Abstract

Shallow poorly-consolidated viscous oil bearing sandstones in Kuwait were deposited in a complex fluvio-deltaic environment that was episodically influenced by estuarine-transitional-marine settings. Ongoing reservoir characterization is uncovering high matrix contents along with various cement phases, predominantly calcite, dolomite, and clay minerals that control the pore-networks with inter-granular primary porosity and generation of secondary pores, thus impacting the overall lithofacies and fluid flow-path used to design the development strategy.

A high-resolution Sequence Stratigraphy model revealed the dominant lowstand and highstand-transgressive depositional regimes for reservoir development. In the model sand bodies commonly represent multi-stacked fluvial to distributary channel-fills and associated facies resulting with variable degree of fluid saturations.

Using Sequence Stratigraphy first time, for an unconventional oil reservoir in Kuwait, this model is aimed to: 1) improve the understanding of depositional facies, evolution and distribution of reservoir sand trends within a chronostratigraphic framework, and 2) address the predictability of lateral and vertical complexity and distribution of the reservoir/non-reservoir Lithofacies.

A Gamma Ray/Density model was built in Petrel® software module, allowing creating a log-based property model and applied it to a set of logs, defining 11 lithofacies which have been calibrated with sedimentary core descriptions and divided in three categories; pay reservoir, non-pay reservoir (cemented baffles) and non-permeable facies. Discontinuous shale/siltstone/cemented baffles would act as thief zones and may cause cross-formational flow and conductive heat loss; this must be taken into consideration for thermal recovery strategy.

The developed Sequence Stratigraphy model has established a pattern of Systems Tracts that would address to define the lateral and vertical complexity and distribution of the reservoir lithofacies, and the model would provide a greater ability to identify and predict individual pay and non-pay zones with inherent rock lithologies and heterogeneity to result in a predictive sand-architecture framework for proper thermal development.

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