Three-dimensional petroleum systems modeling of the Mensa and Thunder Horse intraslope basins, northern deep-water Gulf of Mexico: A case study

摘要

The petroleum systems of two adjacent Miocene intraslope mini-basins in the northern deep-water Gulf of Mexico are modeled to investigate why one of them produces primarily gas but the other produces oil. Specifically, the Mensa field produces gas from a faulted four-way closure that overlies a turtle structure, whereas the adjacent Thunder Horse field produces from a turtle structure with four-way structural closure. To resolve this issue, a three-dimensional petroleum-system model was constructed, whose results indicate that the Lower Cretaceous source interval, comprising type II kerogen, matured significantly earlier in the Mensa basin; the oil window was reached between 11.4 and 9.0 Ma, and the thermogenic gas window was reached between 6.2 and 0.0Ma. By contrast, within the Thunder Horse basin, the source interval reached the oil window by 10.75 to 9.4Ma and largely remains in the oil window. The Thunder Horse trap had formed by 13.05Ma, which was before the end of the oil window. The Mensa trap (9.0-8.2Ma) was not in place when the source rock passed though the oil window.