New Opportunities from 4D Seismic and Lithology Prediction at Ringhorne Field, Norwegian North Sea

Time-lapse (4D) seismic data from the Ringhorne field in the North Sea are used to monitor water movement in both Paleocene and Jurassic age reservoir sands, improve existing geologic and simulation models, and enable more cost-effective field operations. The structural complexity of the reservoirs, their proximity to the high-impedance Cretaceous chalk, and a relatively small 4D response required a significant effort in seismic acquisition and processing which resulted in a highly repeatable survey. In addition to the 4D interpretation, Vp/Vs derived from simultaneous elastic inversion is diagnostic of sand and provides additional constraints on Ringhorne subsurface models. Connected volumes based on Vp/Vs correlate to areas of water sweep seen in the 4D data and reduce uncertainty in 4D interpretation. Relative P-wave impedance changes calculated from 4D inversion are consistent with pre-survey predictions. The 4D seismic and inversion results help explain water breakthrough timing, improve our understanding of field production history, and were critical inputs to an updated geologic model used for reservoir simulation. The data have resulted in an increase in the reserves base and the identification of additional infill well opportunities.