Estimating Mature Plays
57
Play Resource and Potential Distribution
Play Resource Distribution
A geological model can generate a variety of play resource values when
using the superpopulation concept. All these resource values constitute the play resource distribution for the superpopulation.
In PETRIMES, the play resource distribution, T, is the sum of all
pool sizes of the play. If the pool sizes are approximated using lognormal distributions, then the play resource distributions are the sum of
the lognormal distributions. Because this summation does not have an
analytical form, the summation is executed using a Monte Carlo simulation procedure. The mean and variance of the play resource distribution are as follows:
E [T ] = E [X ] × E [N ]
(3.13)
s T = s × E [N ] + (E [X ]) × s N
(3.14)
where E [T ] is the mean of the play resource distribution, E [X ] is the
mean of the pool-size distribution, E [N ] is the mean of the number-ofpools distribution, σ T is the variance of the play resource distribution,
σ is the variance of the pool-size distribution, and σ N is the variance of
the number-of-pools distribution.
The play resource distribution was derived from the total number of
pools, N, and the lognormal or nonparametric pool-size distribution.
Figure 3.15B displays the play resource distribution for the Beaverhill
Lake play. There is a 90% chance that the play will have a resource
ranging from 530 × 10
6 m
3 to 1670 × 10
6 m
3 , and a 50% chance that the
play will have a resource ranging from 789 × 10
6 m
3 to 1262 × 10
6 m
3 of
oil-in-place. The expected value is 1042 × 10
6 m
3
. The amount of oil that
has already been discovered is 947 × 10
6 m
3
.
Table 3.4. Examples of Pool Ratios of the
Beaverhill Lake Play
Ratios
Upper percentiles
95
50
5
1/2
1.106
2.03
16.27
1/3
1.32
3.60
32.33