June 1, 2014
Title: Mapping Shale Potential in Europe
Publication: PESGB Newsletter (June 2014)
Author: Roman Boros, GIS Analyst, Rystad Energy
Even though direct extraction of oil and gas from the source rock is currently only actively developed in America (United States, Canada and Argentina), European nations have the geological capabilities to develop shale resources, too. Rystad Energy has identified more than 40 prospective shale formations (within 20+ basins) in Europe, which fulfill the early geologic requirements for shale development.
Shale Gas Resource Potential in Europe
Some shale development efforts have already been reported in Poland, with limited results. Meanwhile, exploration plans have already been reported in the UK and Ukraine. Rystad Energy has identified 40+ prospective shale formations in Europe that satisfy early geologic requirements for shale development. Figure 1 shows economically recoverable shale resources for the ten most promising shale holder countries in Europe, split by gas and liquids (includes light oil and NGL).
The European shale resources are distributed along 20+ basins, as shown in Figure 2. In each shale prospective basin, the shale plays are displayed in colours by initial geologic period. We also include an overlay of the total sediment thickness map layer to distinguish between the areas with total sediments of less and more than 2,000 meters. The first case is displayed with higher transparency.
Where Are the Play Fairways
Rystad Energy developed a GIS method to estimate the prospectivity throughout the shale play. This automated method does not attempt to replace expert geologic exploration research, but rather samples a GIS valuation model, which enables relative comparison of shale play acreage. It observes variation of geological parameters across the plays and determines zones, which are more prospective than others, using the proved analogies from North American shale plays. The GIS valuation model looks for optimal combination of key geological parameters, such as play depth, thermal maturity and thickness, in order to identify play fairways. The method is further briefly described on the Poland Silurian shale play in the Baltic-Podlasie-Lublin basin (Figure 3).
The depth of the play continuously increases from 500m below surface in the northeast to 5,500m in the southwest of the basin. Based on analogies in North American shale plays, the ideal depth is in the range of 1,500-2,100m (~ 5,000-7,000 ft). This ideal depth range receives the highest score in the model. The score of shallower areas will be lower because of possible low deliverability of the formation (lower formation pressure), while deeper areas get lower scores because the well would become more expensive to drill. Another key geologic parameter is the thermal maturity of a play, indicated by vitrinite reflectance (%Ro). Scoring in the model is based on price differentiation of different hydrocarbon types. Wet gas/condensate (1.1-1.3 %Ro) window receives the highest score, followed by oil (0.6-1.1 %Ro) and dry gas (>1.3 %Ro) windows. The occurrence of the thermal maturity windows correlates with the play depth in Poland Silurian shale play, with oil window in the northeast and gas window in the southwest portion of the play. The third input in the model is the play thickness, where scoring increases continuously with higher isopachs. Poland Silurian shale play is thickest in the northern part – in the Baltic basin with a maximum of 60m (~ 200 ft). The weighted overlay of these three scored inputs results in the final prospectivity map (Figure 4). The combination of the best scores of play depth, thermal maturity and thickness determines the fairway of the Poland Silurian shale play, with highest prospectivity in the Podlasie basin and coastline areas of the Baltic basin.