Technology Focus: Multilateral/Extended Reach (May 2014)
Authors: Negrao Alvaro Felippe 
Published: February 2015

Technology Focus
The oil industry has always been innovative, even under adverse and challenging conditions imposed by the nature of upstream projects. In the past, drilling and completion activities have faced the complexity of the wells and tougher operational and environmental regulations with ingenuity and efficiency.
Some prospects considered not feasible 5 years ago are delivering an attractive rate of return to shareholders after the implementation of new techniques. On a day-by- day basis, deepwater, extended-reach, slimhole, and environmentally sensitive drilling projects are reaching the limit of industry capability and pushing for faster evolution in terms of technology, equipment, and procedures. It is not rare anymore to deal with prospects that require pressure ratings of 20,000 psi, temperatures greater than 350°F, and measured depths to 40,000 ft.
These challenging project characteristics are leading to a review of conventional techniques and the use of innovative technology for wellbore positioning in a thin oil column, long horizontal drilling and completion legs, extremely low fracture margin in deepwater wells, and downhole tool telemetry. In the case of extended-reach wells (ERWs), the extension of horizontal legs aligned with low gradient fracture in deepwater projects requires an appropriate pressure-management system to mitigate the effect of friction losses at bottomhole conditions.
The horizontal legs of multilaterals and ERWs are reaching lengths of 11,000 to 12,000 ft, with corresponding high friction losses that preclude the setting of casing shoes at planned depth in conventional drilling methods because of the equivalent circulating density (ECD). This challenge becomes even more critical when dealing with deepwater environments. Techniques such as the Reelwell drilling method (RDM) and managed-pressure drilling (MPD) have advanced considerably in recent years and are now feasible alternatives to mitigate the ECD and, consequently, are helping the execution of ERWs onshore and offshore.
For example, RDM has a unique flow architecture that uses a conventional drillstring combined with an inner string to form a dual-conduit drillstring. This arrangement allows the return fluid containing cuttings to be transported back through the inside of the drillstring, thus eliminating the ECD. RDM also has the advantage of increasing the drilling envelope for ERWs because of torque and drag reduction and optional hydraulic weight on bit caused by a piston-type arrangement at the drillstring.
It is difficult to comment about all the new available technologies in this summary, but the following papers address other advancements that are making possible the continuity of drilling and completion activities in a responsible, safe, and feasible way. JPT
Recommended additional reading at OnePetro: www.onepetro.org.
SPE 166143 Multilateral Wells in the Urucu Field of Western Brazil: Reducing Environmental Impact in the Amazon by Sandro Mendes, Petrobras, et al.
OTC 23985 Combining Contemporary and Tested Technologies To Achieve Successful Deepwater Extended-Reach Completions by Ray Brister, Chevron, et al.
SPE/IADC 168049 New Rotary- Shouldered Connection Expands the Capability of World-Record ERD Operation by S.R. Sanford, ExxonMobil, et al.