From Advanced Drilling Solutions: Lessons from the FSU, Volume II

Introduction

Utilization of air (or gas) instead of drilling fluid for well borehole cleaning from drill cuttings was the clearest example of the effect the Law of Differential Pressure on drilling efficiency, one of the most general laws of the well drilling process. This differential pressure effect in the conditions of using drilling mud has been discussed in this book before see Chapter 5.

The author of this chapter witnessed this effect for the first time in 1957, while drilling one of the exploratory wells at the Telnovsky coal prospect in the Sakhalin Island. When the drillers had 40 m left to drill to the TD at the depth of 165 m, a rapid temperature drop caused freezing of the stream that was used as a source of water for making drill mud. The unsuccessful attempt was then made to use the melted snow for the borehole cleaning because of the very intensive lost circulation at the bottomhole.

At this point, the decision was made to proceed with well drilling to the TD using air for the borehole cleaning. The drillers used a compressor unit to pump air downhole. The first trial of the new method was extremely successful. In andesite and hard siltstone, a TCI drillbit showed 7 m/hr rate of penetration, which was several times faster, as compared to the earlier results of drilling using the conventional method of the borehole cleaning. In the 1950s, similar results were achieved in other areas of the FSU, such as...

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Topics of Interest

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