A NEW METHOD FOR STABILIZATION OF FRIABLE AND UNCONSOLIDATED CORE SAMPLES AT WELL-SITE

In order to protect friable/unconsolidated whole cores from damage dur ing handling and transport from the rig to the core analysis laborator y, it has become common practice to inject a stabilizing material in t he annulus between the core and the core liner. Current methods are ba sed on a two-component resin system in order to control hardening time . The usual chemicals contain toxic isocyanates which are able to prod uce surface active materials in side reactions with drilling muds and polar crude oil components. A study to investigate the effects of comm only used resins on the wettability of core samples has been undertake n. It is concluded that some chemicals involved may have the ability t o alter wettability. However, the health and safety aspects related to these materials are considerable. A new method, using gypsum, for cor e protection has been developed. Extensive laboratory testing, measuri ng its effects on porosity, permeability, wettability and saturation w as conducted, but the petrophysical properties appeared unchanged. Fur thermore, the gypsum protection does not affect spectral gamma ray rec ordings. Several successful field tests, under various conditions, hav e since been performed. The method is operationally simpler than the i socyanate system and does not involve hazardous chemicals. The costs o f the chemicals are low, and the pump system is cheaper, simpler and h as lower weight compared to the resin system. The gypsum is either app lied as a pseudo two-component or one-component system. Field tests in dicate that the one-component system is the best in practical use. Was te disposal problems are eliminated, as only water is involved in the cleaning of equipment. Neither health nor environmental :risks are pre sent. Tile new, patented method should become industry standard becaus e of its simplicity and both technical and environmental advantages. ( C) 1998 Elsevier Science B.V.