The author has proved in his doctor thesis1 that the 4-cone 4-nozzle insert-bit2,3  (Fig. 1), patente by the author, has superiour performance than that of the conventional 3-cone 3-nozzle insert-bit (Fig. 2) when drilling was performed both in laboratory and in the field in the same hard and very hard abrasive formations and under the same drilling conditions (weight on bit, rotary speed, and rate of flow of the same drilling fluid).

With the 4-cone insert-bit, footage drilled was more than three times that drilled with the 3-cone insert bit, while penetration rate was about two to three times that of the 3-cone insert-bit.

In the same line, this research work studied and analyized the drilling performance of the 3-cone insert-bit in hard and very hard formations and a solution to the problem "How to increase both penetration rate and bit footage in hard and very hard formations and consequently the unit drilling cost can sharply be reduced" was offered. This includes a new design concerning the distribution and the number of the inserts on the three cones of the bit.

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