Monitoring drilling mud

Abstract

The invention in one aspect provides a method of testing drilling mud in use which comprises periodically sampling the circulating mud and analyzing its aqueous filtrate at the rig site by ion chromatography for selected positive and negative ions; one or more other parameters of the sampled mud and/or mud filtrate (e.g. pH, temperature) may also be measured; preferably the composition of the mud filtrate thus monitored is interpreted to indicate downhole interactions, with the composition of the mud supplied to the hole being adjusted to or towards the optimum as drilling proceeds. The invention also provides a method in which the solids of the periodically sampled mud are analyzed at the rig site, e.g. for sorbed ions and/or for cation exchange capacity; the values so obtained are preferably combined with those for the mud filtrate analysis and used in the diagnosis of downhole conditions for adjustment of the composition of freshly supplied mud. The invention further provides a method of analyzing drilled shale solids in drilling mud in use which comprises drying and separating these solids from the mud, extracting ions from the separated solids into solution, and analyzing the resulting solution by ion chromatography for selected positive and negative ions; these operations are conducted at the rig site, and the resultant data, usually along with analyses of the circulating mud composition, are preferably used to indicate appropriate adjustment of the composition of the mud supply to or towards the optimum as drilling proceeds.