Underbalanced Drilling and Managed Pressure Drilling techniques make the undrillable well drillable. Drilling challenges such as drilling through trouble zones, have been minimized through underbalanced, near balanced and Managed Pressure Drilling techniques.

However, when it came time to mitigate unique drilling challenges or to complete the well drilled with these techniques, the operator was faced with a limited number of ways to capitalize on the benefits that these drilling processes provided.

By combining Underbalanced Drilling practices and tools with drilling with casing technologies and expandable technology products, such as solid expandable Openhole Cladthru- Clad Liners and Expandable Sand Screens additional benefits such as:

  • Mitigation of drilling hazards,

  • Protection of sensitive hydrocarbon producing formations and

  • Completion of the well with optimum high-rate completions without the need to kill the well become possible.

In addition, Managed Pressure Drilling techniques can be combined with the Drilling with Casing processes to add a new level of tools to the operator's drilling "Tool Box" to mitigate drilling hazards.

This paper briefly describes these system components and the practical application of combinations of these technologies, highlighting the applications that can be used to create the most cost effective and productive well when confronting drilling challenges.

Encountering well remediation challenges such as the excessive influx of produced water can minimize or totally negate the advantages of drilling a horizontal, underbalanced well. Producing significant water in the heel of the well can overshadow the influx of oil from the lateral or toe of the well. Short solid expandable liners have been used to effectively shut-off these water zones while not causing the well's geometry to be downsized.

The value of drilling an underbalanced well to minimize skin effect and formation damage and to maximize production can be negated when the well has to be killed to set casing to facilitate zonal isolation when completing several zones. The availability of Solid "Expandable Zonal Isolation" barriers combined with Expandable Sand Screens now allow the underbalanced drilled well to be completed without the need to kill the well during its completion phase.

The above-mentioned practices can be used to optimize well performance and create a very prolific well, while retaining well construction cost controls and selective completion options.

The paper discusses how controlled drilling methods and systems work together with expandable technology products to create maximum bore wells, eliminating costly "flat" time on the well's drilling curve1 and yet maintaining the selectivity required to have long term flexibility of producing or selectively shutting off zones. The well construction process will also be discussed, showing how these systems are installed and how operational risks are managed through each phase of the well construction and completion process to ensure safety while minimizing well costs.


Underbalanced Drilling (UBD) techniques in various forms have been used for more than 20 years2. In particular, reservoir drilling employing UBD has steadily evolved since 19893. This is in large part because of the many advantages it provides over traditional drilling and completion methodologies.

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