A New Look at Deepwater Drilling Problems Combined with New PDC Technology Produces Savings of $5.9MM

Abstract

Abstract During project execution planning for a Gulf of Mexico (Green Canyon) deepwater project, the well construction team looked at all possible options that might reduce time on each well. This investigation indicated that the biggest opportunities in the drilling phase were increased ROP and reduced number of trips. The original plan had included the use of underreamers and roller cone bits. It was known that PDC bi-centers were a cost effective replacement for underreamers due to their ability to simultaneously drill and underream. Also, that ROP was higher with PDC bits (both bi-center and conventional PDC bits). Previous use of PDC bits had, however, resulted in hole-cleaning problems due to the large volume and type (gumbo) of cuttings. Problems were also historically encountered with PDC directional characteristics, especially kicking off in the larger hole sizes and angle dropping in the tangent sections. Based on the recent introduction of new PDC technology it was decided to take a new look at making PDC bits more effective. To counter the problem of hole cleaning, it was decided to increase flow rates by utilizing a larger drill string. In the upper section of the well where underreaming was planned, a new type of bi-center was used. The bi-center used new technology that allowed it to drill out (saving an additional trip over conventional bi-centers). In the lower section, a radically new PDC drill bit design was used that contained features to significantly increase ROP. Both of the new PDC designs contained new features to significantly improve directional characteristics. A variety of other improvements/modifications are mentioned in the paper. Results: The new technology bi-center bits (17 × 20 and 14 ½ × 17 ½), provided the biggest time savings by eliminating trips, producing very high ROP, and successfully kicking off and building angle (one case as high as 68 degrees). The new PDC drill bits used in long tangent sections (one was 9300’ at 63 degrees) had ROPs that in most cases doubled that of similar offsets while reducing slide times to as little as 1%. The new plan resulted in four wells being drilled in 115 days less than the original project AFE estimates (52% reduction), for a savings of $5.9MM.