G. Gallino et al., New formulations of potassium acetate and potassium formate polymer muds greatly improved drilling and waste disposal operations in South Italy, SPE DRILL C, 14(1), 1999, pp. 64-70
This paper discusses the field results of innovative K-Acetate or K-Formate
mud formulations that have been used by ENI S.p.A./Agip Division to drill
several wells through very plastic shales in South Italy. Field muds have b
een carefully designed and evaluated as far as drilling and waste disposal
activities an concerned. While drilling, the integration between field obse
rvations, standard laboratory tests, and nonconventional rheological approa
ches provided the assessment of useful correlations between rheological pro
perties, performance, and formulations of field muds. These findings permit
ted a gradual improvement of the mud effectiveness with a large reduction i
n dilution rates, bit balling, and hole cleaning problems. At the rig, the
strict cooperation between all the people involved in field operations repr
esented a key factor for the successful application of the know-how acquire
d. With respect to the previous wells drilled in the field with traditional
dispersed muds, the optimization and careful management of the new muds co
ntributed, in spite of the increased ROP, to a considerable reduction both
in time spent to remove bit balling or reaming and in tons of wastes produc
ed per hole volume. These improvements led to great savings in drilling and
disposal costs that largely compensated the 8.4% increase in the mud mixin
g costs per hole volume due to the presence of potassium salts.