Abstract: Effect of Core-Derived Archie Parameters on Water Saturation Calculations: Pennsylvanian Cross Cut Sandstone, Runnels County, Texas

HENDERSON, S. K., Halliburton Energy Services, Odessa, Texas andG. S. ASQUITH, Department of Geosciences and The Center for Applied Petrophysical Studies, Texas Tech University, Lubbock, Texas

The task of field-wide log analysis can be quite cumbersome, especially when large numbers of logs are available. In most cases the use of computers has simplified this task, regardless of whether commercially available software or personally constructed spreadsheets are employed. Computers generally resolve most inconsistencies (i.e., "human error") in the process of analyzing large amounts of data. Still, various assumptions must be made when determining a zone's productive potential. This is particularly true with respect to cementation exponent (m) and saturation exponent (n). The use of commonly accepted "textbook" values for these important parameters may yield inaccurate, and sometimes misleading, results.

Presented here is a case example in which field-wide determination of productive potential is facilitated through "customizing" the Archie (1942) water saturation equation for the Cross Cut sandstone in the TWP Field of Runnels County, Texas. This is accomplished by employing core-derived values of both cementation exponent (m) and saturation exponent (n). With the analysis of rotary sidewall core samples, operators can define a more accurate Archie equation for a particular field, thus leading to more consistent and reliable water saturation calculations (and more optimistic hydrocarbon saturation values). Data presented will emphasize the differences that may exist between water saturation calculations using both core-derived and commonly accepted values of cementation exponent (m) and saturation exponent (n).

AAPG Search and Discovery Article #90936©1998 AAPG Southwest Section Meeting, Wichita Falls, Texas