Publications

One of the challenges in monitoring commingle wells is the identification of the bypassed oil zones. The occurrences of these zones are due to the varying rock properties (permeability, saturation, porosity, etc.) and in part, also due to differences in the layers reservoir pressure. In addition, running logs often requires the wells to be shut-in which would also cause the wellbore fluids to re-invade back into the formation. This makes evaluating bypass oil more complicated.Further complications arise when the wells are being produced using ESPs due to the depleted nature of most of the fields here, in Indonesia. To allow intervention operations (mainly wireline logging) while still having the ability to put the well on production, Y-Tools are used. The usage of YTools have been relatively rare in this country and limited for production logging survey.The Reservoir Saturation Tool (RSTPro) is often run in carbon-oxygen (CO) mode to get the most recent hydrocarbon oil saturation (SO). Normally run in shut-in conditions to reduce the effect of reinvasion which could mislead the saturation reading, all the open perforation zones are normally squeezed prior to logging. Another alternative to mitigate the invasion effect is to acquire the log in flowing conditions, which was chosen for this intervention. In addition to logging during the shutin period, the RSTPro was run in flowing condition in this well, mainly to investigate the effects of the re-invasion of wellbore fluids into the formation. This is not a common practice done in Indonesia.The results from the flowing condition give a clearer evaluation of each zones performance. The difference in the computed oil saturations between the flowing and shut-in conditions gives an indication of the amount of invasion occurring in each zone, boosting the confidence level in the bypass oil identification results. The results were later corroborated by the production history and production log which was run separately in this well.The combination of the results from the RSTPro and PLT logs, run through the Y-Tool offers a unique solution for the production evaluation (including the identification of bypassed hydrocarbons and the determination water production zones) in older wells and for wells in mature and depleted fields in Indonesia.