Page 21 - Well Logging and Formation Evaluation

Basics 11

• Repeat sections to be performed
• Data items and format to be included in the log header
• Procedures for numbering and splicing different runs in a hole
• Scales to be used in the presentation of logs
• Format and media required for digital data
• Requirements for reporting of time breakdown of logging operation,
personnel on site, serial numbers of tools used, inventory of explosives,
and radioactive sources
• Specific safety procedures to be followed
• Provision of backup tools
• Fishing equipment to be provided

Generally speaking, the more the oil company specifies its require-
ments, the better. Having a strict system in place for controlling the
logging operation and presentation of results ensures a smooth operation
and results in high-quality data that will be consistent with previous
runs.

1.4 PREPARING A LOGGING PROGRAM

At the FDP stage in a field development, the outline of the logging strat-
egy should be developed. Based on the type of well being proposed, deci-
sions have to be made about whether to go principally for an LWD type
of approach or conventional wireline and about the types of tool to be run.
In general, early in the life of a field, particularly during the exploration
phase, data have a high value, since they will be used to quantify the
reserves and influence the whole development strategy. Moreover, lack of
good-quality data can prove to be extremely expensive, particularly for
offshore developments, if facilities are designed that are either too big or
too small for the field.
Later in field life, particularly in tail-end production, where much of
the log data will not even be used for updating the static model, since it
is influenced by depletion effects, the value of data becomes much less.
However, even in mature fields, it may be the case that extensions to the
main accumulation are still being discovered, and existing assumptions
such as those regarding the position of the FWL may need to be locally
revised.
The FDP should lay down the broad strategy for data acquisition, which
will take into account the relevant uncertainties remaining in the STOIIP
and the options for adapting the wider development strategy. It is obvi-