The benefits of a properly executed Underbalance Operation (UBO) can result in a well of higher quality and value than that of a conventional well, if proper planning and execution is achieved. This paper discusses the importance of detailed planning when undertaking a UBO and the consequences when conducted improperly.

UBO has demonstrated numerous times that:

  • Higher penetration rates (>2X) can be realized

  • Higher productivity (>2X) can be achieved

  • Higher reserves recovery are achieved

UBO has proven to reduce development costs, on multi-well projects. The timing for this cost reduction depends largely upon:

  • the well construction staff in charge of the operation

  • the rate of knowledge transfer from the experienced personnel (service technicians) to the operator

  • the utilization of the information by the operator.

The current knowledge base of UBO is miniscule compared to conventional Overbalance Operation (OBO) knowledge. Access to this knowledge base and implementing the value of the knowledge are critical to expansion of the technology and the establishment of credible operating practices. Global industry organizations such as the International Association of Drilling Contractors (IADC), Society of Petroleum Engineers (SPE), and Gas Technology Institute (GTI) have dedicated significant time and resources to promote the exchange of knowledge and develop safe operating practices of UBO. These organizations should be accessed to reduce the learning time for companies considering the use of UBO equipment and services.

The critical keys to achieving the benefits of UBO, are planning and execution. Several real case histories are presented, which demonstrate the impact of critical planning and execution on project cost. Accessing the knowledge base and implementing lessons learned will enable the user to achieve a successful UB Operation.

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