OpsFlo for oilfield service companies.
See OpsFlo →
Built by the team behind OpsFlo — field service & billing software for oilfield service companies. Capture tickets at the wellsite and bill in days, not weeks.
Where oil and gas come from and why they collect where they do — source rock, migration, reservoir rock, traps, and the difference between conventional and shale resources.
Oil and gas don't sit in underground lakes — they're held in the pores of rock. A working accumulation needs a complete petroleum system: a source rock that generated the hydrocarbons, a path for them to migrate, a porous reservoir rock to hold them, and a trap and seal to keep them from escaping.
This guide explains each element, plus the porosity and permeability that make a reservoir produce — and why unconventional shale plays break the classic rules.
The five elements explained.
Read →Where hydrocarbons are born.
Read →Porosity and permeability.
Read →How oil and gas move.
Read →Structural and stratigraphic traps.
Read →Why shale is different.
Read →Two properties that matter most.
Read →
Built by the team behind OpsFlo — field service & billing software for oilfield service companies. Capture tickets at the wellsite and bill in days, not weeks.
A source rock is an organic-rich sedimentary rock, usually marine shale, that contains kerogen — the buried remains of plankton and algae. With enough heat and burial, the kerogen matures into oil and gas.
Porosity is the percentage of void space in a rock that can hold fluids; permeability is how well those pores connect so fluid can flow. A good reservoir needs both — high porosity to store hydrocarbons and high permeability to produce them.
In conventional reservoirs, oil and gas migrated out of the source rock into a permeable trap. In unconventional (shale/tight) reservoirs, the hydrocarbons remain locked in the very low-permeability source rock itself, so they only flow economically with horizontal drilling and hydraulic fracturing.