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.

BD Gas Field is located in offshore in the Madura Strait, Indonesia, and has a total of four producing wells - one vertical (Well Y1) and three horizontal (Well Y2, Well Y3, and Well Y4) from an unmanned platform. Its reservoir was considered near HPHT and critical sour with 8,100 psi bottom hole pressure, 300°F bottom hole temperature, 5.5% CO2 and 5,000 ppm H2S. This paper highlights on the Company journey to maintain well integrity during well design phase, well construction phase, and production phase of BD Gas Field. During well design phase, material selection and design for 9-5/8 in. intermediate casing, 7 in. production casing, and 4-1/2 in. tubing were based on the expected life of the well and reservoir properties in accordance to the requirements of NACE. Cementing design for 7 in. production casing cement was tested and analyzed in the laboratory for 60 days in the HPHT chamber simulating reservoir properties. Top of cement was designed to the mud line to minimize wellhead growth. Completion design was monobore type and divided into lower, intermediate, and upper completion strings. All packers were V-0 (zero bubble) rating. Maintaining well integrity during well construction phase was challenging. Batch drilling and completion was applied, and at all times, the wells were required to be suspended with proper and adequate barriers. During drilling and well clean-up phase, inter-casing pressure management (i.e., annulus pressure, wellhead growth monitoring, bleed off program, etc.) was implemented to maintain the casing and tubing integrity. During production phase, routine wellhead growth measurement, constant monitoring and bleed off program were developed and communicated with related departments. Pressure control valves and alarm system were installed and tested to the annulus. In additional to the wellhead growth, transverse wellhead movement was observed in one of the wells especially during rough sea conditions. In order to reduce the tranverse wellhead movement which may induce more stress on the surface pipings and connections, it was planned to install under water shims in between the conductor pipe and platform jacket guide funnel. Some surface piping and platform modification were also considered because wellhead growth leads to limitations on gas production to prevent safety issues.