NIEMANN, JAMES C., Chevron North American Exploration and Production Co., New Orleans, LA
Abstract: Statistical Distribution of Hydrocarbon Column Heights For Gulf of Mexico Trap Types and Seals
A statistical distribution
of hydrocarbon column heights has been documented for Gulf of Mexico oil
and gas trap types based on a database of 804 reservoirs in 305 fields.
The data clearly show that column heights follow a skewed, log normal distribution,
assuming there is a sufficient population of reservoirs to analyze. Prospect
economic analysis using probability distributions of column height in conjunction
with structural
maps
appears to be valid for determination of the area
extent of potential hydrocarbon accumulations. Five percent, 10%, 50%,
90% and 95% cumulative probability distributions have been calculated for
a wide variety of traps and lateral seal combinations. Fault seal traps
in
sections
with hydrostatic or low over-pressure gradients (<14.8 kPa/m,
<12.5 PPG), composing nearly half of all GOM traps in this study, show
a relatively narrow distribution. However, distributions for trap types
along salt flanks and for traps in
sections
with high-pressure gradients
are significantly broader. The database can be used to analyze the effects
on probability distributions of varied phenomena such as salt, stratigraphic
traps, supernormal pressure, fault timing, geologic age and single versus
dual phase hydrocarbon reservoirs.These results suggest that other natural
phenomena such as pay thickness and recovery factors may have log normal
distributions and can be analyzed in a probabilistic manner also.
AAPG Search and Discovery Article #90923@1999 International Conference and Exhibition, Birmingham, England