Time-Lapse Seismic Used to Qualify the Drainage and IOR Strategies on the Snorre Field

Abstract

Abstract Hypothesis associated with drainage and IOR strategies are often justified theoretically or by small scale experiments. The effectiveness of reservoir development measures is therefore often uncertain. The Snorre field is a large North Sea oil field with a thick, heavily faulted, eroded and heterogeneous (fluvial) reservoir with a complex production history with a large IOR potential. The field's economy relies on an effective IOR strategy. A multidisciplinary time-lapse seismic interpretation project has been carried out. A workflow was designed where all data types, models, tools and disciplines were integrated in the analysis, documentation and presentation of results. 3D Geobodies populated with difference seismic amplitudes were imported in relevant software's for visualization and analysis. The analysis has been done by a dedicated project team, while close cooperation with operational teams and applicants of the results has assured that results incorporate detailed operational experience and are properly implemented and quality assured. Aside from producing explanations to individual seismic effects, observations were used to support or weaken hypothesis relating to the drainage and IOR strategies. The results are integrated qualitatively in the history matching, and adjustments due to 4D information gave significant improvements. A fault seal analysis was extended with time-lapse observations. Gas injection is assumed to improve oil mobility as gas dissolves in the oil, which is not always in line with 4D observations. Gas flooding, migration and stacking (attic gas) are better understood from 4D data. Also, bypassed or unswept oil is detectable from the 4D seismic. The results have already influenced drilling decisions and well interventions. The conclusions will also play an important role evaluating the overall drainage strategy, existing IOR strategy and upcoming IOR initiatives. The work demonstrated how time-lapse can be taken beyond geophysics to become an integral tool in reservoir development.