A new method for stabilization of friable and unconsolidated core samples at well-site

Abstract

In order to protect friable/unconsolidated whole cores from damage during handling and transport from the rig to the core analysis laboratory, it has become common practice to inject a stabilizing material in the annulus between the core and the core liner. Current methods are based on a two-component resin system in order to control hardening time. The usual chemicals contain toxic isocyanates which are able to produce surface active materials in side reactions with drilling muds and polar crude oil components. A study to investigate the effects of commonly used resins on the wettability of core samples has been undertaken. It is concluded that some chemicals involved may have the ability to alter wettability. However, the health and safety aspects related to these materials are considerable. A new method, using gypsum, for core protection has been developed. Extensive laboratory testing, measuring its effects on porosity, permeability, wettability and saturation was conducted, but the petrophysical properties appeared unchanged. Furthermore, the gypsum protection does not affect spectral gamma ray recordings. Several successful field tests, under various conditions, have since been performed. The method is operationally simpler than the isocyanate system and does not involve hazardous chemicals. The costs of the chemicals are low, and the pump system is cheaper, simpler and has lower weight compared to the resin system. The gypsum is either applied as a pseudo two-component or one-component system. Field tests indicate that the one-component system is the best in practical use. Waste disposal problems are eliminated, as only water is involved in the cleaning of equipment. Neither health nor environmental risks are present. The new, patented method should become industry standard because of its simplicity and both technical and environmental advantages.