CHAPTER 1 INTRODUCTION (DIFFERENCES BETWEEN ONSHORE AND OFFSHORE INSTALLATIONS)

1.1       DIFFERENCES BETWEEN ONSHORE AND OFFSHORE INSTALLATIONS

This manual deals with those matters affecting onshore installations which differ from those of offshore installations.  All aspects of offshore plant and systems are dealt with in detail in the other manuals of the Electrical series, and many of them apply equally to onshore plant.

Areas where there are notable differences between onshore and offshore practice are as follows:

(a)        Power supplies for onshore installations are taken from the National Grid and not from local generators.

(b)        Electrical energy, taken from the grid in England and Wales through Area Electricity Boards, but in Scotland, in the absence of separate Area Authorities, taken direct from the grid, must be paid for under a tariff.  On an offshore installation the energy comes mainly from the installation’s own well-gas, which in tariff terms can be regarded as ‘free’, whereas onshore it must be paid for.

(c)        All offshore staff live, sleep and eat on board, and full facilities must be provided for personnel.  Most onshore staff live away from the station, and only limited living facilities need be provided.

(d)        Onshore installations do not have the heavy electrical loads associated with drilling and well processes such as water injection, gas injection and mud pumping.

(e)        Offshore installations require heckling facilities, marine/air radio communications, navigation aids, lifeboats and similar services, none of which is needed onshore.

(f)        Because of tariff requirements there is need onshore for power-factor control and, if necessary, power-factor correction.

Where they are relevant, these aspects, insofar as they affect onshore installations in general, are dealt with in the following chapters.