X. Block is the exploration ultra-deep water block in Brazil and the average water depth is about 2000m, and the reservoir target zone depth is about 5800m. The major challenges of drilling in X. Block are pipe stuck in shale and salt formation, losses in carbonate formation and low ROP in pre-salt formation that cause too much NPT (about 37% NPT) and sidetracking (1-2 sidetracking points). So the actual drilling duration is longer than the planed and drilling cost is higher than the budget.
This paper discusses the optimization processes of drilling operation in X. Block to cope with the drilling challenges including casing program optimization and drilling fluid system and properties optimization to deal with the stuck in shale and salt formation, MPD to solve losses in carbonate formation and to increase ROP in pre-salt reservoir formation. In addition, advanced drilling ship equipped with double derrick and advanced drilling operation management system to improve drilling efficiency and decrease NPT to make drilling operation from better to best have been mentioned in the paper.
Stuck NPT in shale and salt formation is decreased from 18% to 2% and sidetracking is avoided by optimizing casing program and drilling fluid system and properties. The average flow rate is enhanced 40% and the ROP is increased 37% by MPD in the carbonate losses formation. The average ROP in pre-salt formation is improved from 2.1 m/h to 3.5m/h and the drilling speed is increased by 66.7% by the optimizing bit type. Well drilling duration is sharply shortened by 45% and the total NPT is decreased from 37% to 5.6%-9.5%.
This paper will highlight the ultra-deep water well drilling challenges in X. Block of Brazil, matching drilling technologies respectively for stuck in shale and salt formation, losses in carbonate formation and low ROP in pre-salt formation as well as the application results of optimization. The experiences presented in this paper can give a light to ultra-deep water drilling operation optimization.