Geometry and compartmentalization of fluvial meander-belt reservoirs at the bar-form scale: Quantitative insight from outcrop, modern and subsurface analogues

Abstract

The preserved deposits of fluvial meander belts typically take the form of patchworks of sand-prone bar-form elements bordered by genetically related, muddy channel fills. In meander belts that act as hydrocarbon reservoirs, characteristics of sedimentary architecture, including the geometry of point-bar elements and the internal compartmentalization exerted by the presence of mud-prone abandoned channel fills, control the effectiveness of primary and enhanced hydrocarbon recovery. Therefore, a quantitative description of meander-belt architectures is desired to provide constraints to subsurface predictions.To this end, an examination of sedimentological datasets, enabled by database-assisted analysis, is undertaken. Sixty-four database case studies of modern, ancient outcropping and subsurface fluvial depositional systems are characterized in a quantitative manner, to assess the relative importance of different styles of lithological compartmentalization, and to provide constraints that can be applied to inform predictions of the geometry and connectivity of bar-scale sandbodies in meander-belt reservoirs. The results of this study include: (i) a set of empirical relationships that relate dimensional parameters describing the geometry of point-bar elements, associated channel fills, channel complexes and potentially unswept compartments; (ii) probabilistic descriptions that relate well density to both the proportion of compartments intersected by a well array, and the maximum volume of untapped bar-form compartments.The resulting predictive tools can be applied to assist reservoir development and production, either directly or through incorporation into reservoir models. For example, it is shown how to use these quantitative constraints to predict the likely volume of point-bar reservoir compartments with potential bypassed hydrocarbons, and to optimize drilling strategies (e.g., whether and how to perform infill drilling or horizontal drilling), by providing a measure of the likely presence, size, spacing, and orientation of bypassed hydrocarbon volumes.

Three‐dimensional forward stratigraphic modelling of the sedimentary architecture of meandering‐river successions in evolving half‐graben rift basins

“…Great morphological variability exists in the geometrical characteristics of meandering river systems (Blum, Martin, Milliken, & Garvin, 2013;Colombera, Mountney, Russell, Shiers, & McCaffrey, 2017;Milliken, Blum, Snedden, & Galloway, 2018); with particular reference to extensional settings, the modelled channel-belts resemble in scale those of the Late Quaternary succession of the Rhine-Meuse delta, the Netherlands, in terms of width (40-500 m) and depth (4-10 m) of channels and width of the meander-belts (40-3,200 m) (Cohen, Stouthamer, & Berendsen, 2002). The style of fault evolution, the structural asymmetry of a half-graben, and the magnitude and frequency of hangingwall subsidence exert a great impact on the three-dimensional external morphology and internal stratal geometry and facies heterogeneity of axial channel-belts developed within the evolving basin.…”

“…The point-bar elements modelled in the presented example display expansional and rotational styles of meander transformation, and incorporate fining-upwards and fining-outwards lithofacies trends; thus, the morphological and depositional characteristics typical of fluvial meandering river systems are reproduced. Great morphological variability exists in the geometrical characteristics of meandering river systems (Blum, Martin, Milliken, & Garvin, 2013;Colombera, Mountney, Russell, Shiers, & McCaffrey, 2017;Milliken, Blum, Snedden, & Galloway, 2018); with particular reference to extensional settings, the modelled channel-belts resemble in scale those of the Late Quaternary succession of the Rhine-Meuse delta, the Netherlands, in terms of width (40-500 m) and depth (4-10 m) of channels and width of the meander-belts (40-3,200 m) (Cohen, Stouthamer, & Berendsen, 2002). Spatial variations of hangingwall tilt induced by fault slip and resulting accommodation, the latter expressed as a progressive decrease from the centre of a fault along the fault strike and away from the fault (Chronis, Piper, & Anagnostou, 1991), can affect alluvial channel processes and drive lateral migration of channels towards the fault zone; this results in the development of asymmetrical channel-belts in planform, a phenomenon widely found in tectonically controlled meandering river systems .…”

A 3D forward stratigraphic model of fluvial meander-bend evolution for prediction of point-bar lithofacies architecture

“…In this study, model inputs to constrain channel-form and bar geometries have been acquired from field-based measurements of outcrops and modern systems, from remotely sensed satellite imagery, and from subsurface data (e.g., seismic, cores and well logs). Data that describe such real-world examples are held in the Fluvial Architecture Knowledge Transfer System (FAKTS) -a relational database that stores quantified sedimentological data from many modern classified fluvial systems and analogue ancient fluvial successions (see details in Colombera et al, 2012Colombera et al, , 2013Colombera et al, , 2017, which is populated with sedimentological data from the published literature and our own field studies.…”

“…Overall, our ability to unequivocally reconstruct the complex spatio-temporal evolutionary history and internal architecture of meander bends and their deposits remains limited (Bridge, 2003;Miall, 1996;Colombera et al, 2017).…”

Detailed quantitative description of fluvial reservoirs: A case study of L6-3 Layer of Sandgroup 6 in the second member of Shahejie Formation, Shengtuo Oilfield, China

“…The modern reservoir architecture theory guided by outcrop and modern sedimentation can establish the river channel sand body geometry model, and can identify the isochronous nature of the sand body (Blacknell, 1982;Miall, 1988;Zhang et al, 1996;Yin et al, 1998;Xie et al, 2003;Willis, 2006;Nichols and Fisher, 2007;Wu et al, 2007;Yue et al, 2007;Donselaar and Overeem, 2008;Ma et al, 2008;Yu et al, 2008;Willis and Tang, 2010;Ghinassi, 2011;Kukulski et al, 2013;Colombera et al, 2017), which provides a new direction for the fine characterization of the river facies strata, and has achieved important results in the relevant areas (Jiao and Li, 1998;Liang et al, 2013;Li et al, 2015;Sun et al, 2018Sun et al, , 2020aSun et al, , 2020b . This is a big breakthrough in predicting the shape, extension characteristics and connectivity of the sand bodies with higher accuracy.…”