One Derivable Indicator for Subaqueous Fan in from Offshore Field

Guangjun Chen¹, Guo Wei¹, and Helin Wang^2
1Schlumberger, Beijing, China
²PetroChina, Tianjin, China

The nearshore subaqueous fans are widespread in many Mesozoic and Cenozoic fault lake basins in eastern China, sometimes there is very high reservoir potential of the fan sandstone. It is the major net pay zone in the Guanjiapu oil field of the shallow sea area of the Bohai Bay. The sand is usually thin and inhomogeneous while the field is situated within two major faults. There are already 16 wells drilled and some of them have been producing at a relatively high rate. How to identify and characterize the subaqueous fan is the key to further exploration and field development.

In an attempt to characterize the subaqueous fan sands, seismic attribute analysis was used. Some specific attribute such like Seismic Arc Length can highlight the dissimilarity of seismic traces and produces much sharper and more distinct terminations than those observed in normal amplitude data, so they can help identify and describe inconspicuous sand, more distinctly focusing on a specific layer. Guided by fine geological classification, we calibrated the target layers exactly through vertical seismic profile processing. Controlled by well log processing and integrated interpretation data, we applied seismic attribute analysis to identify and to describe the intended subaqueous fan.

Finally, we were able to identify the subaqueous fans around some major producers within the field and we described their distributions laterally. These identifications and descriptions could be verified and validated by existing and producing wells. Then the results were output to a static model that we can subsequently optimize for further exploration and development.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery