In order to improve the cost efficiency of petroleum exploration and production, it is required to develop improved technology. The Reelwell Drilling Method (RDM) is a multi purpose drilling method with a unique arrangement for Extended Reach Drilling and Managed Pressure Drilling. A conventional drill string with a special inner string forms a dual concentric drill string, which is used to remove drill cuttings from the bottom of the well. A separate hydraulic fluid system is used to push the drilling assembly forward using fluid pressure from the surface. The development of RDM started in 2004 and has since then been through several full scale operations in Norway. In 2009 RDM was successfully used to directional drill the 8 ½" section of a land well. The proof of concept and the practical application on conventional drilling rigs has been verified, as well as the features of the system, such as: - Managed Pressure Drilling (MPD) – Unique isolation using a new downhole valve solution. - Very precise well pressure management and flow control (gain/loss). - Efficient hole cleaning and cutting removal from wellbore - Efficient hydraulic traction and WOB control. The RDM is currently planned to be used for drilling horizontal wells in Canada. The potential to increase the reach for horizontal wells is here further discussed.

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.