Abstract

The hydrocarbon producing pay zones undergo changes such as increase in water saturation and rise in free water level with time. In an old brown field where closely spaced wells drilled in different periods are available, changes in reservoir properties can be monitored at no extra cost with the help of already acquired open hole logs and production performance of the wells. This is systemized by making composite log triplets of three closely spaced old, intermediate and new wells. For nearby wells, change in oil saturation is represented by change in formation resistivity. So, a comparison of resistivity of nearby old, intermediate and new wells along with production data gives valuable information about the extent of depletion, water rise, bypassed oil and status of the pay sand. This is illustrated with examples from Lakwa field.