Ann: Mukuyu-2 fluid sampling progress update, page-672

Agreed, and even with an effective filter cake in place, the most permeable zones continue to allow a limited amount of mud fitrate invasion into the reservoir sands, assuming the fluid loss characteristics of the mud are good and the mud weight is not too high. If there was no fluid transfer across the filter cake, there would be no tendency to cause differential sticking.

Differential sticking is caused by differential pressure due to being overbalanced in the column of drilling mud with respect to the formation pore pressure. Differential pressure creates a force which acts on the wireline cable, logging tool, or a drill string (when stationary) against a filter cake deposited on a permeable formation.

The uppermost sands in the Upper Angwa have been open for about 4 weeks? That is why I am interested in monitoring the cumulative mud loss.