Exploration Insights September 2020 | Page 10

10 | Halliburton Landmark Petroleum System Index Proven Frontier Number of reservoirs Petroleum System Index © 2020 Halliburton 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.