Opportunities and Challenges for Bringing PRM to the Field

During the past decade Shell has actively participated in the full range of permanent reservoir monitoring (PRM) activities including economic justification, acquisition planning, proof-of-concept trials, participation in two actual field deployments in joint-venture assets, and 4D processing and interpretation. Key learnings from the past show that permanent installations offer significant technical benefits over streamer-based systems such as: 1) improved survey repeatability (NRMS), 2) cost-effective frequent repeats for filtering noise, 3) use of sparse acquisition methods, 4) use of other wave types such as refracted p-waves, Scholte waves, and mode-converted waves, 5) improved processing through addition of true WAZ and long offsets, 6) ability to detect rapid changes in the subsurface, and 7) additional capability for monitoring production-induced hazards around our producing and injecting wells. The past has also presented us with a number of challenges that need to be overcome. Examples are 1) the high upfront costs in the presence of uncertainty on both signal strength and differential value as compared to streamer 4D, 2) the complexity and cost of cable deployment in the vicinity of platforms, subsea infrastructure, and other man-made and natural obstacles, and 3) uncertainties about the reliable lifetimes of these systems over field life.