Planning and Implementation of the Repsol-YPF-MAXUS Krisna Underbalanced Drilling Project

Abstract

Due to the previous history of high mud losses and stuck pipe, Repsol - YPF - MAXUS Southeast Sumatra B. V. decided to implement underbalanced drilling technology in the development drilling campaign in the Krisna Field offshore Indonesia. Although Underbalanced drilling is not a new technology, it has been used infrequently in drilling from an offshore structure. Underbalanced drilling from a jack-up rig causes some unique planning and implementation issues. Planning and implementation are made more complex by the space limitations and logistics. These were compounded by the lack of infrastructure in Indonesia for underbalanced applications. The Krisna D12 production interval was successfully drilled underbalanced from 10 June 2000 through 20 June 2000 from the Reading and Bates Falcon jack-up Roger W. Mowell. A total of 1159 feet of formation was drilled Underbalanced without any significant drilling related problems. Although the project encountered problems during the initial start up, modifications to the system and changing the fluid system to a diesel mist eliminated the majority of the issues. By the end of the well, the Underbalanced system was working well. This paper presents the pre-engineering, project management and field implementation results for the drilling of the Krisna D12. Introduction The Krisna field is located 60 miles offshore Java Indonesia, a part of the South East Sumatra (SES) production sharing contract, and is operated by Repsol-YPF-MAXUS Southeast Sumatra B. V. The main production comes from the Upper Bata Raja formation, which has a BHP of 650 psi (2.98 ppge). Massive lost circulation (losses in excess of 50,000 bbls of fluid) occurred while attempting to drill the first horizontal well in the field. The primary goal for drilling the production interval Underbalanced was to eliminate the loss of fluids to the formation. Secondary goals of the project were to demonstrate the ability to maintain an Underbalanced condition, reduce formation damage and increase productivity of the well, and evaluate the formation and identify fractures real time while drilling the formation. Planning and Engineering Underbalanced drilling is a multi-disciplined operation that involves drilling engineers, production systems engineers, drilling operations personnel, geologist and reservoir engineers.The rig contractor and the service sector heavily supported the Krisna UBD project. The project integrated the different disciplines into one team to come up with an engineered solution specific to the Krisna wells. Rig interface coordination was a critical step. The drilling operation was to be tied in to the Krisna D production platform; therefore it was deemed critical that proper interfaces were set up between the production and the drilling departments.Shutting down the production platform for any reason would have significant economic consequences. In view of this arrangement, on-site engineering and interdepartmental coordination was vital.

Numerical Modelling of Cuttings Transport with Foam in Inclined Wells

“…Field applications have proven that UBD techniques have many advantages including minimized formation damage, increased drilling rate, improved formation evaluation while drilling, minimized lost circulation, reduced occurrence of differential pipe and logging tools sticking, enhanced detection of all producing zones, and enhanced earlier production from reservoir [3][4][5][6][7][8][9][10][11].…”