Changes

====Tectonic phenomena====

====Tectonic phenomena====

Tectonic phenomena also produce overpressures. In the Gulf of Alaska, fluid pore pressures up to 0.85 psi per ft were found due to horizontal compressive stress in the rocks. In Western Alberta, large thicknesses of Paleozoic carbonates have been thrust over soft Cretaceous shales, resulting in overpressuring of the lenticular oil-bearing sandstones that extend under the overthrust (such as Leafland and Pembina).

Tectonic phenomena also produce overpressures. In the Gulf of Alaska, fluid pore pressures up to 0.85 psi per ft were found due to horizontal compressive stress in the rocks. In Western Alberta, large thicknesses of Paleozoic carbonates have been thrust over soft Cretaceous shales, resulting in overpressuring of the lenticular oil-bearing sandstones that extend under the [[overthrust]] (such as Leafland and Pembina).

====Thermal cracking of organic matter====

====Thermal cracking of organic matter====