Study on Rotary Percussion Tool Parameters Optimization and Trial Test Evaluation

Drilling in hard and abrasive formation represents a major challenge due to the low rate of penetration (ROP). Rotary percussive drilling tools take advantage of both the shear action of drill bit cutters and axial percussion energy to increase the drilling efficiency. Such tools have shown a significant benefit in drilling efficiency enhancement, especially in air drilling with an air hammer. This study focuses on a fluid-type rotary percussive drilling tool development and application to address the significant drilling challenge in drilling hard and highly abrasive sandstone formations. A rock mechanical study is carried out to get the compressive strength and the internal friction of the hard and abrasive formation. Then, a 6-3/4 inch rotary percussive tool is designed and optimized based on a relationship between rock mechanics and the output energy and frequency of the tool. Next, the tool was thoroughly tested in the workshop, and the key parameters were acquired and compared with the design. The tool was trial tested in a hard and abrasive formation dominated by fine sandstone and siltstone in the upper section and a softer formation below. The new 6-3/4 inch tool was run in the test well and drilled DV tools, cement, float collar, and float shoe, then penetrated the hard and abrasive formation. The hammer drilled 912ft with an ROP of 10.5 ft/h with a pure drilling time of 87 hours. The ROP increase is around 30% for the same depth and formation with less WOB and RPM. Drilling efficiency was increased in the top section with less WOB and RPM compared with the same formation and depth of an offset well section drilled with hybrid bits. The differences of the wells in the hard abrasive formation thickness, bit type, BHA, bits dull grading, and RPM are studied. The tool performance evaluation and lessons learned from optimization and trial tests are summarized. The future direction of this work is also discussed.