Source rocks migration

Gas from a source rock migrates vertically upwards into a trap which is closed by a seal. 

Keywords plate tectonics, sedimentary basins, source rocks, maturation, migration, reservoir rocks, traps, seismic, gravity survey, magnetic survey, geochemistry, mudlogs, field studies. 

The maturation of source rocks is followed by the migration of the produced hydrocarbons from the deeper, hotter parts of the basin into suitable structures. Hydrocarbons are lighter than water and will therefore move upwards through permeable strata. 

Objecfive Method Basin Source Rock Maturation Migration Rese rvoir Rock Trap Fluids oil, gas, water... 

Migration (primary) the movement of hydrocarbons (oil and natural gas) from mature, organic-rich source rocks to a point where the oil and gas can collect as droplets or as a continuous phase of liquid hydrocarbon. 

Although coal and kerogen in shale do not migrate, continents do. This could lead to useful correlation studies similar to those done presently on petroleum reserves and source rocks. Presently, biological marker analysis by GC-MS, together with isotope analysis and geological considerations, are used to characterize known oil fields. Using this and correlation data from source rocks and reservoirs facilitates prediction of possible location, age, and depth of new reservoirs. 

Littke R., Baker D. R., and Leythaeuser D. (1988) Microscopic and sedimentologic evidence for the generation and migration of hydrocarbons in Toarcian sources rocks of different maturities. Org. Geochem. 13, 549—559. 

Talukdar S., Gallango O., Vallejos C., and Ruggiero A. (1987) Observations on the primary migration of oil in the La Luna source rocks of the Maracaibo Basin, Venezuela. In Migration of Hydrocarbons in Sedimentary Basins (ed. B. Doligez). Editions Technip, Paris, France, pp. 59-78. 

The concentration of individual biomarkers in a crude oil are relatively low (Peters and Moldowan, 1992 Figure 7), but their information content is significant and related to source, depositional environments, maturity, age, migration, and extent of biodegradation. The complete biomarker fingerprints obtained by MID are used extensively for the purpose of undertaking oil/oU or oil/source rock correlation studies. There are numerous papers and books which have documented the utilization of biomarkers in petroleum exploration only a few examples of the major applications will be... 

The data described above can be used to predict the location of better source rocks in vertically drained basins, especially in deltaic-type environments with relatively young source rocks. With long-distance vertical migration, some of the biomarker parameters may become skewed. A number of factors must first be considered before applying this approach first, some of the parameters vary with maturity second, C30 steranes are not present in lacustrine samples and so the approach will not work in that situation and finally, it will not work where the oils were deposited prior to land plant evolution, since no vitrinite was present at that time. Oils from mixed source rocks also complicate the issue. The ability to predict source rock properties on the basis of biomarker distributions in cmde oils is a very interesting concept, since most exploration efforts try to discover oil and not source rocks. 

An important aspect of the formation of petroleum accumulations is timing. The reservoir must have been deposited prior to petroleum migrating from the source rock to the reservoir rock. The seal and trap must have been developed prior to petroleum accumulating in the reservoir, or else the petroleum would have migrated farther. The source rock must have been exposed to the appropriate temperature and pressure conditions over long periods of time to change the organic matter to petroleum. The necessary coincidence of several conditions is difficult to achieve in nature. 

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