Field Case: Complex Water Inflow Risk Evaluation by Various Surveillance Methods

Abstract

Complex surveillance to assess the water inflow risk of a well with an openhole completion in a fractured carbonate reservoir using temperature and geochemistry. The production rate on the subject well was constrained to mitigate the risk of water production from a lower interval in the naturally fractured carbonate reservoir. Due to a wellbore restriction a production log could not be run to help diagnose the risk of the water inflow. Temperature from the permanent downhole gauge (PDHG) was used to estimate the inflow interval and geochemistry of production oil was used to evaluate the water inflow risk. The analysis of temperature from the permanent downhole gauge indicated that production was coming from the shallower water free interval. Geochemistry using HRGC (High Resolution Gas Chromatography) and LTM-GC (Low Thermal Mass Gas Chromatograph) analysis was used to assess if the wellbore was connected to the lower wet interval through the fracture network. If the wellbore was not connected to the fracture network, the production constraint could be removed, and the rate increased by approximately 6000 STBPD. The production rate was increased in stages with periodic oil sampling and HRGC analysis to check for a water washing signature which would indicate inflow from the lower wet interval. The well was successfully ramped-up and is still producing water free. In the absence of production log (PLT) data and a clear difference in fingerprinting signature between producing Units, Oil Geochemistry was used to differentiate producing intervals due to water wash effect of the produced oil signature.