| Popis: |
The drilling experience in the Kola SD-3 super-deep borehole showed that drilling in crystalline rocks, the traditional approach with respect to drilling mud composition and properties, based on the experience of drilling of terrigenous sediments, was insufficient. The following general factors essentially changed the field of application and the efficiency of influence of many chemical reagents, and also brought about the reevaluation of most of the technological properties of the drilling mud when drilling super-deep boreholes in crystalline rocks: 1. Freedom from wall-mud filter cake; 2. Decrease of the influence of drilling-mud filter properties upon the borehole wall stability; 3. Extreme hardness and abrasiveness of rocks; 4. Drill-string and borehole-wall interaction in the regime of boundary friction, leading to a lack of adhesion strength and pressing action of the pressure differential. |
