A Comprehensive Approach for Drilling and Completion to Improve Production in a Shallow, Off-shore Well in Indonesia

The Tunu field, located in the swamps and shallow waters of the outer margin of the Mahakam delta, is a gas and condensate field in east Kalimantan, Indonesia. Because of the low incremental reserves per well, the field development team was challenged to either reduce the cost of developing and operating the well to achieve target economics or to increase producibility. In this case, the operator was able to achieve both. Gas-bearing reservoirs, found from 2,200 to 4,000 m, are known to contain sensitive shales. Consequently, synthetic oilbased drilling fluid has traditionally been used for drilling the reservoir, followed by the installation of a gravel pack completion for sand control. Significant costs associated with the handling and disposal of oil-based mud cuttings are also eliminated through the use of water-based muds. The operator’s goals for this particular well included altering the completion design to standalone screens and drilling with a highly inhibitive water-based drilling fluid to protect the reservoir while reducing cost. To achieve these goals, a rigorous fluid design program was implemented to evaluate shale inhibitors and optimize the formulation to ensure that no issues would be encountered while running in the standalone screens. The selected drilling fluid contained a novel blend of shale inhibitors with an optimized bridging and fluid compatibility; it was specifically tailored for the Tunu reservoir. This paper discusses the design of an enhanced drilling fluid that prevents formation damage in sensitive shales and facilitates a simpler and more economical completion method, which reduces costs and improves production.