Paper illustrates that how the application of innovative technology and principles of integrated reservoir management can improve recovery efficiency in a mature oil field. The paper discusses key principle of effective reservoir management. Effective reservoir management is a combination of capability, viability and processes. The application of the principle is illustrated with an example of a case study of Wafra Ratawi reservoir, a lower craterous Oolite reservoir is in a giant mature oil field Wafra.
The field was discovered in 1954 and is located in the Neutral Zone between Kuwait and Saudi Arabia. The mineral rights in this region are shared equally by both countries. The field is now operated jointly by Saudi Arabian Chevron (100 % owned subsidiary of Chevron) and Kuwait Gulf Oil Co. The reservoir is an anticline with 2 lobes East Wafra and Main Area. The reservoir has varying oil gravity with low bubble point pressure. The Production from this reservoir started in 1957. The field was shut in during the first Gulf war, and the increase in average reservoir pressure was observed, signaling for existence of partial aquifer support.
After an extensive geologic and engineering study, the production strategy to produce above the bubble point pressure was adopted. However, because of the weak aquifer support, the reservoir pressure started to decline rapidly. The simulation model in 1995 indicated a significant opportunity to enhance the asset value through recovery improvement (IOR) techniques.
Based on the sound reservoir engineering practices, detailed reservoir studies, low cost and higher economic benefits the peripheral water injection was selected as preferred method for initiating reservoir pressure maintenance. The pressure maintenance project (PMP) was implemented in 1998. The Pressure Maintenance Plant was designed to handle all produced waters in the Wafra field with varying salinity and H2S contents.
A depletion strategy objected at optimum reservoir management and maximum oil recovery was adopted. Following are the key features of depletion strategy.
Target Injection rate
a) Phase -1 Injection/Production rate > 1
b) Phase-2 Injection/ Production rate ~ 1
Maintain Optimum Draw Down in producing wells.
Take maximum benefit of water front movement.
Manage problems related to vertical permeability distribution.