Method Study for Quantitative Evaluation of Flood Zone Using Cased-Hole Resistivity Logging-Take F Oilfield, South Sudan as an Example

Cased-Hole Resistivity Logging (CHRL) is a post-casing logging evaluation technology for quick evaluation of water-flooded zones through measurement of the formation resistivity and comparison with the deep lateral resistivity of the open hole. Firstly, based on the actual logging data, the limitations of the technology are discussed. Secondly, different qualitative criteria for identifying flood zones are formulated under different formation resistivity conditions, on the basis of different functional relationship between cased-hole resistivity and deep lateral resistivity. To quantitatively calculate the water-flooded zones parameters, data from laboratory is fully used to obtain the shift value of water saturation and water cut. Draw the intersection of these two parameters and quantitative evaluation standards for no flood, weak flood, middle flood and strong flood level are built, then a set of comprehensive evaluation method for water-flooded zones is formed. Studies show the formation resistivity error will increase while the formation resistivity is greater than 100 Ω.m. This comprehensive method clarifies different threshold value for different flood levels. Verification from 3 wells shows coincidence rate of interpretation and production test is 87.6%. This method does realize quantitative evaluation of water-flooded zones.