In this paper are discussed the field performances of innovative K-Acetate or K-Formate mud formulations that have been used by Agip S.p.A to drill several wells through very plastic shales in South Italy.

Field muds have been carefully designed and evaluated as far as drilling and waste disposal activities are concerned. While drilling, the integration between field observations, standard laboratory tests and non conventional rheological approaches provided the assessment of useful correlations between rheological properties, performances and formulations of field muds.

These findings permitted a gradual improvement of the muds performances with a large reduction in dilution rates, bit balling and hole cleaning problems.

At the rig, the strict cooperation between all the people involved in field operations represented a key factor for the successful application of the know-how acquired.

With respect to the previously wells drilled in the field with traditional dispersed muds, the optimization and careful management of the new muds contributed, in spite of the increased ROP, to a considerable reduction both in time spent for bit balling or reaming and in ton of wastes produced per hole volume. These improvements led to great savings in drilling and disposal costs that largely compensated the 8.4% increase in the mud mixing costs per hole volume due to the presence of potassium salts.

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