Optional components include: 



1. Open storage for coated submarine pipe 



2. Open storage for anchors and chains 



3. Machine shops, repair, maintenance and 



welding facilities 



(A site plan of a new permanent supply base in Lerwick, the Shetland 

 Islands, is reproduced in Figure 28). 



An onshore support base will also need an area set aside for a 

 mineral-processing plant, and space for vessel repair and maintenance. 

 The former is required to prepare drilling mud, an essential component 

 of all drilling operations. The basic drilling-mud composition tailored 

 to meet specific down-hole requirements is prepared at the plant, 

 although it may be slightly altered by the drilling-mud engineer on 

 s i te . 



Back-up services might include [34]: 



1. Specialized drilling services 



2. Engineering services (repairs to equipment 



and small fabrication) 



3. Inspection services 



4. Diving (underwater inspection and 



maintenance) 



5. Catering services 



6. Air services 



7. Freight handling, customs documentation, etc. 



8. Agents of supply boats, tugs, etc. 



9. Dredging and harbor works 



10. Communications 



11. Secretarial services 



12. Emergency medical services 



An important distinction is to be made between temporary and 

 permanent service bases. During exploration and exploratory drilling, 

 only temporary facilities are developed. Temporary service bases are 

 comparatively small operations, and the limited acreage (5 to 10 acres) 

 which they use is usually leased on a short-term basis. Public port 

 facilities already in operation are often used during the exploratory 

 phase. 



After a commercial find has been located, land for a permanent base 

 (usually 50 to 100 acres) will be purchased or leased on a long-term 

 basis (more than one year). (Figure 27 is for permanent service bases.) 

 During field development, service bases supply essentially the same 

 types of goods and services required during exploratory drilling. 

 However, the scale and intensity of support services increases signifi- 

 cantly for two reasons. First, as many as 60 wells can be drilled from 



122 



