One of the most challenging theaters in modern drilling and production is that of the development of High Pressure High Temperature (HPHT) reservoirs. A great deal of research and development is continuing, in both Operating and Service Companies, and much resources being dedicated to the design and materials of construction challenges associated with HPHT drilling equipment, particularly in the areas of downhole tools such as mud motors, monitoring equipment etc. In the meantime conventional thinking still seems to dictate that the drilling of HPHT reservoirs be done with conventional mud systems with returns open to the atmosphere, perhaps ignoring some existing technologies that can be of assistance in both economic and Health, Safety and Environment (HSE) issues. The Rotating Control Device (RCD) is in common use in many parts of the world in Underbalanced drilling operations (UBD).and Performance Drilling (air, mist, foam etc.) where it is a necessity. However, it tends to be ignored in other applications.
In North Eastern Brazil a 4 well HPHT campaign has been completed in which the RCD was used very successfully, not as a device for drilling underbalanced or for Performance Drilling, but for drilling safely using a Managed Pressure Drilling (MPD) approach. In this mode it provides more time to react when kick events occur, as opposed to an open drilling system and has a definite impact on HSE due to tightly controlling the synthetic based drilling fluid that is in common use.
In this paper the author will discuss the application of an RCD in this drilling campaign and describe the main lessons learned in an environment where use of conventional open drilling systems presents higher risk from both an economical and an operational viewpoint. The author will conclude that use of an RCD will be integral to the future development of this and other HPHT fields in Brazil and should be considered in such operations in other areas.
The drilling and development of HPHT reservoirs presents many challenges to the Industry and as a result continued research into and development of equipment suitable for use in this environment is essential to crossing this frontier successfully. Among the challenges are:
The highly pressured reservoirs present unique challenges in well control.
The high temperatures mandate the development of downhole tools capable of operating in that environment.
The high temperatures also require special mud systems, since water based mud is typically unsuitable in that environment. This means the use of a synthetic or oilbased mud is necessary which is environmentally speaking less desirable and brings its own problems in the areas of handling, containing spills etc.
The industry has tended to spend a lot of resources on developing new equipment and fluids systems for this environment, meanwhile using conventional approaches to drilling and occasionally overlooking existing and well proven equipment that may have application.