Drilling a well in deep oceans is a daunting task due to both downhole drilling hazards and excessive floating rig package. Traditionally many of these challenging wells are drilled with a low-pressure 21" marine drilling riser stretched from mudline to surface. A huge rig with high weight, space, and tensioning requirement is vital to handle this monster fluid conduit. Moreover, a reliable station keeping system is essential for the rig to keep it in a very tight operating radius to have drilling operations running uninterruptedly. When we move to deeper waters and harsher environments, it becomes more difficult, and in many cases becomes even impossible to reach reservoir targets in such challenging environments. The problem of narrow formation pressure window also exists and adds up. Reelwell Drilling Method has been proven by series of tests and theoretical studies to have the potential to alleviate the main drilling challenges by (1) elimination of the marine drilling riser to extend the capability of drilling in ultra deepwaters, (2) providing a closed-loop circulation system to make it possible for the industry to deploy Controlled Pressure Drilling (CPD) techniques and overcome many downhole pressure related challenges including narrow pressure window which is a common problem in deepwaters (Mir Rajabi 2009).

Managed Pressure Drilling has been proven to be a tool for extending access to previously unattainable drilling targets in many deepwater areas across the world, such as deepwater Gulf of Mexico. 21" Low-Pressure risers do not allow for application of Constant Bottom Hole Pressure (CBHP) technique by floaters. Since it is not designed to hole the pressure, it prevents setting up a closed circulation loop in our drilling system which is an essential tool for MPD.A high-pressure riser along with a surface Rotating Control Device is required to perform CBHP drilling technique. However, we know that deployment of such high pressure risers in long lengths and harsh environments has not come to be practical.An alternative drilling method from floaters at any water depth proves to be Reelwell Drilling Method (RDM). Reelwell AS, Shell, StatoilHydro, and the Research Council of Norway launched a JIP in 2005 to develop RDM, which is a riserless drilling method based on concentric drill pipe. Mud is circulated in a closed loop in this system. The pressure and flow of mud is dynamically controlled by a computer system on the return path on the surface. Many tests including the latest pilot test in March 2009 has proven that the downhole pressure can be controlled precisely and that the system fits perfectly for CBHP. Deployment of this technology by smaller floating rigs is possible with no limitation on water depth as huge and long 21" LP riser is eliminated from the system. The volume of mud is limited to bring about even more cost and rig space savings.

In recent years, operators have been drilling wells in ever increasing water depths. Drilling wells in deepwaters is a daunting task due to both downhole drilling hazards and excessive floating rig packages. Traditionally, these challenging wells are drilled with a low-pressure 21" drilling riser stretching from mudline to surface. A high day-rate gigantic floating rigs with high weight, space, and tensioning requirement is essential to handle this huge and long LP marine riser in deepwaters.Today, the industry is contemplating drilling in water depths of 10,000 ft and beyond, while current equipment can hardly (or even not) take the industry into such depths without changes. The 21" marine drilling riser cannot be pushed much further by existing rigs, and even if the rig could support the riser length and weigh, the riser itself cannot withstand the stresses. Furthermore, if all of these problems are tackled, many downhole drilling challenges are yet to be answered.So, needs for change in current deepwater drilling technology seems to be necessary if the industry is to reach deep targets successfully in deepwaters. Our approach to this problem is changing drilling method; we intend to introduce a newly born drilling technology called Reelwell Drilling Method which is a riserless drilling method by nature and facilitates drilling at any water depth by smaller and less expansive floating rigs, with fewer difficulties.RDM is also promising in delivering closed circulation system which turns it into a competent tool for Managed Pressure Drilling. This feature of RDM can make a big difference in drilling operations in environments with narrow pressure margin which is the case in deepwaters, HPHT, and depleted reservoirs.

MPD enables drillers to navigate through narrow drilling windows to reach designed target depths. After a hole section is drilled, pressure management is still required to pull drill strings out and run and cement liners. Conventional cementing programs and procedures may not be practical for a challenging hole section that has been drilled by MPD. Elaborate wellbore pressure management is required to ensure safe and efficient cementing operations. The same closed loop circulation system utilized for drilling is used to manage the wellbore pressure during cement operations. The technique of pressure management during liner cement jobs was utilized repeatedly by a major client in one of the most challenging HPHT campaigns in the North Sea. This paper provides an insight into the technique as well as information on the procedures, challenges and lessons learned pertinent to these operations. Various cases studies describing the setup, planning and execution of operations, simulation vs measured data will be compared. Drilling wells in complex environments with century-old technology is difficult at best and unsafe at worst. From drilling through narrow pore-pressure/fracture-pressure gradient windows to mitigating kicks and differential sticking, managed pressure drilling (MPD) succeeds when conventional techniques are likely to fail. MPD entails the use of specialized equipment to control wellbore pressure profiles more precisely than is possible with conventional drilling methods. MPD enables drillers to navigate through narrow drilling windows to reach designed target depths. After a hole section is drilled, pressure management is still required to pull drill strings out and run and cement liners. Conventional cementing programs and procedures may not be practical for a challenging hole section that has been drilled by MPD. Elaborate wellbore pressure management is required to ensure safe and efficient cementing operations. The same closed loop circulation system utilized for drilling is used to manage the wellbore pressure during cement operations. A case study describing the setup, planning and execution of operations, and simulation is presented in this paper.

A previous attempt to drill an exploration well in ultra-deepwater in the Gulf of Mexico (GoM) did not reach its objective due to an inability to maintain a Water Based Mud (WBM) system light enough to maintain circulation. For the next round of exploration drilling, a system was sought that allows dynamic management of Equivalent Circulation Density (ECD). Conventional Rotating Control Device (RCD) based Constant Bottom Hole Pressure (CBHP) management systems were not suitable, as no drilling fluid light enough to manage ECD via backpressure could be applied for this campaign. AGR has developed a pumped riser Managed Pressure Drilling (MPD) system named EC-Drill that facilitates an automated control of mud level inside the riser to a specific BHP set point to mitigate the problems of tight drilling margins in deep waters and low pressure reservoir. This allowed drilling from a semisubmersible with an adjustable mud level, effectively reducing BHP and managing ECD without using any types of backpressure devices. Fluid level inside the riser is adjusted by a field proven subsea pump system. EC-Drill detects influxes and fluid losses quickly, allowing the driller to respond before significant problem occurs. In this paper we will discuss how EC-Drill is planned to pave the way for the operator to access a previously unattainable ultra deepwater target. EC-Drill principles, well design, equipment, and planning will be covered.