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Connectivity Estimation between Turbiditic Channels and Overflow Deposits from the Modelling of an Outcrop Analogue (Pab Formation, Maastrichitan, Pakistan)

Eschard, Remi 1; Deschamps, Remy *1; Doligez, Brigitte 1; Euzen, Tristan 1
(1) Inst Francais de Petrole, Rueil Malmaison, France.

The facies associations of the overflow deposits associated to turbidite channels were studied in the outcrops of the Maastrichitian 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 turbiditic channel complex crops out in 3D, and consists of a dozen of channels and their overflow deposits, including levees, crevasse lobes and spill over lobes.

The overflow deposits can directly be 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 3D static model describing the heterogeneity distribution was compiled in a site where two channels were laterally connected by overflow deposits. Petro-acoustic properties were assigned to the facies from a subsurface data-base. Seismic simulation showed that the channel base can easily be misinterpreted. Well test and stream-line simulations were also performed from the model to assess the reservoir behaviour to fluid flow.

The overflow deposits connecting the channel homogenised 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 trough the spill-over lobes, or because the flow slowed downed when it reached the heterogeneity along the channel margin.

 

AAPG Search and Discovery Article #90142 © 2012 AAPG Annual Convention and Exhibition, April 22-25, 2012, Long Beach, California