Zonal Isolation Remedial Solutions in Mature Fields Using Sealant Polymer and Straddle Assembly

Abstract

Water and gas management in mature fields is a daily challenge. It is even more critical when re-development is required using existing assets to be side tracked. The severe depletion of the oil zones creates significant pressure contrast with water and gas layers that need to be properly isolated. Failure to correctly cement the casings or liners generally ends up by generating cross flows, not only affecting the current well but also other wells producing from same levels. The paper is based on a successful case history, performed in Congo for a major, where the restoration of the zonal isolation on highly deviated wells was required. The objective of the paper is to describe the methodology process to determine the source of water in a well, the merge of oil field competencies to engineer a chemical and mechanic solution, the fluid design and the full operational deployment on location to cure the problem. The combination of several specialties provided an innovative solution that gave the following benefits: -Minimize the number of runs, with only two trips required to perforate the liner to access the cross flow area and to set a straddle assembly-Minimize well restrictions and still give access to the lower completion-Minimize risks of getting stuck using sealant polymer instead of cement-Provide complete annular isolation and restore casing integrity in a same run-Evaluation and control of the cross flow before sealing operation-Protect the lower oil producing zone during the entire remedial operation At the end, the objective of the paper is to give best practices to perform remedial cement operations in similar well architectures.