ABSTRACT
Selecting specific zones to stimulate in wells is a major problem in designing stimulation treatments for low permeability reservoirs, such as the Devonian shale. Treatments should be concentrated over small intervals of a well, so the selection of the most productive intervals is critical. The Dye Leachback technique helps to locate these zones by determining the areas of highest permeability on the borehole wall.
This patented technique involves measuring the rate of dye penetration into rock cuttings under controlled conditions. The degree of penetration is measured by allowing the dye to diffuse out of the cuttings into an initially clear solution. This process is termed leachback. Dye Leachback Coefficients are calculated from time windows associated with dye immersion, rinse, and leachback. Leachback Coefficients are plotted versus depth of the sample to obtain a permeability profile. The profile indicates zones in the well which are more conducive to gas flow. Profiles from drill cuttings we have analyzed correlate reasonably with gas production zones in the wells. Therefore, the profile information can be used to assist in the selection of intervals for stimulation treatments in a well.
