1963 Paper (L)

APPLICATION OF THE GAMMA DENSITY LOG TO FORMATION EVALUATION IN THE ARKOMA BASIN

F. S. Millard: Humble Oil and Refining Company - Central Region

ABSTRACT

Formation evaluation of the gas producing sands in the Arkoma basin of southeastern Oklahoma and west-central Arkansas is difficult because of the nature of the formations encountered and the borehole conditions. Air or gas drilling as well as rotary drilling utilizing conductive mud systems are used.

The producing sands are often shaly or silty with fair to poor porosity and permeability. Microsurveys have been used, however, results are generally poor because of shaliness, moderate to low porosity range and variable residual gas saturation. Acoustic logs are also adversely affected by shaliness and gas saturation causing frequent cycle skipping and attenuation. Gamma density logs have been run in a number of wells with useable information for porosity evaluation. Some difficulties are encountered in the low permeability range which may be due to inadequate flushing of the gas.

A number of gamma density logs have been compared with core analysis of the Atokan sandstones. Fair to good porosity resolution is observed in most instances. Difficulty of interpretation is due to low permeability and some variation in lithology as well as a rugose or eroded borehole condition.