Underbalanced Drilling (UBD), which uses lower downhole pressure to reduce wellbore damage by allowing the production of oil and gas while drilling, is being used in 14 active Shell drilling programs this year compared to just seven by Shell's top four competitors combined.
The technique, which was traditionally used to overcome drilling problems, is now recognized as leading to improvements in well production of between 50 and 800 percent compared to wells drilled by conventional "overbalanced" methods, when applied correctly in the appropriate geological and reservoir settings. It has been used successfully by Shell in both onshore and offshore fields.
UBD also provides valuable information in real time on a reservoir's properties and potential, particularly to identify fractures and sweet spots that may otherwise go unnoticed. Some operating units have also increased recoverable reserves due to success with UBD, as the technique has been shown to improve recovery efficiency in many cases.
Brian Truelove, Shell's Global Implementation Manager for UBD, is leading the quick deployment of the technique in Shell operating units around the globe. By 2004 he aims to have more than 20 UBD operations, across every region of the world.
"UBD provides a real-time well test whilst drilling which is giving us information we never had before. For several fields this has completely changed the way we go about developing these reservoirs, with substantial capital savings as a result in some cases," he said.
In Syria, for example, UBD has reduced the drilling time from 70 days to 40 and a further slimming of the well design is expected to save US$20 million on well costs. In the North Sea, UBD provided a lifeline to a field that looked like it would be abandoned because reservoir pressure had dropped to a few hundred p.s.i. Using UBD the field is still producing, more than two years later.
UBD also contributes to Shell's commitment to sustainable development by reducing the number of wells needed and getting the most out of the Group's existing assets by improving recovery efficiency. In addition, the Shell UBD Global Implementation Team is developing local expertise in the communities in which Shell operates. For example, Omani staff have gained skills and knowledge as a lead implementer operating unit within Shell. They are now able to help other Shell UBD operations in the Middle East region with the knowledge they have gained.
Mr. Truelove emphasized that UBD is effective in certain reservoir types, and cannot be applied in all operating conditions, particularly in areas with borehole instability. He said: "Extensive planning and preparations are required before drilling can begin, and involvement of experienced personnel is essential to avoid HSE problems and to derive the most benefit from UBD."
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