A number of qualitative and quantitative methods exist in the industry to monitor steam chest growth and reduction in cased hole wells in steamflooded reservoirs. It is challenging for an operator to select the method that is best suited technically and economically for a given steamflood. Five methods of quantifying steam saturations in cased hole wells are described: 1. Pulsed Neutron Capture (PNC) With Constant Sigma Matrix 2. PNC With Variable Sigma Matrix 3. PNC Service Company "X" 4. PNC Near/Far Count Overlay 5. Open Hole/Cased Hole Neutron Overlay The basis for these various quantitative methods are explained. Examples of applying these methods in active steamfloods in Indonesia and California are shown. These quantitative methods are compared to more traditional qualitative steam identification techniques. Limitations of calculating steam saturations using PNC tools include the accuracy by which various input parameters may be estimated, such as the macroscopic capture cross section Sigma of the rock matrix. A significant limitation of the open hole/cased hole neutron overlay method is accounting for temperature variation over time. Ultimately, the accuracy of calculated steam saturations directly impacts the accuracy of remaining/residual oil estimates, and thus in turn plays a significant role in steamflood optimization.
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