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Sorrento field: water saturation (view source)
Revision as of 16:15, 21 November 2014
, 16:15, 21 November 2014no edit summary
[[file:predicting-reservoir-system-quality-and-performance_fig9-95.png|left|400px|thumb|{{figure number|1}}An S<sub>w</sub>-elevation plot. From Hartmann and Coalson.<ref name=Hartmannandcoalson_1990>Hartmann, D. J., and E. B. Coalson, 1990, Evaluation of the Morrow sandstone in Sorrento field, Cheyenne County, Colorado, ''in'' S. A. Sonnenberg, L. T. Shannon, K. Rader, W. F. von Drehle, and G.W. Martin, eds., Morrow Sandstones of Southeast Colorado and Adjacent Areas: RMAG Symposium, p. 91-100.</ref> Courtesy Rocky Mountain Association of Geologists.]]
[[file:predicting-reservoir-system-quality-and-performance_fig9-95.png|left|400px|thumb|{{figure number|1}}An S<sub>w</sub>-elevation plot. From Hartmann and Coalson.<ref name=Hartmannandcoalson_1990>Hartmann, D. J., and E. B. Coalson, 1990, Evaluation of the Morrow sandstone in Sorrento field, Cheyenne County, Colorado, ''in'' S. A. Sonnenberg, L. T. Shannon, K. Rader, W. F. von Drehle, and G.W. Martin, eds., Morrow Sandstones of Southeast Colorado and Adjacent Areas: RMAG Symposium, p. 91-100.</ref> Courtesy Rocky Mountain Association of Geologists.]]
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==Method==
[[Basic_open_hole_tools#Density|Density logs]] were the primary source of [[porosity]] values. Matrix density appears to be about 2.68 g/cc, based on core-measured grain densities (consistent with the presumed mineralogy of the sandstones). Crosspiot porosities were not used to avoid introducing a systematic error in these variably shaly sandstones.<ref name=ch09r42>Patchett, J., G., Coalson, E., B., 1982, The determination of porosity in sandstone and shaly sandstone, part 2: effects of complex mineralogy and hydrocarbons: 23rd Annual SPWLA Logging Symposium, July 6–9, paper T, 50 p.</ref>
==Pickett plot==
<gallery mode=packed heights=300px widths=300px>
predicting-reservoir-system-quality-and-performance_fig9-89.png|{{figure number|1}}Data from well 11. From Hartmann and Coalson.<ref name=Hartmannandcoalson_1990>Hartmann, D. J., and E. B. Coalson, 1990, Evaluation of the Morrow sandstone in Sorrento field, Cheyenne County, Colorado, ''in'' S. A. Sonnenberg, L. T. Shannon, K. Rader, W. F. von Drehle, and G.W. Martin, eds., Morrow Sandstones of Southeast Colorado and Adjacent Areas: RMAG Symposium, p. 91-100.</ref> Courtesy Rocky Mountain Association of Geologists.
predicting-reservoir-system-quality-and-performance_fig9-88.png|{{figure number|2}}Capillary pressure curve. From Hartmann and Coalson.<ref name=Hartmannandcoalson_1990 /> Courtesy Rocky Mountain Association of Geologists.
</gallery>
Formation-water resistivities and water saturations were estimated from Pickett plots (see [[Pickett plot construction]]). The inferred cementation exponent ''(m)'' is 1.8 because of the presence of clays, well-connected solution pores (e.g., <ref name=ch09r31>James, S., W., 1989, Diagenetic history and reservoir characteristics of a deep Minnelusa reservoir, Hawk Point field, Powder River basin, Wyoming, ''in'' Coalson, E., B., Kaplan, S., S., Keighin, C., W., Oglesby, C., A., Robinson, J., W., eds., Petrogenesis and Petrophysics of Selected Sandstone Reservoirs of the Rocky Mountain Region: Rocky Mountain Association of Geologists Symposium, p. 81–96.</ref>, <ref name=ch09r39>Muller, M., M., Coalson, E., B., 1989, Diagenetic and petrophysical variations of the Dakota sandstone, Henry field, Green River basin, Wyoming, ''in'' Coalson, E., B., Kaplan, S., S., Keighin, C., W., Oglesby, C., A., Robinson, J., W., eds., Petrogenesis and Petrophysics of Selected Sandstone Reservoirs of the Rocky Mountain Region: Rocky Mountain Association of Geologists Symposium, p. 149–158.</ref>, or [[Wikipedia:Pyrite|pyrite]] [Kristinick, personal communication]). Formation factors measured on core samples from well 1 support this interpretation.
The Pickett plot in [[:file:predicting-reservoir-system-quality-and-performance_fig9-89.png|Figure 1]] shows data from well 11. The number labels represent the flow units from [[:file:predicting-reservoir-system-quality-and-performance_fig9-88.png|Figure 2]].
==Saturation exponents, ''n''==
Saturation exponents ''(n)'' measured on samples from well 1 showed variations that relate to pore geometry. Microporous siltstones displayed ''n'' greater than 2, indicating either very tortuous pore systems or incomplete saturation by brine during testing. Saturation exponents were less than 2 in the best porosity type. This implies the reservoir is somewhat shaly. However, ''n'' was assumed equal to 2 for log calculations because the lab data were not far from that value and because lab measurements of saturation exponents are notoriously difficult.
==See also==
==See also==