The Perpetual Mystery of Petroleum Migration

Abstract

As petroleum explorationists, we live with the ultimate embarrassment. We have no tangible proof of how gas and oil come to be in the places where we find them. Many pages of our journals are devoted to “upstream” organic sources and “downstream” reservoir traps. We have some reasonable ideas of where those places are, but in between is that no-man’s land of migration. I think the mystery can be solved by viewing the entire petroliferous system, upstream and downstream, as a three-dimensional, water-driven, fluid continuum. If we can accept the idea that the colloidal admixtures of hydrocarbons we know as gas and oil are assembled in the downstream traps from water-borne organic derivatives (e.g., acids, salts, hydrocarbons, etc.), the bulk migration of pre-formed, separate-phase gas and/or oil becomes unnecessary. Let us admit that the movement of significant quantities of gas and/or oil over significant distances has never been factually observed or proven to occur, even for the largest accumulations. An analogy to mineral deposits, which likewise do not move in bulk form, is suggested.

The concept of a water-driven petroliferous continuum raises questions about some popular assumptions (e.g., temperature windows, episodic fluid movement, buoyancy, differential entrapment) which characterize our literature. For some of these, alternatives based on field observations can be offered. Although we are dealing with a noisy, complicated system, I think we can simplify and improve our understanding of it. It could make finding the remaining gas and oil reserves easier and less expensive.