The Chestnut oilfield was discovered in 1986 and lies within Block 22/2a, Licence P354, of the UK Central North Sea. The field is approximately 7 km south of the Britannia gas condensate field and 8 km SE of the Alba oilfield on the southern edge of the Witch Ground Graben. The field comprises injected Lower Eocene Nauchlan sandstone encased within Horda Formation shales. The Chestnut Field began production in 2008 through the Hummingbird floating production vessel by means of two producer wells and one injector well. The complex reservoir geometries present seismic imaging challenges, and production data have indicated a larger connected volume than mapped from seismic data. In 2017, an infill producer well was drilled to arrest production decline. This well proved the presence and connectivity of sandstone beyond the field interior and increased confidence in using seismic data for predicting the injectite reservoir distribution.

We present the results of multiattribute imaging and geobody delineation applied to stratigraphic targets such as Jurassic channels and Triassic beaches and spits, imaged in data from the Norwegian sector of the North Sea. Interpretation based on the examination of seismic amplitude alone is challenging due to the complexity and subtleness of these features. To improve the definition of these Mesozoic targets, we have applied a multiattribute approach, combining frequency decomposition, seismic attribute analysis techniques, advanced visualization, and a new method of multiattribute geobody delineation. Attributes have been selected that are sensitive to the edge and magnitude response of sedimentary structures, while the use of narrow band spectral magnitude volumes allows small scale frequency variations to be analyzed. These different sources are corendered using advanced color and opacity blending, providing multiattribute composite image volumes for subsequent interpretation and as input to further geobody delineation. The use of such advanced visualization has resulted in a collection of 3D volumes that successfully distinguish the internal and overbank geometry of chan

The Ensign Field is located in UK offshore licence Blocks 48/14a, 48/15a and 48/15b. The field is located 100 km east of the Humberside coast within the Sole Pit area of the Southern North Sea. The reservoir consists of sandstones of the Permian Rotliegend Group (Leman Sandstone Formation). Reservoir quality has been impacted by diagenesis during deep burial, whereby illitization has reduced permeability to sub-millidarcy scale. The field has been developed with two horizontal production wells, both completed with five hydraulic fracture stages. First gas from the field was achieved in 2012 via the Ensign normally unmanned installation and exported through the Lincolnshire Offshore Gas Gathering System. The field is compartmentalized by multiple regional-scale De Keyser fault zones. A heterogeneous natural fracture network exists with only a limited contribution to flow. Well performance and ultimate gas recovery have been lower than originally anticipated due to sub-optimal completions and a higher degree of compartmentalization than originally expected. The volume of gas that is connected to the wells is limited by low-offset faults, which have been identified by integrating long-term production data, and core, log and reprocessed seismic data. Production ceased in 2018 when the original export route was decommissioned.