Diagenesis: information from petrology
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Petrophysical, petrological, geochemical, production, pressure, and other subsurface data must be used to locate diagenetic traps. Petrological data, in conjunction with subsurface shows, can be a powerful tool in mapping and predicting traps.
Using petrological information
Petrographic data can provide information about migration timing, trap preservation, and facies vs. diagenetic controls on hydrocarbon distribution. The table below lists examples of applying petrological information.
Petrological information | Exploration significance | Exploration application |
---|---|---|
Oil-filled fluid inclusions in reservoir or carrier beds | Indicates migration pathways and absolute timing of migration | Migration routes that existed during migration |
Oil-filled fluid inclusions in seals | Indicates leaky seals and timing of leakage | Column height may be small and/or updip (spilled) accumulations may exist |
Primary porosity preservation | Indicates facies patterns may control hydrocarbon distribution | Map depositional facies |
Dissolution porosity present | Diagenesis may be critical for trap location; mineralogy and/or facies may control location of dissolution porosity | Use sequence stratigraphy, hydrologic, or thermal maturity models.[1][2][3][4] |
Postmigration burial cements present | Indicates potential cementation of water leg | Map diagenetic facies |
Example: using cementation timing
In the example shown in Figure 1, Cambrian sandstones in the Lublin Basin (Poland) contain fluorescing oil inclusions trapped before the formation of quartz cements, which degraded the reservoir's quality. Oil traps could occur updip if seals were present during the migration event.
See also
References
- ↑ Tobin, R. C., 1991a, Diagenesis, thermal maturation and burial history of the Upper Cambrian Bonneterre Dolomite, southeastern Missouri: an interpretation of thermal history from petrographic and fluid inclusion evidence: Organic Geochemistry, vol. 17, no. 2, p 142–152.
- ↑ Tobin, R. C., 1991b, Pore system evolution vs. paleotemperature in carbonate rocks: a predictable relationship?: Organic Geochemistry, vol. 17, no. 2, p. 271., 10., 1016/0146-6380(91)90087-Z
- ↑ Read, J. F., C. Kerans, J. F. Sarg, and F. M. Wright, 1995, Milankovitch Sea-Level Changes, Cycles, and Reservoirs on Carbonate Platforms in Greenhouse and Ice-House Worlds: SEPM Short Course 35, 79 p.
- ↑ Wilson, M. D., ed., 1994, Reservoir quality Assessment and Prediction in Clastic Rocks: SEPM (Society of Sedimentary Geology) Short Course 30, 432 p.