Quantitative, Three-dimensional Analysis of Compartmentalisation in a Wave-dominated, Shallow Marine Reservoir Analogue: ABSTRACT

Abstract

The value of outcrop reservoir analogues lies in their use as models of subsurface variability, as sources of quantitative data for reservoir modelling and as deterministic representations of geology for quantifying [open quote]what matters[close quotes] for various flow processes. Analysis of large-scale outcrops (35 by 25km) of the Grassy Member of the Blackhawk Formation has revealed quantitatively, the variability of geometries and stacking patterns of stratigraphic elements, and the influence these characteristics have on reservoir compartmentalisation. Parasequences display a distinctive basinward thickening-thinning morphology in which the major [open quote]reservoir[close quote] facies are concentrated in the updip 60-70% of the unit. The detailed internal architecture of the para- sequences is controlled by the stacking patterns of the intraparasequence [open quotes]compartments[close quotes]. These have the same morphology as the parasequences, but through differences in offset (ranging from 2.2 to 3.5km), exert a strong control on the vertical compartmentalisation of individual parasequences. Definition of the major stratigraphic elements is aided by the presence of shales along the significant bounding surfaces. These continuous shales do not display simple updip pinchouts, but instead commonly pass updip into zones of discontinuous shales. Other discontinuous shales are common in the middle and lower shoreface facies associations. Incorporationmore » of the data into flow simulation models has enabled the influence on flow process of compartmentalisation and shales to be assessed. Flow simulation experiments suggest that the presence of these shales can cause significant decreases in recovery during waterflooding.« less