud, etc. (Carmichael, 1975: 52). 



Of course, dynamic positioning is needed to keep the drill- 

 ship from drifting while drilling, but it is also needed to be 

 used in conjunction with the sonar reentry system to reenter 

 the wellhole. The dynamic positioning system must bring the 

 drilling equipment to within 2 ft. of the wellhole center- 

 line. From that point, the sonar reentry system will further 

 align it to within eight inches of center, which is within the 

 capability of the connector at the wellhole to adjust and make 

 final connection with the well (Robertson, 1976: 63). 



Since conventional riser systems are not able to support 

 the added weight of the drill string, mud, etc. , new systems 

 are being developed that use bouyant riser joints to reduce 

 the above water pull required to support the riser system. 



81 



