High-resolution borehole image analysis in a slope fan setting: examples from the late Miocene Mt Messenger Formation, New Zealand
Published:January 01, 2005
M. Johansson, 2005. "High-resolution borehole image analysis in a slope fan setting: examples from the late Miocene Mt Messenger Formation, New Zealand", Submarine Slope Systems: Processes and Products, David M. Hodgson, Stephen S. Flint
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High-resolution resistivity image surveys and core were acquired from two wells 150 m apart within the late Miocene Mt Messenger Formation. The wells were located at Pukearuhe Beach, Taranaki, New Zealand and were situated along strike of the palaeoslope. The formation is interpreted as a slope fan setting and the interval logged was dominated by a major channel that incised into older channel-levee and overbank fan facies. The scour surface and the distinctive channel-fill enabled the two wells, Pukearuhe Central and Pukearuhe North, to be correlated with the local outcrop. The sedimentary deposits within the studied section were divided into three facies associations: channel-fill, channel levee and overbank deposits. The channel deposits exhibited similar facies in both wells. The dip data from the image logs indicate that the original channel was in-filled by sedimentation dipping towards the NW, the same orientation as the regional palaeoslope. In contrast, analysis of the levee and overbank deposits indicated little correlatability between the two wells, with beds dipping, locally up to 10°, in directions ranging from up-slope (SE) to oblique (NE) to the palaeoslope. The variation in dip directions in the levee and overbank deposits is attributed to scouring and infilling of irregular topography at and beyond the channel margin. As a reservoir prospect the thicker channel sands would be a preferential play to the laterally discontinuous thin beds.
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Submarine Slope Systems: Processes and Products
Submarine slopes provide the critical link between shallow-water and deep-water sedimentary environments. They accumulate a sensitive record of sediment supply, accommodation creation/destruction, and tectonic processes during basin filling. There is a complex stratigraphic response to the interplay between parameters that control the evolution of submarine slope systems, e.g. slope gradient, topographic complexity, sediment flux and calibre, base-level change,tectonic setting, and post-depositional sediment remobilization processes. The increased understanding of submarine slope system has been driven partly by the discovery of large hydrocarbon fields in morphologically complex slope settings, such as the Gulf of Mexico and offshore West Africa, and has led to detailed case studies and improved generic models for their evolution. This volume brings together research papers from modern, outcrop and subsurface settings to highlight these recent advances in understanding of the stratigraphic evolution of submarine slope systems.