If these predicted pumping times are unacceptable, then the testing tool should be moved to a new location within the formation to determine whether filtrate pooling is less in some places. In general, when sampling crude oil in OBM wells, good buildup curves are obtained and this new method usually agrees with laboratory results. For several of these cases, multiple laboratory tests on the same samples yielded significant variability in results. Perhaps some base oils are more problematic than others. Also, operator error can be significant for wellsite and laboratory contamination measurements.
Work is in progress to analyze and reduce discrepancies.
Conclusions Many examples2 show that optical analysis can be used to determine the OBM filtrate contamination in real-time. The new methods also predict the magnitude of filtrate reduction with continued pumping.