Understanding Deepwater Field Size Distributions
Ryan J. Wilson
Anadarko Petroleum Corporation, The
Woodlands, TX
The method of using basin-wide field size distributions to predict the
expected size of discoveries in a new play
tends to under-predict reserves
compared to actual results. Over time, the mean field size for a
play
in a basin
becomes smaller as the
play
matures. This happens because companies target the
largest risk weighted prospects first in order to maximize their return on
investment, hence inadvertently applying a weighting factor to the distribution
of outcomes through time. This concept is well illustrated by analyzing recent
exploration results in deepwater basins worldwide. The estimated mean field size
for a deepwater prospect can be as much as ten times under-predicted when using
non-deepwater basin statistics as a guideline. Under-predicting the initial
field size distribution in a new
play
translates directly into the economic
analysis
and can result in poor portfolio management decisions. Therefore,
temporal
analysis
of field size distributions, as well as other petroleum system
characteristics, should be utilized when constructing reserve distributions for
prospects in new plays and frontier areas.
AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005