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Line 79: − − [[file:evaluating-diagenetically-complex-reservoirs_fig1.png|thumb|{{figure number|1}}Cross section in the Crane Field, Richland County, Montana, showing extreme irregularities in the development of porous dolomite zones in the Red River Formation below the C-anhydrite. (From <ref name=pt06r78 />.)]]
Diagenetically complex reservoir evaluation (view source)
Revision as of 21:04, 17 January 2014
, 21:04, 17 January 2014→Diagenetic events that create reservoir heterogeneities
==Diagenetic events that create reservoir heterogeneities==
==Diagenetic events that create reservoir heterogeneities==
Diagenetic alterations are defined here as all physical and chemical alterations that affect a sediment subsequent to deposition, including tectonically produced fractures and faults. Diagenetic alterations that have been observed to generate reservoir heterogeneities having a major influence on reservoir rock properties are shown in Table 1. In sandstone reservoirs, carbonate and anhydrite cementation, clay authigenesis, secondary porosity generation, and fracturing are the most commonly reported alterations. In carbonate reservoirs, the diagenetic components most often observed are gypsum/anhydrite cementation, dolomite replacement, secondary porosity generation, and stylolitization. A cross section from Longman<ref name=pt06r78>Longman, M. W., Fertal, T. G., Glennie, J. S., 1983, Origin and geometry of Red River Dolomite reservoirs, western Williston basin: AAPG Bulletin, v. 67, p. 744–771.</ref> illustrates the complexity of porosity development in one of the few well-documented examples of a diagenetically complex reservoir (Figure 1).
[[file:evaluating-diagenetically-complex-reservoirs_fig1.png|left|thumb|{{figure number|1}}Cross section in the Crane Field, Richland County, Montana, showing extreme irregularities in the development of porous dolomite zones in the Red River Formation below the C-anhydrite.<ref name=pt06r78 />]]
Diagenetic alterations are defined here as all physical and chemical alterations that affect a sediment subsequent to deposition, including tectonically produced fractures and faults. Diagenetic alterations that have been observed to generate reservoir heterogeneities having a major influence on reservoir rock properties are shown in Table 1. In sandstone reservoirs, carbonate and anhydrite cementation, clay authigenesis, secondary porosity generation, and fracturing are the most commonly reported alterations. In carbonate reservoirs, the diagenetic components most often observed are gypsum/anhydrite cementation, dolomite replacement, secondary porosity generation, and stylolitization. A cross section from Longman<ref name=pt06r78>Longman, M. W., Fertal, T. G., Glennie, J. S., 1983, Origin and geometry of Red River Dolomite reservoirs, western Williston basin: AAPG Bulletin, v. 67, p. 744–771.</ref> illustrates the complexity of porosity development in one of the few well-documented examples of a diagenetically complex reservoir ([[:file:evaluating-diagenetically-complex-reservoirs_fig1.png|Figure 1]]).
{| class = "wikitable"
{| class = "wikitable"
| <ref name=pt06r77>Lindquist, S. J., 1983, Nugget Formation reservoir characteristics affecting production the Overthrust Belt of southwestern Wyoming: Journal of Petroleum Technology, July, p. 1355–1365.</ref>
| <ref name=pt06r77>Lindquist, S. J., 1983, Nugget Formation reservoir characteristics affecting production the Overthrust Belt of southwestern Wyoming: Journal of Petroleum Technology, July, p. 1355–1365.</ref>
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Zones of cementation, dissolution, and replacement may exhibit a wide variety of distributions. To prepare an accurate reservoir description, the geologist needs to understand the diagenetic processes, and the controls on these processes, which generated the heterogeneities present in the reservoir under investigation.
Zones of cementation, dissolution, and replacement may exhibit a wide variety of distributions. To prepare an accurate reservoir description, the geologist needs to understand the diagenetic processes, and the controls on these processes, which generated the heterogeneities present in the reservoir under investigation.