Gas Production Potential Determined by Dye Leachbach

Richmond Bennett, Paul D. Schettler, Richard Parmeley, George H. Bowles, B. F. Morton

Dye leachback is a simple, inexpensive technique for locating formations with gas production potential using rotary or cable-tool cuttings obtained at the well site during drilling. The process itself is field adaptable and can produce a permeability profile while the drilling is proceeding. Dye leachback is not only quicker than standard logging techniques, but gives information that heretofore has been unavailable. Although logging tools exist that indirectly measure permeability, these tools are not always reliable. Direct permeability measurements made in a laboratory on whole or sidewall cores are much more expensive and very time consuming.

The dye leachback procedure consists of soaking the rock cuttings in an aqueous dye solution, rinsing all the dye off the surface, and then measuring the rate that dye diffuses out of various microscopic and submicroscopic pores and fractures into an initially clear solution. Dye leachback coefficients are calculated from the windows associated with dye immersion, rinse, and leachback. Leachback coefficients are plotted vs. sample depth to obtain a permeability profile. The profile indicates zones that 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 can be used to assist in the selection of intervals for perforation and stimulation.

The automated system consists of a fluorimeter, peristaltic pump, minicomputer, and interfacing electronic circuitry. This system permits us to make rapid, continuous measurements and calculate dye leachback coefficients on drill cuttings or sidewall cores.

AAPG Search and Discovery Article #91023©1989 AAPG Eastern Section, Sept. 10-13, 1989, Bloomington, Indiana.