Question

To determine the maximum hydrocarbon column height a trap can hold, what must the capillary entry pressure of the seal rock exceed?

Accepted Answer

To determine the maximum hydrocarbon column height a trap can hold, the capillary entry pressure of the seal rock must exceed the buoyancy pressure exerted by the accumulated hydrocarbon column. Capillary entry pressure is the minimum pressure required to force a non-wetting fluid, such as oil or gas, into the smallest interconnected pore throats of a rock that is saturated with a wetting fluid, typically water. Buoyancy pressure is the upward force generated by the density difference between the hydrocarbon column and the surrounding formation water, which increases linearly with the height of the column. As hydrocarbons accumulate in a trap, the column height increases, causing the buoyancy pressure at the base of the seal to rise. When the buoyancy pressure exactly equals the capillary entry pressure of the seal, the seal can no longer prevent the hydrocarbons from migrating through its pore network. Therefore, the seal is only effective as long as its capillary entry pressure is greater than the buoyancy pressure created by the maximum height of the stored hydrocarbon column.

Home → All Courses → Science and Mathematics Courses → Petroleum Geology → Flashcard

To determine the maximum hydrocarbon column height a trap can hold, what must the capillary entry pressure of the seal rock exceed?