Reservoir and Porosity Prediction Using Statistical Rock Physics and Simultaneous Inversion: a Case Study, Onshore Ukraine

The Semyrenky field of the Poltava Basin, onshore Ukraine, lies within the NW-SE trending Late Devonian Dneiper-Donets rift basin. The targets for field development are clastic reservoir sandstones of the post-rift sequence, which are buried to depths down to 5500 m where high levels of compaction limit reservoir porosities to less than 13 %. Deciding where to place production wells within the Semyrenky onshore gas field can be challenging and uncertain when using only reflectivity data. The ability to correctly predict sand distribution and porosity over the field is therefore of great value. The QI workflow applied used a combination of statistical rock physics (to capture variability and uncertainty in rock properties) and high-quality seismic data, obtained through a bespoke re-processing solution. Seismic inversion was used to generate rock property volumes, which were quantitatively compared to the rock physics model to produce probabilistic estimates of lithology. Existing wells within the field validate the reservoir and porosity predictions produced by this study. Well production data was compared to predicted reservoir quality and showed good correlation. Results at two wells drilled post-study also show a good match between predicted results and well logs for both reservoir presence and quality.