Sorrento water saturation calculations
Method
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.[1]
Pickett plot
Formation-water resistivities and water saturations were estimated from Pickett plots. The inferred cementation exponent (m) is 1.8 because of the presence of clays, well-connected solution pores (e.g., [2][3] or pyrite (Kristinick, personal communication). Formation factors measured on core samples from well 1 support this interpretation.
The Pickett below shows data from well 11. The number labels represent the flow units from Figure 9-88.
Saturation exponents, n
Saturation exponents in) 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
References
- ↑ 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.
- ↑ 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: RMAG Symposium, p. 81–96.
- ↑ 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: RMAG Symposium, p. 149–158.
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