Ann: Mukuyu 1 & Sidetrack Well Results Amendment, page-698

"Hopefully this is the same at depth (I'd assume so?)"

Only if rocks at depth have undergone exactly the same history in terms of compaction and diagenesis (chemical and physical changes that sedimentary rocks undergo during and after burial).

Diagenesis includes the deposition of secondary quartz and other minerals around the quartz clasts making up a sandstone and restrict the pore throats...resulting in a reduction in porosity and permeability. This process is controlled both by depth of burial and thermal history of the basin. Generally with depth you get a reduction in porosity and permeability.