Spatial variability in depositional reservoir quality of deep-water channel-fill and lobe deposits

Daniel Bell, Ian Kane, Anna Ponten, Stephen Flint, David M. Hodgson, Bonita J Barrett

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Abstract

Initial porosity and permeability in deep-water systems are controlled by primary sedimentary texture and mineralogy. Therefore, understanding the sedimentary processes that control changes in primary texture is critical for improved reservoir quality predictions. A well-constrained, exhumed submarine lobe in the Jaca Basin, and a submarine channel-fill element in the Aínsa Basin, northern Spain, were studied to characterize the depositional reservoir quality in axial to marginal/fringe positions. Construction of architectural panels and strategic sampling enabled analysis of the spatial changes in textural properties, and their relationship to reservoir quality distribution. Samples were analyzed in thin-section to establish how depositional processes inferred from outcrop observations affect textural properties. Results show that high-density turbidites are concentrated in lobe- and channel-axis positions and exhibit good depositional reservoir quality. Lobe off-axis deposits contain high- and low-density turbidites and have moderate depositional reservoir quality. Conversely, low-density turbidites dominate lobe fringe and channel-margin positions and have relatively poor depositional reservoir quality. There is a sharp decrease in depositional reservoir quality between the lobe off-axis and lobe fringe due to: 1) an abrupt increase in matrix content; 2) an abrupt decrease in sandstone amalgamation; and 3) a decrease in grain-size. There is an abrupt increase in depositional reservoir quality from channel margin to channel axis corresponding to: 1) an increase in total sandstone thickness and amalgamation; 2) an increase in grain-size, 3) a decrease in matrix content. Rates of change of key properties are up to two orders of magnitude greater between channel-fill sub-environments compared to lobe sub-environments. Spatial variability in properties of discrete architectural elements, and rates of changes, provides input to reservoir models during exploration, appraisal, and development phases of hydrocarbon fields.
Original languageEnglish
Pages (from-to)97-115
Number of pages18
JournalMarine and Petroleum Geology
Volume98
Early online date26 Jul 2018
DOIs
Publication statusPublished - Dec 2018

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