This question is a bit tricky because it's not about a single scientist, but rather a process involving multiple disciplines and advancements. Here's a breakdown:

* Geology: Geologists are fundamental. They study the Earth's structure, rock formations, and the history of sediment deposition. They use this knowledge to identify potential oil-bearing formations.

* Geophysics: Geophysicists use various techniques like seismic surveys to create images of the subsurface. These images help locate potential oil traps and estimate the size of the reservoir.

* Petroleum Engineers: These engineers design and implement methods to extract oil from the reservoir. They work with geologists and geophysicists to optimize production.

The "discovery" is often a collaborative effort:

* A geologist might identify a promising area based on geological maps and rock samples.

* A geophysicist then conducts seismic surveys to refine the target and potentially identify traps.

* Drilling is undertaken, and the petroleum engineer analyzes the data to confirm the presence of oil and optimize production.

Therefore, it's not just one scientist, but a team of specialists using various tools and techniques to build a comprehensive understanding of the subsurface and locate oilfields.

Let me know if you have any other questions about the process of discovering oilfields!