The increased use of sidewall core samples for gravel pack design can lead to the improper selection of gravel pack sand size if analyzed by standard sieve analysis techniques. Sidewall cores, which are obtained from the near wellbore region after drilling, are usually contaminated with drilling mud material lost to the formation as filter cake buildup occurs. This artificially introduced material is fine in particle size and can skew a sieve analysis of the sample, indicating a smaller median particle size than that of the true formation.

A commercial particle size analyzer, which operates by the light blockage principle has been used to successfully analyze sidewall core samples while excluding the major effects of mud contamination. This results in a more representative size distribution of the formation sand and a more accurate basis for selection of the proper gravel pack sand size. Its ability to rapidly analyze small amounts of sample means a larger number of samples can be evaluated in a comparatively shorter period of time.

Results of field application of the analyzer has shown that larger, and therefore more productive, gravel pack sands have been recommended for several wells where finer sands were indicated by conventional sieve analysis. Production reports have shown that these wells show high productivity with no evidence of significant sand production or gravel pack plugging by formation material.

You can access this article if you purchase or spend a download.