10 | Halliburton Landmark
Petroleum System Index
Proven Frontier
Number of reservoirs
Petroleum System Index
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0.35 0.4 0.45 0.5 0.55 0.6 0.65 0.7 0.75 0.8 0.85 0.9 0.95
Figure 7 > Cross plot of holistic petroleum system index scores versus number of identified reservoir intervals . Note that the range of qualities identified in frontier systems approximates that of proven systems . This suggests that the collated dataset is appropriate for analogue identification .
The first group comprises petroleum systems where the processes that operated had a better score than the elements within the system ( shown in purple on Figure 6 ). These are by far the most numerous , making up 66 % of sampled petroleum systems .
The second group comprises those petroleum systems that have elements with a better score than the processes that operated ( shown in blue on Figure 6 ). This population is the smallest , accounting for 14 % of the sample .
The final group comprises petroleum systems that have both high-quality elements and highquality processes ( shown in yellow on Figure 6 ). This population makes up 20 % of the sample .
In hindsight , the observed abundance of processenhanced petroleum systems is not surprising , as processes control the retention of hydrocarbons over time .
Systematic Analogue Definition
One of the main objectives of the defined schema was to compare potential between proven and frontier petroleum systems ( Figure 7 ). When the qualities of these systems are compared , there is significant overlap between them ; although , proven petroleum systems do have a greater range of qualities at both ends of the spectrum ( Figure 7 ). This reflects the level of knowledge that can be attributed to the proven systems . For example , proven systems are often associated with many more reservoir intervals than frontier systems . This is likely because proven petroleum systems are better explored , so more reservoirs have been identified .
Due to the substantial overlap in the range of index scores , it is suggested that the subset of proven plays will provide a good analogue dataset for the range of frontier plays . One way of defining appropriate analogues is to identify those petroleum systems that occupy a similar domain on the cross plots shown in Figure 6 .
CONCLUSIONS
The holistic , semi-quantitative petroleum system index defined here not only has a significant impact on qualifying and understanding the character of a petroleum system , but can also provide a method for identifying similarities or differences between these complex systems . As shown by the use cases discussed , the index can reveal factors that limit the development of petroleum systems , and enable better analogues to be defined when considering frontier petroleum systems .