| Summary: | A new bottom hole assembly (BHA) with a triangular prism drill collar and a flexible joint was developed to enhance the BHA’s ability of deviation prevention and correction in drilling. The deformation of the conventional BHA and the triangular prism drill collar BHA under working loads were simulated by finite element method. The result showed that the ability of the triangular prism drill collar BHA to prevent deviation in vertical well was superior to that of the conventional BHA and the triangular prism drill collar BHA had some certain ability to correct deviation in deviated well. The flexible joint length had an effect on the performance of the triangular prism drill collar BHA: when the length of the flexible joint was less than 6 m, the shorter the flexible joint length, the better the deviation prevention ability in vertical well, when the length of the flexible joint was within the range of 9–12 m, the longer the flexible joint length, the better the deviation correction ability in deviated well. Different kinds of BHAs were used in single well and adjacent well for field contrast test. The result showed that in anti-deflection fast drilling, the triangular prism drill collar BHA had excellent deviation prevention ability and it was helpful to get straight and smooth well track.
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