Migration distance: vertical and lateral
| Exploring for Oil and Gas Traps | |
| |
| Series | Treatise in Petroleum Geology |
|---|---|
| Part | Critical elements of the petroleum system |
| Chapter | Migration of petroleum |
| Author | Martin D. Matthews |
| Link | Web page |
| Store | AAPG Store |
Distance of migration from source to reservoir varies greatly. The rule that the first sealed reservoir in a trapping configuration has the highest probability of containing hydrocarbons has been proven over and over again. Lateral migration distances, established by oil-source geochemical fingerprinting, reach hundreds of kilometers; vertical distances reach tens of kilometers. Estimation of migration distance is based on geochemical observations and inferences. These include maturity of product, geothermal gradients, fingerprint matching between source and reservoir, and geological estimation of the nearest rock unit of source quality.
Vertical migration
A reservoired hydrocarbon is analyzed geochemically to determine the maturity of the source from which it was derived. Using this information and an estimate of the change in maturity, the minimum vertical depth of origin is determined. The change in maturity with depth is estimated from measurement or modeling. Detailed geochemical studies of extracts, including isotopic analysis, often show a smoothly increasing gradient of maturity, suggesting local genesis and short migration distances. Superimposed on this gradient are isolated spikes of hydrocarbons with maturities characteristic of much deeper conditions. These represent migrated product.
Long-distance migration factors
The factors that influence the distance hydrocarbons may travel are complexly interrelated. Such a detailed knowledge of the petroleum system and the stratigraphy of the area is required that prediction of migration distance is next to impossible. It requires source–reservoir correlation, knowledge of the extent of the source rock, and knowledge that there are no other potential sources. The dominant factors favoring long-distance transport of hydrocarbons include the following:
- Large volume of hydrocarbons
- Efficient expulsion
- High-quality carrier beds
- Uninterrupted updip pathways
- High-quality regional seal
See also
- Migration pathways
- Formation-scale migration pathways
- Defining migration pathways from source to trap
- Migration rate
External links
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