Connectivity estimation between turbiditic channels and overbank deposits from the modelling of an outcrop analogue (Pab Formation, Maastrichtian, Pakistan)

Abstract

The facies associations of the overflow deposits associated with turbidite channels were studied in the outcrops of the Maastrichtian Pab Sandstone, in SW Pakistan. In this area, a basin-floor fan was preserved from the platform to the deep basin setting. In the mid-fan setting, a channel complex crops out in three dimensions, and consists of a dozen channels and their overflow deposits, including levees, crevasse lobes and spill-over lobes. The overbank deposits can be directly in contact with the channel-fill, but, in many cases, matrix-supported debris-flow deposits made lenses close to the channel base. Heterolithic drapes of thin-bedded turbidite deposits were also preserved along the channel margins. A three-dimensional (3D) static model describing the heterogeneity distribution within the turbiditic channel complex was compiled using both stochastic and deterministic approaches in a site where two channels were laterally connected by overbank deposits. Petro-acoustic properties derived from a subsurface database were then assigned to the facies to perform seismic simulations. The synthetic seismic simulations showed that the channel base can easily be misinterpreted compared to the geological model. Dynamic modelling, such as well test and streamline simulations, was also performed using the model to assess the transition between the channel and overbank deposits from a dynamic point of view. As a result of the streamline simulations, the overbank deposits connecting the channel homogenized the pressure regime in the reservoir. However, the sweeping efficiency of water injection can be affected by the heterogeneity distribution along the channel margins. A significant volume of oil could also be by-passed because of the occurrence of early water breakthrough through the spill-over lobes, or because the flow slowed down when it reached the heterogeneity along the channel margin.

Insight into Heterogeneous Calcite Cementation of Turbidite Channel-Fills from UAV Photogrammetry

“…The above model provides probabilistic constraints on spatial distribution of calcite-cemented concretions which can be used, in combination with sedimentary facies, to inform fine-scale geostatistical modelling of poro-permebility properties of hydrocarbon reservoirs hosted in turbidite channel-fill [2,6,14,25,64].…”

The application of outcrop analogues in geological modelling: a review, present status and future outlook

“…The papers cover a range of clastic depositional environments from fluvial (Alsop et al 2013;Pranter et al 2013;Rittersbacher et al 2013;Keogh et al 2014;Nordahl et al 2014) through paralic (Massey et al 2013;Rarity et al 2013) to deep marine (Eschard et al 2013). Two deal with LiDAR and virtual outcrop techniques from a ground base (Rarity et al 2013) and from a helicopter platform (Rittersbacher et al 2013); ground-based LiDAR was also used by Keogh et al (2014).…”

“…Luthi & Flint (2013) summarize the current state of the art in the use of behind outcrop borehole studies that provide a crucial link from our outcrop analogue studies to the datasets most commonly used for subsurface analysis. The link between outcrop and subsurface data was also closed by Eschard et al (2013), who built synthetic seismic profiles from their outcrop data in Pakistan as a means of determining which aspects would be resolvable under normal subsurface conditions.…”