Abstract

With increasing drilling costs it is important to receive information needed for decision-making as early as possible. Information gained while drilling will often give substantial savings.

Hydrocarbon information is one such topic which might reduce costs strongly if available at an early stage. An instrument which will give such information has been developed and used in connection with drilling for oil and gas in the North Sea. The instrument will give detailed information on free hydrocarbons in cap rocks, reservoir rocks and source rocks. The instrument will determine oil shows, type of hydrocarbons in reservoirs, i.e. light oil, heavy oil, biodegraded oil and residual oil; together with the sealing property of a cap rock and the oil water contact in a reservoir. Detailed information on kerogen richness and type in a source rock is also given. This detailed information is also available when oil-based mud is used and within 1 hour after the samples arrive on the rig deck. Examples of the use of this instrument from various wells in the North Sea are discussed in detail.