Challenges and Innovations in Water Shut off for Naturally Fractured Reservoir in Subsea Wells

Abstract

Water management has become a trending topic in today's operation in Oil and Gas. The water breakthrough phenomena are even more complex when the problem occurs on naturally fractured reservoirs (NFR), where the challenging to perform a Water Shut Off (WSO) will raise on chemicals selection and placement procedure. The scope of the paper is to present the study and the application of WSO treatment in NFR with the increased difficulty of Subsea operations. The WSO treatment was designed starting from the Eni experiences in NFR. The candidates were selected among the high water production wells in the field and a detailed analysis of the drilling performances, well sketches, log parameters and production data was conducted to define the suitable treatment. Several Business partners have been investigated, with the aim to select the best chemicals for the reservoir, taking into consideration the tight delivery schedule imposed by the production needs. After the analysis phase, a detailed program was set for each well. The major observation to point out is the peculiarity of the application that implies several operations not common in Subsea well intervention activities, as Production Logging Tool (PLT) data acquisition, Coil Tubing Operation, Plug and Cement placement. Some technical points have been identified as crucial to perform the job in an efficient way, as:PLT to verify the water entry pointsChemicals selection and compatibility study. In our application two chemicals have been selected to perform the job with different purposesCoil tubing challenges for chemicals placement All the above aspects were included in the outline program and flowchart/decision tree have been made available to build a guideline for future WSO project. The real novel of the paper is related to the complexity of every single operation selected to perform the entire treatment. The scouting of the market and experience in the industry highlighted that PLT, Coil Tubing Operation, Plug and Cement placement are risky operations in subsea wells and they have been combined to reach an ultimate goal, in our case of a successful WSO operation.