Predicting Viscosity in an Undrilled Panel of a Deep-Offshore West African Basin Field

Prospect E resides in the undrilled western Panel E of Bombadil Field in a deep-offshore West African basin. Bombadil Field produces from a mid-Miocene channel complex. Normal fault separated panels D and E show reservoir juxtaposition and a clear DHI event suggesting an OWC in panel E.

The main risk for Prospect E is fluid quality due to observed biodegradation resulting in high viscosities and disappointing production in Bombadil D Field.

The fluid distribution in panel D indicates an abnormal viscosity trend which cannot be explained by biodegradation processes alone. Evidence of extreme gas stripping correlates with high viscosity fluids and coincides with a spectacular gas chimney observed directly above the crest of panel D. Despite pressure continuity and an absence of barriers, viscosity variations inside panel D suggest transitory fluid disequilibrium.

Bombadil Field has experienced a very complex history. Fluid properties are controlled by its charge history, competing biodegradation and gas stripping processes. Bombadil Field’s fluids consist of a mixture of biodegraded and fresh recharged oil in various quantities which improves oil quality.

Detailed geological mapping, seismic analysis combined with fluid geochemistry, and PVT data is integrated in a cohesive geological model which enables viscosity prediction at prospect E.