Wax Core Preservation - Extended Review of Existing Methodologies

Mathilde Rousselle, ALS Petrophysics,
Jean-Valery Garcia, ALS Petrophysics,
Mike Gay, ExxonMobil URC

This paper was prepared for presentation at the International Symposium of the Society of Core
Analysts held in Avignon, France, 8-11 September, 2014

Abstract:
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.

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About the Society of Core Analysts

Objectives
The name of this organization is the Society of Core Analysts (SCA) and was founded in 1986. This organization is a Chapter-at-Large of The Society of Petrophysicists and Well Log Analysts (SPWLA) and is established with two objectives:

• To promote the aims, purposes, and membership of the SPWLA which is a non-profit scientific organization.
• To serve the interests of all persons who use or obtain reservoir evaluation information from rock and core samples.

As a guide for fulfilment of the first objective, this Chapter stands responsible to, and subject to, the rules and regulations of the SPWLA.

As a means toward the second objective this Chapter will sponsor technical speakers, projects, and presentation of papers dealing with formation evaluation. This Chapter will hold membership open to all core analysts, log analysts, geologists, geophysicists engineers, service company personnel and all others interested in the study of rocks and their interstitial fluids. This Chapter will also actively encourage membership and participation in the activities of the SPWLA.

Website: www.scaweb.org