From the effect of global energy demands, many oil industries are forced to search for hydrocarbons in more challenging environments. For example, drilling under high pressure-high temperature (HPHT) conditions has become common practice over the past 15 years, and new technologies are being developed to keep up with the need to drill safely and efficiently, minimize formation damage, and improve the production rate.
The decision to drill two highly deviated and horizontal gas wells in the "S" field located in South Sumatera, Indonesia led to a detailed drilling strategy for managing the HPHT - sour gas environment and the narrow pressure window. Subsurface simulation confirmed that these well designs will provide additional gas recovery compared to existing vertical wells and also extend the plateau time production accordingly. The main challenge was to connect two vertical wells into one horizontal that would contribute to 60% of gas recovery from this structure.
Managed pressure drilling (MPD) was the main option for drilling this well in terms of drilling risk, compared to conventional techniques. The MPD method provides better control over formation damage along the horizontal section. Stimulating deep, hot, sour gas wells can be risky, and the chance of gas recovery is less when conventional drilling practices are used. Therefore, MPD coupled with the constant bottomhole pressure (CBHP) technique was chosen to fulfill the technical requirements.
The initial well production test result shows that the MPD technique succeeded in minimizing drilling-related problems along with minimizing formation skin damage. This allowed the well to meet the proposed production rate targeted by the subsurface team.
This paper describes the planning process for designing MPD HPHT drilling in a sour environment well and includes the implementation results and lessons learned from the drilling process.