Optimization of hydrocarbon production from sand injectite systems: some rules of thumb

By constructing and dynamically simulating a three-dimensional geological model of a hydrocarbon prospect in the North Sea, several development strategies were tested to assess how hydrocarbon fields in sand injectite systems could be optimized. Significant reductions in water production and a moderate increase in oil can be achieved if a well is placed at a shallow depth in a sand-injectite system within an interval where sand injectites are not normally resolved on seismic data, net-to-gross (N/G) is low (typically less than 0.1) and stand-off to the oil–water-contact (OWC) is maximized. The low N/G of such wells challenges the paradigm that a successful development well must have a high proportion of net sand. While the cumulative volume of oil production may be similar to a development well placed closer to an OWC in a seismically mapped drill target, the cumulative volume of water produced may be significantly reduced. In the simulations presented here a broad K v / K h range was used to test the gross vertical connectivity uncertainty within the sand injectite system. A sweet spot exists at a K v / K h of around 0.1 – above that value water breakthrough and cut were accelerated, while below that sand injectite connectivity and water flood were choked back. The gross architecture and flow potential of both seismically mapped and non-seismically resolved sand injectites should be considered. Scenarios may exist where lateral sweep within a seismically mapped sand injectite is enhanced due to reduced vertical connectivity within the non-seismically resolved sand injectites.