Slimhole drilling is a method of lowering well costs by reducing consumables used during the drilling and completion process. The technique has been used to drill high pressure high temperature wells in the North Sea from floating installations.

A three year development program between a major operator and a service company has led to the development of the "retrofit" slimhole drilling concept which allows a slimhole to be drilled using modified conventional equipment from any rig. The problems of well safety and drilling efficiencies have been addressed in the project.

An enhanced kick detection system has been successfully used to detect influxes of less than 1 barrel, and alarm levels as low as 10 gallon/minute influx rate can be used.

The use of high temperature downhole motors and anti-vibration technology ensures that drilling efficiencies and drillstring integrity are maintained during slimhole operations. Well engineered drilling fluids reduce total system pressure losses and improve the hydraulic power available for the bit and downhole tools.

The design of a high pressure high temperature well to T.D. in 5-¾" or 4-⅛" can lead to total cost savings of up to 15 %.

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