WAX CORE PRESERVATION – EXTENDED REVIEW OF EXISTING METHODOLOGIES

摘要

Core preservation of plugs taken at the rig site or of whole core sections is a common practice during a core handling operation. This is a fundamental step for maintaining the connate fluids saturation in place and preventing the core or plug sample from drying over a long period prior to any core analysis at the laboratory. A standard procedure for core preservation consists of wrapping the sample with plastic film and aluminum foil before dip coating it. For the purposes of this paper,the term’wax’will be used to describe the meltable coating used to cover the wrapped core plug or whole core section. The exact composition of the wax may vary in practice but are described concerning these experiments. API recommended practices for core preservation(RP40)[1] provide guidance on the various steps from wrapping to dipping. However,at the well-site,actual procedures differ from the RP40 in terms of wrapping material type and layers and composition and properties of the waxes used. Mishandling can also occur during the operation: trapping of air or water in the wrappings or in the wax or the sample falling into the wax bath. This study reviews the effects of different materials and practices on the efficiency of core fluid preservation over one month period. Results show that wax dipping and cooling are key steps where malpractices can have a major effect on the core fluid content.