Looking for oil in new complex areas pushes the drilling engineering to new limits. Nowadays, extended reach drilling (ERD) becomes a state of art. An extended reach well (ERW) can be defined in many ways because it is still a subject of debate, but in general it is defined based on the depth ratio. The depth ratio is the horizontal departure divided by the vertical depth, if this ratio is greater than 2, then the well can be considered as ERW ( Extended Reach Well). Many types of wells make the drilling technology in its limit; these wells can be considered as ERW. For example: 3D wells, deviated wells which challenge the capacities of the rig.
Drilling an ERW is a real challenge at all levels (ِClick Here). Drilling technology and personal competency are the most important issues. Planning an ERW can involve many issues. BHA design, casing program, hole cleaning, ECD management, and directional control can be considered as obstacles which have to be overcome (Click Here).
There are many advantages and benefits of drilling an ERW. Reducing environmental impacts, recover more oil from larger area, maximizing the drainage capability and productivity.
ERD Achievements and Records
Through the history of drilling industry, challenging the world records was an objective of many big companies. Breaking these records, it is not just an issue of publicity, but also developing new technologies and being a leader in larger technological area.
In 1993, Statoil achieved the level of 7290 m as a horizontal displacement, their well 33/9-C2 had a measured depth of 8761 m and they drilled it in 118 days. The MD/TVD reached the level of 3.14 which made the 33/9-C2 well the longest ERW at that time. BP is famous by its Wytch Farm field. The longest ERW are drilled in this field during the 1990’s. At that time, conventional ERD technology allowed the drilling of wells with a departure up to 20000 ft, beyond this level the casing running was really a problem to deal with. The BP had run 30000 ft of 9 5/8’’ intermediate casing in its 10+ Km well using new running techniques.
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| Fig 01- ERD Envelope |
In 2002, The A-10 well with 30000ft measured depth and 20000ft horizontal displacement was drilled in the Gulf of Mexico from a TLP. This well was sidetracked for many times because it was facing real troublesome formations. Borehole fatigue and instability were among the greatest downhole problems while drilling problems.
The OPA2 well was drilled in Hibernia field (Offshore Canada) extended the borders of the ERD envelope. The OPA2 has a 33209 ft measured depth. Many companies were involved the planning and operations: ExxonMobil, Chevron, Suncor and Statoil. The operations started in 2007, but due to the difficulties the well was temporarily abandoned. After a deeper study and analysis of the problems faced in drilling the original hole, the main problem was the changes of the lithology when crossing the faults. The well OPA2 was re-drilled and the target was reached successfully.
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