Successful Mitigation of Deepwater Shallow Flows in the East Mediterranean Region—Case Histories

摘要

In 2008 deepwater drilling marked a decade of operation in the Nile Delta region of the East Mediterranean Sea. The operating water depths ranged from 200 m to ultra deepwaters greater than 2600 m. The Nile Delta region has been no exception to the challenges of shallow gas and water-flow hazards observed in many of the deepwater projects of the world (Furlow 1998; Alberty 1998). An obvious consequence of an unexpected, shallow-fluid flow is an uncontrolled blowout situation with no drilling control equipment in place. In some reported cases, even after the flow was controlled before running casing, fluid flow occurred after cementing the surface pipe. Incidentally, this phenomenon is not only limited to deepwater operations in Egypt; similar blowout situations can be observed anywhere in the offshore Nile Delta. This paper reviews two recent examples of shallow flows that occurred in the surface holes of two different wells. Each operation cost the operator between 1.5 and 4 million dollars to address the problem. Alternatively, several examples are also provided that illustrate how understanding the flow mechanism, predicting its occurrence, taking necessary precautions while drilling, and designing cement slurries suitable for deepwater cementing have resolved the issue. Proper well preparation, correct mud design, and foamed cementing have been effective solutions. Additionally, advances made in cementing designs for deepwater situations with low margins between pore pressure and fracture gradient, cool seabed temperatures, and unpredictable shallow flows, each working adversely on the slurry design, are discussed to help deliver safe and competent wellbores.