BD Field is the first development project of Husky-CNOOC Madura Limited (HCML) in Madura Strait, Indonesia which has a pressure of 8,100 psi and a temperature of 300°F. This Kujung gas reservoir contains of 5.5% CO2 and 5,000 ppm H2S, indicating that the reservoir is near High Pressure High Temperature (HPHT) and critical sour environment. This paper describes the best practices, lessons learned and strategy to control drilling issues such as slim hole, horizontal, near High Pressure-High Temperature, high density, and sour/acid gas environment to achieve the well TD with torque and ECD limitation, without compromising production target. Kujung reservoir section was drilled with an overbalance mud system as per CNOOC HPHT and sour well requirement. Drill-In fluid (DIF) system treated with potassium formate and manganese tetraoxide as weighting agents was chosen for drilling the 5-7/8-in. reservoir section. Throughout the drilling operation, higher torque and ECD value was identified compared with Torque and Drag (T&D) Calculation and Hydraulics simulation. This can lead to shallower TD decision, which has consequence of possibility not achieving initial target depth/production. Calibrating T&D model using the pickup/rotate/slack-off value from actual measurements on both cased and open holes was done in order to match the model with actual condition. Several analysis and review of all possible causes was performed, including performance of solids control equipment, inadequate hole cleaning, dog leg severity, wellbore direction and/or formation lithology changes. T&D and hydraulics simulation was also performed to foresee the possible operation limitation with several lateral lengths to ensure having successful drilling operation without compromising both operational safety and future well production. Based on the original model, with friction factor values of 0.25 (cased hole) and 0.35 (open hole), 1000-1500 ft lateral length of 5-7/8-in. slim hole section can be achieved. However, with calibrated T&D model, friction factor values were almost double the original model. Comprehensive planning was done to accomplish the drilling objectives, such as re-plan well trajectory to reduce dog leg severity, selection of drill fluid lubricant additives to ensure its stability at pH > 11 environment as planned to control sour gas and compatibility with other products, maximize centrifuge usage to minimize excessive LGS build-up caused by successive and repetitive mud system re-use for batch drilling operations, and diluted system using rehabilitation mud. Reduced friction factors and decreased torque values were the key parameters to successful drilling through the updated planned horizontal length. In terms of gas well production, the objective of well productivity was achieved during unloading operation when gas production result from the wells yielded higher Absolute Open Flow (AOF) as compared to the planned target. Hence a successful BD wells had been delivered to production.

BD is a near high pressure-high temperature (HPHT) critical sour gas field located in offshore Madura Strait in water depth of 152 ft. An exploration and appraisal well were drilled in 1987 and 1992 respectively, targeting BD reef at depth of 10,676ft SSTVD. Both well test results confirmed the limestone formation has characteristic of 305°F and 8,105 psi, with 5,000 ppm of H2S and 5.5% of CO2 content. Four (4) development wells including three (3) horizontal and one (1) vertical well, were drilled to drain the reserves from BD field. The project was expected to deliver 120 MMSCFD of gas and 6,000 bpd of condensate for a period of 15 years production from BD field. Design, equipment and material to complete the well need to meet the target and be selected based on industry guidance and the environment to ensure the integrity of the well during the production time. Completion for BD wells adapts multiple tie-back concept to provide consistent large flow area and big bore advantages, providing flexibility for future well intervention. It consists of 3 (three) main assemblies and was designed based on series of load cases to predict the completion reliability to withstand the load during the life of the well. During the installation, the assemblies were run in different batches and fluid environment. Despite the challenges encountered during the preparation and installation, all wells were successfully completed and cleaned up safely without any incident. The completion could exceed the initial production target set by the reservoir engineering team. This paper will discuss about the completion process from the first near HPHT sour field development project in Indonesia. It describes the design process, preparation and installation of the BD completion especially in the horizontal well. Challenges, basis of design, material selection, lessons learned and optimization taken to safely deliver the completion are also covered in this paper.

The Company had successfully drilled 4 challenging BD Development Wells (1 vertical and 3 horizontal). BD Field reservoir is aKujung 1 limestone reef, considered near HPHT and critical sour with 8,100 psi Bottom Hole Pressure (BHP), 300℉ Bottom Hole Temperature (BHT), 5.5% CO2 and 5,000 ppm H2S. This paper highlights the design phase and well deliverability covering pressure window, casing design, material selection, wellhead and Christmas tree, directional drilling planning, drilling fluid, cementing consideration, well completion, annulus pressure management, and project challenges. The data from two offset wells with surface location radius fewer than 2,000 ft from BD Platform were used as reference for lessons learnt and design for the casing seat selection. Based on the Wellbore Stability Study and the offset wells data, there exists a narrow mud weight window between pore pressure and fracture pressure. The directional plan was developed to have sufficient well separation in the upper hole section and enable fewer dog leg severity requirement to drill in the down hole section. Material selection for casing was designed based on the expected life of the well and reservoir properties in accordance to the requirements of NACE. Drill-in fluid system (Potassium Formate and Manganese Tetraoxide) with mud weight of 14.9 ppg was used to drill the limestone reservoir section providing minimal damage to the reservoir. Production casing cement was tested and analyzed in the laboratory for 60days in the HPHT chamber simulating reservoir properties. Open Hole Monobore Completion approach was selected to complete the well. In order not to compromise well integrity, annulus pressure management technique was fully implemented during drilling, completion, and well clean up phases. The wells were successfully executed despite several challenges which required unique mitigations to manage. During well clean ups, all wells were able to exceed the Absolute Open Flow (AOF) expectations.