Sakhalin I 3D Seismic Interpretation Leads to Discovery of Significant Oil Leg at Chayvo Field

A 3D seismic survey acquired over Chayvo Field, offshore Sakhalin Island, in 1997 identified the likely<br>presence of large oil rims in reservoirs which had tested mostly gas in crestal wells. The rims were identified<br>from pairs of amplitude anomalies that conformed to structural contours and were interpreted as gas-oil and<br>oil-water contacts. Several interpretation techniques were used to increase confidence in the postulated<br>contacts and predict contact depths. The oil rims and contact depths were tested and confirmed with an<br>appraisal well drilled in 2000, resulting in a significant oil project in a field thought to contain mostly gas.