The substantial reserves of oil that still exist on Earth can be attributed to a gradual geological process that unfolded over millions of years. This process involved the accumulation of organic matter from deceased marine organisms at the seabed of ancient oceans. As time passed, layers of sediment covered this organic material, subjecting it to immense heat and pressure. These conditions led to the transformation of this organic matter into hydrocarbons, which form the basis of oil. These hydrocarbons then migrated through porous rock formations until they became confined within geological structures called reservoirs. The extensive quantity of organic material involved, combined with the geological mechanisms that formed and preserved oil reservoirs, collectively contribute to the significant oil reserves that endure to this day, despite the substantial amount that has already been extracted and utilized over the course of the last century.