Sequence stratigraphic-based analysis of reservoir connectivity: influence of depositional architecture – a case study from a marginal marine depositional setting

Abstract

This case study of the Sunrise and Troubadour fields (offshore northwest Australia) concentrates on the impact of primary depositional architecture on reservoir connectivity via a sequence stratigraphic-based, 3D reservoir modelling approach. The marginal marine reservoir is composed of fluvial-dominated and wave-dominated depositional environments. The succession is divided into six sequences and 12 systems tracts. Each systems tract is subdivided into parasequences which form the basic building blocks of the 3D model. The connectivity of sandbodies within each parasequence, systems tract and sequence were calculated when the models were palinspastically restored to a depositional datum.The findings indicate that depositional connectivity trends within a sequence stratigraphic framework are predictable. Connectivity trends can be related directly to depositional and stratigraphic trends and to position in the sequence stratigraphic hierarchy. Therefore, with a good understanding of depositional settings and high resolution sequence stratigraphic subdivision of strata, predictions of depositional connectivity trends at all stratigraphic hierarchical levels can be made. All connectivity trends at sequence and systems tract stratigraphic hierarchical levels remained the same when the area of the model was reduced by a factor of four and the volume of the model was reduced by truncation below the gas-water contact. Hence, the relationships between the stratigraphic trends and the connectivity trends for the thicker stratigraphic units can be said to be scale invariant.Three-dimensional reservoir models currently provide the best means of quantitatively assessing and predicting reservoir connectivity. However, in low fault density settings, initial screening of reservoir connectivity can be made using connectivity indicators calculated from simple parameters derived from well data such as 'Thickness divided by Sand/Shale ratio'.

Towards the standardization of sequence stratigraphy

“…1993; Ainsworth, 1994;Nummedal and Molenaar, 1995;Pemberton and MacEachern, 1995;Helland-Hansen and Martinsen, 1996;MacEachern et al, 1998;Plint and Nummedal, 2000;Bhattacharya and Willis, 2001;Posamentier, 2002;Hampson and Storms, 2003;Ainsworth, 2005). Arguably, sequence stratigraphy is easiest to apply in these environments, where the shifts in depositional trends are more evident and all sequence stratigraphic surfaces may form (Figure 17).…”

Sedimentology and reservoir properties of tabular and erosive offshore transition deposits in wave-dominated, shallow-marine strata: Book Cliffs, USA

“…Galloway et al 2000;Husmo et al 2003;Ainsworth 2005) and are typically less heterogeneous than their tide-and river-dominated counterparts (MacDonald & Aasen 1994;Howell et al 2008. Commonly used facies models (e.g.…”

Distribution of discontinuous mudstone beds within wave-dominated shallow-marine deposits: Star Point Sandstone and Blackhawk Formation, Eastern Utah, USA

“…Galloway et al, 2000), and numerous Tertiary delta systems of South East Asia (e.g. Hodgetts et al, 2001;Ainsworth et al, 2005). These reservoirs typically have simpler depositional architectures and are therefore easier to produce than reservoirs within fluvialand tide-dominated shoreline systems (Ainsworth et al 2005;Martinius et al, 2005;Howell et al, 2008a;Howell et al, 2008b;).…”

“…Hodgetts et al, 2001;Ainsworth et al, 2005). These reservoirs typically have simpler depositional architectures and are therefore easier to produce than reservoirs within fluvialand tide-dominated shoreline systems (Ainsworth et al 2005;Martinius et al, 2005;Howell et al, 2008a;Howell et al, 2008b;). Wave-dominated shallow marine systems are commonly treated as "tanks of sand", in which the shoreface is modeled as a shore-parallel belt of homogeneous sandstone (MacDonald and Aasen 1994;Howell et al, 2008a).…”