Publications

Enau Field was discovered in 1970, in Central Sumatera Basin, Riau Province. It is a four way anticline structure with 15x5 km coverage area, and it is controlled by echelon faults bearing north-south direction. The main oil production comes from estuary channel “B1” sand, and it has been peripheral waterflood since 1992. Since it is considered as a mature oil field, the biggest challenges are to know where the remaining oil located, and how to manage the waterflood recovery to maintain production performance. This study delivers an approach to map the lateral distribution of the current oil pay thickness by integrating historical well swab data and seismic channel propagation to know waterflood behavior in the “B1” sand. The well data comes from perforation thickness length from 309 wells at “B1” sand. Perforation well in B1 sand with swab-test < 99% water cut is consider still has remaining oil with current pay thickness of the perforation length. The “B1” sand is a multi-history estuary channel deposit with net thickness ranges from 15-62 feet, and it has amplitude contrast with the top sealing shale above it. The contrast can be distinguished in seismic wavelet across the field. Seismic propagator tool is able to detect and differentiate seismic wavelet similarity that leads to interpretation of channel geo-body based on the waveform tracking algorithm. From the waveform algorithm, the “B1” sand has 6 geo-bodies of estuary channel with width ranges from 650-1,000 meters with orientation from the NE to the SW, coherent to the paleocurrent direction, and it is individually accrete from the SE to the NW closure. Each of those “B1” geo-bodies from seismic propagator is difficult to differentiate only based on log data. The waterfront line or the zero pay thickness line and channel geo-body from seismic propagator shows a very good correlation. Area along the axis of individual channel geo-body axis shows quick water injection movement and breakthrough. The water injection tends to move following the rock properties in a specific channel geo-body, which suggests that there is an imaginary baffle or rock property contrast between individual geo-body that prohibits the water injection moves to the adjacent channel geo-body. This new approach of integrating the estimated current pay thickness map with seismic propagator has given an excellent view of knowing the water injection behavior in “B1” sand. It gives good information to manage water injection allocation for each peripheral injector. Re-allocation of water injection rate in each individual channel has successfully increase oil production.