Recent trends in the Oil & Gas industry have been toward the utilization of new technologies in order to optimize production and improve recovery. The National Oil Corporation (NOC) of Libya is considering deploying Under-balanced Drilling (UBD) technology as one of the most effective methods when it is effectively applied in conjunction with horizontal and/or Multi-lateral well drilling and completion techniques

Under-Balanced Drilling Technology has enabled the commercial development of numerous oil and gas reservoirs around the world that would have otherwise not been exploited due to technical and/or economic limitations. Under-Balanced Drilling has only become possible as a result of the integration of many developing technologies that facilitate directional control of the well trajectory, control of the bottom hole circulating pressure and the safe handling of drilling fluids and drill cuttings on surface.

When drilling Under-balanced, the annular pressure profile is maintained below the expected reservoir pore pressure and is particularly beneficial in evaluating the productivity of prospective formations in their virgin state. This means that the formation can be evaluated without being subjected to damage during conventional drilling and the required clean-up operations.

As of today, a total of three wells have been drilled under-balanced by ZUEITINA Oil Company in Libya. Through three examples, the paper will demonstrate that the key to selecting appropriate Reservoir candidates for UBD is achieving a balance of Technical, Safety and Economic factors.

This paper describes the Front End Engineering Design, Project Management, Risk Mitigation, Operational Results and Lessons Learned for this project.

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