Geology and Development Challenges of Deepwater Deposits (KC Field Case Study, Nigeria)

Ufot Ekanem Ebong
Shell Petroleum Development Company, Nigeria, Port Harcourt, Nigeria

The E2000 reservoir in KC field, located in the Niger Delta, Nigeria, is SPDC's single largest reservoir. A year after it came on stream, the reservoir attained a peak production of 43,500 Mbopd. However, 5 years after, severe and rapid pressure drop was observed and production was cut back, leading to loss in projected revenue.

To maintain the pressure and rejuvenate the production from the field, a water injection scheme was installed. This scheme lasted for about 20 years with minimal impact. However, with a significant reserve of about 434 MMstb still remaining, an integrated subsurface study was carried out recently in order to identify further development opportunities.

At the conclusion of the study, it became apparent that the lack of early identification of the deepwater origin and the internal reservoir architecture of the E2000 reservoir had a direct link with the production challenges and production history. By integrating all well and seismic data with sequence stratigraphy, the E2000 reservoir, previously interpreted as an upper shoreface sand (<10 m water depth) is now interpreted as detached shoreface sediments deposited at water depths of >200m (deepwater).

The production implication is that the former interpretation assumed a laterally extensive sand body with strong aquifer whereas the latter interpretation, though still showing shoreface sedimentary attributes, would indicate a restricted sand body, entombed in shaly deposits on the slope. The reservoir under this scenario is expected to have very weak aquifer. This better explains the earlier production performance and challenges. Optimisation based on this knowledge has raised daily production by ~ 8000 Mbopd since 2000.